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Xie C, Yang Y, Yu H, He Q, Yuan M, Dong B, Zhang L, Yang M. RNA velocity prediction via neural ordinary differential equation. iScience 2024; 27:109635. [PMID: 38623336 PMCID: PMC11016905 DOI: 10.1016/j.isci.2024.109635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 12/04/2023] [Accepted: 03/26/2024] [Indexed: 04/17/2024] Open
Abstract
RNA velocity is a crucial tool for unraveling the trajectory of cellular responses. Several approaches, including ordinary differential equations and machine learning models, have been proposed to interpret velocity. However, the practicality of these methods is constrained by underlying assumptions. In this study, we introduce SymVelo, a dual-path framework that effectively integrates high- and low-dimensional information. Rigorous benchmarking and extensive studies demonstrate that SymVelo is capable of inferring differentiation trajectories in developing organs, analyzing gene responses to stimulation, and uncovering transcription dynamics. Moreover, the adaptable architecture of SymVelo enables customization to accommodate intricate data and diverse modalities in forthcoming research, thereby providing a promising avenue for advancing our understanding of cellular behavior.
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Affiliation(s)
- Chenxi Xie
- MGI, BGI-Shenzhen, Shenzhen 518083, China
| | | | - Hao Yu
- Peking University, Beijing 100871, China
| | - Qiushun He
- MGI, BGI-Shenzhen, Shenzhen 518083, China
| | | | - Bin Dong
- Peking University, Beijing 100871, China
| | - Li Zhang
- Peking University, Beijing 100871, China
| | - Meng Yang
- MGI, BGI-Shenzhen, Shenzhen 518083, China
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2
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Chou X, Li X, Ma K, Shen Y, Min Z, Xiao W, Zhang J, Wu Q, Sun D. N-methyl-d-aspartate receptor 1 activation mediates cadmium-induced epithelial-mesenchymal transition in proximal tubular cells. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 904:166955. [PMID: 37704144 DOI: 10.1016/j.scitotenv.2023.166955] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 08/25/2023] [Accepted: 09/08/2023] [Indexed: 09/15/2023]
Abstract
Cadmium (Cd) is a commonly found environmental pollutant and is known to damage multiple organs with kidneys being the most common one. N-methyl-d-aspartate receptor 1 (NMDAR1) is a ligand-gated ion channel that is highly permeable to calcium ion (Ca2+). Because Cd2+ and Ca2+ have structural and physicochemical similarities, whether and how Cd could interfere NMDAR1 function to cause renal epithelial cells dysfunction remains unknown. In this study, we investigated the role of NMDAR1 in Cd-induced renal damage and found that Cd treatment upregulated NMDAR1 expression and promoted epithelial-mesenchymal transition (EMT) in mouse kidneys in vivo and human proximal tubular epithelial HK-2 cells in vitro, which were accompanied with activation of the inositol-requiring enzyme 1 (IRE-1α) / spliced X box binding protein-1 (XBP-1s) pathway, an indicative of endoplasmic reticulum (ER) stress. Mechanistically, NMDAR1 upregulation by Cd promoted Ca2+ channel opening and Ca2+ influx, resulting in ER stress and subsequently EMT in HK-2 cells. Inhibition of NMDAR1 by pharmacological antagonist MK-801 significantly attenuated Cd-induced Ca2+ influx, ER stress, and EMT. Pretreatment with the IRE-1α/XBP-1s pathway inhibitor STF-083010 also restored the epithelial phenotype of Cd-treated HK-2 cells. Therefore, our findings suggest that NMDAR1 activation mediates Cd-induced EMT in proximal epithelial cells likely through the IRE-1α/XBP-1s pathway, supporting the idea that NMDAR1 could be a potential therapeutic target for Cd-induced renal damage.
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Affiliation(s)
- Xin Chou
- Department of Occupational Disease, Shanghai Pulmonary Hospital affiliated to Tongji University, Shanghai 200433, China
| | - Xiaohu Li
- Union Hospital of Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province 430022, China
| | - Kunpeng Ma
- Department of Occupational Disease, Shanghai Pulmonary Hospital affiliated to Tongji University, Shanghai 200433, China
| | - Yue Shen
- Department of Occupational Disease, Shanghai Pulmonary Hospital affiliated to Tongji University, Shanghai 200433, China
| | - Zhen Min
- Department of Occupational Disease, Shanghai Pulmonary Hospital affiliated to Tongji University, Shanghai 200433, China
| | - Wusheng Xiao
- Department of Toxicology, School of Public Health, Peking University, Beijing 100191, China; Beijing Key Laboratory of Toxicological Research and Risk Assessment for Food Safety, Peking University, Beijing 100191, China; Key Laboratory of State Administration of Traditional Chinese Medicine for Compatibility Toxicology, School of Public Health, Peking University, Beijing 100191, China
| | - Jingbo Zhang
- Department of Occupational Disease, Shanghai Pulmonary Hospital affiliated to Tongji University, Shanghai 200433, China
| | - Qing Wu
- Department of Toxicology, School of Public Health, Fudan University, 130 Dong'an Road, Shanghai 200032, China
| | - Daoyuan Sun
- Department of Occupational Disease, Shanghai Pulmonary Hospital affiliated to Tongji University, Shanghai 200433, China.
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3
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Activation of non-classical NMDA receptors by glycine impairs barrier function of brain endothelial cells. Cell Mol Life Sci 2022; 79:479. [PMID: 35951110 PMCID: PMC9372018 DOI: 10.1007/s00018-022-04502-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 07/04/2022] [Accepted: 07/16/2022] [Indexed: 12/24/2022]
Abstract
Blood–brain barrier (BBB) integrity is necessary to maintain homeostasis of the central nervous system (CNS). NMDA receptor (NMDAR) function and expression have been implicated in BBB integrity. However, as evidenced in neuroinflammatory conditions, BBB disruption contributes to immune cell infiltration and propagation of inflammatory pathways. Currently, our understanding of the pathophysiological role of NMDAR signaling on endothelial cells remains incomplete. Thus, we investigated NMDAR function on primary mouse brain microvascular endothelial cells (MBMECs). We detected glycine-responsive NMDAR channels, composed of functional GluN1, GluN2A and GluN3A subunits. Importantly, application of glycine alone, but not glutamate, was sufficient to induce NMDAR-mediated currents and an increase in intracellular Ca2+ concentrations. Functionally, glycine-mediated NMDAR activation leads to loss of BBB integrity and changes in actin distribution. Treatment of oocytes that express NMDARs composed of different subunits, with GluN1 and GluN3A binding site inhibitors, resulted in abrogation of NMDAR signaling as measured by two-electrode voltage clamp (TEVC). This effect was only detected in the presence of the GluN2A subunits, suggesting the latter as prerequisite for pharmacological modulation of NMDARs on brain endothelial cells. Taken together, our findings argue for a novel role of glycine as NMDAR ligand on endothelial cells shaping BBB integrity.
