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Lin Y, Lee C, Sung J, Chen C. Genetic exploration of roles of acid-sensing ion channel subtypes in neurosensory mechanotransduction including proprioception. Exp Physiol 2024; 109:66-80. [PMID: 37489658 PMCID: PMC10988671 DOI: 10.1113/ep090762] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 07/03/2023] [Indexed: 07/26/2023]
Abstract
Although acid-sensing ion channels (ASICs) are proton-gated ion channels responsible for sensing tissue acidosis, accumulating evidence has shown that ASICs are also involved in neurosensory mechanotransduction. However, in contrast to Piezo ion channels, evidence of ASICs as mechanically gated ion channels has not been found using conventional mechanoclamp approaches. Instead, ASICs are involved in the tether model of mechanotransduction, with the channels gated via tethering elements of extracellular matrix and intracellular cytoskeletons. Methods using substrate deformation-driven neurite stretch and micropipette-guided ultrasound were developed to reveal the roles of ASIC3 and ASIC1a, respectively. Here we summarize the evidence supporting the roles of ASICs in neurosensory mechanotransduction in knockout mouse models of ASIC subtypes and provide insight to further probe their roles in proprioception.
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Affiliation(s)
- Yi‐Chen Lin
- Department of Neurology, Wan Fang HospitalTaipei Medical UniversityTaipeiTaiwan
- The Ph.D. Program for Translational MedicineTaipei Medical University and Academia SinicaNew Taipei CityTaiwan
- Taipei Neuroscience InstituteTaipei Medical UniversityNew Taipei CityTaiwan
- Institute of Biomedical SciencesAcademia SinicaTaipeiTaiwan
| | - Cheng‐Han Lee
- Institute of Biomedical SciencesAcademia SinicaTaipeiTaiwan
- Neuroscience Program of Academia SinicaAcademia SinicaTaipeiTaiwan
| | - Jia‐Ying Sung
- Department of Neurology, Wan Fang HospitalTaipei Medical UniversityTaipeiTaiwan
- Taipei Neuroscience InstituteTaipei Medical UniversityNew Taipei CityTaiwan
- Department of Neurology, School of Medicine, College of MedicineTaipei Medical UniversityTaipeiTaiwan
| | - Chih‐Cheng Chen
- The Ph.D. Program for Translational MedicineTaipei Medical University and Academia SinicaNew Taipei CityTaiwan
- Institute of Biomedical SciencesAcademia SinicaTaipeiTaiwan
- Neuroscience Program of Academia SinicaAcademia SinicaTaipeiTaiwan
- Taiwan Mouse Clinic – National Comprehensive Mouse Phenotyping and Drug Testing CenterAcademia SinicaTaipeiTaiwan
- TMU Neuroscience Research Center, Taipei Medical UniversityNew Taipei CityTaiwan
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2
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Hung CH, Chin Y, Fong YO, Lee CH, Han DS, Lin JH, Sun WH, Chen CC. Acidosis-related pain and its receptors as targets for chronic pain. Pharmacol Ther 2023; 247:108444. [PMID: 37210007 DOI: 10.1016/j.pharmthera.2023.108444] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 04/24/2023] [Accepted: 05/15/2023] [Indexed: 05/22/2023]
Abstract
Sensing acidosis is an important somatosensory function in responses to ischemia, inflammation, and metabolic alteration. Accumulating evidence has shown that acidosis is an effective factor for pain induction and that many intractable chronic pain diseases are associated with acidosis signaling. Various receptors have been known to detect extracellular acidosis and all express in the somatosensory neurons, such as acid sensing ion channels (ASIC), transient receptor potential (TRP) channels and proton-sensing G-protein coupled receptors. In addition to sense noxious acidic stimulation, these proton-sensing receptors also play a vital role in pain processing. For example, ASICs and TRPs are involved in not only nociceptive activation but also anti-nociceptive effects as well as some other non-nociceptive pathways. Herein, we review recent progress in probing the roles of proton-sensing receptors in preclinical pain research and their clinical relevance. We also propose a new concept of sngception to address the specific somatosensory function of acid sensation. This review aims to connect these acid-sensing receptors with basic pain research and clinical pain diseases, thus helping with better understanding the acid-related pain pathogenesis and their potential therapeutic roles via the mechanism of acid-mediated antinociception.
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Affiliation(s)
- Chih-Hsien Hung
- Department of Neurology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan; School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Yin Chin
- Department of Life Science & Institute of Genome Sciences, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Yi-On Fong
- Department of Neurology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan; School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Cheng-Han Lee
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan
| | - Der-Shen Han
- Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Bei-Hu Branch, Taipei, Taiwan
| | - Jiann-Her Lin
- Neuroscience Research Center, Taipei Medical University, Taipei, Taiwan; Department of Neurosurgery, Taipei Medical University Hospital, Taipei, Taiwan
| | - Wei-Hsin Sun
- Department of Life Science & Institute of Genome Sciences, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Chih-Cheng Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan; Neuroscience Research Center, Taipei Medical University, Taipei, Taiwan; Neuroscience Program of Academia Sinica, Academia Sinica, Taipei, Taiwan.
