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Chen Y, Luan P, Liu J, Wei Y, Wang C, Wu R, Wu Z, Jing M. Spatiotemporally selective astrocytic ATP dynamics encode injury information sensed by microglia following brain injury in mice. Nat Neurosci 2024; 27:1522-1533. [PMID: 38862791 DOI: 10.1038/s41593-024-01680-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 05/13/2024] [Indexed: 06/13/2024]
Abstract
Injuries to the brain result in tunable cell responses paired with stimulus properties, suggesting the existence of intrinsic processes that encode and transmit injury information; however, the molecular mechanism of injury information encoding is unclear. Here, using ATP fluorescent indicators, we identify injury-evoked spatiotemporally selective ATP dynamics, Inflares, in adult mice of both sexes. Inflares are actively released from astrocytes and act as the internal representations of injury. Inflares encode injury intensity and position at their population level through frequency changes and are further decoded by microglia, driving changes in their activation state. Mismatches between Inflares and injury severity lead to microglia dysfunction and worsening of injury outcome. Blocking Inflares in ischemic stroke in mice reduces secondary damage and improves recovery of function. Our results suggest that astrocytic ATP dynamics encode injury information and are sensed by microglia.
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Affiliation(s)
- Yue Chen
- Chinese Institute for Brain Research, Beijing, China
| | - Pengwei Luan
- Chinese Institute for Brain Research, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Juan Liu
- Chinese Institute for Brain Research, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Yelan Wei
- Chinese Institute for Brain Research, Beijing, China
- Department of College of Physical Education and Sport, Beijing Normal University, Beijing, China
| | - Chenyu Wang
- Chinese Institute for Brain Research, Beijing, China
- Capital Medical University, Basic Medical Sciences, Beijing, China
| | - Rui Wu
- Chinese Institute for Brain Research, Beijing, China
- China Agricultural University, Beijing, China
| | - Zhaofa Wu
- State Key Laboratory of Membrane Biology, Peking University School of Life Sciences, Beijing, China
- PKU-IDG/McGovern Institute for Brain Research, Beijing, China
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Miao Jing
- Chinese Institute for Brain Research, Beijing, China.
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2
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Wang L, Cao L, Li Z, Shao Z, Chen X, Huang Z, He X, Zheng J, Liu L, Jia XM, Xiao H. ATP-elicited Cation Fluxes Promote Volume-regulated Anion Channel LRRC8/VRAC Transport cGAMP for Antitumor Immunity. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2024; 213:347-361. [PMID: 38847616 DOI: 10.4049/jimmunol.2300812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 05/20/2024] [Indexed: 07/17/2024]
Abstract
The cyclic GMP-AMP synthase (cGAS)-stimulator of IFN genes (STING) pathway is instrumental to antitumor immunity, yet the underlying molecular and cellular mechanisms are complex and still unfolding. A new paradigm suggests that cancer cells' cGAS-synthesized cGAMP can be transferred to tumor-infiltrating immune cells, eliciting STING-dependent IFN-β response for antitumor immunity. Nevertheless, how the tumor microenvironment may shape this process remains unclear. In this study, we found that extracellular ATP, an immune regulatory molecule widely present in the tumor microenvironment, can potentiate cGAMP transfer, thereby boosting the STING signaling and IFN-β response in murine macrophages and fibroblasts. Notably, genetic ablation or chemical inhibition of murine volume-regulation anion channel LRRC8/volume-regulated anion channel (VRAC), a recently identified cGAMP transporter, abolished ATP-potentiated cGAMP transfer and STING-dependent IFN-β response, revealing a crucial role of LRRC8/VRAC in the cross-talk of extracellular ATP and cGAMP. Mechanistically, ATP activation of the P2X family receptors triggered Ca2+ influx and K+ efflux, promoting reactive oxygen species production. Moreover, ATP-evoked K+ efflux alleviated the phosphorylation of VRAC's obligate subunit LRRC8A/SWELL1 on S174. Mutagenesis studies indicated that the phosphorylation of S174 on LRRC8A could act as a checkpoint for VRAC in the steady state and a rheostat of ATP responsiveness. In an MC38-transplanted tumor model, systemically blocking CD39 and ENPP1, hydroxylases of extracellular ATP and cGAMP, respectively, elevated antitumor NK, NKT, and CD8+ T cell responses and restrained tumor growth in mice. Altogether, this study establishes a crucial role of ATP in facilitating LRRC8/VRAC transport cGAMP in the tumor microenvironment and provides new insight into harnessing cGAMP transfer for antitumor immunity.
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Affiliation(s)
- Li Wang
- Clinical Medicine Scientific and Technical Innovation Center, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
- Key Laboratory of Immune Response and Immunotherapy, Shanghai Institute of Immunity and Infection, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Limin Cao
- Key Laboratory of Immune Response and Immunotherapy, Shanghai Institute of Immunity and Infection, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Zhihong Li
- State Key Laboratory of New Drug and Pharmaceutical process, Shanghai Institute of Pharmaceutical Industry, China State Institute of Pharmaceutical Industry, Shanghai, China
| | - Zhugui Shao
- Key Laboratory of Immune Response and Immunotherapy, Shanghai Institute of Immunity and Infection, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
- Key Laboratory of Infection and Immunity of Shandong Province and Department of Immunology, School of Biomedical Sciences, Shandong University, Jinan, China
| | - Xia Chen
- State Key Laboratory for Animal Disease Control and Prevention, College of Veterinary Medicine, Lanzhou University, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, China
| | - Zhicheng Huang
- Key Laboratory of Immune Response and Immunotherapy, Shanghai Institute of Immunity and Infection, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Xiaoxiao He
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Junke Zheng
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Li Liu
- State Key Laboratory of New Drug and Pharmaceutical process, Shanghai Institute of Pharmaceutical Industry, China State Institute of Pharmaceutical Industry, Shanghai, China
| | - Xin-Ming Jia
- Clinical Medicine Scientific and Technical Innovation Center, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Hui Xiao
- Key Laboratory of Immune Response and Immunotherapy, Shanghai Institute of Immunity and Infection, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
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Liu R, Collier JM, Abdul-Rahman NH, Capuk O, Zhang Z, Begum G. Dysregulation of Ion Channels and Transporters and Blood-Brain Barrier Dysfunction in Alzheimer's Disease and Vascular Dementia. Aging Dis 2024; 15:1748-1770. [PMID: 38300642 PMCID: PMC11272208 DOI: 10.14336/ad.2023.1201] [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: 09/13/2023] [Accepted: 12/01/2023] [Indexed: 02/02/2024] Open
Abstract
The blood-brain barrier (BBB) plays a critical role in maintaining ion and fluid homeostasis, essential for brain metabolism and neuronal function. Regulation of nutrient, water, and ion transport across the BBB is tightly controlled by specialized ion transporters and channels located within its unique cellular components. These dynamic transport processes not only influence the BBB's structure but also impact vital signaling mechanisms, essential for its optimal function. Disruption in ion, pH, and fluid balance at the BBB is associated with brain pathology and has been implicated in various neurological conditions, including stroke, epilepsy, trauma, and neurodegenerative diseases such as Alzheimer's disease (AD). However, knowledge gaps exist regarding the impact of ion transport dysregulation on BBB function in neurodegenerative dementias. Several factors contribute to this gap: the complex nature of these conditions, historical research focus on neuronal mechanisms and technical challenges in studying the ion transport mechanisms in in vivo models and the lack of efficient in vitro BBB dementia models. This review provides an overview of current research on the roles of ion transporters and channels at the BBB and poses specific research questions: 1) How are the expression and activity of key ion transporters altered in AD and vascular dementia (VaD); 2) Do these changes contribute to BBB dysfunction and disease progression; and 3) Can restoring ion transport function mitigate BBB dysfunction and improve clinical outcomes. Addressing these gaps will provide a greater insight into the vascular pathology of neurodegenerative disorders.
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Affiliation(s)
- Ruijia Liu
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, China.
- Department of Neurology, The Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA, USA.
| | - Jenelle M Collier
- Department of Neurology, The Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA, USA.
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA.
| | | | - Okan Capuk
- Department of Neurology, The Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA, USA.
| | - Zhongling Zhang
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang, China.
| | - Gulnaz Begum
- Department of Neurology, The Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA, USA.
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Tan W, Ikoma Y, Takahashi Y, Konno A, Hirai H, Hirase H, Matsui K. Anxiety control by astrocytes in the lateral habenula. Neurosci Res 2024; 205:1-15. [PMID: 38311032 DOI: 10.1016/j.neures.2024.01.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 01/17/2024] [Accepted: 01/21/2024] [Indexed: 02/06/2024]
Abstract
The potential role of astrocytes in lateral habenula (LHb) in modulating anxiety was explored in this study. The habenula are a pair of small nuclei located above the thalamus, known for their involvement in punishment avoidance and anxiety. Herein, we observed an increase in theta-band oscillations of local field potentials (LFPs) in the LHb when mice were exposed to anxiety-inducing environments. Electrical stimulation of LHb at theta-band frequency promoted anxiety-like behavior. Calcium (Ca2+) levels and pH in the cytosol of astrocytes and local brain blood volume changes were studied in mice expressing either a Ca2+ or a pH sensor protein specifically in astrocytes and mScarlet fluorescent protein in the blood plasma using fiber photometry. An acidification response to anxiety was observed. Photoactivation of archaerhopsin-T (ArchT), an optogenetic tool that acts as an outward proton pump, results in intracellular alkalinization. Photostimulation of LHb in astrocyte-specific ArchT-expressing mice resulted in dissipation of theta-band LFP oscillation in an anxiogenic environment and suppression of anxiety-like behavior. These findings provide evidence that LHb astrocytes modulate anxiety and may offer a new target for treatment of anxiety disorders.
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Affiliation(s)
- Wanqin Tan
- Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577 Japan
| | - Yoko Ikoma
- Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577 Japan
| | - Yusuke Takahashi
- Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577 Japan; Systems Bioinformatics, Graduate School of Information Sciences, Tohoku University, Sendai 980-8579 Japan
| | - Ayumu Konno
- Department of Neurophysiology and Neural Repair, Gunma University Graduate School of Medicine, Maebashi 371-8511, Gunma, Japan; Viral Vector Core, Gunma University Initiative for Advanced Research, Maebashi 371-8511, Gunma, Japan
| | - Hirokazu Hirai
- Department of Neurophysiology and Neural Repair, Gunma University Graduate School of Medicine, Maebashi 371-8511, Gunma, Japan; Viral Vector Core, Gunma University Initiative for Advanced Research, Maebashi 371-8511, Gunma, Japan
| | - Hajime Hirase
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen N, Denmark; Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Ko Matsui
- Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577 Japan.
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Okada Y. Physiology of the volume-sensitive/regulatory anion channel VSOR/VRAC: part 2: its activation mechanisms and essential roles in organic signal release. J Physiol Sci 2024; 74:34. [PMID: 38877402 PMCID: PMC11177392 DOI: 10.1186/s12576-024-00926-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2024] [Accepted: 06/01/2024] [Indexed: 06/16/2024]
Abstract
The volume-sensitive outwardly rectifying or volume-regulated anion channel, VSOR/VRAC, which was discovered in 1988, is expressed in most vertebrate cell types, and is essentially involved in cell volume regulation after swelling and in the induction of cell death. This series of review articles describes what is already known and what remains to be uncovered about the functional and molecular properties as well as the physiological and pathophysiological roles of VSOR/VRAC. This Part 2 review article describes, from the physiological and pathophysiological standpoints, first the pivotal roles of VSOR/VRAC in the release of autocrine/paracrine organic signal molecules, such as glutamate, ATP, glutathione, cGAMP, and itaconate, as well as second the swelling-independent and -dependent activation mechanisms of VSOR/VRAC. Since the pore size of VSOR/VRAC has now well been evaluated by electrophysiological and 3D-structural methods, the signal-releasing activity of VSOR/VRAC is here discussed by comparing the molecular sizes of these organic signals to the channel pore size. Swelling-independent activation mechanisms include a physicochemical one caused by the reduction of intracellular ionic strength and a biochemical one caused by oxidation due to stimulation by receptor agonists or apoptosis inducers. Because some organic substances released via VSOR/VRAC upon cell swelling can trigger or augment VSOR/VRAC activation in an autocrine fashion, swelling-dependent activation mechanisms are to be divided into two phases: the first phase induced by cell swelling per se and the second phase caused by receptor stimulation by released organic signals.
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Affiliation(s)
- Yasunobu Okada
- National Institute for Physiological Sciences (NIPS), 5-1 Higashiyama, Myodaiji, Okazaki, Aichi, 444-8787, Japan.
- Department of Integrative Physiology, Graduate School of Medicine, Akita University, Akita, Japan.
- Department of Physiology, School of Medicine, Aichi Medical University, Nagakute, Japan.
- Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa, Japan.
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Asano Y, Sasaki D, Ikoma Y, Matsui K. Glial tone of aggression. Neurosci Res 2024; 202:39-51. [PMID: 38007191 DOI: 10.1016/j.neures.2023.11.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 11/16/2023] [Accepted: 11/20/2023] [Indexed: 11/27/2023]
Abstract
Anger transition is often abrupt. In this study, we investigated the mechanisms responsible for switching and modulating aggression levels. The cerebellum is considered a center for motor coordination and learning; however, its connection to social behavior has long been observed. Here, we used the resident-intruder paradigm in male mice and examined local field potential (LFP) changes, glial cytosolic ion fluctuations, and vascular dynamics in the cerebellar vermis throughout various phases of a combat sequence. Notably, we observed the emergence of theta band oscillations in the LFP and sustained elevations in glial Ca2+ levels during combat breakups. When astrocytes, including Bergmann glial cells, were photoactivated using channelrhodopsin-2, the theta band emerged and an early combat breakup occurred. Within a single combat sequence, rapid alteration of offensive (fight) and passive (flight) responses were observed, which roughly correlated with decreases and increases in glial Ca2+, respectively. Neuron-glial interactions in the cerebellar vermis may play a role in adjusting Purkinje cell excitability and setting the tone of aggression. Future anger management strategies and clinical control of excessive aggression and violent behavior may be realized by developing a therapeutic strategy that adjusts glial activity in the cerebellum.