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Tabusi M, Thorsdottir S, Lysandrou M, Narciso AR, Minoia M, Srambickal CV, Widengren J, Henriques-Normark B, Iovino F. Neuronal death in pneumococcal meningitis is triggered by pneumolysin and RrgA interactions with β-actin. PLoS Pathog 2021; 17:e1009432. [PMID: 33760879 PMCID: PMC7990213 DOI: 10.1371/journal.ppat.1009432] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Accepted: 02/28/2021] [Indexed: 12/14/2022] Open
Abstract
Neuronal damage is a major consequence of bacterial meningitis, but little is known about mechanisms of bacterial interaction with neurons leading to neuronal cell death. Streptococcus pneumoniae (pneumococcus) is a leading cause of bacterial meningitis and many survivors develop neurological sequelae after the acute infection has resolved, possibly due to neuronal damage. Here, we studied mechanisms for pneumococcal interactions with neurons. Using human primary neurons, pull-down experiments and mass spectrometry, we show that pneumococci interact with the cytoskeleton protein β-actin through the pilus-1 adhesin RrgA and the cytotoxin pneumolysin (Ply), thereby promoting adhesion and invasion of neurons, and neuronal death. Using our bacteremia-derived meningitis mouse model, we observe that RrgA- and Ply-expressing pneumococci co-localize with neuronal β-actin. Using purified proteins, we show that Ply, through its cholesterol-binding domain 4, interacts with the neuronal plasma membrane, thereby increasing the exposure on the outer surface of β-actin filaments, leading to more β-actin binding sites available for RrgA binding, and thus enhanced pneumococcal interactions with neurons. Pneumococcal infection promotes neuronal death possibly due to increased intracellular Ca2+ levels depending on presence of Ply, as well as on actin cytoskeleton disassembly. STED super-resolution microscopy showed disruption of β-actin filaments in neurons infected with pneumococci expressing RrgA and Ply. Finally, neuronal death caused by pneumococcal infection could be inhibited using antibodies against β-actin. The generated data potentially helps explaining mechanisms for why pneumococci frequently cause neurological sequelae.
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Affiliation(s)
- Mahebali Tabusi
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, BioClinicum J7:20, Stockholm, Sweden
- Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden
| | - Sigrun Thorsdottir
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, BioClinicum J7:20, Stockholm, Sweden
- Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden
| | - Maria Lysandrou
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, BioClinicum J7:20, Stockholm, Sweden
- Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden
| | - Ana Rita Narciso
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, BioClinicum J7:20, Stockholm, Sweden
- Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden
| | - Melania Minoia
- Department of Molecular Biosciences, The Wenner-Gren Institutet, Stockholm University, Stockholm, Sweden
| | | | - Jerker Widengren
- Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Birgitta Henriques-Normark
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, BioClinicum J7:20, Stockholm, Sweden
- Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden
| | - Federico Iovino
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, BioClinicum J7:20, Stockholm, Sweden
- Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden
- * E-mail:
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Urbano FJ, Bisagno V, Garcia-Rill E. Gamma oscillations in the pedunculopontine nucleus are regulated by F-actin: neuroepigenetic implications. Am J Physiol Cell Physiol 2019; 318:C282-C288. [PMID: 31747316 DOI: 10.1152/ajpcell.00374.2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The pedunculopontine nucleus (PPN) is part of the reticular activating system (RAS) in charge of arousal and rapid eye movement sleep. The presence of high-frequency membrane oscillations in the gamma-band range in the PPN has been extensively demonstrated both in vivo and in vitro. Our group previously described histone deacetylation (HDAC) inhibition in vitro induced protein changes in F-actin cytoskeleton and intracellular Ca2+ concentration regulation proteins in the PPN. Here, we present evidence that supports the presence of a fine balance between HDAC function and calcium calmodulin kinase II-F-actin interactions in the PPN. We modified F-actin polymerization in vitro by using jasplakinolide (1 μM, a promoter of F-actin stabilization), or latrunculin-B (1 μM, an inhibitor of actin polymerization). Our results showed that shifting the balance in either direction significantly reduced PPN gamma oscillation as well as voltage-dependent calcium currents.
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Affiliation(s)
- Francisco J Urbano
- Instituto de Investigaciones Farmacológicas, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Veronica Bisagno
- Instituto de Fisiología, Biología Molecular, y Neurociencias, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Edgar Garcia-Rill
- Center for Translational Neuroscience, University of Arkansas for Medical Sciences, Little Rock, Arakansas
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Yin W, Kim HT, Wang S, Gunawan F, Wang L, Kishimoto K, Zhong H, Roman D, Preussner J, Guenther S, Graef V, Buettner C, Grohmann B, Looso M, Morimoto M, Mardon G, Offermanns S, Stainier DYR. The potassium channel KCNJ13 is essential for smooth muscle cytoskeletal organization during mouse tracheal tubulogenesis. Nat Commun 2018; 9:2815. [PMID: 30022023 PMCID: PMC6052067 DOI: 10.1038/s41467-018-05043-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 05/25/2018] [Indexed: 12/22/2022] Open
Abstract
Tubulogenesis is essential for the formation and function of internal organs. One such organ is the trachea, which allows gas exchange between the external environment and the lungs. However, the cellular and molecular mechanisms underlying tracheal tube development remain poorly understood. Here, we show that the potassium channel KCNJ13 is a critical modulator of tracheal tubulogenesis. We identify Kcnj13 in an ethylnitrosourea forward genetic screen for regulators of mouse respiratory organ development. Kcnj13 mutants exhibit a shorter trachea as well as defective smooth muscle (SM) cell alignment and polarity. KCNJ13 is essential to maintain ion homeostasis in tracheal SM cells, which is required for actin polymerization. This process appears to be mediated, at least in part, through activation of the actin regulator AKT, as pharmacological increase of AKT phosphorylation ameliorates the Kcnj13-mutant trachea phenotypes. These results provide insight into the role of ion homeostasis in cytoskeletal organization during tubulogenesis.