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3
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Zhang L, Zheng L, Yang X, Yao S, Wang H, An J, Jin H, Wen G, Tuo B. Pathology and physiology of acid‑sensitive ion channels in the digestive system (Review). Int J Mol Med 2022; 50:94. [PMID: 35616162 PMCID: PMC9170189 DOI: 10.3892/ijmm.2022.5150] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 05/11/2022] [Indexed: 11/16/2022] Open
Abstract
As a major proton-gated cation channel, acid-sensitive ion channels (ASICs) can perceive large extracellular pH changes. ASICs play an important role in the occurrence and development of diseases of various organs and tissues including in the heart, brain, and gastrointestinal tract, as well as in tumor proliferation, invasion, and metastasis in acidosis and regulation of an acidic microenvironment. The permeability of ASICs to sodium and calcium ions is the basis of their physiological and pathological roles in the body. This review summarizes the physiological and pathological mechanisms of ASICs in digestive system diseases, which plays an important role in the early diagnosis, treatment, and prognosis of digestive system diseases related to ASIC expression.
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Affiliation(s)
- Li Zhang
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Liming Zheng
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Xingyue Yang
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Shun Yao
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Hui Wang
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Jiaxing An
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Hai Jin
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Guorong Wen
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Biguang Tuo
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
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4
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Sivils A, Yang F, Wang JQ, Chu XP. Acid-Sensing Ion Channel 2: Function and Modulation. MEMBRANES 2022; 12:membranes12020113. [PMID: 35207035 PMCID: PMC8880099 DOI: 10.3390/membranes12020113] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Revised: 01/14/2022] [Accepted: 01/17/2022] [Indexed: 01/08/2023]
Abstract
Acid-sensing ion channels (ASICs) have an important influence on human physiology and pathology. They are members of the degenerin/epithelial sodium channel family. Four genes encode at least six subunits, which combine to form a variety of homotrimers and heterotrimers. Of these, ASIC1a homotrimers and ASIC1a/2 heterotrimers are most widely expressed in the central nervous system (CNS). Investigations into the function of ASIC1a in the CNS have revealed a wealth of information, culminating in multiple contemporary reviews. The lesser-studied ASIC2 subunits are in need of examination. This review will focus on ASIC2 in health and disease, with discussions of its role in modulating ASIC function, synaptic targeting, cardiovascular responses, and pharmacology, while exploring evidence of its influence in pathologies such as ischemic brain injury, multiple sclerosis, epilepsy, migraines, drug addiction, etc. This information substantiates the ASIC2 protein as a potential therapeutic target for various neurological, psychological, and cerebrovascular diseases.
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Affiliation(s)
| | | | | | - Xiang-Ping Chu
- Correspondence: ; Tel.: +1-816-235-2248; Fax: +1-816-235-6517
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Kitcher SR, Pederson AM, Weisz CJC. Diverse identities and sites of action of cochlear neurotransmitters. Hear Res 2021; 419:108278. [PMID: 34108087 DOI: 10.1016/j.heares.2021.108278] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 04/30/2021] [Accepted: 05/18/2021] [Indexed: 11/18/2022]
Abstract
Accurate encoding of acoustic stimuli requires temporally precise responses to sound integrated with cellular mechanisms that encode the complexity of stimuli over varying timescales and orders of magnitude of intensity. Sound in mammals is initially encoded in the cochlea, the peripheral hearing organ, which contains functionally specialized cells (including hair cells, afferent and efferent neurons, and a multitude of supporting cells) to allow faithful acoustic perception. To accomplish the demanding physiological requirements of hearing, the cochlea has developed synaptic arrangements that operate over different timescales, with varied strengths, and with the ability to adjust function in dynamic hearing conditions. Multiple neurotransmitters interact to support the precision and complexity of hearing. Here, we review the location of release, action, and function of neurotransmitters in the mammalian cochlea with an emphasis on recent work describing the complexity of signaling.
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Affiliation(s)
- Siân R Kitcher
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States
| | - Alia M Pederson
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States
| | - Catherine J C Weisz
- Section on Neuronal Circuitry, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD 20892, United States.