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Affiliation(s)
- Yuki Asano
- Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577 Japan
| | - Daichi Sasaki
- Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577 Japan
| | - Yoko Ikoma
- Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577 Japan
| | - Ko Matsui
- Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577 Japan.
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Untiet V. Astrocytic chloride regulates brain function in health and disease. Cell Calcium 2024; 118:102855. [PMID: 38364706 DOI: 10.1016/j.ceca.2024.102855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 02/02/2024] [Accepted: 02/06/2024] [Indexed: 02/18/2024]
Abstract
Chloride ions (Cl-) play a pivotal role in synaptic inhibition in the central nervous system, primarily mediated through ionotropic mechanisms. A recent breakthrough emphathizes the significant influence of astrocytic intracellular chloride concentration ([Cl-]i) regulation, a field still in its early stages of exploration. Typically, the [Cl-]i in most animal cells is maintained at lower levels than the extracellular chloride [Cl-]o, a critical balance to prevent cell swelling due to osmotic pressure. Various Cl- transporters are expressed differently across cell types, fine-tuning the [Cl-]i, while Cl- gradients are utilised by several families of Cl- channels. Although the passive distribution of ions within cells is governed by basic biophysical principles, astrocytes actively expend energy to sustain [Cl-]i at much higher levels than those achieved passively, and much higher than neuronal [Cl-]i. Beyond the role in volume regulation, astrocytic [Cl-]i is dynamically linked to brain states and influences neuronal signalling in actively behaving animals. As a vital component of brain function, astrocytic [Cl-]i also plays a role in the development of disorders where inhibitory transmission is disrupted. This review synthesises the latest insights into astrocytic [Cl-]i, elucidating its role in modulating brain function and its implications in various pathophysiological conditions.
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Affiliation(s)
- Verena Untiet
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen, Denmark.
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Kostritskaia Y, Klüssendorf M, Pan YE, Hassani Nia F, Kostova S, Stauber T. Physiological Functions of the Volume-Regulated Anion Channel VRAC/LRRC8 and the Proton-Activated Chloride Channel ASOR/TMEM206. Handb Exp Pharmacol 2024; 283:181-218. [PMID: 37468723 DOI: 10.1007/164_2023_673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2023]
Abstract
Volume-regulated anion channels (VRACs) and the acid-sensitive outwardly rectifying anion channel (ASOR) mediate flux of chloride and small organic anions. Although known for a long time, they were only recently identified at the molecular level. VRACs are heteromers consisting of LRRC8 proteins A to E. Combining the essential LRRC8A with different LRRC8 paralogues changes key properties of VRAC such as conductance or substrate selectivity, which is how VRACs are involved in multiple physiological functions including regulatory volume decrease, cell proliferation and migration, cell death, purinergic signalling, fat and glucose metabolism, insulin signalling, and spermiogenesis. VRACs are also involved in pathological conditions, such as the neurotoxic release of glutamate and aspartate. Certain VRACs are also permeable to larger, organic anions, including antibiotics and anti-cancer drugs, making them an interesting therapeutic target. ASOR, also named proton-activated chloride channel (PAC), is formed by TMEM206 homotrimers on the plasma membrane and on endosomal compartments where it mediates chloride flux in response to extracytosolic acidification and plays a role in the shrinking and maturation of macropinosomes. ASOR has been shown to underlie neuronal swelling which causes cell death after stroke as well as promoting the metastasis of certain cancers, making them intriguing therapeutic targets as well.
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Affiliation(s)
- Yulia Kostritskaia
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Malte Klüssendorf
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Yingzhou Edward Pan
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Fatemeh Hassani Nia
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Simona Kostova
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Tobias Stauber
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany.
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Liu T, Li Y, Wang D, Stauber T, Zhao J. Trends in volume-regulated anion channel (VRAC) research: visualization and bibliometric analysis from 2014 to 2022. Front Pharmacol 2023; 14:1234885. [PMID: 37538172 PMCID: PMC10394876 DOI: 10.3389/fphar.2023.1234885] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 07/10/2023] [Indexed: 08/05/2023] Open
Abstract
Objective: In this study, we utilized bibliometric methods to assess the worldwide scientific output and identify hotspots related to the research on the volume-regulated anion channel (VRAC) from 2014 to 2022. Methods: From Web of Science, we obtained studies related to VRAC published from 2014 to 2022. To analyzed the data, we utilized VOSviewer, a tool for visualizing network, to create networks based on the collaboration between countries, institutions, and authors. Additionally, we performed an analysis of journal co-citation, document citation, and co-occurrence of keywords. Furthermore, we employed CiteSpace (6.1. R6 Advanced) to analyzed keywords and co-cited references with the strongest burst. Results: The final analysis included a total of 278 related articles and reviews, covering the period from 2014 to 2022. The United States emerged as the leading country contributing to this field, while the University of Copenhagen stood out as the most prominent institution. The author with most publications and most citations was Thomas J. Jentsch. Among the cited references, the article by Voss et al. published in Science (2014) gained significant attention for its identification of LRRC8 heteromers as a crucial component of the volume-regulated anion channel VRAC. Pflügers Archiv European Journal of Physiology and Journal of Physiology-London were the leading journals in terms of the quantity of associated articles and citations. Through the analysis of keyword co-occurrence, it was discovered that VRAC is involved in various physiological processes including cell growth, migration, apoptosis, swelling, and myogenesis, as well as anion and organic osmolyte transport including chloride, taurine, glutamate and ATP. VRAC is also associated with related ion channels such as TMEM16A, TMEM16F, pannexin, and CFTR, and associated with various diseases including epilepsy, leukodystrophy, atherosclerosis, hypertension, cerebral edema, stroke, and different types of cancer including gastric cancer, glioblastoma and hepatocellular carcinoma. Furthermore, VRAC is involved in anti-tumor drug resistance by regulating the uptake of platinum-based drugs and temozolomide. Additionally, VRAC has been studied in the context of pharmacology involving DCPIB and flavonoids. Conclusion: The aim of this bibliometric analysis is to provide an overall perspective for research on VRAC. VRAC has become a topic of increasing interest, and our analysis shows that it continues to be a prominent area. This study offers insights into the investigation of VRAC channel and may guide researchers in identifying new directions for future research.
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Affiliation(s)
- Tianbao Liu
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China
- Shandong Key Laboratory of Endocrinology and Lipid Metabolism, Jinan, Shandong, China
- Shandong Institute of Endocrine and Metabolic Disease, Jinan, Shandong, China
| | - Yin Li
- Department of Oncology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Shandong Provincial Hospital, Jinan, Shandong, China
| | - Dawei Wang
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China
- Shandong Key Laboratory of Endocrinology and Lipid Metabolism, Jinan, Shandong, China
- Shandong Institute of Endocrine and Metabolic Disease, Jinan, Shandong, China
- Department of Endocrinology, Shandong Provincial Hospital, Shandong University, Jinan, Shandong, China
| | - Tobias Stauber
- Institute for Molecular Medicine, MSH Medical School Hamburg, Hamburg, Germany
| | - Jiajun Zhao
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education, Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, China
- Shandong Key Laboratory of Endocrinology and Lipid Metabolism, Jinan, Shandong, China
- Shandong Institute of Endocrine and Metabolic Disease, Jinan, Shandong, China
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10
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Liu Y, Wang XR, Jiang YH, Li T, Ling S, Wang HY, Yu JW, Jia SW, Liu XY, Hou CM, Parpura V, Wang YF. Interactions between the Astrocytic Volume-Regulated Anion Channel and Aquaporin 4 in Hyposmotic Regulation of Vasopressin Neuronal Activity in the Supraoptic Nucleus. Cells 2023; 12:1723. [PMID: 37443757 PMCID: PMC10341125 DOI: 10.3390/cells12131723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 06/11/2023] [Accepted: 06/19/2023] [Indexed: 07/15/2023] Open
Abstract
We assessed interactions between the astrocytic volume-regulated anion channel (VRAC) and aquaporin 4 (AQP4) in the supraoptic nucleus (SON). Acute SON slices and cultures of hypothalamic astrocytes prepared from rats received hyposmotic challenge (HOC) with/without VRAC or AQP4 blockers. In acute slices, HOC caused an early decrease with a late rebound in the neuronal firing rate of vasopressin neurons, which required activity of astrocytic AQP4 and VRAC. HOC also caused a persistent decrease in the excitatory postsynaptic current frequency, supported by VRAC and AQP4 activity in early HOC; late HOC required only VRAC activity. These events were associated with the dynamics of glial fibrillary acidic protein (GFAP) filaments, the late retraction of which was mediated by VRAC activity; this activity also mediated an HOC-evoked early increase in AQP4 expression and late subside in GFAP-AQP4 colocalization. AQP4 activity supported an early HOC-evoked increase in VRAC levels and its colocalization with GFAP. In cultured astrocytes, late HOC augmented VRAC currents, the activation of which depended on AQP4 pre-HOC/HOC activity. HOC caused an early increase in VRAC expression followed by a late rebound, requiring AQP4 and VRAC, or only AQP4 activity, respectively. Astrocytic swelling in early HOC depended on AQP4 activity, and so did the early extension of GFAP filaments. VRAC and AQP4 activity supported late regulatory volume decrease, the retraction of GFAP filaments, and subside in GFAP-VRAC colocalization. Taken together, astrocytic morphological plasticity relies on the coordinated activities of VRAC and AQP4, which are mutually regulated in the astrocytic mediation of HOC-evoked modulation of vasopressin neuronal activity.
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Affiliation(s)
- Yang Liu
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China (H.-Y.W.)
| | - Xiao-Ran Wang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China (H.-Y.W.)
| | - Yun-Hao Jiang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China (H.-Y.W.)
| | - Tong Li
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China (H.-Y.W.)
- Neuroscience Laboratory for Translational Medicine, School of Mental Health, Qiqihar Medical University, Qiqihar 161006, China
| | - Shuo Ling
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China (H.-Y.W.)
| | - Hong-Yang Wang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China (H.-Y.W.)
| | - Jia-Wei Yu
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China (H.-Y.W.)
| | - Shu-Wei Jia
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China (H.-Y.W.)
| | - Xiao-Yu Liu
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China (H.-Y.W.)
| | - Chun-Mei Hou
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China (H.-Y.W.)
| | - Vladimir Parpura
- International Translational Neuroscience Research Institute, Zhejiang Chinese Medical University, Hangzhou 310053, China
| | - Yu-Feng Wang
- Department of Physiology, School of Basic Medical Sciences, Harbin Medical University, Harbin 150081, China (H.-Y.W.)
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11
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Kanaya T, Ito R, Morizawa YM, Sasaki D, Yamao H, Ishikane H, Hiraoka Y, Tanaka K, Matsui K. Glial modulation of the parallel memory formation. Glia 2023. [PMID: 37364894 DOI: 10.1002/glia.24431] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 06/04/2023] [Accepted: 06/09/2023] [Indexed: 06/28/2023]
Abstract
Actions from glial cells could affect the readiness and efficacy of learning and memory. Using a mouse cerebellar-dependent horizontal optokinetic response motor learning paradigm, short-term memory (STM) formation during the online training period and long-term memory (LTM) formation during the offline rest period were studied. A large variability of online and offline learning efficacies was found. The early bloomers with booming STM often had a suppressed LTM formation and late bloomers with no apparent acute training effect often exhibited boosted offline learning performance. Anion channels containing LRRC8A are known to release glutamate. Conditional knockout of LRRC8A specifically in astrocytes including cerebellar Bergmann glia resulted in a complete loss of STM formation while the LTM formation during the rest period remained. Optogenetic manipulation of glial activity by channelrhodopsin-2 or archaerhodopsin-T (ArchT) during the online training resulted in enhancement or suppression of STM formation, respectively. STM and LTM are likely to be triggered simultaneously during online training, but LTM is expressed later during the offline period. STM appears to be volatile and the achievement during the online training is not handed over to LTM. In addition, we found that glial ArchT photoactivation during the rest period resulted in the augmentation of LTM formation. These data suggest that STM formation and LTM formation are parallel separate processes. Strategies to weigh more on the STM or the LTM could depend on the actions of the glial cells.
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Affiliation(s)
- Teppei Kanaya
- Super-Network Brain Physiology, Graduate School of Medicine, Tohoku University, Sendai, Japan
| | - Ryo Ito
- Super-Network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Yosuke M Morizawa
- Super-Network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Daichi Sasaki
- Super-Network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Hiroki Yamao
- Super-Network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Hiroshi Ishikane
- Department of Psychology, Graduate School of Humanities, Senshu University, Kawasaki, Japan
| | - Yuichi Hiraoka
- Laboratory of Molecular Neuroscience, Medical Research Institute (MRI), Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Kohichi Tanaka
- Laboratory of Molecular Neuroscience, Medical Research Institute (MRI), Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Ko Matsui
- Super-Network Brain Physiology, Graduate School of Medicine, Tohoku University, Sendai, Japan
- Super-Network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
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12
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Balkaya M, Dohare P, Chen S, Schober AL, Fidaleo AM, Nalwalk JW, Sah R, Mongin AA. Conditional deletion of LRRC8A in the brain reduces stroke damage independently of swelling-activated glutamate release. iScience 2023; 26:106669. [PMID: 37182109 PMCID: PMC10173736 DOI: 10.1016/j.isci.2023.106669] [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: 12/30/2022] [Revised: 03/03/2023] [Accepted: 04/11/2023] [Indexed: 05/16/2023] Open
Abstract
The ubiquitous volume-regulated anion channels (VRACs) facilitate cell volume control and contribute to many other physiological processes. Treatment with non-specific VRAC blockers or brain-specific deletion of the essential VRAC subunit LRRC8A is highly protective in rodent models of stroke. Here, we tested the widely accepted idea that the harmful effects of VRACs are mediated by release of the excitatory neurotransmitter glutamate. We produced conditional LRRC8A knockout either exclusively in astrocytes or in the majority of brain cells. Genetically modified mice were subjected to an experimental stroke (middle cerebral artery occlusion). The astrocytic LRRC8A knockout yielded no protection. Conversely, the brain-wide LRRC8A deletion strongly reduced cerebral infarction in both heterozygous (Het) and full KO mice. Yet, despite identical protection, Het mice had full swelling-activated glutamate release, whereas KO animals showed its virtual absence. These findings suggest that LRRC8A contributes to ischemic brain injury via a mechanism other than VRAC-mediated glutamate release.