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Affiliation(s)
- Wenguang Yin
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, 61231, Germany.
| | - Hyun-Taek Kim
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, 61231, Germany
| | - ShengPeng Wang
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research, Bad Nauheim, 61231, Germany
- Cardiovascular Research Center, School of Basic Medical Sciences, Xi'an Jiaotong University, Xi'an, 710061, China
| | - Felix Gunawan
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, 61231, Germany
| | - Lei Wang
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research, Bad Nauheim, 61231, Germany
| | - Keishi Kishimoto
- Laboratory for Lung Development, RIKEN Center for Developmental Biology, Kobe, 650-0047, Japan
| | - Hua Zhong
- Departments of Pathology and Immunology and Molecular and Human Genetics, Integrative Molecular and Biomedical Sciences Program, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Dany Roman
- Departments of Pathology and Immunology and Molecular and Human Genetics, Integrative Molecular and Biomedical Sciences Program, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Jens Preussner
- Max Planck Institute for Heart and Lung Research, ECCPS Bioinformatics and Deep Sequencing Platform, Bad Nauheim, 61231, Germany
| | - Stefan Guenther
- Max Planck Institute for Heart and Lung Research, ECCPS Bioinformatics and Deep Sequencing Platform, Bad Nauheim, 61231, Germany
| | - Viola Graef
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, 61231, Germany
| | - Carmen Buettner
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, 61231, Germany
| | - Beate Grohmann
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, 61231, Germany
| | - Mario Looso
- Max Planck Institute for Heart and Lung Research, ECCPS Bioinformatics and Deep Sequencing Platform, Bad Nauheim, 61231, Germany
| | - Mitsuru Morimoto
- Laboratory for Lung Development, RIKEN Center for Developmental Biology, Kobe, 650-0047, Japan
| | - Graeme Mardon
- Departments of Pathology and Immunology and Molecular and Human Genetics, Integrative Molecular and Biomedical Sciences Program, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Stefan Offermanns
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research, Bad Nauheim, 61231, Germany
- Center for Molecular Medicine, Goethe University, Frankfurt, 60590, Germany
| | - Didier Y R Stainier
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, 61231, Germany.
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7
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Zhou X, Cheng Y, Zhang R, Li G, Yang B, Zhang S, Wu J. Alpha7 nicotinic acetylcholine receptor agonist promotes retinal ganglion cell function via modulating GABAergic presynaptic activity in a chronic glaucomatous model. Sci Rep 2017; 7:1734. [PMID: 28496108 PMCID: PMC5431927 DOI: 10.1038/s41598-017-02092-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 04/05/2017] [Indexed: 01/01/2023] Open
Abstract
Alpha-7 nicotinic acetylcholine receptor (α7-nAChR) agonists can prevent glutamate-induced excitotoxicity in cultured retinal ganglion cells (RGCs). However, the neuroprotective effects and the mechanism of action of PNU-282987, an α7-nAChR agonist, in a chronic in vivo rat glaucoma model are poorly understood. We found that elevated intraocular pressure (IOP) downregulated retinal α7-nAChR expression. Electroretinography revealed that the amplitude of the photopic negative response (PhNR) decreased in parallel with the loss of RGCs caused by elevated IOP. PNU-282987 enhanced RGC viability and function and decreased terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive signals in RGCs. Patch-clamp recordings revealed differences in the baseline frequencies and decay times of the miniature GABAergic inhibitory postsynaptic currents (mIPSCs) of RGCs between control and glaucomatous retinal slices. The results of western blotting and immunostaining showed that glutamic acid decarboxylase 65/67 and GABA deficits persisted in glaucomatous retinas and that these deficits were reversed by PNU-282987. Patch-clamp recordings also showed that PNU-282987 significantly increased the frequency and amplitude of the GABAergic mIPSCs of RGCs. The protective effects of PNU-292987 were blocked by intravitreal administration of selective GABAA receptor antagonists. The modulation of GABAergic synaptic transmission by PNU-282987 causes de-excitation of ganglion cell circuits and suppresses excitotoxic processes.
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Affiliation(s)
- Xujiao Zhou
- Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, 200032, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, 200032, China.,Key Laboratory of Myopia, Ministry of Health, Shanghai, 200032, China
| | - Yun Cheng
- Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, 200032, China
| | - Rong Zhang
- Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, 200032, China
| | - Gang Li
- Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, 200032, China
| | - Boqi Yang
- Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, 200032, China
| | - Shenghai Zhang
- Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, 200032, China
| | - Jihong Wu
- Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, 200032, China. .,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, 200032, China. .,Key Laboratory of Myopia, Ministry of Health, Shanghai, 200032, China.
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8
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Farrell SR, Rankin DR, Brecha NC, Barnes S. Somatostatin receptor subtype 4 modulates L-type calcium channels via Gβγ and PKC signaling in rat retinal ganglion cells. Channels (Austin) 2015; 8:519-27. [PMID: 25483286 DOI: 10.4161/19336950.2014.967623] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Somatostatin subtype-4 receptors (sst4) inhibit L-type calcium channel currents (ICa) in retinal ganglion cells (RGCs). Here we identify the signaling pathways involved in sst4 stimulation leading to suppression of ICa in RGCs. Whole cell patch clamp recordings were made on isolated immunopanned RGCs using barium as a charge carrier to isolate ICa. Application of the selective sst4 agonist, L-803 (10 nM), reduced ICa by 41.2%. Pretreatment of cells with pertussis toxin (Gi/o inhibitor) did not prevent the action of L-803, which reduced ICa by 34.7%. To determine the involvement of Gβγ subunits after sst4 activation, depolarizing pre-pulse facilitation paradigms were used to remove voltage-dependent inhibition of calcium channels. Pre-pulse facilitation did not reverse the inhibitory effects of L-803 on ICa (8.4 vs. 8.8% reductions, ctrl vs. L-803); however, pharmacologic inhibition of Gβγ reduced ICa suppression by L-803 (23.0%, P < 0.05). Inhibition of PKC (GF109203X; GFX) showed a concentration-dependent effect in preventing the action of L-803 on ICa (1 μM GFX, 34.3%; 5 μM GFX, 14.6%, P < 0.05). When both PKC and Gβγ were inhibited, the effects of L-803 on ICa were blocked (1.8%, P < 0.05). These results suggest that sst4 stimulation modulates RGC calcium channels via Gβγ and PKC activation. Since reducing intracellular Ca(2+) is known to be neuroprotective in RGCs, modulating these sst4 signaling pathways may provide insights to the discovery of unique therapeutic targets to reduce intracellular Ca(2+) levels in RGCs.