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Citric Acid in Drug Formulations Causes Pain by Potentiating Acid-Sensing Ion Channel 1. J Neurosci 2021; 41:4596-4606. [PMID: 33888605 PMCID: PMC8260239 DOI: 10.1523/jneurosci.2087-20.2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 12/08/2020] [Accepted: 04/10/2021] [Indexed: 11/21/2022] Open
Abstract
Pain at the injection site is a common complaint of patients receiving therapeutic formulations containing citric acid. Despite the widely acknowledged role of acid-sensing ion channels (ASICs) in acid-related perception, the specific ASIC subtype mediating pain caused by subcutaneous acid injection and the mechanism by which citrate affects this process are less clear. Here, male mice subjected to intraplantar acid injection responded by executing a withdrawal reflex, and this response was abolished by ASIC1 but not ASIC2 knockout. Although intraplantar injection of neutral citrate solution did not produce this response, intraplantar injection of acidic citrate solution produced a withdrawal reflex greater than that produced by acidity alone. Consistent with the behavioral data, neutral citrate failed to produce an electrophysiological response in HEK293 cells, which express ASIC1, but acidic citrate produced a whole-cell inward current greater than that produced by acidity alone. Saturating the intracellular solution with citrate had no effect on the potentiating effect of extracellular citrate, suggesting that citrate acted extracellularly to potentiate ASIC1. Moreover, exposure to citrate immediately before acid stimulation failed to potentiate ASIC1 currents, which ruled out the involvement of a metabotropic receptor gated by a citrate metabolite. Finally, removal of calcium ions from the extracellular solution mimicked the potentiating effect of citrate and prevented citrate from further potentiating ASIC1. Our data demonstrate that ASIC1 is necessary for the nociceptive response caused by subcutaneous acid infusion and that neutral citrate, despite not inducing ASIC1 currents or nociceptive behavior on its own, potentiates acid nociception by removing the inhibitory effect of extracellular calcium ions on ASIC1. SIGNIFICANCE STATEMENT Citric acid is a common ingredient used in pharmaceutical formulations. Despite the widespread clinical use of these formulations, it remains unclear how citric acid causes pain when injected into patients. We identified ASIC1 as the key receptor used to detect injection-site pain caused by acid, and we showed that neutral citrate does not stimulate ASIC1; instead, citrate substantially potentiates ASIC1 activation when injected simultaneously with acid. In addition, we demonstrated that citrate potentiates ASIC1 by removing the inhibitory action of calcium on the extracellular side of the receptor. Given that injection-site pain is the primary complaint of patients receiving citrate-containing medical products, our data provide mechanistic insight into a common medical complaint and suggest a means of avoiding injection pain.
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Wang K, Kretschmannova K, Prévide RM, Smiljanic K, Chen Q, Fletcher PA, Sherman A, Stojilkovic SS. Cell-Type-Specific Expression Pattern of Proton-Sensing Receptors and Channels in Pituitary Gland. Biophys J 2020; 119:2335-2348. [PMID: 33098866 DOI: 10.1016/j.bpj.2020.10.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 06/29/2020] [Accepted: 10/15/2020] [Indexed: 12/14/2022] Open
Abstract
In mammalian cells, extracellular protons act as orthosteric and allosteric ligands for multiple receptors and channels. The aim of this study is to identify proton sensors in the rat pituitary gland. qRT-PCR analysis indicated the expression of G-protein-coupled receptor 68 gene (Gpr68) and acid-sensing ion channel (ASIC) genes Asic1, Asic2, and Asic4 in anterior pituitary cells and Asic1 and Asic2 in immortalized GH3 pituitary cells. Asic1a and Asic2b were the dominant splice isoforms. Single anterior pituitary cell RNA sequencing and immunocytochemical analysis showed that nonexcitable folliculostellate cells express GPR68 gene and protein, whereas excitable secretory cells express ASIC genes and proteins. Asic1 was detected in all secretory cell types, Asic2 in gonadotrophs, thyrotrophs, and somatotrophs, and Asic4 in lactotrophs. Extracellular acidification activated two types of currents in a concentration-dependent manner: a fast-developing, desensitizing current with an estimated EC50-value of pH 6.7 and a slow-developing, non-desensitizing current that required a higher proton concentration for activation. The desensitizing current was abolished by removal of bath sodium and application of amiloride, a blocker of ASIC channels, whereas the non-desensitizing current was amiloride insensitive and voltage dependent. Activation of both currents increased the excitability of secretory pituitary cells, consistent with their potential physiological relevance in control of voltage-gated calcium influx and calcium-dependent cellular functions.
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Affiliation(s)
- Kai Wang
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland
| | - Karla Kretschmannova
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland
| | - Rafael M Prévide
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland
| | - Kosara Smiljanic
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland
| | - Qing Chen
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland
| | - Patrick A Fletcher
- Laboratory of Biological Modeling, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Arthur Sherman
- Laboratory of Biological Modeling, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Stanko S Stojilkovic
- Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland.