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Affiliation(s)
- Mustafa Balkaya
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Preeti Dohare
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Sophie Chen
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Alexandra L. Schober
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Antonio M. Fidaleo
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Julia W. Nalwalk
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
| | - Rajan Sah
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Alexander A. Mongin
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, NY 12208, USA
- Corresponding author
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13
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Kern DM, Bleier J, Mukherjee S, Hill JM, Kossiakoff AA, Isacoff EY, Brohawn SG. Structural basis for assembly and lipid-mediated gating of LRRC8A:C volume-regulated anion channels. Nat Struct Mol Biol 2023:10.1038/s41594-023-00944-6. [PMID: 36928458 DOI: 10.1038/s41594-023-00944-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 02/22/2023] [Indexed: 03/18/2023]
Abstract
Leucine-rich repeat-containing protein 8 (LRRC8) family members form volume-regulated anion channels activated by hypoosmotic cell swelling. LRRC8 channels are ubiquitously expressed in vertebrate cells as heteromeric assemblies of LRRC8A (SWELL1) and LRRC8B-E subunits. Channels of different subunit composition have distinct properties that explain the functional diversity of LRRC8 currents across cell types. However, the basis for heteromeric LRRC8 channel assembly and function is unknown. Here we leverage a fiducial-tagging strategy to determine single-particle cryo-EM structures of heterohexameric LRRC8A:C channels in multiple conformations. Compared to homomers, LRRC8A:C channels show pronounced differences in architecture due to heterotypic LRR interactions that displace subunits away from the conduction axis and poise the channel for activation. Structures and functional studies further reveal that lipids embedded in the channel pore block ion conduction in the closed state. These results provide insight into determinants for heteromeric LRRC8 channel assembly, activity and gating by lipids.
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Affiliation(s)
- David M Kern
- Department of Molecular & Cell Biology, University of California, Berkeley, CA, USA.,Helen Wills Neuroscience Institute, University of California, Berkeley, CA, USA.,California Institute for Quantitative Biology (QB3), University of California, Berkeley, CA, USA
| | - Julia Bleier
- Helen Wills Neuroscience Institute, University of California, Berkeley, CA, USA
| | - Somnath Mukherjee
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA.,Institute for Biophysical Dynamics, University of Chicago, Chicago, IL, USA
| | - Jennifer M Hill
- Department of Molecular & Cell Biology, University of California, Berkeley, CA, USA
| | - Anthony A Kossiakoff
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA.,Institute for Biophysical Dynamics, University of Chicago, Chicago, IL, USA
| | - Ehud Y Isacoff
- Department of Molecular & Cell Biology, University of California, Berkeley, CA, USA.,Helen Wills Neuroscience Institute, University of California, Berkeley, CA, USA.,California Institute for Quantitative Biology (QB3), University of California, Berkeley, CA, USA
| | - Stephen G Brohawn
- Department of Molecular & Cell Biology, University of California, Berkeley, CA, USA. .,Helen Wills Neuroscience Institute, University of California, Berkeley, CA, USA. .,California Institute for Quantitative Biology (QB3), University of California, Berkeley, CA, USA.
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14
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Aquaporins and Ion Channels as Dual Targets in the Design of Novel Glioblastoma Therapeutics to Limit Invasiveness. Cancers (Basel) 2023; 15:cancers15030849. [PMID: 36765806 PMCID: PMC9913334 DOI: 10.3390/cancers15030849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/20/2023] [Accepted: 01/28/2023] [Indexed: 01/31/2023] Open
Abstract
Current therapies for Glioblastoma multiforme (GBM) focus on eradicating primary tumors using radiotherapy, chemotherapy and surgical resection, but have limited success in controlling the invasive spread of glioma cells into a healthy brain, the major factor driving short survival times for patients post-diagnosis. Transcriptomic analyses of GBM biopsies reveal clusters of membrane signaling proteins that in combination serve as robust prognostic indicators, including aquaporins and ion channels, which are upregulated in GBM and implicated in enhanced glioblastoma motility. Accumulating evidence supports our proposal that the concurrent pharmacological targeting of selected subclasses of aquaporins and ion channels could impede glioblastoma invasiveness by impairing key cellular motility pathways. Optimal sets of channels to be selected as targets for combined therapies could be tailored to the GBM cancer subtype, taking advantage of differences in patterns of expression between channels that are characteristic of GBM subtypes, as well as distinguishing them from non-cancerous brain cells such as neurons and glia. Focusing agents on a unique channel fingerprint in GBM would further allow combined agents to be administered at near threshold doses, potentially reducing off-target toxicity. Adjunct therapies which confine GBM tumors to their primary sites during clinical treatments would offer profound advantages for treatment efficacy.
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15
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Zhang J, Toremurat Z, Liang Y, Cheng J, Sun Z, Huang Y, Liu J, Chaogetu BUREN, Ren G, Chen H. Study on the Association between LRRC8B Gene InDel and Sheep Body Conformation Traits. Genes (Basel) 2023; 14:genes14020356. [PMID: 36833283 PMCID: PMC9956668 DOI: 10.3390/genes14020356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 12/23/2022] [Accepted: 01/16/2023] [Indexed: 01/31/2023] Open
Abstract
Marker-assisted selection is an important method for livestock breeding. In recent years, this technology has been gradually applied to livestock breeding to improve the body conformation traits. In this study, the LRRC8B (Leucine Rich Repeat Containing 8 VRAC Subunit B) gene was selected to evaluate the association between its genetic variations and the body conformation traits in two native sheep breeds in China. Four body conformation traits, including withers height, body length, chest circumference, and body weight, were collected from 269 Chaka sheep. We also collected the body length, chest width, withers height, chest depth, chest circumference, cannon bone circumference, and height at hip cross of 149 Small-Tailed Han sheep. Two different genotypes, ID and DD, were detected in all sheep. Our data showed that the polymorphism of the LRRC8B gene was significantly associated with chest depth (p < 0.05) in Small-Tailed Han sheep, and it is greater in sheep with DD than those with ID. In conclusion, our data suggested that the LRRC8B gene could serve as a candidate gene for marker-assisted selection in Small-Tailed Han sheep.
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Affiliation(s)
- Jiaqiang Zhang
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Xianyang 712100, China
| | - Zhansaya Toremurat
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Xianyang 712100, China
| | - Yilin Liang
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Xianyang 712100, China
| | - Jie Cheng
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Xianyang 712100, China
| | - Zhenzhen Sun
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Xianyang 712100, China
| | - Yangming Huang
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Xianyang 712100, China
| | - Junxia Liu
- College of Life Sciences, Northwest A&F University, Xianyang 712100, China
| | - BUREN Chaogetu
- Animal Disease Control Center of Haixi Mongolian and Tibetan Autonomous Prefecture, Delingha 817000, China
| | - Gang Ren
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Xianyang 712100, China
- Correspondence: (G.R.); (H.C.); Tel.: +86-029-87092102 (H.C.); Fax: +86-029-87092164 (H.C.)
| | - Hong Chen
- Key Laboratory of Animal Genetics, Breeding and Reproduction of Shaanxi Province, College of Animal Science and Technology, Northwest A&F University, Xianyang 712100, China
- College of Animal Science, Xinjiang Agricultural University, Urumqi 830052, China
- Correspondence: (G.R.); (H.C.); Tel.: +86-029-87092102 (H.C.); Fax: +86-029-87092164 (H.C.)
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16
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Wang Z, Choi K. Pharmacological modulation of chloride channels as a therapeutic strategy for neurological disorders. Front Physiol 2023; 14:1122444. [PMID: 36935741 PMCID: PMC10017882 DOI: 10.3389/fphys.2023.1122444] [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: 12/12/2022] [Accepted: 02/09/2023] [Indexed: 03/06/2023] Open
Abstract
Chloride homeostasis is critical in the physiological functions of the central nervous system (CNS). Its concentration is precisely regulated by multiple ion-transporting proteins such as chloride channels and transporters that are widely distributed in the brain cells, including neurons and glia. Unlike ion transporters, chloride channels provide rapid responses to efficiently regulate ion flux. Some of chloride channels are also permeable to selected organic anions such as glutamate and γ-aminobutyric acid, suggesting neuroexcitatory and neuroinhibitory functions while gating. Dysregulated chloride channels are implicated in neurological disorders, e.g., ischemia and neuroinflammation. Modulation of chloride homeostasis through chloride channels has been suggested as a potential therapeutic approach for neurological disorders. The drug design for CNS diseases is challenging because it requires the therapeutics to traverse the blood-brain-barrier. Small molecules are a well-established modality with better cell permeability due to their lower molecular weight and flexibility for structure optimization compared to biologics. In this article, we describe the important roles of chloride homeostasis in each type of brain cells and introduce selected chloride channels identified in the CNS. We then discuss the contribution of their dysregulations towards the pathogenesis of neurological disorders, emphasizing the potential of targeting chloride channels as a therapeutic strategy for CNS disease treatment. Along with this literature survey, we summarize the small molecules that modulate chloride channels and propose the potential strategy of optimizing existing drugs to brain-penetrants to support future CNS drug discovery.
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17
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Ghouli MR, Jonak CR, Sah R, Fiacco TA, Binder DK. Regulation of the Volume-Regulated Anion Channel Pore-Forming Subunit LRRC8A in the Intrahippocampal Kainic Acid Model of Mesial Temporal Lobe Epilepsy. ASN Neuro 2023; 15:17590914231184072. [PMID: 37410995 PMCID: PMC10331354 DOI: 10.1177/17590914231184072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Revised: 05/22/2023] [Accepted: 06/07/2023] [Indexed: 07/08/2023] Open
Abstract
Volume-regulated anion channels (VRACs) are a group of ubiquitously expressed outwardly-rectifying anion channels that sense increases in cell volume and act to return cells to baseline volume through an efflux of anions and organic osmolytes, including glutamate. Because cell swelling, increased extracellular glutamate levels, and reduction of the brain extracellular space (ECS) all occur during seizure generation, we set out to determine whether VRACs are dysregulated throughout mesial temporal lobe epilepsy (MTLE), the most common form of adult epilepsy. To accomplish this, we employed the IHKA experimental model of MTLE, and probed for the expression of LRRC8A, the essential pore-forming VRAC subunit, at acute, early-, mid-, and late-epileptogenic time points (1-, 7-, 14-, and 30-days post-IHKA, respectively). Western blot analysis revealed the upregulation of total dorsal hippocampal LRRC8A 14-days post-IHKA in both the ipsilateral and contralateral hippocampus. Immunohistochemical analyses showed an increased LRRC8A signal 7-days post-IHKA in both the ipsilateral and contralateral hippocampus, along with layer-specific changes 1-, 7-, and 30-days post-IHKA bilaterally. LRRC8A upregulation 1 day post-IHKA was observed primarily in astrocytes; however, some upregulation was also observed in neurons. Glutamate-GABA/glutamine cycle enzymes glutamic acid decarboxylase, glutaminase, and glutamine synthetase were also dysregulated at the 7-day timepoint post status epilepticus. The timepoint-dependent upregulation of total hippocampal LRRC8A and the possible subsequent increased efflux of glutamate in the epileptic hippocampus suggest that the dysregulation of astrocytic VRAC may play an important role in the development of epilepsy.
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Affiliation(s)
- Manolia R. Ghouli
- Division of Biomedical Sciences, School of Medicine, University of California—Riverside, Riverside, CA, USA
- Center for Glial-Neuronal Interactions, University of California—Riverside, Riverside, CA, USA
| | - Carrie R. Jonak
- Division of Biomedical Sciences, School of Medicine, University of California—Riverside, Riverside, CA, USA
- Center for Glial-Neuronal Interactions, University of California—Riverside, Riverside, CA, USA
| | - Rajan Sah
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Todd A. Fiacco
- Center for Glial-Neuronal Interactions, University of California—Riverside, Riverside, CA, USA
- Department of Cell Biology and Neuroscience, University of California—Riverside, Riverside, CA, USA
| | - Devin K. Binder
- Division of Biomedical Sciences, School of Medicine, University of California—Riverside, Riverside, CA, USA
- Center for Glial-Neuronal Interactions, University of California—Riverside, Riverside, CA, USA
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18
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Álvarez-Merz I, Fomitcheva IV, Sword J, Hernández-Guijo JM, Solís JM, Kirov SA. Novel mechanism of hypoxic neuronal injury mediated by non-excitatory amino acids and astroglial swelling. Glia 2022; 70:2108-2130. [PMID: 35802030 PMCID: PMC9474671 DOI: 10.1002/glia.24241] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 06/14/2022] [Accepted: 06/24/2022] [Indexed: 11/08/2022]
Abstract
In ischemic stroke and post-traumatic brain injury (TBI), blood-brain barrier disruption leads to leaking plasma amino acids (AA) into cerebral parenchyma. Bleeding in hemorrhagic stroke and TBI also release plasma AA. Although excitotoxic AA were extensively studied, little is known about non-excitatory AA during hypoxic injury. Hypoxia-induced synaptic depression in hippocampal slices becomes irreversible with non-excitatory AA, alongside their intracellular accumulation and increased tissue electrical resistance. Four non-excitatory AA (l-alanine, glycine, l-glutamine, l-serine: AGQS) at plasmatic concentrations were applied to slices from mice expressing EGFP in pyramidal neurons or astrocytes during normoxia or hypoxia. Two-photon imaging, light transmittance (LT) changes, and electrophysiological field recordings followed by electron microscopy in hippocampal CA1 st. radiatum were used to monitor synaptic function concurrently with cellular swelling and injury. During normoxia, AGQS-induced increase in LT was due to astroglial but not neuronal swelling. LT raise during hypoxia and AGQS manifested astroglial and neuronal swelling accompanied by a permanent loss of synaptic transmission and irreversible dendritic beading, signifying acute damage. Neuronal injury was not triggered by spreading depolarization which did not occur in our experiments. Hypoxia without AGQS did not cause cell swelling, leaving dendrites intact. Inhibition of NMDA receptors prevented neuronal damage and irreversible loss of synaptic function. Deleterious effects of AGQS during hypoxia were prevented by alanine-serine-cysteine transporters (ASCT2) and volume-regulated anion channels (VRAC) blockers. Our findings suggest that astroglial swelling induced by accumulation of non-excitatory AA and release of excitotoxins through antiporters and VRAC may exacerbate the hypoxia-induced neuronal injury.