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Affiliation(s)
- Spring R Farrell
- a Department of Physiology & Biophysics ; Dalhousie University ; Halifax , NS , Canada
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9
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Stradleigh TW, Ishida AT. Fixation strategies for retinal immunohistochemistry. Prog Retin Eye Res 2015; 48:181-202. [PMID: 25892361 PMCID: PMC4543575 DOI: 10.1016/j.preteyeres.2015.04.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 04/06/2015] [Accepted: 04/06/2015] [Indexed: 10/23/2022]
Abstract
Immunohistochemical and ex vivo anatomical studies have provided many glimpses of the variety, distribution, and signaling components of vertebrate retinal neurons. The beauty of numerous images published to date, and the qualitative and quantitative information they provide, indicate that these approaches are fundamentally useful. However, obtaining these images entailed tissue handling and exposure to chemical solutions that differ from normal extracellular fluid in composition, temperature, and osmolarity. Because the differences are large enough to alter intercellular and intracellular signaling in neurons, and because retinae are susceptible to crush, shear, and fray, it is natural to wonder if immunohistochemical and anatomical methods disturb or damage the cells they are designed to examine. Tissue fixation is typically incorporated to guard against this damage and is therefore critically important to the quality and significance of the harvested data. Here, we describe mechanisms of fixation; advantages and disadvantages of using formaldehyde and glutaraldehyde as fixatives during immunohistochemistry; and modifications of widely used protocols that have recently been found to improve cell shape preservation and immunostaining patterns, especially in proximal retinal neurons.
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Affiliation(s)
- Tyler W Stradleigh
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, CA 95616, USA
| | - Andrew T Ishida
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, CA 95616, USA; Department of Ophthalmology and Vision Science, University of California, Sacramento, CA 95817, USA.
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10
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Chen T, Yang YF, Luo P, Liu W, Dai SH, Zheng XR, Fei Z, Jiang XF. Homer1 knockdown protects dopamine neurons through regulating calcium homeostasis in an in vitro model of Parkinson's disease. Cell Signal 2013; 25:2863-70. [PMID: 24036210 DOI: 10.1016/j.cellsig.2013.09.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 08/15/2013] [Accepted: 09/02/2013] [Indexed: 11/26/2022]
Abstract
Homer1 protein is an important scaffold protein at postsynaptic density and has been demonstrated to play a central role in calcium signaling in the central nervous system. The aim of this study was to investigate the effects of Homer1 knockdown on MPP(+) induced neuronal injury in cultured dopamine (DA) neurons. We found that down-regulating Homer1 expression with specific small interfering RNA (siRNA) significantly suppressed LDH release, reduced Propidium iodide (PI) or Hoechst staining, increased the number of tyrosine hydroxylase (TH) positive cells and DA uptake, and attenuated apoptotic and necrotic cell death after MPP(+) injury. Homer1 knockdown decreased intracellular reactive oxygen species (ROS) generation through inhibition of intracellular calcium overload, but did not affect the endogenous antioxidant enzyme activities. Calcium imaging was used to examine the changes of intracellular Ca(2+) concentration ([Ca(2+)]cyt) and Ca(2+) in endoplasmic reticulum (ER) ([Ca(2+)]ER), and the results showed that Homer1 siRNA transfection attenuated ER Ca(2+) release up to 120min after MPP(+) injury. Furthermore, decrease of [Ca(2+)]cyt induced by Homer1 knockdown in MPP(+) treated neurons was further enhanced by NMDA receptor antagonists MK-801 and AP-5, but not canonical transient receptor potential (TRPC) channel antagonist SKF-96365. l-type calcium antagonist isradipine but not nimodipine further inhibited intracellular calcium overload after MPP(+) insult in Homer1 down-regulated neurons. These results suggest that Homer1 knockdown has protective effects against neuronal injury in in vitro PD model by reducing calcium overload mediated ROS generation, and this protection may be dependent at least in part on the regulatory effects on the function of calcium channels in both plasma membrane and ER.
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Affiliation(s)
- Tao Chen
- Department of Neurosurgery, Xijing Institute of Clinical Neuroscience, Xijing Hospital, Fourth, Military Medical University, Xi'an, Shaanxi 710032, China; Department of Neurosurgery, The 123th Hospital of PLA, Bengbu, Anhui 233000, China
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11
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Heckman CA, Plummer HK. Filopodia as sensors. Cell Signal 2013; 25:2298-311. [PMID: 23876793 DOI: 10.1016/j.cellsig.2013.07.006] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 07/04/2013] [Accepted: 07/09/2013] [Indexed: 12/19/2022]
Abstract
Filopodia are sensors on both excitable and non-excitable cells. The sensing function is well documented in neurons and blood vessels of adult animals and is obvious during dorsal closure in embryonic development. Nerve cells extend neurites in a bidirectional fashion with growth cones at the tips where filopodia are concentrated. Their sensing of environmental cues underpins the axon's ability to "guide," bypassing non-target cells and moving toward the target to be innervated. This review focuses on the role of filopodia structure and dynamics in the detection of environmental cues, including both the extracellular matrix (ECM) and the surfaces of neighboring cells. Other protrusions including the stereocilia of the inner ear and epididymus, the invertebrate Type I mechanosensors, and the elongated processes connecting osteocytes, share certain principles of organization with the filopodia. Actin bundles, which may be inside or outside of the excitable cell, function to transduce stress from physical perturbations into ion signals. There are different ways of detecting such perturbations. Osteocyte processes contain an actin core and are physically anchored on an extracellular structure by integrins. Some Type I mechanosensors have bridge proteins that anchor microtubules to the membrane, but bundles of actin in accessory cells exert stress on this complex. Hair cells of the inner ear rely on attachments between the actin-based protrusions to activate ion channels, which then transduce signals to afferent neurons. In adherent filopodia, the focal contacts (FCs) integrated with ECM proteins through integrins may regulate integrin-coupled ion channels to achieve signal transduction. Issues that are not understood include the role of Ca(2+) influx in filopodia dynamics and how integrins coordinate or gate signals arising from perturbation of channels by environmental cues.
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Affiliation(s)
- C A Heckman
- Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403-0212, USA.
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12
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Swartz MM, Linn DM, Linn CL. Tropisetron as a neuroprotective agent against glutamate-induced excitotoxicity and mechanisms of action. Neuropharmacology 2013; 73:111-21. [PMID: 23727438 DOI: 10.1016/j.neuropharm.2013.05.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 04/23/2013] [Accepted: 05/07/2013] [Indexed: 11/30/2022]
Abstract
The objective of this study was to determine the neuroprotective role of tropisetron on retinal ganglion cells (RGCs) as well as to explore the possible mechanisms associated with alpha7 nAChR-induced neuroprotection. Adult pig RGCs were isolated from all other retinal tissue using a two-step panning technique. Once isolated, RGCs were cultured for 3 days under control untreated conditions, in the presence of 500 μM glutamate to induce excitotoxicity, and when tropisetron was applied before glutamate to induce neuroprotection. 500 μM glutamate decreased RGC survival by an average of 62% compared to control conditions. However, RGCs pretreated with 100 nM tropisetron before glutamate increased cell survival to an average of 105% compared to controls. Inhibition studies using the alpha7 nAChR antagonist, MLA (10 nM), support the hypothesis that tropisetron is an effective neuroprotective agent against glutamate-induced excitotoxicity; mediated by α7 nAChR activation. ELISA studies were performed to determine if signaling cascades normally associated with excitotoxicity and neuroprotection were up- or down-regulated after tropisetron treatment. Tropisetron had no discernible effects on pAkt levels but significantly decreased p38 MAPK levels associated with excitotoxicity from an average of 15 ng/ml to 6 ng/ml. Another mechanism shown to be associated with neuroprotection involves internalization of NMDA receptors. Double-labeled immunocytochemistry and electrophysiology studies provided further evidence that tropisetron caused internalization of NMDA receptor subunits. The findings of this study suggest that tropisetron could be an effective therapeutic agent for the treatment of degenerative disorders of the central nervous system that involves excitotoxicity.