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8
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Fuster-García C, García-García G, Jaijo T, Blanco-Kelly F, Tian L, Hakonarson H, Ayuso C, Aller E, Millán JM. Expanding the Genetic Landscape of Usher-Like Phenotypes. Invest Ophthalmol Vis Sci 2020; 60:4701-4710. [PMID: 31725169 DOI: 10.1167/iovs.19-27470] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Usher syndrome (USH) is a rare disorder characterized by retinitis pigmentosa (RP) and sensorineural hearing loss. Several genes are responsible for the disease, but not all cases are explained by mutations in any of these, supporting the fact that there remain other unknown genes that have a role in the syndrome. We aimed to find the genetic cause of presumed USH patients lacking pathogenic mutations in the known USH genes. Methods Whole exome sequencing was performed on a priori USH-diagnosed subjects from nine unrelated families, which had shown negative results for an USH-targeted panel in a previous study. Results We identified possible pathogenic variants in six of the studied families. One patient harbored mutations in REEP6 and TECTA, each gene tentatively causative of one of the two main symptoms of the disease, mimicking the syndrome. In three patients, only the retinal degeneration causative mutations were detected (involving EYS, WDR19, and CNGB1 genes). Another family manifested a dementia-linked retinal dystrophy dependent on an allele dosage in the GRN gene. Last, another case presented a homozygous mutation in ASIC5, a gene not yet associated with USH. Conclusions Our findings demonstrate that pending cases should be clinically and genetically carefully assessed, since more patients than expected may be either related phenocopies or affected by a more complex disease encompassing additional symptoms rather than classical USH.
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Affiliation(s)
- Carla Fuster-García
- Grupo de Investigación en Biomedicina Molecular, Celular y Genómica, Instituto de Investigación Sanitaria La Fe (IIS La Fe), Valencia, Spain.,CIBER de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Gema García-García
- Grupo de Investigación en Biomedicina Molecular, Celular y Genómica, Instituto de Investigación Sanitaria La Fe (IIS La Fe), Valencia, Spain.,CIBER de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Teresa Jaijo
- Grupo de Investigación en Biomedicina Molecular, Celular y Genómica, Instituto de Investigación Sanitaria La Fe (IIS La Fe), Valencia, Spain.,CIBER de Enfermedades Raras (CIBERER), Madrid, Spain.,Unidad de Genética y Diagnóstico Prenatal, Hospital Universitario y Politécnico La Fe, Valencia, Spain
| | - Fiona Blanco-Kelly
- CIBER de Enfermedades Raras (CIBERER), Madrid, Spain.,Servicio de Genética, Fundación Jiménez Díaz, University Hospital, Instituto de Investigación Sanitaria Fundación Jiménez Díaz IIS-FJD, UAM, Madrid, Spain
| | - Lifeng Tian
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Pennsylvania, United States
| | - Hakon Hakonarson
- Center for Applied Genomics, The Children's Hospital of Philadelphia, Pennsylvania, United States.,Department of Pediatrics, The Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Carmen Ayuso
- CIBER de Enfermedades Raras (CIBERER), Madrid, Spain.,Servicio de Genética, Fundación Jiménez Díaz, University Hospital, Instituto de Investigación Sanitaria Fundación Jiménez Díaz IIS-FJD, UAM, Madrid, Spain
| | - Elena Aller
- Grupo de Investigación en Biomedicina Molecular, Celular y Genómica, Instituto de Investigación Sanitaria La Fe (IIS La Fe), Valencia, Spain.,CIBER de Enfermedades Raras (CIBERER), Madrid, Spain.,Unidad de Genética y Diagnóstico Prenatal, Hospital Universitario y Politécnico La Fe, Valencia, Spain
| | - José M Millán
- Grupo de Investigación en Biomedicina Molecular, Celular y Genómica, Instituto de Investigación Sanitaria La Fe (IIS La Fe), Valencia, Spain.,CIBER de Enfermedades Raras (CIBERER), Madrid, Spain
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Cakir Z, Yildirim C, Buran I, Önalan EE, Bal R. Acid-sensing ion channels (ASICs) influence excitability of stellate neurons in the mouse cochlear nucleus. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2019; 205:769-781. [PMID: 31451914 DOI: 10.1007/s00359-019-01365-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 08/08/2019] [Accepted: 08/13/2019] [Indexed: 02/06/2023]
Abstract
Acid-sensing ion channels (ASICs) are voltage-independent and proton-gated channels. In this study, we aimed to test the hypothesis whether ASICs might be involved in modifying the excitability of stellate cells in the cochlear nucleus (CN). We determined gene expressions of ASIC1, ASIC2 and ASIC3 in the CN of BALB/mice. ASIC currents in stellate cells were characterized by using whole-cell patch-clamp technique. In the voltage-clamp experiments, inward currents were recorded upon application of 2-[N-Morpholino ethanesulfonic acid]-normal artificial cerebrospinal fluid (MES-aCSF), whose pH 50 was 5.84. Amiloride inhibited the acid-induced currents in a dose-dependent manner. Inhibition of the ASIC currents by extracellular Ca2+ and Pb2+ (10 μM) was significant evidence for the existence of homomeric ASIC1a subunits. ASIC currents were increased by 20% upon extracellular application of Zn2+ (300 μM) (p < 0.05, n = 13). In current-clamp experiments, application of MES-aCSF resulted in the depolarization of stellate cells. The results show that the ASIC currents in stellate cells of the cochlear nucleus are carried largely by the ASIC1a and ASIC2a channels. ASIC channels affect the excitability of the stellate cells and therefore they appear to have a role in the processing of auditory information.