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Affiliation(s)
- Iris Álvarez-Merz
- Dept. de Farmacología y Terapéutica, ITH, Facultad de Medicina, Universidad Autónoma de Madrid, IRYCIS, 28029 Madrid, Spain
- Servicio de Neurobiología-Investigación, Hospital Universitario Ramón y Cajal, IRYCIS, 28034 Madrid, Spain
- Dept. of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, Georgia 30912, USA
| | - Ioulia V. Fomitcheva
- Dept. of Neurosurgery, Medical College of Georgia at Augusta University, Augusta, Georgia 30912, USA
| | - Jeremy Sword
- Dept. of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, Georgia 30912, USA
| | - Jesús M. Hernández-Guijo
- Dept. de Farmacología y Terapéutica, ITH, Facultad de Medicina, Universidad Autónoma de Madrid, IRYCIS, 28029 Madrid, Spain
| | - José M. Solís
- Servicio de Neurobiología-Investigación, Hospital Universitario Ramón y Cajal, IRYCIS, 28034 Madrid, Spain
| | - Sergei A. Kirov
- Dept. of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, Georgia 30912, USA
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19
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Ghouli MR, Fiacco TA, Binder DK. Structure-function relationships of the LRRC8 subunits and subdomains of the volume-regulated anion channel (VRAC). Front Cell Neurosci 2022; 16:962714. [PMID: 36035259 PMCID: PMC9399500 DOI: 10.3389/fncel.2022.962714] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 07/18/2022] [Indexed: 11/19/2022] Open
Abstract
Volume Regulated Anion Channels (VRAC) are critical contributors to cell volume homeostasis and are expressed ubiquitously in all vertebrate cells. VRAC sense increases in cell volume, and act to return cells to baseline volume in a process known as regulatory volume decrease (RVD) through the efflux of anions and organic osmolytes. This review will highlight seminal studies that elucidated the role of VRAC in RVD, their characteristics as a function of subunit specificity, and their clinical relevance in physiology and pathology. VRAC are also known as volume-sensitive outward rectifiers (VSOR) and volume-sensitive organic osmolyte/anion channels (VSOAC). In this review, the term VRAC will be used to refer to this family of channels.
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Affiliation(s)
- Manolia R. Ghouli
- Division of Biomedical Sciences, School of Medicine, University of California–Riverside, Riverside, CA, United States
| | - Todd A. Fiacco
- Department of Cell Biology and Neuroscience, Center for Glial-Neuronal Interactions, University of California–Riverside, Riverside, CA, United States
| | - Devin K. Binder
- Division of Biomedical Sciences, School of Medicine, University of California–Riverside, Riverside, CA, United States
- *Correspondence: Devin K. Binder
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20
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Walch E, Bilas A, Bebawy V, Lam A, Murphy TR, Sriram S, Fiacco TA. Contributions of Astrocyte and Neuronal Volume to CA1 Neuron Excitability Changes in Elevated Extracellular Potassium. Front Cell Neurosci 2022; 16:930384. [PMID: 35936495 PMCID: PMC9352931 DOI: 10.3389/fncel.2022.930384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 06/21/2022] [Indexed: 11/17/2022] Open
Abstract
Rapid increases in cell volume reduce the size of the extracellular space (ECS) and are associated with elevated brain tissue excitability. We recently demonstrated that astrocytes, but not neurons, rapidly swell in elevated extracellular potassium (∧[K+]o) up to 26 mM. However, effects of acute astrocyte volume fluctuations on neuronal excitability in ∧[K+]o have been difficult to evaluate due to direct effects on neuronal membrane potential and generation of action potentials. Here we set out to isolate volume-specific effects occurring in ∧[K+]o on CA1 pyramidal neurons in acute hippocampal slices by manipulating cell volume while recording neuronal glutamate currents in 10.5 mM [K+]o + tetrodotoxin (TTX) to prevent neuronal firing. Elevating [K+]o to 10.5 mM induced astrocyte swelling and produced significant increases in neuronal excitability in the form of mixed α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/N-methyl-D-aspartate (NMDA) receptor mEPSCs and NMDA receptor-dependent slow inward currents (SICs). Application of hyperosmolar artificial cerebrospinal fluid (ACSF) by addition of mannitol in the continued presence of 10.5 mM K+ forced shrinking of astrocytes and to a lesser extent neurons, which resisted swelling in ∧[K+]o. Cell shrinking and dilation of the ECS significantly dampened neuronal excitability in 10.5 mM K+. Subsequent removal of mannitol amplified effects on neuronal excitability and nearly doubled the volume increase in astrocytes, presumably due to continued glial uptake of K+ while mannitol was present. Slower, larger amplitude events mainly driven by NMDA receptors were abolished by mannitol-induced expansion of the ECS. Collectively, our findings suggest that cell volume regulation of the ECS in elevated [K+]o is driven predominantly by astrocytes, and that cell volume effects on neuronal excitability can be effectively isolated in elevated [K+]o conditions.
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Affiliation(s)
- Erin Walch
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
- Center for Glial-Neuronal Interactions, University of California, Riverside, Riverside, CA, United States
| | - Alexander Bilas
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, CA, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, CA, United States
| | - Valine Bebawy
- Undergraduate Major in Biology, University of California, Riverside, Riverside, CA, United States
| | - Angelina Lam
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, CA, United States
| | - Thomas R. Murphy
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA, United States
- Center for Glial-Neuronal Interactions, University of California, Riverside, Riverside, CA, United States
| | - Sandhya Sriram
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, CA, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, CA, United States
| | - Todd A. Fiacco
- Center for Glial-Neuronal Interactions, University of California, Riverside, Riverside, CA, United States
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, Riverside, CA, United States
- Interdepartmental Graduate Program in Neuroscience, University of California, Riverside, Riverside, CA, United States
- *Correspondence: Todd A. Fiacco,
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21
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Ramírez-Guerrero S, Guardo-Maya S, Medina-Rincón GJ, Orrego-González EE, Cabezas-Pérez R, González-Reyes RE. Taurine and Astrocytes: A Homeostatic and Neuroprotective Relationship. Front Mol Neurosci 2022; 15:937789. [PMID: 35866158 PMCID: PMC9294388 DOI: 10.3389/fnmol.2022.937789] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 06/17/2022] [Indexed: 12/20/2022] Open
Abstract
Taurine is considered the most abundant free amino acid in the brain. Even though there are endogenous mechanisms for taurine production in neural cells, an exogenous supply of taurine is required to meet physiological needs. Taurine is required for optimal postnatal brain development; however, its brain concentration decreases with age. Synthesis of taurine in the central nervous system (CNS) occurs predominantly in astrocytes. A metabolic coupling between astrocytes and neurons has been reported, in which astrocytes provide neurons with hypotaurine as a substrate for taurine production. Taurine has antioxidative, osmoregulatory, and anti-inflammatory functions, among other cytoprotective properties. Astrocytes release taurine as a gliotransmitter, promoting both extracellular and intracellular effects in neurons. The extracellular effects include binding to neuronal GABAA and glycine receptors, with subsequent cellular hyperpolarization, and attenuation of N-methyl-D-aspartic acid (NMDA)-mediated glutamate excitotoxicity. Taurine intracellular effects are directed toward calcium homeostatic pathway, reducing calcium overload and thus preventing excitotoxicity, mitochondrial stress, and apoptosis. However, several physiological aspects of taurine remain unclear, such as the existence or not of a specific taurine receptor. Therefore, further research is needed not only in astrocytes and neurons, but also in other glial cells in order to fully comprehend taurine metabolism and function in the brain. Nonetheless, astrocyte’s role in taurine-induced neuroprotective functions should be considered as a promising therapeutic target of several neuroinflammatory, neurodegenerative and psychiatric diseases in the near future. This review provides an overview of the significant relationship between taurine and astrocytes, as well as its homeostatic and neuroprotective role in the nervous system.
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Affiliation(s)
- Sofía Ramírez-Guerrero
- Grupo de Investigación en Neurociencias (NeURos), Centro de Neurociencias Neurovitae-UR, Instituto de Medicina Traslacional (IMT), Escuela de Medicina y Ciencias de la Salud, Universidad del Rosario, Bogotá, Colombia
| | - Santiago Guardo-Maya
- Grupo de Investigación en Neurociencias (NeURos), Centro de Neurociencias Neurovitae-UR, Instituto de Medicina Traslacional (IMT), Escuela de Medicina y Ciencias de la Salud, Universidad del Rosario, Bogotá, Colombia
| | - Germán J. Medina-Rincón
- Grupo de Investigación en Neurociencias (NeURos), Centro de Neurociencias Neurovitae-UR, Instituto de Medicina Traslacional (IMT), Escuela de Medicina y Ciencias de la Salud, Universidad del Rosario, Bogotá, Colombia
| | - Eduardo E. Orrego-González
- Grupo de Investigación en Neurociencias (NeURos), Centro de Neurociencias Neurovitae-UR, Instituto de Medicina Traslacional (IMT), Escuela de Medicina y Ciencias de la Salud, Universidad del Rosario, Bogotá, Colombia
| | - Ricardo Cabezas-Pérez
- Grupo de Investigación en Ciencias Biomédicas GRINCIBIO, Facultad de Medicina, Universidad Antonio Nariño, Bogotá, Colombia
| | - Rodrigo E. González-Reyes
- Grupo de Investigación en Neurociencias (NeURos), Centro de Neurociencias Neurovitae-UR, Instituto de Medicina Traslacional (IMT), Escuela de Medicina y Ciencias de la Salud, Universidad del Rosario, Bogotá, Colombia
- *Correspondence: Rodrigo E. González-Reyes,
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22
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Shen Z, Xiang M, Chen C, Ding F, Wang Y, Shang C, Xin L, Zhang Y, Cui X. Glutamate excitotoxicity: Potential therapeutic target for ischemic stroke. Biomed Pharmacother 2022; 151:113125. [PMID: 35609367 DOI: 10.1016/j.biopha.2022.113125] [Citation(s) in RCA: 50] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 05/01/2022] [Accepted: 05/13/2022] [Indexed: 11/29/2022] Open
Abstract
Glutamate-mediated excitotoxicity is an important mechanism leading to post ischemic stroke damage. After acute stroke, the sudden reduction in cerebral blood flow is most initially followed by ion transport protein dysfunction and disruption of ion homeostasis, which in turn leads to impaired glutamate release, reuptake, and excessive N-methyl-D-aspartate receptor (NMDAR) activation, promoting neuronal death. Despite extensive evidence from preclinical studies suggesting that excessive NMDAR stimulation during ischemic stroke is a central step in post-stroke damage, NMDAR blockers have failed to translate into clinical stroke treatment. Current treatment options for stroke are very limited, and there is therefore a great need to develop new targets for neuroprotective therapeutic agents in ischemic stroke to extend the therapeutic time window. In this review, we highlight recent findings on glutamate release, reuptake mechanisms, NMDAR and its downstream cellular signaling pathways in post-ischemic stroke damage, and review the pathological changes in each link to help develop viable new therapeutic targets. We then also summarize potential neuroprotective drugs and therapeutic approaches for these new targets in the treatment of ischemic stroke.
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Affiliation(s)
- Zihuan Shen
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China; Clinical Medical School, Beijing University of Traditional Chinese Medicine, Beijing 100029, China
| | - Mi Xiang
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China
| | - Chen Chen
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China
| | - Fan Ding
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China; Clinical Medical School, Beijing University of Traditional Chinese Medicine, Beijing 100029, China
| | - Yuling Wang
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China; Clinical Medical School, Beijing University of Traditional Chinese Medicine, Beijing 100029, China
| | - Chang Shang
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China; Clinical Medical School, Beijing University of Traditional Chinese Medicine, Beijing 100029, China
| | - Laiyun Xin
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China
| | - Yang Zhang
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China.
| | - Xiangning Cui
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China.
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23
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Eitelmann S, Stephan J, Everaerts K, Durry S, Pape N, Gerkau NJ, Rose CR. Changes in Astroglial K + upon Brief Periods of Energy Deprivation in the Mouse Neocortex. Int J Mol Sci 2022; 23:ijms23094836. [PMID: 35563238 PMCID: PMC9102782 DOI: 10.3390/ijms23094836] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/21/2022] [Accepted: 04/24/2022] [Indexed: 11/16/2022] Open
Abstract
Malfunction of astrocytic K+ regulation contributes to the breakdown of extracellular K+ homeostasis during ischemia and spreading depolarization events. Studying astroglial K+ changes is, however, hampered by a lack of suitable techniques. Here, we combined results from fluorescence imaging, ion-selective microelectrodes, and patch-clamp recordings in murine neocortical slices with the calculation of astrocytic [K+]. Brief chemical ischemia caused a reversible ATP reduction and a transient depolarization of astrocytes. Moreover, astrocytic [Na+] increased by 24 mM and extracellular [Na+] decreased. Extracellular [K+] increased, followed by an undershoot during recovery. Feeding these data into the Goldman-Hodgkin-Katz equation revealed a baseline astroglial [K+] of 146 mM, an initial K+ loss by 43 mM upon chemical ischemia, and a transient K+ overshoot of 16 mM during recovery. It also disclosed a biphasic mismatch in astrocytic Na+/K+ balance, which was initially ameliorated, but later aggravated by accompanying changes in pH and bicarbonate, respectively. Altogether, our study predicts a loss of K+ from astrocytes upon chemical ischemia followed by a net gain. The overshooting K+ uptake will promote low extracellular K+ during recovery, likely exerting a neuroprotective effect. The resulting late cation/anion imbalance requires additional efflux of cations and/or influx of anions, the latter eventually driving delayed astrocyte swelling.