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Affiliation(s)
- Michael M Swartz
- Western Michigan University, Department of Biological Sciences, Kalamazoo, MI 49008, USA
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13
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Iwamoto K, Mata D, Linn DM, Linn CL. Neuroprotection of rat retinal ganglion cells mediated through alpha7 nicotinic acetylcholine receptors. Neuroscience 2013; 237:184-98. [PMID: 23402849 DOI: 10.1016/j.neuroscience.2013.02.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 01/23/2013] [Accepted: 02/01/2013] [Indexed: 12/18/2022]
Abstract
Glutamate-induced excitotoxicity is thought to play an important role in several neurodegenerative diseases in the central nervous system (CNS). In this study, neuroprotection against glutamate-induced excitotoxicity was analyzed using acetylcholine (ACh), nicotine and the α7 specific nicotinic acetylcholine receptor (α7 nAChR) agonist, N-[(3R)-1-azabicyclo[2.2.2]oct-3-yl]-4-chlorobenzamide hydrochloride (PNU-282987), in cultured adult rat retinal neurons. Adult Long Evans rat retinas were dissociated and retinal ganglion cells (RGCs) were isolated from all other retinal tissue using a two-step panning technique. Once isolated, RGCs were cultured under various pharmacological conditions to demonstrate excitotoxicity and neuroprotection against excitotoxicity. After 3 days, RGCs were immunostained with antibodies against the glycoprotein, Thy 1.1, counted and cell survival was assessed relative to control untreated conditions. 500 μM glutamate induced excitotoxicity in large and small RGCs in an adult rat dissociated culture. After 3 days in culture with glutamate, the cell survival of large RGCs decreased by an average of 48.16% while the cell survival of small RGCs decreased by an average of 42.03%. Using specific glutamate receptor agonists and antagonists, we provide evidence that the excitotoxic response was mediated through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainic acid (KA) and N-methyl-d-aspartate (NMDA) glutamate receptors through an apoptotic mechanism. However, the excitotoxic effect of glutamate on all RGCs was eliminated if cells were cultured for an hour with 10 μM ACh, 100 μM nicotine or 100 nM of the α7 nAChR agonist, PNU-282987, before the glutamate insult. Inhibition studies using 10nM methyllycaconitine (MLA) or α-bungarotoxin (α-Bgt) supported the hypothesis that neuroprotection against glutamate-induced excitotoxicity on rat RGCs was mediated through α7 nAChRs. In immunocytochemical studies, double-labeled experiments using antibodies against Thy 1.1 and α7 nAChR subunits demonstrated that both large and small RGCs contained α7 nAChR subunits. The data presented in this study support the hypothesis that ACh and nicotinic acetylcholine receptor (nAChR) agonists provide neuroprotection against glutamate-induced excitotoxicity in adult rat RGCs through activation of α7 nAChR subunits. These studies lay the groundwork required for analyzing the effect of specific α7 nAChR agonists using in vivo models of excitotoxicity. Understanding the type of ACh receptors involved in neuroprotection in the rat retina could ultimately lead to therapeutic treatment for any CNS disease that involves excitotoxicity.
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Affiliation(s)
- K Iwamoto
- Western Michigan University, Department of Biological Sciences, Kalamazoo, MI 49008, USA
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14
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Mercer AJ, Thoreson WB. Tracking quantum dot-tagged calcium channels at vertebrate photoreceptor synapses: retinal slices and dissociated cells. CURRENT PROTOCOLS IN NEUROSCIENCE 2013; Chapter 2:Unit 2.18. [PMID: 23315944 PMCID: PMC3707139 DOI: 10.1002/0471142301.ns0218s62] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
At synapses in the central nervous system, precisely localized assemblies of presynaptic proteins, neurotransmitter-filled vesicles, and postsynaptic receptors are required to communicate messages between neurons. Our understanding of synaptic function has been significantly advanced using electrophysiological methods, but the dynamic spatial behavior and real-time organization of synapses remains poorly understood. In this unit, we describe a method for labeling individual presynaptic calcium channels with photostable quantum dots for single-particle tracking analysis. We have used this technique to examine the mobility of L-type calcium channels in the presynaptic membrane of rod and cone photoreceptors in the retina. These channels control release of glutamate-filled synaptic vesicles at the ribbon synapses in photoreceptor terminals. This technique offers the advantage of providing a real-time biophysical readout of ion channel mobility and can be manipulated by pharmacological or electrophysiological methods. For example, the combination of electrophysiological and single-particle tracking experiments has revealed that fusion of nearby vesicles influences calcium channel mobility and changes in channel mobility can influence release. These approaches can also be readily adapted to examine membrane proteins in other systems.
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Affiliation(s)
- Aaron J Mercer
- Departments of Molecular and Integrative Physiology, University Of Michigan, Ann Arbor, USA
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15
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Ischemia-induced apoptosis of intestinal epithelial cells correlates with altered integrin distribution and disassembly of F-actin triggered by calcium overload. J Biomed Biotechnol 2012; 2012:617539. [PMID: 22701305 PMCID: PMC3369571 DOI: 10.1155/2012/617539] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 03/23/2012] [Indexed: 12/18/2022] Open
Abstract
The present study examined intestinal epithelial cell (IEC) integrin distribution and disassembly of actin cytoskeleton in response to ischemia-anoxia. Protective effects of calcium channel blocker(CCB) were further examined to explore underlying mechanisms of cellular injury. Materials and Methods. Primary cultures of rat IECs and an in vitro model of ischemia/anoxia were established. IECs were exposed to ischemia/anoxia in the presence and absence of verapamil. The extent of exfoliation was determined using light microscopy while apoptosis rate was measured using flow cytometry. Changes in intracellular calcium, the distribution of integrins and the morphology of F-actin were assessed by confocal microscopy. Results. Detachment and apoptosis of IECs increased following ischemia/anoxia-induced injury. Treatment with verapamil inhibited the detachment and apoptosis. Under control conditions, the strongest fluorescent staining for integrins appeared on the basal surface of IECs while this re-distributed to the apical membrane in response to ischemic injury. Depolymerization of F-actin was also observed in the injured cells. Verapamil attenuated both changes of integrins and F-actin. Conclusions. Redistribution of integrins and disruption of F-actin under ischemia/anoxia injury is associated with IEC detachment and increased apoptosis. These events appeared to be triggered by an increase in Ca2+i suggesting a potential use for CCB in prevention and treatment of intestinal injury.