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Affiliation(s)
- Ziya Cakir
- Department of Physiology, Faculty of Medicine, Tokat Gaziosmanpasa University, 60250, Tokat, Turkey
| | - Caner Yildirim
- Department of Physiology, Faculty of Medicine, Kafkas University, 36100, Kars, Turkey
| | - Ilay Buran
- Department of Medical Biology, Faculty of Medicine, Firat University, 23100, Elazig, Turkey
| | - Ebru Etem Önalan
- Department of Medical Biology, Faculty of Medicine, Firat University, 23100, Elazig, Turkey
| | - Ramazan Bal
- Department of Physiology, Faculty of Medicine, Gaziantep University, 27310, Gaziantep, Turkey.
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Vesicular Glutamatergic Transmission in Noise-Induced Loss and Repair of Cochlear Ribbon Synapses. J Neurosci 2019; 39:4434-4447. [PMID: 30926748 DOI: 10.1523/jneurosci.2228-18.2019] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 03/22/2019] [Accepted: 03/25/2019] [Indexed: 12/11/2022] Open
Abstract
Noise-induced excitotoxicity is thought to depend on glutamate. However, the excitotoxic mechanisms are unknown, and the necessity of glutamate for synapse loss or regeneration is unclear. Despite absence of glutamatergic transmission from cochlear inner hair cells in mice lacking the vesicular glutamate transporter-3 (Vglut3KO ), at 9-11 weeks, approximately half the number of synapses found in Vglut3WT were maintained as postsynaptic AMPA receptors juxtaposed with presynaptic ribbons and voltage-gated calcium channels (CaV1.3). Synapses were larger in Vglut3KO than Vglut3WT In Vglut3WT and Vglut3 +/- mice, 8-16 kHz octave-band noise exposure at 100 dB sound pressure level caused a threshold shift (∼40 dB) and a loss of synapses (>50%) at 24 h after exposure. Hearing threshold and synapse number partially recovered by 2 weeks after exposure as ribbons became larger, whereas recovery was significantly better in Vglut3WT Noise exposure at 94 dB sound pressure level caused auditory threshold shifts that fully recovered in 2 weeks, whereas suprathreshold hearing recovered faster in Vglut3WT than Vglut3 +/- These results, from mice of both sexes, suggest that spontaneous repair of synapses after noise depends on the level of Vglut3 protein or the level of glutamate release during the recovery period. Noise-induced loss of presynaptic ribbons or postsynaptic AMPA receptors was not observed in Vglut3KO , demonstrating its dependence on vesicular glutamate release. In Vglut3WT and Vglut3 +/-, noise exposure caused unpairing of presynaptic ribbons and presynaptic CaV1.3, but not in Vglut3KO where CaV1.3 remained clustered with ribbons at presynaptic active zones. These results suggest that, without glutamate release, noise-induced presynaptic Ca2+ influx was insufficient to disassemble the active zone. However, synapse volume increased by 2 weeks after exposure in Vglut3KO , suggesting glutamate-independent mechanisms.SIGNIFICANCE STATEMENT Hearing depends on glutamatergic transmission mediated by Vglut3, but the role of glutamate in synapse loss and repair is unclear. Here, using mice of both sexes, we show that one copy of the Vglut3 gene is sufficient for noise-induced threshold shift and loss of ribbon synapses, but both copies are required for normal recovery of hearing function and ribbon synapse number. Impairment of the recovery process in mice having only one functional copy suggests that glutamate release may promote synapse regeneration. At least one copy of the Vglut3 gene is necessary for noise-induced synapse loss. Although the excitotoxic mechanism remains unknown, these findings are consistent with the presumption that glutamate is the key mediator of noise-induced synaptopathy.
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11
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Soto E, Ortega-Ramírez A, Vega R. Protons as Messengers of Intercellular Communication in the Nervous System. Front Cell Neurosci 2018; 12:342. [PMID: 30364044 PMCID: PMC6191491 DOI: 10.3389/fncel.2018.00342] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 09/14/2018] [Indexed: 12/18/2022] Open
Abstract
In this review, evidence demonstrating that protons (H+) constitute a complex, regulated intercellular signaling mechanisms are presented. Given that pH is a strictly regulated variable in multicellular organisms, localized extracellular pH changes may constitute significant signals of cellular processes that occur in a cell or a group of cells. Several studies have demonstrated that the low pH of synaptic vesicles implies that neurotransmitter release is always accompanied by the co-release of H+ into the synaptic cleft, leading to transient extracellular pH shifts. Also, evidence has accumulated indicating that extracellular H+ concentration regulation is complex and implies a source of protons in a network of transporters, ion exchangers, and buffer capacity of the media that may finally establish the extracellular proton concentration. The activation of membrane transporters, increased production of CO2 and of metabolites, such as lactate, produce significant extracellular pH shifts in nano- and micro-domains in the central nervous system (CNS), constituting a reliable signal for intercellular communication. The acid sensing ion channels (ASIC) function as specific signal sensors of proton signaling mechanism, detecting subtle variations of extracellular H+ in a range varying from pH 5 to 8. The main question in relation to this signaling system is whether it is only synaptically restricted, or a volume modulator of neuron excitability. This signaling system may have evolved from a metabolic activity detection mechanism to a highly localized extracellular proton dependent communication mechanism. In this study, evidence showing the mechanisms of regulation of extracellular pH shifts and of the ASICs and its function in modulating the excitability in various systems is reviewed, including data and its role in synaptic neurotransmission, volume transmission and even segregated neurotransmission, leading to a reliable extracellular signaling mechanism.