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24
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Wang Z, Li Y, Zeng Z, Guo S, Chen W, Luo Y. Leucine-rich repeat containing 8A contributes to the expansion of The potential role of leucine-rich repeat-containing protein 8A in central nervous system: current situation and prospect. Neuroscience 2022; 488:122-131. [PMID: 35276302 DOI: 10.1016/j.neuroscience.2022.03.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 02/24/2022] [Accepted: 03/01/2022] [Indexed: 12/12/2022]
Abstract
Cell swelling usually initiates the regulatory volume decrease (RVD) process mediated mainly by volume-regulated anion channels (VRACs), which are formed by multiple different leucine-rich repeat-containing protein 8 (LRRC8) family members. VRAC currents have been widely recorded in astrocytes, neurons and microglia in the brain, and VRACs have been suggested to be involved in the important pathogenesis of cell swelling-related central nervous system (CNS) diseases, such as ischemic stroke, epilepsy and epileptogenesis, glioblastoma (GBM), and so on. Recently, the increasing studies started to focus on LRRC8A (SWELL1), an obligatory subunit of VRAC indentified in 2014, which may be the key target to regulate the VRAC functions. After cerebral ischemia, the swollen astrocytes, neurons and microglia can activate LRRC8A-dependent VRACs, which may respectively promote the release of excitatory amino acids (EAA), interaction with ionotropic glutamate receptors, and regulating inflammation, suggesting the pleiotropic roles of LRRC8A in swollen brain cells. For the treatment of cell swelling-related CNS diseases, specific targeting LRRC8A may be a superior strategy to inhibit swollen-induced VRAC hyperactivity without blocking the normal VRAC function.
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Affiliation(s)
- Zhuo Wang
- Department of Neurology, Zhongnan Hospital of Wuhan University, Wuhan 430071, Hubei, China; Wuhan Institute for Neuroscience and Neuroengineering, South-Central University for Nationalities, Wuhan 430074, Hubei, China
| | - Yunhui Li
- National Key Laboratory of Medical Immunology & Institute of Immunology, Second Military Medical University, Shanghai 200433, China
| | - Zhikun Zeng
- Department of Laboratory Medicine, Zhongnan Hospital of Wuhan University, Wuhan 430071, Hubei, China
| | - Shuang Guo
- Department of Laboratory Medicine, Zhongnan Hospital of Wuhan University, Wuhan 430071, Hubei, China
| | - Wei Chen
- Department of Laboratory Medicine, Zhongnan Hospital of Wuhan University, Wuhan 430071, Hubei, China
| | - Yi Luo
- Department of Laboratory Medicine, Zhongnan Hospital of Wuhan University, Wuhan 430071, Hubei, China.
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25
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Kovermann P, Kolobkova Y, Franzen A, Fahlke C. Mutations associated with epileptic encephalopathy modify EAAT2 anion channel function. Epilepsia 2021; 63:388-401. [PMID: 34961934 DOI: 10.1111/epi.17154] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 12/09/2021] [Accepted: 12/09/2021] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Mutations in the gene solute carrier family member 1A2 (SLC1A2) encoding the excitatory amino acid transporter 2 (EAAT2) are associated with severe forms of epileptic encephalopathy. EAAT2 is expressed in glial cells and presynaptic nerve terminals and represents the main l-glutamate uptake carrier in the mammalian brain. It does not only function as a secondary active glutamate transporter, but also as an anion channel. How naturally occurring mutations affect these two transport functions of EAAT2 and how such alterations cause epilepsy is insufficiently understood. METHODS Here we studied the functional consequences of three disease-associated mutations, which predict amino acid exchanges p.Gly82Arg (G82R), p.Leu85Pro (L85P), and p.Pro289Arg (P289R), by heterologous expression in mammalian cells, biochemistry, confocal imaging, and whole-cell patch-clamp recordings of EAAT2 l-glutamate transport and anion current. RESULTS G82R and L85P exchange amino acid residues contribute to the formation of the EAAT anion pore. They enlarge the pore diameter sufficiently to permit the passage of l-glutamate and thus function as l-glutamate efflux pathways. The mutation P289R decreases l-glutamate uptake, but increases anion currents despite a lower membrane expression. SIGNIFICANCE l-glutamate permeability of the EAAT anion pore is an unexpected functional consequence of naturally occurring single amino acid substitutions. l-glutamate efflux through mutant EAAT2 anion channels will cause glutamate excitotoxicity and neuronal hyperexcitability in affected patients. Antagonists that selectively suppress the EAAT anion channel function could serve as therapeutic agents in the future.
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Affiliation(s)
- Peter Kovermann
- Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Institute of Biological Information Processing, Jülich, Germany
| | - Yulia Kolobkova
- Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Institute of Biological Information Processing, Jülich, Germany
| | - Arne Franzen
- Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Institute of Biological Information Processing, Jülich, Germany
| | - Christoph Fahlke
- Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Institute of Biological Information Processing, Jülich, Germany
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26
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Kolobkova Y, Pervaiz S, Stauber T. The expanding toolbox to study the LRRC8-formed volume-regulated anion channel VRAC. CURRENT TOPICS IN MEMBRANES 2021; 88:119-163. [PMID: 34862024 DOI: 10.1016/bs.ctm.2021.10.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The volume-regulated anion channel (VRAC) is activated upon cell swelling and facilitates the passive movement of anions across the plasma membrane in cells. VRAC function underlies many critical homeostatic processes in vertebrate cells. Among them are the regulation of cell volume and membrane potential, glutamate release and apoptosis. VRAC is also permeable for organic osmolytes and metabolites including some anti-cancer drugs and antibiotics. Therefore, a fundamental understanding of VRAC's structure-function relationships, its physiological roles, its utility for therapy of diseases, and the development of compounds modulating its activity are important research frontiers. Here, we describe approaches that have been applied to study VRAC since it was first described more than 30 years ago, providing an overview of the recent methodological progress. The diverse applications reflecting a compromise between the physiological situation, biochemical definition, and biophysical resolution range from the study of VRAC activity using a classic electrophysiology approach, to the measurement of osmolytes transport by various means and the investigation of its activation using a novel biophysical approach based on fluorescence resonance energy transfer.
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Affiliation(s)
- Yulia Kolobkova
- Department of Human Medicine and Institute for Molecular Medicine, MSH Medical School Hamburg, Germany
| | - Sumaira Pervaiz
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Germany
| | - Tobias Stauber
- Department of Human Medicine and Institute for Molecular Medicine, MSH Medical School Hamburg, Germany; Institute of Chemistry and Biochemistry, Freie Universität Berlin, Germany.
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27
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Abstract
Chloride transport across cell membranes is broadly involved in epithelial fluid transport, cell volume and pH regulation, muscle contraction, membrane excitability, and organellar acidification. The human genome encodes at least 53 chloride-transporting proteins with expression in cell plasma or intracellular membranes, which include chloride channels, exchangers, and cotransporters, some having broad anion specificity. Loss-of-function mutations in chloride transporters cause a wide variety of human diseases, including cystic fibrosis, secretory diarrhea, kidney stones, salt-wasting nephropathy, myotonia, osteopetrosis, hearing loss, and goiter. Although impactful advances have been made in the past decade in drug treatment of cystic fibrosis using small molecule modulators of the defective cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel, other chloride channels and solute carrier proteins (SLCs) represent relatively underexplored target classes for drug discovery. New opportunities have emerged for the development of chloride transport modulators as potential therapeutics for secretory diarrheas, constipation, dry eye disorders, kidney stones, polycystic kidney disease, hypertension, and osteoporosis. Approaches to chloride transport-targeted drug discovery are reviewed herein, with focus on chloride channel and exchanger classes in which recent preclinical advances have been made in the identification of small molecule modulators and in proof of concept testing in experimental animal models.
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Affiliation(s)
- Alan S Verkman
- Department of Medicine, University of California, San Francisco, California.,Department of Physiology, University of California, San Francisco, California
| | - Luis J V Galietta
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy.,Department of Translational Medical Sciences, University of Naples Federico II, Naples, Italy
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28
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Thompson B, Satin LS. Beta-Cell Ion Channels and Their Role in Regulating Insulin Secretion. Compr Physiol 2021; 11:1-21. [PMID: 34636409 PMCID: PMC8935893 DOI: 10.1002/cphy.c210004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Beta cells of the pancreatic islet express many different types of ion channels. These channels reside in the β-cell plasma membrane as well as subcellular organelles and their coordinated activity and sensitivity to metabolism regulate glucose-dependent insulin secretion. Here, we review the molecular nature, expression patterns, and functional roles of many β-cell channels, with an eye toward explaining the ionic basis of glucose-induced insulin secretion. Our primary focus is on KATP and voltage-gated Ca2+ channels as these primarily regulate insulin secretion; other channels in our view primarily help to sculpt the electrical patterns generated by activated β-cells or indirectly regulate metabolism. Lastly, we discuss why understanding the physiological roles played by ion channels is important for understanding the secretory defects that occur in type 2 diabetes. © 2021 American Physiological Society. Compr Physiol 11:1-21, 2021.
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29
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Ye X, Liu X, Wei W, Yu H, Jin X, Yu J, Li C, Xu B, Guo X, Mao J. Volume-activated chloride channels contribute to lipopolysaccharide plus nigericin-induced pyroptosis in bone marrow-derived macrophages. Biochem Pharmacol 2021; 193:114791. [PMID: 34582774 DOI: 10.1016/j.bcp.2021.114791] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 09/17/2021] [Accepted: 09/24/2021] [Indexed: 01/15/2023]
Abstract
The representative morphological features of pyroptosis are excessive cell swelling and subsequent membrane rupture. However, the mechanism underlying the cell's inherent inability to regulate volume during the progression of pyroptosis is poorly understood. In the current study, we found that both volume-activated chloride currents (Icl, vol) and the regulatory volume decrease (RVD) were markedly decreased in bone marrow-derived macrophages (BMDMs) undergoing pyroptosis induced by lipopolysaccharides (LPS) and nigericin. The inhibition of ICl, vol and RVD by the chloride channel blockers, tamoxifen or DCPIB, led to the emergence of pyroptosis-like phenotypes such as activated-caspase-1, pyroptotic-body-like bubbles, and a fried-egg-like appearance. Moreover, the expression of the volume-activated chloride channel (VRAC) constituent protein Leucine-Rich Repeat-Containing 8A (LRRC8A) was significantly down-regulated in pyroptotic BMDMs treated with LPS and nigericin. The silencing of LRRC8A expression by small interfering RNA (si)-LRRC8A transfection not only reduced ICl, vol and RVD, but also caused BMDMs to show pyroptosis-like manifestations such as activated-caspase-1, membrane bubbles, and have a fried-egg-like appearance. These results reveal a new mechanism for the loss of volume regulation in the process of pyroptotic cell swelling and strongly suggest that a functional deficiency of VRAC/LRRC8A plays a key role in this disorder.
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Affiliation(s)
- Xiaomin Ye
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances and School of Life Sciences and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou 510006, PR China
| | - Xiaoyong Liu
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances and School of Life Sciences and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou 510006, PR China
| | - Wenjun Wei
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances and School of Life Sciences and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou 510006, PR China
| | - Huiping Yu
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances and School of Life Sciences and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou 510006, PR China
| | - Xiaobao Jin
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances and School of Life Sciences and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou 510006, PR China
| | - Jinwei Yu
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances and School of Life Sciences and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou 510006, PR China
| | - Chunmei Li
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances and School of Life Sciences and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou 510006, PR China
| | - Bin Xu
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances and School of Life Sciences and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou 510006, PR China
| | - Xinmin Guo
- Department of Ultrasound, Guangzhou Red Cross Hospital, Medical College, Jinan University, Guangzhou, Guangdong 510220, PR China.
| | - Jianwen Mao
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances and School of Life Sciences and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou 510006, PR China.
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30
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Deneka D, Rutz S, Hutter CAJ, Seeger MA, Sawicka M, Dutzler R. Allosteric modulation of LRRC8 channels by targeting their cytoplasmic domains. Nat Commun 2021; 12:5435. [PMID: 34521847 PMCID: PMC8440666 DOI: 10.1038/s41467-021-25742-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 08/26/2021] [Indexed: 11/09/2022] Open
Abstract
Members of the LRRC8 family form heteromeric assemblies, which function as volume-regulated anion channels. These modular proteins consist of a transmembrane pore and cytoplasmic leucine-rich repeat (LRR) domains. Despite their known molecular architecture, the mechanism of activation and the role of the LRR domains in this process has remained elusive. Here we address this question by generating synthetic nanobodies, termed sybodies, which target the LRR domain of the obligatory subunit LRRC8A. We use these binders to investigate their interaction with homomeric LRRC8A channels by cryo-electron microscopy and the consequent effect on channel activation by electrophysiology. The five identified sybodies either inhibit or enhance activity by binding to distinct epitopes of the LRR domain, thereby altering channel conformations. In combination, our work provides a set of specific modulators of LRRC8 proteins and reveals the role of their cytoplasmic domains as regulators of channel activity by allosteric mechanisms.