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16
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The dynamic architecture of photoreceptor ribbon synapses: cytoskeletal, extracellular matrix, and intramembrane proteins. Vis Neurosci 2012; 28:453-71. [PMID: 22192503 DOI: 10.1017/s0952523811000356] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Rod and cone photoreceptors possess ribbon synapses that assist in the transmission of graded light responses to second-order bipolar and horizontal cells of the vertebrate retina. Proper functioning of the synapse requires the juxtaposition of presynaptic release sites immediately adjacent to postsynaptic receptors. In this review, we focus on the synaptic, cytoskeletal, and extracellular matrix proteins that help to organize photoreceptor ribbon synapses in the outer plexiform layer. We examine the proteins that foster the clustering of release proteins, calcium channels, and synaptic vesicles in the presynaptic terminals of photoreceptors adjacent to their postsynaptic contacts. Although many proteins interact with one another in the presynaptic terminal and synaptic cleft, these protein-protein interactions do not create a static and immutable structure. Instead, photoreceptor ribbon synapses are remarkably dynamic, exhibiting structural changes on both rapid and slow time scales.
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17
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Bozic M, de Rooij J, Parisi E, Ortega MR, Fernandez E, Valdivielso JM. Glutamatergic signaling maintains the epithelial phenotype of proximal tubular cells. J Am Soc Nephrol 2011; 22:1099-111. [PMID: 21597037 DOI: 10.1681/asn.2010070701] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Epithelial-mesenchymal transition (EMT) contributes to the progression of renal tubulointerstitial fibrosis. The N-methyl-d-aspartate receptor (NMDAR), which is present in proximal tubular epithelium, is a glutamate receptor that acts as a calcium channel. Activation of NMDAR induces actin rearrangement in cells of the central nervous system, but whether it helps maintain the epithelial phenotype of the proximal tubule is unknown. Here, knockdown of NMDAR1 in a proximal tubule cell line (HK-2) induced changes in cell morphology, reduced E-cadherin expression, and increased α-SMA expression. Induction of EMT with TGF-β1 led to downregulation of both E-cadherin and membrane-associated β-catenin, reorganization of F-actin, expression of mesenchymal markers de novo, upregulation of Snail1, and increased cell migration; co-treatment with NMDA attenuated all of these changes. Furthermore, NMDA reduced TGF-β1-induced phosphorylation of Erk1/2 and Akt and the activation of Ras, suggesting that NMDA antagonizes TGF-β1-induced EMT by inhibiting the Ras-MEK pathway. In the unilateral ureteral obstruction model, treatment with NMDA blunted obstruction-induced upregulation of α-SMA, FSP1, and collagen I and downregulation of E-cadherin. Taken together, these results suggest that NMDAR plays a critical role in preserving the normal epithelial phenotype and modulating tubular EMT.
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Affiliation(s)
- Milica Bozic
- Nephrology Research Laboratory, IRB LLEIDA, University Hospital Arnau de Vilanova, Lleida, Spain
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18
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Tiago T, Marques-da-Silva D, Samhan-Arias AK, Aureliano M, Gutierrez-Merino C. Early disruption of the actin cytoskeleton in cultured cerebellar granule neurons exposed to 3-morpholinosydnonimine-oxidative stress is linked to alterations of the cytosolic calcium concentration. Cell Calcium 2011; 49:174-83. [PMID: 21356558 DOI: 10.1016/j.ceca.2011.01.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2010] [Revised: 01/29/2011] [Accepted: 01/31/2011] [Indexed: 02/07/2023]
Abstract
Cytoskeleton damage is a frequent feature in neuronal cell death and one of the early events in oxidant-induced cell injury. This work addresses whether actin cytoskeleton reorganization is an early event of SIN-1-induced extracellular nitrosative/oxidative stress in cultured cerebellar granule neurons (CGN). The actin polymerization state, i.e. the relative levels of G-/F-actin, was quantitatively assessed by the ratio of the fluorescence intensities of microscopy images obtained from CGN double-labelled with Alexa594-DNase-I (for actin monomers) and Bodipy-FL-phallacidin (for actin filaments). Exposure of CGN to a flux of peroxynitrite as low as 0.5-1μM/min during 30min (achieved with 0.1mM SIN-1) was found to promote alterations of the actin cytoskeleton dynamics as it increases the G-actin/F-actin ratio. Because L-type voltage-operated Ca(2+) channels (L-VOCC) are primary targets in CGN exposed to SIN-1, the possible role of Ca(2+) dynamics on the perturbation of the actin cytoskeleton was also assessed from the cytosolic Ca(2+) concentration response to the L-VOCC's agonist FPL-64176 and to the L-VOCC's blocker nifedipine. The results showed that SIN-1 induced changes in the actin polymerization state correlated with its ability to decrease Ca(2+) influx through L-VOCC. Combined analysis of cytosolic Ca(2+) concentration and G-actin/F-actin ratio alterations by SIN-1, cytochalasin D, latrunculin B and jasplakinolide support that disruption of the actin cytoskeleton is linked to cytosolic calcium concentration changes.
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Affiliation(s)
- Teresa Tiago
- Dept. Biochemistry and Molecular Biology, Faculty of Sciences, University of Extremadura, 06006-Badajoz, Spain
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19
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Eichhoff G, Brawek B, Garaschuk O. Microglial calcium signal acts as a rapid sensor of single neuron damage in vivo. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1813:1014-24. [PMID: 21056596 DOI: 10.1016/j.bbamcr.2010.10.018] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 10/13/2010] [Accepted: 10/25/2010] [Indexed: 10/18/2022]
Abstract
In the healthy adult brain microglia, the main immune-competent cells of the CNS, have a distinct (so-called resting or surveying) phenotype. Resting microglia can only be studied in vivo since any isolation of brain tissue inevitably triggers microglial activation. Here we used in vivo two-photon imaging to obtain a first insight into Ca(2+) signaling in resting cortical microglia. The majority (80%) of microglial cells showed no spontaneous Ca(2+) transients at rest and in conditions of strong neuronal activity. However, they reliably responded with large, generalized Ca(2+) transients to damage of an individual neuron. These damage-induced responses had a short latency (0.4-4s) and were localized to the immediate vicinity of the damaged neuron (< 50 μm cell body-to-cell body distance). They were occluded by the application of ATPγS as well as UDP and 2-MeSADP, the agonists of metabotropic P2Y receptors, and they required Ca(2+) release from the intracellular Ca(2+) stores. Thus, our in vivo data suggest that microglial Ca(2+) signals occur mostly under pathological conditions and identify a Ca(2+) store-operated signal, which represents a very sensitive, rapid, and highly localized response of microglial cells to brain damage. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.