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Affiliation(s)
- Enrique Soto
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | | | - Rosario Vega
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
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Cheng YR, Jiang BY, Chen CC. Acid-sensing ion channels: dual function proteins for chemo-sensing and mechano-sensing. J Biomed Sci 2018; 25:46. [PMID: 29793480 PMCID: PMC5966886 DOI: 10.1186/s12929-018-0448-y] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 05/15/2018] [Indexed: 12/22/2022] Open
Abstract
Background Acid-sensing ion channels (ASICs) are a group of amiloride-sensitive ligand-gated ion channels belonging to the family of degenerin/epithelial sodium channels. ASICs are predominantly expressed in both the peripheral and central nervous system and have been characterized as potent proton sensors to detect extracellular acidification in the periphery and brain. Main body Here we review the recent studies focusing on the physiological roles of ASICs in the nervous system. As the major acid-sensing membrane proteins in the nervous system, ASICs detect tissue acidosis occurring at tissue injury, inflammation, ischemia, stroke, and tumors as well as fatiguing muscle to activate pain-sensing nerves in the periphery and transmit pain signals to the brain. Arachidonic acid and lysophosphocholine have been identified as endogenous non-proton ligands activating ASICs in a neutral pH environment. On the other hand, ASICs are found involved in the tether model mechanotransduction, in which the extracellular matrix and cytoplasmic cytoskeletons act like a gating-spring to tether the mechanically activated ion channels and thus transmit the stimulus force to the channels. Accordingly, accumulating evidence has shown ASICs play important roles in mechanotransduction of proprioceptors, mechanoreceptors and nociceptors to monitor the homoeostatic status of muscle contraction, blood volume, and blood pressure as well as pain stimuli. Conclusion Together, ASICs are dual-function proteins for both chemosensation and mechanosensation involved in monitoring physiological homoeostasis and pathological signals.
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Affiliation(s)
- Yuan-Ren Cheng
- Department of Life Science, National Taiwan University, Taipei, 106, Taiwan.,Institute of Biomedical Sciences, Academia Sinica, 128, Academia Rd. Sec. 2, Taipei, 115, Taiwan
| | - Bo-Yang Jiang
- Department of Life Science, National Taiwan University, Taipei, 106, Taiwan.,Institute of Biomedical Sciences, Academia Sinica, 128, Academia Rd. Sec. 2, Taipei, 115, Taiwan
| | - Chih-Cheng Chen
- Department of Life Science, National Taiwan University, Taipei, 106, Taiwan. .,Institute of Biomedical Sciences, Academia Sinica, 128, Academia Rd. Sec. 2, Taipei, 115, Taiwan. .,Taiwan Mouse Clinic - National Comprehensive Mouse Phenotyping and Drug Testing Center, Academia Sinica, Taipei, 115, Taiwan.
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13
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Acid-Sensing Ion Channels as Potential Therapeutic Targets in Neurodegeneration and Neuroinflammation. Mediators Inflamm 2017; 2017:3728096. [PMID: 29056828 PMCID: PMC5625748 DOI: 10.1155/2017/3728096] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2017] [Revised: 07/29/2017] [Accepted: 08/13/2017] [Indexed: 12/21/2022] Open
Abstract
Acid-sensing ion channels (ASICs) are a family of proton-sensing channels that are voltage insensitive, cation selective (mostly permeable to Na+), and nonspecifically blocked by amiloride. Derived from 5 genes (ACCN1-5), 7 subunits have been identified, 1a, 1b, 2a, 2b, 3, 4, and 5, that are widely expressed in the peripheral and central nervous system as well as other tissues. Over the years, different studies have shown that activation of these channels is linked to various physiological and pathological processes, such as memory, learning, fear, anxiety, ischemia, and multiple sclerosis to name a few, so their potential as therapeutic targets is increasing. This review focuses on recent advances that have helped us to better understand the role played by ASICs in different pathologies related to neurodegenerative diseases, inflammatory processes, and pain.