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Affiliation(s)
- Dawid Deneka
- Department of Biochemistry University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Sonja Rutz
- Department of Biochemistry University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Cedric A J Hutter
- Institute of Medical Microbiology University of Zurich, Gloriastrasse 28/30, CH-8006, Zurich, Switzerland
| | - Markus A Seeger
- Institute of Medical Microbiology University of Zurich, Gloriastrasse 28/30, CH-8006, Zurich, Switzerland
| | - Marta Sawicka
- Department of Biochemistry University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
| | - Raimund Dutzler
- Department of Biochemistry University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
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31
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Wilson CS, Dohare P, Orbeta S, Nalwalk JW, Huang Y, Ferland RJ, Sah R, Scimemi A, Mongin AA. Late adolescence mortality in mice with brain-specific deletion of the volume-regulated anion channel subunit LRRC8A. FASEB J 2021; 35:e21869. [PMID: 34469026 PMCID: PMC8639177 DOI: 10.1096/fj.202002745r] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 07/27/2021] [Accepted: 08/09/2021] [Indexed: 11/11/2022]
Abstract
The leucine-rich repeat-containing family 8 member A (LRRC8A) is an essential subunit of the volume-regulated anion channel (VRAC). VRAC is critical for cell volume control, but its broader physiological functions remain under investigation. Recent studies in the field indicate that Lrrc8a disruption in the brain astrocytes reduces neuronal excitability, impairs synaptic plasticity and memory, and protects against cerebral ischemia. In the present work, we generated brain-wide conditional LRRC8A knockout mice (LRRC8A bKO) using NestinCre -driven Lrrc8aflox/flox excision in neurons, astrocytes, and oligodendroglia. LRRC8A bKO animals were born close to the expected Mendelian ratio and developed without overt histological abnormalities, but, surprisingly, all died between 5 and 9 weeks of age with a seizure phenotype, which was confirmed by video and EEG recordings. Brain slice electrophysiology detected changes in the excitability of pyramidal cells and modified GABAergic inputs in the hippocampal CA1 region of LRRC8A bKO. LRRC8A-null hippocampi showed increased immunoreactivity of the astrocytic marker GFAP, indicating reactive astrogliosis. We also found decreased whole-brain protein levels of the GABA transporter GAT-1, the glutamate transporter GLT-1, and the astrocytic enzyme glutamine synthetase. Complementary HPLC assays identified reduction in the tissue levels of the glutamate and GABA precursor glutamine. Together, these findings suggest that VRAC provides vital control of brain excitability in mouse adolescence. VRAC deletion leads to a lethal phenotype involving progressive astrogliosis and dysregulation of astrocytic uptake and supply of amino acid neurotransmitters and their precursors.
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Affiliation(s)
- Corinne S Wilson
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
| | - Preeti Dohare
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
| | - Shaina Orbeta
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
| | - Julia W Nalwalk
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
| | - Yunfei Huang
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
| | - Russell J Ferland
- Department of Biomedical Sciences, University of New England College of Osteopathic Medicine, Biddeford, Maine, USA
| | - Rajan Sah
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Annalisa Scimemi
- Department of Biology, University at Albany, State University of New York, Albany, New York, USA
| | - Alexander A Mongin
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
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32
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Syrjanen J, Michalski K, Kawate T, Furukawa H. On the molecular nature of large-pore channels. J Mol Biol 2021; 433:166994. [PMID: 33865869 PMCID: PMC8409005 DOI: 10.1016/j.jmb.2021.166994] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 04/08/2021] [Accepted: 04/08/2021] [Indexed: 12/25/2022]
Abstract
Membrane transport is a fundamental means to control basic cellular processes such as apoptosis, inflammation, and neurodegeneration and is mediated by a number of transporters, pumps, and channels. Accumulating evidence over the last half century has shown that a type of so-called "large-pore channel" exists in various tissues and organs in gap-junctional and non-gap-junctional forms in order to flow not only ions but also metabolites such as ATP. They are formed by a number of protein families with little or no evolutionary linkages including connexin, innexin, pannexin, leucine-rich repeat-containing 8 (LRRC8), and calcium homeostasis modulator (CALHM). This review summarizes the history and concept of large-pore channels starting from connexin gap junction channels to the more recent developments in innexin, pannexin, LRRC8, and CALHM. We describe structural and functional features of large-pore channels that are crucial for their diverse functions on the basis of available structures.
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Affiliation(s)
- Johanna Syrjanen
- W.M. Keck Structural Biology Laboratory, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | - Kevin Michalski
- W.M. Keck Structural Biology Laboratory, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | - Toshimitsu Kawate
- Department of Molecular Medicine, Fields of Biochemistry, Molecular, and Cell Biology (BMCB), and Biophysics, Cornell University, Ithaca, NY 14853, USA
| | - Hiro Furukawa
- W.M. Keck Structural Biology Laboratory, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
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Sherwood MW, Oliet SHR, Panatier A. NMDARs, Coincidence Detectors of Astrocytic and Neuronal Activities. Int J Mol Sci 2021; 22:7258. [PMID: 34298875 PMCID: PMC8307462 DOI: 10.3390/ijms22147258] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 06/30/2021] [Accepted: 06/30/2021] [Indexed: 12/18/2022] Open
Abstract
Synaptic plasticity is an extensively studied cellular correlate of learning and memory in which NMDARs play a starring role. One of the most interesting features of NMDARs is their ability to act as a co-incident detector. It is unique amongst neurotransmitter receptors in this respect. Co-incident detection is possible because the opening of NMDARs requires membrane depolarisation and the binding of glutamate. Opening of NMDARs also requires a co-agonist. Although the dynamic regulation of glutamate and membrane depolarization have been well studied in coincident detection, the role of the co-agonist site is unexplored. It turns out that non-neuronal glial cells, astrocytes, regulate co-agonist availability, giving them the ability to influence synaptic plasticity. The unique morphology and spatial arrangement of astrocytes at the synaptic level affords them the capacity to sample and integrate information originating from unrelated synapses, regardless of any pre-synaptic and post-synaptic commonality. As astrocytes are classically considered slow responders, their influence at the synapse is widely recognized as modulatory. The aim herein is to reconsider the potential of astrocytes to participate directly in ongoing synaptic NMDAR activity and co-incident detection.
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Affiliation(s)
- Mark W. Sherwood
- University of Bordeaux, INSERM, Neurocentre Magendie, U1215, F-3300 Bordeaux, France;
| | | | - Aude Panatier
- University of Bordeaux, INSERM, Neurocentre Magendie, U1215, F-3300 Bordeaux, France;
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Huo C, Liu Y, Li X, Xu R, Jia X, Hou L, Wang X. LRRC8A contributes to angiotensin II-induced cardiac hypertrophy by interacting with NADPH oxidases via the C-terminal leucine-rich repeat domain. Free Radic Biol Med 2021; 165:191-202. [PMID: 33515753 DOI: 10.1016/j.freeradbiomed.2021.01.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/08/2021] [Accepted: 01/10/2021] [Indexed: 12/22/2022]
Abstract
Cardiac hypertrophy, an important cause of heart failure, is characterized by an increase in heart weight, the ventricular wall, and cardiomyocyte volume. The volume regulatory anion channel (VRAC) is an important regulator of cell volume. However, its role in cardiac hypertrophy remains unclear. The purpose of this study was to investigate the effect of leucine-rich repeat-containing 8A (LRRC8A), an essential component of the VRAC, on angiotensin II (AngII)-induced cardiac hypertrophy. Our results showed that LRRC8A expression, NADPH oxidase activity, and reactive oxygen species (ROS) production were increased in AngII-induced hypertrophic neonatal mouse cardiomyocytes and the myocardium of C57/BL/6 mice. In addition, AngII activated VRAC currents in cardiomyocytes. The delivery of adeno-associated viral (AAV9) bearing siRNA against mouse LRRC8A into the left ventricular wall inhibited AngII-induced cardiac hypertrophy and fibrosis. Accordingly, the knockdown of LRRC8A attenuated AngII-induced cardiomyocyte hypertrophy and VRAC currents in vitro. Furthermore, knockdown of LRRC8A suppressed AngII-induced ROS production, NADPH oxidase activity, the expression of NADPH oxidase membrane-bound subunits Nox2, Nox4, and p22phox, and the translocation of NADPH oxidase cytosolic subunits p47phox and p67phox. Immunofluorescent staining showed that LRRC8A co-localized with NADPH oxidase membrane subunits Nox2, Nox4, and p22phox. Co-immunoprecipitation and analysis of a C-terminal leucine-rich repeat domain (LRRD) mutant showed that LRRC8A physically interacts with Nox2, Nox4, and p22phox via the LRRD. Taken together, the results of this study suggested that LRRC8A might play an important role in promoting AngII-induced cardiac hypertrophy by interacting with NADPH oxidases via the LRRD.
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Affiliation(s)
- Cong Huo
- Department of Geriatrics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, PR China
| | - Yan Liu
- Department of Geriatrics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, PR China
| | - Xing Li
- Department of Geriatrics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, PR China
| | - Rong Xu
- Department of Geriatrics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, PR China
| | - Xin Jia
- Department of Geriatrics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, PR China
| | - Liming Hou
- Department of Geriatrics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, PR China
| | - Xiaoming Wang
- Department of Geriatrics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, PR China.
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Tscherner AK, Macaulay AD, Ortman CS, Baltz JM. Initiation of cell volume regulation and unique cell volume regulatory mechanisms in mammalian oocytes and embryos. J Cell Physiol 2021; 236:7117-7133. [PMID: 33634482 DOI: 10.1002/jcp.30352] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 02/09/2021] [Accepted: 02/17/2021] [Indexed: 11/07/2022]
Abstract
The period beginning with the signal for ovulation, when a fully-grown oocyte progresses through meiosis to become a mature egg that is fertilized and develops as a preimplantation embryo, is crucial for healthy development. The early preimplantation embryo is unusually sensitive to cell volume perturbations, with even moderate decreases in volume or dysregulation of volume-regulatory mechanisms resulting in developmental arrest. To prevent this, early embryos possess mechanisms of cell volume control that are apparently unique to them. These rely on the accumulation of glycine and betaine (N, N, N-trimethylglycine) as organic osmolytes-compounds that can provide intracellular osmotic support without the deleterious effects of inorganic ions. Preimplantation embryos also have the same mechanisms as somatic cells that mediate rapid responses to deviations in cell volume, which rely on inorganic ion transport. Both the unique, embryo-specific mechanisms that use glycine and betaine and the inorganic ion-dependent mechanisms undergo major changes during meiotic maturation and preimplantation development. The most profound changes occur immediately after ovulation is triggered. Before this, oocytes cannot regulate their volume, since they are strongly attached to their rigid extracellular matrix shell, the zona pellucida. After ovulation is triggered, the oocyte detaches from the zona pellucida and first becomes capable of independent volume regulation. A complex set of developmental changes in each cell volume-regulatory mechanism continues through egg maturation and preimplantation development. The unique cell volume-regulatory mechanisms in eggs and preimplantation embryos and the developmental changes they undergo appear critical for normal healthy embryo development.
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Affiliation(s)
- Allison K Tscherner
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
- Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, Ontario, Canada
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Angus D Macaulay
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
- Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, Ontario, Canada
| | - Chyna S Ortman
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
- Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, Ontario, Canada
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Jay M Baltz
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
- Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, Ontario, Canada
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada
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Beppu K, Kubo N, Matsui K. Glial amplification of synaptic signals. J Physiol 2021; 599:2085-2102. [PMID: 33527421 DOI: 10.1113/jp280857] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 01/27/2021] [Indexed: 12/20/2022] Open
Abstract
KEY POINTS Recent studies have repeatedly demonstrated the cross-talk of heterogeneous signals between neuronal and glial circuits. Here, we investigated the mechanism and the influence of physiological interactions between neurons and glia in the cerebellum. We found that the cerebellar astrocytes, Bergmann glial cells, react to exogenously applied glutamate, glutamate transporter substrate (d-aspartate) and synaptically released glutamate. In response, the Bergmann glial cells release glutamate through volume-regulated anion channels. It is generally assumed that all of the postsynaptic current is mediated by presynaptically released glutamate. However, we showed that a part of the postsynaptic current is mediated by glutamate released from Bergmann glial cells. Optogenetic manipulation of Bergmann glial state with archaerhodpsin-T or channelrhodopsin-2 reduced or augmented the amount of glial glutamate release, respectively. Our data indicate that glutamate-induced glutamate release in Bergmann glia serves as an effective amplifier of excitatory information processing in the brain. ABSTRACT Transmitter released from presynaptic neurons has been considered to be the sole generator of postsynaptic excitatory signals. However, astrocytes of the glial cell population have also been shown to release transmitter that can react on postsynaptic receptors. Therefore, we investigated whether astrocytes take part in generation of at least a part of the synaptic current. In this study, mice cerebellar acute slices were prepared and whole cell patch clamp recordings were performed. We found that Bergmann glial cells (BGs), a type of astrocyte in the cerebellum, reacts to a glutamate transporter substrate, d-aspartate (d-Asp) and an anion conductance is generated and glutamate is released from the BGs. Glutamate release was attenuated or augmented by modulating the state of BGs with activation of light-sensitive proteins, archaerhodopsin-T (ArchT) or channelrhodopsin-2 (ChR2) expressed on BGs, respectively. Glutamate release appears to be mediated by anion channels that can be blocked by a volume-regulated anion channel-specific blocker. Synaptic response to a train of parallel fibre stimulation was recorded from Purkinje cells. The latter part of the response was also attenuated or augmented by glial modulation with ArchT or ChR2, respectively. Thus, BGs effectively function as an excitatory signal amplifier, and a part of the 'synaptic' current is actually mediated by glutamate released from BGs. These data show that the state of BGs have potential for having direct and fundamental consequences on the functioning of information processing in the brain.