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Affiliation(s)
- Gerhard Eichhoff
- Institute of Physiology II, University of Tübingen, Keplerstr. 15, 72074 Tübingen, Germany
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20
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21
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Bax inhibitor 1 increases cell adhesion through actin polymerization: involvement of calcium and actin binding. Mol Cell Biol 2010; 30:1800-13. [PMID: 20123969 DOI: 10.1128/mcb.01357-09] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Bax inhibitor 1 (BI-1), a transmembrane protein with Ca2+ channel-like activity, has antiapoptotic and anticancer activities. Cells overexpressing BI-1 demonstrated increased cell adhesion. Using a proteomics tool, we found that BI-1 interacted with gamma-actin via leucines 221 and 225 and could control actin polymerization and cell adhesion. Among BI-1-/- cells and cells transfected with BI-1 small interfering RNA (siRNA), levels of actin polymerization and cell adhesion were lower than those among BI-1+/+ cells and cells transfected with nonspecific siRNA. BI-1 acts as a leaky Ca2+ channel, but mutations of the actin binding sites (L221A, L225A, and L221A/L225A) did not change intra-endoplasmic reticulum Ca2+, although deleting the C-terminal motif (EKDKKKEKK) did. However, store-operated Ca2+ entry (SOCE) is activated in cells expressing BI-1 but not in cells expressing actin binding site mutants, even those with the intact C-terminal motif. Consistently, actin polymerization and cell adhesion were inhibited among all the mutant cells. Compared to BI-1+/+ cells, BI-1-/- cells inhibited SOCE, actin polymerization, and cell adhesion. Endogenous BI-1 knockdown cells showed a similar pattern. The C-terminal peptide of BI-1 (LMMLILAMNRKDKKKEKK) polymerized actin even after the deletion of four or six charged C-terminal residues. This indicates that the actin binding site containing L221 to D231 of BI-1 is responsible for actin interaction and that the C-terminal motif has only a supporting role. The intact C-terminal peptide also bundled actin and increased cell adhesion. The results of experiments with whole recombinant BI-1 reconstituted in membranes also coincide well with the results obtained with peptides. In summary, BI-1 increased actin polymerization and cell adhesion through Ca2+ regulation and actin interaction.
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22
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Mizuno F, Barabas P, Krizaj D, Akopian A. Glutamate-induced internalization of Ca(v)1.3 L-type Ca(2+) channels protects retinal neurons against excitotoxicity. J Physiol 2010; 588:953-66. [PMID: 20123787 DOI: 10.1113/jphysiol.2009.181305] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Glutamate-induced rise in the intracellular Ca(2+) level is thought to be a major cause of excitotoxic cell death, but the mechanisms that control the Ca(2+) overload are poorly understood. Using immunocytochemistry, electrophysiology and Ca(2+) imaging, we show that activation of ionotropic glutamate receptors induces a selective internalization of Ca(v)1.3 L-type Ca(2+) channels in salamander retinal neurons. The effect of glutamate on Ca(v)1.3 internalization was blocked in Ca(2+)-free external solution, or by strong buffering of internal Ca(2+) with BAPTA. Downregulation of L-type Ca(2+) channel activity in retinal ganglion cells by glutamate was suppressed by inhibitors of dynamin-dependent endocytosis. Stabilization of F-actin by jasplakinolide significantly reduced the ability of glutamate to induce internalization suggesting it is mediated by Ca(2+)-dependent reorganization of actin cytoskeleton. We showed that the Ca(v)1.3 is the primary L-type Ca(2+) channel contributing to kainate-induced excitotoxic death of amacrine and ganglion cells. Block of Ca(v)1.3 internalization by either dynamin inhibition or F-actin stabilization increased vulnerability of retinal amacrine and ganglion cells to kainate-induced excitotoxicity. Our data show for the first time that Ca(v)1.3 L-type Ca(2+) channels are subject to rapid glutamate-induced internalization, which may serve as a negative feedback mechanism protecting retinal neurons against glutamate-induced excitotoxicity.
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Affiliation(s)
- Fengxia Mizuno
- Department of Ophthalmology, NYU Medical Center, New York, NY 10016, USA
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23
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Wang Y, Cunningham DE, Tempel BL, Rubel EW. Compartment-specific regulation of plasma membrane calcium ATPase type 2 in the chick auditory brainstem. J Comp Neurol 2009; 514:624-40. [PMID: 19365819 DOI: 10.1002/cne.22045] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Calcium signaling plays a role in synaptic regulation of dendritic structure, usually on the time scale of hours or days. Here we use immunocytochemistry to examine changes in expression of plasma membrane calcium ATPase type 2 (PMCA2), a high-affinity calcium efflux protein, in the chick nucleus laminaris (NL) following manipulations of synaptic inputs. Dendrites of NL neurons segregate into dorsal and ventral domains, receiving excitatory input from the ipsilateral and contralateral ears, respectively, via nucleus magnocellularis (NM). Deprivation of the contralateral projection from NM to NL leads to rapid retraction of ventral, but not the dorsal, dendrites of NL neurons. Immunocytochemistry revealed symmetric distribution of PMCA2 in two neuropil regions of normally innervated NL. Electron microscopy confirmed that PMCA2 localizes in both NM terminals and NL dendrites. As early as 30 minutes after transection of the contralateral projection from NM to NL or unilateral cochlea removal, significant decreases in PMCA2 immunoreactivity were seen in the deprived neuropil of NL compared with the other neuropil that continued to receive normal input. The rapid decrease correlated with reductions in the immunoreactivity for microtubule-associated protein 2, which affects cytoskeleton stabilization. These results suggest that PMCA2 is regulated independently in ventral and dorsal NL dendrites and/or their inputs from NM in a way that is correlated with presynaptic activity. This provides a potential mechanism by which deprivation can change calcium transport that, in turn, may be important for rapid, compartment-specific dendritic remodeling.