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González-Garrido A, Vega R, Mercado F, López IA, Soto E. Acid-Sensing Ion Channels Expression, Identity and Role in the Excitability of the Cochlear Afferent Neurons. Front Cell Neurosci 2015; 9:483. [PMID: 26733809 PMCID: PMC4686812 DOI: 10.3389/fncel.2015.00483] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 11/30/2015] [Indexed: 12/21/2022] Open
Abstract
Acid-sensing ion channels (ASICs) are activated by an increase in the extracellular proton concentration. There are four genes (ASIC1-4) that encode six subunits, and they are involved in diverse neuronal functions, such as mechanosensation, learning and memory, nociception, and modulation of retinal function. In this study, we characterize the ASIC currents of spiral ganglion neurons (SGNs). These ASIC currents are primarily carried by Na(+), exhibit fast activation and desensitization, display a pH50 of 6.2 and are blocked by amiloride, indicating that these are ASIC currents. The ASIC currents were further characterized using several pharmacological tools. Gadolinium and acetylsalicylic acid reduced these currents, and FMRFamide, zinc (at high concentrations) and N,N,N',N'-tetrakis-(2-piridilmetil)-ethylenediamine increased them, indicating that functional ASICs are composed of the subunits ASIC1, ASIC2, and ASIC3. Neomycin and streptomycin reduced the desensitization rate of the ASIC current in SGNs, indicating that ASICs may contribute to the ototoxic action of aminoglycosides. RT-PCR of the spiral ganglion revealed significant expression of all ASIC subunits. By immunohistochemistry the expression of the ASIC1a, ASIC2a, ASIC2b, and ASIC3 subunits was detected in SGNs. Although only a few SGNs exhibited action potential firing in response to an acidic stimulus, protons in the extracellular solution modulated SGN activity during sinusoidal stimulation. Our results show that protons modulate the excitability of SGNs via ASICs.
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Affiliation(s)
| | - Rosario Vega
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla Puebla, Mexico
| | - Francisco Mercado
- Dirección de Investigaciones en Neurociencias, Instituto Nacional de Psiquiatría Ramón de la Fuente Muñiz México D.F., Mexico
| | - Iván A López
- Department of Head and Neck Surgery, David Geffen School of Medicine, University of California Los Angeles, CA, USA
| | - Enrique Soto
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla Puebla, Mexico
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15
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Cazals Y, Bévengut M, Zanella S, Brocard F, Barhanin J, Gestreau C. KCNK5 channels mostly expressed in cochlear outer sulcus cells are indispensable for hearing. Nat Commun 2015; 6:8780. [PMID: 26549439 PMCID: PMC4659937 DOI: 10.1038/ncomms9780] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 10/01/2015] [Indexed: 01/03/2023] Open
Abstract
In the cochlea, K(+) is essential for mechano-electrical transduction. Here, we explore cochlear structure and function in mice lacking K(+) channels of the two-pore domain family. A profound deafness associated with a decrease in endocochlear potential is found in adult Kcnk5(-/-) mice. Hearing occurs around postnatal day 19 (P19), and completely disappears 2 days later. At P19, Kcnk5(-/-) mice have a normal endolymphatic [K(+)] but a partly lowered endocochlear potential. Using Lac-Z as a gene reporter, KCNK5 is mainly found in outer sulcus Claudius', Boettcher's and root cells. Low levels of expression are also seen in the spiral ganglion, Reissner's membrane and stria vascularis. Essential channels (KCNJ10 and KCNQ1) contributing to K(+) secretion in stria vascularis have normal expression in Kcnk5(-/-) mice. Thus, KCNK5 channels are indispensable for the maintenance of hearing. Among several plausible mechanisms, we emphasize their role in K(+) recycling along the outer sulcus lateral route.
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Affiliation(s)
- Yves Cazals
- Laboratoire de Neurosciences Intégratives et Adaptatives (UMR7260), Fédération de Recherche 3C (Cerveau, Comportement, Cognition), Aix-Marseille-Université and CNRS, Marseille 13331, France
| | - Michelle Bévengut
- Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille (UMR7286), Aix-Marseille-Université and CNRS, Marseille 13344, France
| | - Sébastien Zanella
- Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille (UMR7286), Aix-Marseille-Université and CNRS, Marseille 13344, France
- Institut de Neurosciences de la Timone (UMR7289), Aix-Marseille Université and CNRS, Marseille 13005, France
| | - Frédéric Brocard
- Institut de Neurosciences de la Timone (UMR7289), Aix-Marseille Université and CNRS, Marseille 13005, France
| | - Jacques Barhanin
- Laboratoire de Physio-Médecine Moléculaire (UMR7370), Université de Nice-Sophia Antipolis and CNRS, Nice 06107, France
- Laboratories of Excellence, Ion Channel Science and Therapeutics, France
| | - Christian Gestreau
- Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille (UMR7286), Aix-Marseille-Université and CNRS, Marseille 13344, France
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16
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Deval E, Lingueglia E. Acid-Sensing Ion Channels and nociception in the peripheral and central nervous systems. Neuropharmacology 2015; 94:49-57. [PMID: 25724084 DOI: 10.1016/j.neuropharm.2015.02.009] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 02/10/2015] [Accepted: 02/12/2015] [Indexed: 11/17/2022]
Abstract
Since their molecular cloning in the late 90's, Acid-Sensing Ion Channels (ASICs) have been shown to be involved in many aspects of nociception, both in peripheral and central neurons. In rodents, the combination of specific or non-specific pharmacological modulators of ASICs, together with in vivo knockdown and/or knockout animals has revealed their contribution to the detection, the modulation and the sensitization of the pain message by primary and secondary sensory neurons. Functional ASICs are homo or heterotrimers of different homologous subunits (ASIC1-3). Channels containing ASIC3 or ASIC1 subunits, appear to be important in peripheral nociceptors, where they are subject to intense regulation, while ASIC1a-containing channels also have a prominent role in central neurons, including spinal cord neurons that modulate and transmit the pain signal to the brain. In humans, experiments performed in healthy volunteers using drugs already used in the clinic and acting as poorly-selective inhibitors of ASICs, together with recent in vitro data obtained from stem cell-derived sensory neurons both support a role for these channels in nociception. These data thus suggest a real translational potential in the development of inhibitory strategies of ASICs for the treatment of pain. This article is part of the Special Issue entitled 'Acid-Sensing Ion Channels in the Nervous System'.