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Affiliation(s)
- Kaoru Beppu
- Division of Interdisciplinary Medical Science, Center for Neuroscience, Graduate School of Medicine, Tohoku University, Sendai, 980-8575, Japan
| | - Naoko Kubo
- Division of Interdisciplinary Medical Science, Center for Neuroscience, Graduate School of Medicine, Tohoku University, Sendai, 980-8575, Japan
| | - Ko Matsui
- Division of Interdisciplinary Medical Science, Center for Neuroscience, Graduate School of Medicine, Tohoku University, Sendai, 980-8575, Japan.,Super-network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan
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Okada Y, Sabirov RZ, Sato-Numata K, Numata T. Cell Death Induction and Protection by Activation of Ubiquitously Expressed Anion/Cation Channels. Part 1: Roles of VSOR/VRAC in Cell Volume Regulation, Release of Double-Edged Signals and Apoptotic/Necrotic Cell Death. Front Cell Dev Biol 2021; 8:614040. [PMID: 33511120 PMCID: PMC7835517 DOI: 10.3389/fcell.2020.614040] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 12/15/2020] [Indexed: 12/18/2022] Open
Abstract
Cell volume regulation (CVR) is essential for survival and functions of animal cells. Actually, normotonic cell shrinkage and swelling are coupled to apoptotic and necrotic cell death and thus called the apoptotic volume decrease (AVD) and the necrotic volume increase (NVI), respectively. A number of ubiquitously expressed anion and cation channels are involved not only in CVD but also in cell death induction. This series of review articles address the question how cell death is induced or protected with using ubiquitously expressed ion channels such as swelling-activated anion channels, acid-activated anion channels and several types of TRP cation channels including TRPM2 and TRPM7. The Part 1 focuses on the roles of the volume-sensitive outwardly rectifying anion channels (VSOR), also called the volume-regulated anion channel (VRAC), which is activated by cell swelling or reactive oxygen species (ROS) in a manner dependent on intracellular ATP. First we describe phenotypical properties, the molecular identity, and physical pore dimensions of VSOR/VRAC. Second, we highlight the roles of VSOR/VRAC in the release of organic signaling molecules, such as glutamate, glutathione, ATP and cGAMP, that play roles as double-edged swords in cell survival. Third, we discuss how VSOR/VRAC is involved in CVR and cell volume dysregulation as well as in the induction of or protection from apoptosis, necrosis and regulated necrosis under pathophysiological conditions.
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Affiliation(s)
- Yasunobu Okada
- National Institute for Physiological Sciences, Okazaki, Japan
- Department of Physiology, School of Medicine, Aichi Medical University, Nagakute, Japan
- Department of Physiology, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Ravshan Z. Sabirov
- Laboratory of Molecular Physiology, Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent, Uzbekistan
| | - Kaori Sato-Numata
- Japan Society for the Promotion of Science, Tokyo, Japan
- Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan
| | - Tomohiro Numata
- Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, Japan
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Catacuzzeno L, Sforna L, Esposito V, Limatola C, Franciolini F. Ion Channels in Glioma Malignancy. Rev Physiol Biochem Pharmacol 2020; 181:223-267. [DOI: 10.1007/112_2020_44] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Afzal A, Figueroa EE, Kharade SV, Bittman K, Matlock BK, Flaherty DK, Denton JS. The LRRC8 volume-regulated anion channel inhibitor, DCPIB, inhibits mitochondrial respiration independently of the channel. Physiol Rep 2019; 7:e14303. [PMID: 31814333 PMCID: PMC6900491 DOI: 10.14814/phy2.14303] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
There has been a resurgence of interest in the volume-regulated anion channel (VRAC) since the recent cloning of the LRRC8A-E gene family that encodes VRAC. The channel is a heteromer comprised of LRRC8A and at least one other family member; disruption of LRRC8A expression abolishes VRAC activity. The best-in-class VRAC inhibitor, DCPIB, suffers from off-target activity toward several different channels and transporters. Considering that some anion channel inhibitors also suppress mitochondrial respiration, we systematically explored whether DCPIB inhibits respiration in wild type (WT) and LRRC8A-knockout HAP-1 and HEK-293 cells. Knockout of LRRC8A had no apparent effects on cell morphology, proliferation rate, mitochondrial content, or expression of several mitochondrial genes in HAP-1 cells. Addition of 10 µM DCPIB, a concentration typically used to inhibit VRAC, suppressed basal and ATP-linked respiration in part through uncoupling the inner mitochondrial membrane (IMM) proton gradient and membrane potential. Additionally, DCPIB inhibits the activity of complex I, II, and III of the electron transport chain (ETC). Surprisingly, the effects of DCPIB on mitochondrial function are also observed in HAP-1 and HEK-293 cells which lack LRRC8A expression. Finally, we demonstrate that DCPIB activates ATP-inhibitable potassium channels comprised of heterologously expressed Kir6.2 and SUR1 subunits. These data indicate that DCPIB suppresses mitochondrial respiration and ATP production by dissipating the mitochondrial membrane potential and inhibiting complexes I-III of the ETC. They further justify the need for the development of sharper pharmacological tools for evaluating the integrative physiology and therapeutic potential of VRAC in human diseases.
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Affiliation(s)
- Aqeela Afzal
- Department of Neurological SurgeryVanderbilt UniversityNashvilleTennessee
- Department of MedicineVanderbilt UniversityNashvilleTennessee
| | - Eric E. Figueroa
- Department of PharmacologyVanderbilt UniversityNashvilleTennessee
| | - Sujay V. Kharade
- Department of AnesthesiologyVanderbilt University Medical CenterNashvilleTennessee
| | | | - Brittany K. Matlock
- Vanderbilt Vaccine CenterVanderbilt University Medical CenterNashvilleTennessee
| | - David K. Flaherty
- Vanderbilt Vaccine CenterVanderbilt University Medical CenterNashvilleTennessee
| | - Jerod S. Denton
- Department of PharmacologyVanderbilt UniversityNashvilleTennessee
- Department of AnesthesiologyVanderbilt University Medical CenterNashvilleTennessee
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Absolute Protein Amounts and Relative Abundance of Volume-regulated Anion Channel (VRAC) LRRC8 Subunits in Cells and Tissues Revealed by Quantitative Immunoblotting. Int J Mol Sci 2019; 20:ijms20235879. [PMID: 31771171 PMCID: PMC6928916 DOI: 10.3390/ijms20235879] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 11/11/2019] [Accepted: 11/21/2019] [Indexed: 12/13/2022] Open
Abstract
The volume-regulated anion channel (VRAC) plays an important role in osmotic cell volume regulation. In addition, it is involved in various physiological processes such as insulin secretion, glia-neuron communication and purinergic signaling. VRAC is formed by hetero-hexamers of members of the LRRC8 protein family, which consists of five members, LRRC8A-E. LRRC8A is an essential subunit for physiological functionality of VRAC. Its obligate heteromerization with at least one of its paralogues, LRRC8B-E, determines the biophysical properties of VRAC. Moreover, the subunit composition is of physiological relevance as it largely influences the activation mechanism and especially the substrate selectivity. However, the endogenous tissue-specific subunit composition of VRAC is unknown. We have now developed and applied a quantitative immunoblot study of the five VRAC LRRC8 subunits in various mouse cell lines and tissues, using recombinant protein for signal calibration. We found tissue-specific expression patterns of the subunits, and generally relative low expression of the essential LRRC8A subunit. Immunoprecipitation of LRRC8A also co-precipitates an excess of the other subunits, suggesting that non-LRRC8A subunits present the majority in hetero-hexamers. With this, we can estimate that in the tested cell lines, the number of VRAC channels per cell is in the order of 10,000, which is in agreement with earlier calculations from the comparison of single-channel and whole-cell currents.
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Trothe J, Ritzmann D, Lang V, Scholz P, Pul Ü, Kaufmann R, Buerger C, Ertongur-Fauth T. Hypotonic stress response of human keratinocytes involves LRRC8A as component of volume-regulated anion channels. Exp Dermatol 2019; 27:1352-1360. [PMID: 30252954 DOI: 10.1111/exd.13789] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 09/16/2018] [Indexed: 01/02/2023]
Abstract
The barrier function of the human epidermis is constantly challenged by environmental osmotic fluctuations. Hypotonic stress triggers cell swelling, which is counteracted by a compensatory mechanism called regulatory volume decrease (RVD) involving volume-regulated anion channels (VRACs). Recently, it was discovered that VRACs are composed of LRRC8 heteromers and that LRRC8A functions as the essential VRAC subunit in various mammalian cell types; however, the molecular identity of VRACs in the human epidermis remains to be determined. Here, we investigated the expression of LRRC8A and its role in hypotonic stress response of human keratinocytes. Immunohistological staining showed that LRRC8A is preferentially localized in basal and suprabasal epidermal layers. RNA sequencing revealed that LRRC8A is the most abundant subunit within the LRRC8 gene family in HaCaT cells as well as in primary normal human epidermal keratinocytes (NHEKs). To determine the contribution of LRRC8A to hypotonic stress response, we generated HaCaT- and NHEK-LRRC8A knockout cells by using CRISPR-Cas9. I- influx assays using halide-sensitive YFP showed that LRRC8A is crucially important for mediating VRAC activity in HaCaTs and NHEKs. Moreover, cell volume measurements using calcein-AM dye further revealed that LRRC8A also substantially contributes to RVD. In summary, our study provides new insights into hypotonic stress response and suggests an important role of LRRC8A as VRAC component in human keratinocytes.
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Affiliation(s)
| | | | - Victoria Lang
- Department of Dermatology, Venerology and Allergology, Clinic of the Goethe-University, Frankfurt am Main, Germany
| | | | | | - Roland Kaufmann
- Department of Dermatology, Venerology and Allergology, Clinic of the Goethe-University, Frankfurt am Main, Germany
| | - Claudia Buerger
- Department of Dermatology, Venerology and Allergology, Clinic of the Goethe-University, Frankfurt am Main, Germany
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Lu P, Ding Q, Li X, Ji X, Li L, Fan Y, Xia Y, Tian D, Liu M. SWELL1 promotes cell growth and metastasis of hepatocellular carcinoma in vitro and in vivo. EBioMedicine 2019; 48:100-116. [PMID: 31597595 PMCID: PMC6838441 DOI: 10.1016/j.ebiom.2019.09.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 09/04/2019] [Accepted: 09/05/2019] [Indexed: 12/20/2022] Open
Abstract
Background SWELL1 was recently demonstrated to be an indispensable part of the volume-regulated anion channel (VRAC). VRAC is reported to participate in cell proliferation, survival, and migration. However, the correlation between SWELL1 and hepatocellular carcinoma (HCC) remains poorly-understood. In this study, we tried to explore the role of SWELL1 in HCC. Methods Immunohistochemistry and quantitative real-time-PCR (qRT-PCR) was used to measure SWELL1 expression in HCC samples obtained from patients with HCC. The effects of SWELL1 on HCC cell proliferation, apoptosis, and metastasis were analysed by corresponding cytological experiments including Cell Counting Kit-8 (CCK8), colony-forming, 5-ethynyl-2′-deoxyuridine (EdU), cell cycle analysis, TUNEL, Annexin V and PI staining, wound healing, transwell, and so on. BALB/c nude mice were used for the in vivo assays. qRT-PCR and western blotting was performed for molecular mechanisms. Findings SWELL1 was highly expressed in HCC tissues, and related to the poor prognosis. In vitro, the over-expression of SWELL1 significantly induced cell proliferation and migration, and inhibited apoptosis, whereas suppressing SWELL1 had the opposite effects. Moreover, knockdown of SWELL1 suppressed the growth and metastasis of HCC in vivo. Further experiments revealed that SWELL1 induced cell growth by activating the cyclinD1/CDK2 pathway via the connection with PKCa at the signalling level, and regulated cell migration through the JNK pathway in HCC. Interpretation SWELL1 acts as a promoter in the growth and metastasis of HCC cells and may be a potential intervention target for HCC. Fund This work is supported by the National Natural Science Foundation of China (No. 81572422, 81700515).
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Affiliation(s)
- Panpan Lu
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Qiang Ding
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Xin Li
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Xiaoyu Ji
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Lili Li
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Yuhui Fan
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China; Department of Gastroenterology, Internal Medicine II, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Yujia Xia
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Dean Tian
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China
| | - Mei Liu
- Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, China.
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Figueroa EE, Kramer M, Strange K, Denton JS. CysLT1 receptor antagonists pranlukast and zafirlukast inhibit LRRC8-mediated volume regulated anion channels independently of the receptor. Am J Physiol Cell Physiol 2019; 317:C857-C866. [PMID: 31390227 PMCID: PMC6850990 DOI: 10.1152/ajpcell.00281.2019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Volume-regulated anion channels (VRACs) encoded by the leucine-rich repeat containing 8 (LRRC8) gene family play critical roles in myriad cellular processes and might represent druggable targets. The dearth of pharmacological compounds available for studying VRAC physiology led us to perform a high-throughput screen of 1,184 of US Food and Drug Administration-approved drugs for novel VRAC modulators. We discovered the cysteinyl leukotriene receptor 1 (CysLT1R) antagonist, pranlukast, as a novel inhibitor of endogenous VRAC expressed in human embryonic kidney 293 (HEK293) cells. Pranlukast inhibits VRAC voltage-independently, reversibly, and dose-dependently with a maximal efficacy of only ~50%. The CysLT1R pathway has been implicated in activation of VRAC in other cell types, prompting us to test whether pranlukast requires the CysLT1R for inhibition of VRAC. Quantitative PCR analysis demonstrated that CYSLTR1 mRNA is virtually undetectable in HEK293 cells. Furthermore, the CysLT1R agonist leukotriene D4 had no effect on VRAC activity and failed to stimulate Gq-coupled receptor signaling. Heterologous expression of the CysLT1R reconstituted LTD4-CysLT1R- Gq-calcium signaling in HEK293 cells but had no effect on VRAC inhibition by pranlukast. Finally, we show the CysLT1R antagonist zafirlukast inhibits VRAC with an IC50 of ~17 µM and does so with full efficacy. Our data suggest that both pranlukast and zafirlukast are likely direct channel inhibitors that work independently of the CysLT1R. This study provides clarifying insights into the putative role of leukotriene signaling in modulation of VRAC and identifies two new chemical scaffolds that can be used for development of more potent and specific VRAC inhibitors.