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Affiliation(s)
- Yuan Wang
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, University of Washington School of Medicine, Seattle, Washington 98195, USA
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24
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Huang XR, Knighton RW. Altered F-actin distribution in retinal nerve fiber layer of a rat model of glaucoma. Exp Eye Res 2009; 88:1107-14. [PMID: 19450448 DOI: 10.1016/j.exer.2009.01.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Revised: 01/26/2009] [Accepted: 01/27/2009] [Indexed: 12/11/2022]
Abstract
Glaucoma damages the retinal nerve fiber layer (RNFL). The purpose of this study was to investigate the distribution in RNFL of axonal F-actin, a cytoskeletal component, under the development of glaucoma. Intraocular hypertension was induced in a rat model by translimbal laser photocoagulation of the trabecular meshwork. The retinas of control and treated eyes were obtained after different exposures to elevated IOP. Nerve fiber bundles were identified by fluorescent phalloidin staining of F-actin. Nuclei of cell bodies were identified by DAPI fluorescent counterstain. F-actin distribution in whole-mounted retinas was examined by confocal microscopy. En face and cross-sectional images of RNFL were collected around the optic nerve head (ONH). F-actin in normal RNFL was intensely and uniformly stained. In glaucomatous retina, F-actin staining was not uniform within bundles and total loss of F-actin staining was found in severely damaged areas. Altered F-actin often occurred near the ONH in bundles that appeared normal more peripherally. Both alteration and total loss of F-actin were found most often in dorsal retina. In normal RNFL, F-actin is rich and approximately uniformly distributed within nerve fiber bundles. Elevated IOP changes F-actin distribution in RNFL. Topographic features of F-actin alteration suggest that F-actin near the ONH is more sensitive to glaucomatous damage. The alteration pattern also suggests an ONH location for the glaucomatous insult in this rat model.
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Affiliation(s)
- Xiang-Run Huang
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, 1638 NW 10th Ave, Miami, FL 33136, USA.
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25
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Hartwick ATE, Hamilton CM, Baldridge WH. Glutamatergic calcium dynamics and deregulation of rat retinal ganglion cells. J Physiol 2008; 586:3425-46. [PMID: 18483069 DOI: 10.1113/jphysiol.2008.154609] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
A rise in intracellular calcium levels ([Ca(2+)](i)) is a key trigger for the lethal effects of the excitatory neurotransmitter glutamate in various central neurons, but a consensus has not been reached on the pathways that mediate glutamate-dependent increases of [Ca(2+)](i) in retinal ganglion cells (RGCs). Using Ca(2+) imaging techniques we demonstrated that, in the absence of external Mg(2+), the Ca(2+) signal evoked by glutamate was predominantly mediated by NMDA-type glutamate receptors (NMDA-Rs) in immunopanned RGCs isolated from neonatal or adult rats. Voltage-gated Ca(2+) channels and AMPA/kainate-Rs contributed a smaller portion of the Ca(2+) response at saturating concentrations of glutamate. Consistent with NMDA-R involvement, extracellular Mg(2+) inhibited RGC glutamate responses, while glycine had a potentiating effect. With Mg(2+) present externally, the effect of AMPA/kainate-R antagonists was enhanced and both NMDA- and AMPA/kainate-R antagonists greatly reduced the glutamate-induced increases of RGC [Ca(2+)](i). This finding indicates that the primary contribution of AMPA/kainate-Rs to RGC glutamatergic Ca(2+) dynamics is through the depolarization-dependent relief of the Mg(2+) block of NMDA-R channels. The effect of glutamate receptor antagonists on glutamatergic Ca(2+) signals from RGCs in adult rat retinal wholemounts yielded results similar to those obtained using immunopanned RGCs. Additional experiments on isolated RGCs revealed that during a 1 h glutamate (10-1000 microm) exposure, 18-28% of RGCs exhibited delayed Ca(2+) deregulation (DCD) and the RGCs that underwent DCD were positive for the death marker annexin V. RGCs with larger glutamate-evoked Ca(2+) signals were more likely to undergo DCD, and NMDA-R blockade significantly reduced the occurrence of DCD. Identifying the mechanisms underlying RGC excitotoxicity aids in our understanding of the pathophysiology of retinal ischaemia, and this work establishes a major role for NMDA-R-mediated increases in [Ca(2+)](i) in glutamate-related RGC death.
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Affiliation(s)
- Andrew T E Hartwick
- Retina and Optic Nerve Research Laboratory, Department of Anatomy & Neurobiology, Dalhousie University, Halifax, Nova Scotia, Canada
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26
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Sniadecki NJ, Anguelouch A, Yang MT, Lamb CM, Liu Z, Kirschner SB, Liu Y, Reich DH, Chen CS. Magnetic microposts as an approach to apply forces to living cells. Proc Natl Acad Sci U S A 2007; 104:14553-8. [PMID: 17804810 PMCID: PMC1976246 DOI: 10.1073/pnas.0611613104] [Citation(s) in RCA: 216] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Cells respond to mechanical forces whether applied externally or generated internally via the cytoskeleton. To study the cellular response to forces separately, we applied external forces to cells via microfabricated magnetic posts containing cobalt nanowires interspersed among an array of elastomeric posts, which acted as independent sensors to cellular traction forces. A magnetic field induced torque in the nanowires, which deflected the magnetic posts and imparted force to individual adhesions of cells attached to the array. Using this system, we examined the cellular reaction to applied forces and found that applying a step force led to an increase in local focal adhesion size at the site of application but not at nearby nonmagnetic posts. Focal adhesion recruitment was enhanced further when cells were subjected to multiple force actuations within the same time interval. Recording the traction forces in response to such force stimulation revealed two responses: a sudden loss in contractility that occurred within the first minute of stimulation or a gradual decay in contractility over several minutes. For both types of responses, the subcellular distribution of loss in traction forces was not confined to locations near the actuated micropost, nor uniformly across the whole cell, but instead occurred at discrete locations along the cell periphery. Together, these data reveal an important dynamic biological relationship between external and internal forces and demonstrate the utility of this microfabricated system to explore this interaction.
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Affiliation(s)
- Nathan J. Sniadecki
- *Department of Bioengineering, University of Pennsylvania, 510 Skirkanich Hall, 210 South 33rd Street, Philadelphia, PA 19104; and
| | - Alexandre Anguelouch
- Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218
| | - Michael T. Yang
- *Department of Bioengineering, University of Pennsylvania, 510 Skirkanich Hall, 210 South 33rd Street, Philadelphia, PA 19104; and
| | - Corinne M. Lamb
- Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218
| | - Zhijun Liu
- *Department of Bioengineering, University of Pennsylvania, 510 Skirkanich Hall, 210 South 33rd Street, Philadelphia, PA 19104; and
| | - Stuart B. Kirschner
- Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218
| | - Yaohua Liu
- Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218
| | - Daniel H. Reich
- Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218
| | - Christopher S. Chen
- *Department of Bioengineering, University of Pennsylvania, 510 Skirkanich Hall, 210 South 33rd Street, Philadelphia, PA 19104; and
- To whom correspondence should be addressed. E-mail:
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