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Affiliation(s)
- Eric E. Figueroa
- 1Department of Pharmacology, Vanderbilt University, Nashville, Tennessee
| | - Meghan Kramer
- 2Department of Anesthesiology, Vanderbilt University Medical Center; Nashville, Tennessee
| | - Kevin Strange
- 2Department of Anesthesiology, Vanderbilt University Medical Center; Nashville, Tennessee,3Novo Biosciences, Inc., Bar Harbor, Maine
| | - Jerod S. Denton
- 1Department of Pharmacology, Vanderbilt University, Nashville, Tennessee,2Department of Anesthesiology, Vanderbilt University Medical Center; Nashville, Tennessee
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Chen L, König B, Liu T, Pervaiz S, Razzaque YS, Stauber T. More than just a pressure relief valve: physiological roles of volume-regulated LRRC8 anion channels. Biol Chem 2019; 400:1481-1496. [DOI: 10.1515/hsz-2019-0189] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 04/27/2019] [Indexed: 12/29/2022]
Abstract
Abstract
The volume-regulated anion channel (VRAC) is a key player in the volume regulation of vertebrate cells. This ubiquitously expressed channel opens upon osmotic cell swelling and potentially other cues and releases chloride and organic osmolytes, which contributes to regulatory volume decrease (RVD). A plethora of studies have proposed a wide range of physiological roles for VRAC beyond volume regulation including cell proliferation, differentiation and migration, apoptosis, intercellular communication by direct release of signaling molecules and by supporting the exocytosis of insulin. VRAC was additionally implicated in pathological states such as cancer therapy resistance and excitotoxicity under ischemic conditions. Following extensive investigations, 5 years ago leucine-rich repeat-containing family 8 (LRRC8) heteromers containing LRRC8A were identified as the pore-forming components of VRAC. Since then, molecular biological approaches have allowed further insight into the biophysical properties and structure of VRAC. Heterologous expression, siRNA-mediated downregulation and genome editing in cells, as well as the use of animal models have enabled the assessment of the proposed physiological roles, together with the identification of new functions including spermatogenesis and the uptake of antibiotics and platinum-based cancer drugs. This review discusses the recent molecular biological insights into the physiology of VRAC in relation to its previously proposed roles.
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Affiliation(s)
- Lingye Chen
- Institut für Chemie und Biochemie , Freie Universität Berlin , Thielallee 63 , D-14195 Berlin , Germany
| | - Benjamin König
- Institut für Chemie und Biochemie , Freie Universität Berlin , Thielallee 63 , D-14195 Berlin , Germany
| | - Tianbao Liu
- Institut für Chemie und Biochemie , Freie Universität Berlin , Thielallee 63 , D-14195 Berlin , Germany
| | - Sumaira Pervaiz
- Institut für Chemie und Biochemie , Freie Universität Berlin , Thielallee 63 , D-14195 Berlin , Germany
| | - Yasmin S. Razzaque
- Institut für Chemie und Biochemie , Freie Universität Berlin , Thielallee 63 , D-14195 Berlin , Germany
| | - Tobias Stauber
- Institut für Chemie und Biochemie , Freie Universität Berlin , Thielallee 63 , D-14195 Berlin , Germany
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Liu Y, Zhang H, Men H, Du Y, Xiao Z, Zhang F, Huang D, Du X, Gamper N, Zhang H. Volume-regulated Cl - current: contributions of distinct Cl - channels and localized Ca 2+ signals. Am J Physiol Cell Physiol 2019; 317:C466-C480. [PMID: 31242393 DOI: 10.1152/ajpcell.00507.2018] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The swelling-activated chloride current (ICl,swell) is induced when a cell swells and plays a central role in maintaining cell volume in response to osmotic stress. The major contributor of ICl,swell is the volume-regulated anion channel (VRAC). Leucine-rich repeat containing 8A (LRRC8A; SWELL1) was recently identified as an essential component of VRAC, but the mechanisms of VRAC activation are still largely unknown; moreover, other Cl- channels, such as anoctamin 1 (ANO1), were also suggested to contribute to ICl,swell. In this present study, we investigated the roles of LRRC8A and ANO1 in activation of ICl,swell; we also explored the role of intracellular Ca2+ in ICl,swell activation. We used a CRISPR/Cas9 gene editing approach, electrophysiology, live fluorescent imaging, selective pharmacology, and other approaches to show that both LRRC8A and ANO1 can be activated by cell swelling in HEK293 cells. Yet, both channels contribute biophysically and pharmacologically distinct components to ICl,swell, with LRRC8A being the major component. Cell swelling induced oscillatory Ca2+ transients, and these Ca2+ signals were required to activate both the LRRC8A- and ANO1-dependent components of ICl,swell. Both ICl,swell components required localized rather than global Ca2+ for activation. Interestingly, while intracellular Ca2+ was necessary and sufficient to activate ANO1, it was necessary but not sufficient to activate LRRC8A-mediated currents. Finally, Ca2+ transients linked to the ICl,swell activation were mediated by the G protein-coupled receptor-independent PLC isoforms.
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Affiliation(s)
- Yani Liu
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China.,Department of Pharmacology, School of Pharmacy, Qingdao University, Qingdao, China
| | - Huiran Zhang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China.,Department of Pulmonary Medicine, the Second Hospital of Hebei Medical University, Shijiazhuang, China
| | - Hongchao Men
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
| | - Yuwei Du
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
| | - Ziqian Xiao
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
| | - Fan Zhang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
| | - Dongyang Huang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
| | - Xiaona Du
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
| | - Nikita Gamper
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China.,School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, China.,The Key Laboratory of New Drug Pharmacology and Toxicology, Shijiazhuang, China
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König B, Hao Y, Schwartz S, Plested AJ, Stauber T. A FRET sensor of C-terminal movement reveals VRAC activation by plasma membrane DAG signaling rather than ionic strength. eLife 2019; 8:45421. [PMID: 31210638 PMCID: PMC6597245 DOI: 10.7554/elife.45421] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 06/14/2019] [Indexed: 12/13/2022] Open
Abstract
Volume-regulated anion channels (VRACs) are central to cell volume regulation. Recently identified as hetero-hexamers formed by LRRC8 proteins, their activation mechanism remains elusive. Here, we measured Förster resonance energy transfer (FRET) between fluorescent proteins fused to the C-termini of LRRC8 subunits. Inter-subunit FRET from LRRC8 complexes tracked VRAC activation. With patch-clamp fluorometry, we confirmed that the cytoplasmic domains rearrange during VRAC opening. With these FRET reporters, we determined VRAC activation, non-invasively, in live cells and their subcompartments. Reduced intracellular ionic strength did not directly activate VRACs, and VRACs were not activated on endomembranes. Instead, pharmacological manipulation of diacylglycerol (DAG), and protein kinase D (PKD) activity, activated or inhibited plasma membrane-localized VRACs. Finally, we resolved previous contradictory reports concerning VRAC activation, using FRET to detect robust activation by PMA that was absent during whole-cell patch clamp. Overall, non-invasive VRAC measurement by FRET is an essential tool for unraveling its activation mechanism.
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Affiliation(s)
- Benjamin König
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Yuchen Hao
- Institute of Biology, Humboldt Universität zu Berlin, Berlin, Germany.,Leibniz Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,NeuroCure, Charité Universitätsmedizin, Berlin, Germany
| | - Sophia Schwartz
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Andrew Jr Plested
- Institute of Biology, Humboldt Universität zu Berlin, Berlin, Germany.,Leibniz Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,NeuroCure, Charité Universitätsmedizin, Berlin, Germany
| | - Tobias Stauber
- Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
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Wilson CS, Bach MD, Ashkavand Z, Norman KR, Martino N, Adam AP, Mongin AA. Metabolic constraints of swelling-activated glutamate release in astrocytes and their implication for ischemic tissue damage. J Neurochem 2019; 151:255-272. [PMID: 31032919 DOI: 10.1111/jnc.14711] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Revised: 03/01/2019] [Accepted: 04/10/2019] [Indexed: 12/20/2022]
Abstract
Volume-regulated anion channel (VRAC) is a glutamate-permeable channel that is activated by physiological and pathological cell swelling and promotes ischemic brain damage. However, because VRAC opening requires cytosolic ATP, it is not clear if and how its activity is sustained in the metabolically compromised CNS. In the present study, we used cultured astrocytes - the cell type which shows prominent swelling in stroke - to model how metabolic stress and changes in gene expression may impact VRAC function in the ischemic and post-ischemic brain. The metabolic state of primary rat astrocytes was modified with chemical inhibitors and examined using luciferin-luciferase ATP assays and a Seahorse analyzer. Swelling-activated glutamate release was quantified with the radiotracer D-[3 H]aspartate. The specific contribution of VRAC to swelling-activated glutamate efflux was validated by RNAi knockdown of the essential subunit, leucine-rich repeat-containing 8A (LRRC8A); expression levels of VRAC components were measured with qRT-PCR. Using this methodology, we found that complete metabolic inhibition with the glycolysis blocker 2-deoxy-D-glucose and the mitochondrial poison sodium cyanide reduced astrocytic ATP levels by > 90% and abolished glutamate release from swollen cells (via VRAC). When only mitochondrial respiration was inhibited by cyanide or rotenone, the intracellular ATP levels and VRAC activity were largely preserved. Bypassing glycolysis by providing the mitochondrial substrates pyruvate and/or glutamine led to partial recovery of ATP levels and VRAC activity. Unexpectedly, the metabolic block of VRAC was overridden when ATP-depleted cells were exposed to extreme cell swelling (≥ 50% reduction in medium osmolarity). Twenty-four hour anoxic adaptation caused a moderate reduction in the expression levels of the VRAC component LRRC8A, but no significant changes in VRAC activity. Overall, our findings suggest that (i) astrocytic VRAC activity and metabolism can be sustained by low levels of glucose and (ii) the inhibitory influence of diminishing ATP levels and the stimulatory effect of cellular swelling are the two major factors that govern VRAC activity in the ischemic brain.
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Affiliation(s)
- Corinne S Wilson
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
| | - Martin D Bach
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
| | - Zahra Ashkavand
- Department of Regenerative and Cancer Cell Biology, Albany Medical College, Albany, New York, USA
| | - Kenneth R Norman
- Department of Regenerative and Cancer Cell Biology, Albany Medical College, Albany, New York, USA
| | - Nina Martino
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York, USA
| | - Alejandro P Adam
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York, USA
| | - Alexander A Mongin
- Department of Neuroscience and Experimental Therapeutics, Albany Medical College, Albany, New York, USA
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Yang J, Vitery MDC, Chen J, Osei-Owusu J, Chu J, Qiu Z. Glutamate-Releasing SWELL1 Channel in Astrocytes Modulates Synaptic Transmission and Promotes Brain Damage in Stroke. Neuron 2019; 102:813-827.e6. [PMID: 30982627 DOI: 10.1016/j.neuron.2019.03.029] [Citation(s) in RCA: 132] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 12/14/2018] [Accepted: 03/19/2019] [Indexed: 01/01/2023]
Abstract
By releasing glutamate, astrocytes actively regulate synaptic transmission and contribute to excitotoxicity in neurological diseases. However, the mechanisms of astrocytic glutamate release have been debated. Here, we report non-vesicular release of glutamate through the glutamate-permeable volume-regulated anion channel (VRAC). Both cell swelling and receptor stimulation activated astrocytic VRAC, which requires its only obligatory subunit, Swell1. Astrocyte-specific Swell1 knockout mice exhibited impaired glutamatergic transmission due to the decreases in presynaptic release probability and ambient glutamate level. Consistently, the mutant mice displayed hippocampal-dependent learning and memory deficits. During pathological cell swelling, deletion of astrocytic Swell1 attenuated glutamate-dependent neuronal excitability and protected mice from brain damage after ischemic stroke. Our identification of a new molecular mechanism for channel-mediated glutamate release establishes a role for astrocyte-neuron interactions in both synaptic transmission and brain ischemia. It provides a rationale for targeting VRAC for the treatment of stroke and other neurological diseases associated with excitotoxicity.
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Affiliation(s)
- Junhua Yang
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Maria Del Carmen Vitery
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jianan Chen
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - James Osei-Owusu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Jiachen Chu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Zhaozhu Qiu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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The LRRC8-mediated volume-regulated anion channel is altered in glaucoma. Sci Rep 2019; 9:5392. [PMID: 30931966 PMCID: PMC6443673 DOI: 10.1038/s41598-019-41524-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 03/04/2019] [Indexed: 01/07/2023] Open
Abstract
Regulation of cellular volume is an essential process to balance volume changes during cell proliferation and migration or when intracellular osmolality increases due to transepithelial transport. We previously characterized the key role of volume-regulated anion channels (VRAC) in the modulation of the volume of trabecular meshwork (TM) cells and, in turn, the aqueous humour (AH) outflow from the eye. The balance between the secretion and the drainage of AH determines the intraocular pressure (IOP) that is the major casual risk factor for glaucoma. Glaucoma is an ocular disease that causes irreversible blindness due to the degeneration of retinal ganglion cells. The recent identification of Leucine-Rich Repeat-Containing 8 (LRRC8A-E) proteins as the molecular components of VRAC opens the field to elucidate their function in the physiology of TM and glaucoma. Human TM cells derived from non-glaucomatous donors and from open-angle glaucoma patients were used to determine the expression and the functional activity of LRRC8-mediated channels. Expression levels of LRRC8A-E subunits were decreased in HTM glaucomatous cells compared to normotensive HTM cells. Consequently, the activity of VRAC currents and volume regulation of TM cells were significantly affected. Impaired cell volume regulation will likely contribute to altered aqueous outflow and intraocular pressure.
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