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Affiliation(s)
- Emmanuel Deval
- CNRS, Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275, 06560 Valbonne, France; Université de Nice Sophia Antipolis, UMR 7275, 06560 Valbonne, France; LabEx Ion Channel Science and Therapeutics, UMR 7275, 06560 Valbonne, France.
| | - Eric Lingueglia
- CNRS, Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 7275, 06560 Valbonne, France; Université de Nice Sophia Antipolis, UMR 7275, 06560 Valbonne, France; LabEx Ion Channel Science and Therapeutics, UMR 7275, 06560 Valbonne, France
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17
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Lin SH, Sun WH, Chen CC. Genetic exploration of the role of acid-sensing ion channels. Neuropharmacology 2015; 94:99-118. [PMID: 25582292 DOI: 10.1016/j.neuropharm.2014.12.011] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 12/03/2014] [Accepted: 12/04/2014] [Indexed: 12/27/2022]
Abstract
Advanced gene targeting technology and related tools in mice have been incorporated into studies of acid-sensing ion channels (ASICs). A single ASIC subtype can be knocked out specifically and screened thoroughly for expression in the nervous system at the cellular level. Mapping studies have further shed light on the initiation and identification of related behavioral phenotypes. Here we review studies involving genetically engineered mouse models used to investigate the physiological function of individual ASIC subtypes: ASIC1 (and ASIC1a), ASIC2, ASIC3 and ASIC4. We discuss the detailed expression studies and significant phenotypes revealed with gene knockout for most known Asic subtypes. Each strategy designed to manipulate mouse genetics has advantages and disadvantages. We discuss the limitations of these Asic-knockout models and propose future directions to solve the genetic issues. This article is part of the Special Issue entitled 'Acid-Sensing Ion Channels in the Nervous System'.
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Affiliation(s)
- Shing-Hong Lin
- Institute of Life Sciences, National Defense Medical Center, Taipei 114, Taiwan; Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
| | - Wei-Hsin Sun
- Department of Life Sciences, National Central University, Jhongli 32054, Taiwan.
| | - Chih-Cheng Chen
- Institute of Life Sciences, National Defense Medical Center, Taipei 114, Taiwan; Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan; Taiwan Mouse Clinic, National Comprehensive Mouse Phenotyping and Drug Testing Center, Academia Sinica, Taipei 115, Taiwan.
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18
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Effertz T, Scharr AL, Ricci AJ. The how and why of identifying the hair cell mechano-electrical transduction channel. Pflugers Arch 2014; 467:73-84. [PMID: 25241775 DOI: 10.1007/s00424-014-1606-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Revised: 08/28/2014] [Accepted: 09/01/2014] [Indexed: 01/10/2023]
Abstract
Identification of the auditory hair cell mechano-electrical transduction (hcMET) channel has been a major focus in the hearing research field since the 1980s when direct mechanical gating of a transduction channel was proposed (Corey and Hudspeth J Neurosci 3:962-976, 1983). To this day, the molecular identity of this channel remains controversial. However, many of the hcMET channel's properties have been characterized, including pore properties, calcium-dependent ion permeability, rectification, and single channel conductance. At this point, elucidating the molecular identity of the hcMET channel will provide new tools for understanding the mechanotransduction process. This review discusses the significance of identifying the hcMET channel, the difficulties associated with that task, as well as the establishment of clear criteria for this identification. Finally, we discuss potential candidate channels in light of these criteria.
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Affiliation(s)
- Thomas Effertz
- Department of Otolaryngology, School of Medicine, Stanford University, Stanford, CA, 94305, USA
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19
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Abstract
The discovery of new drug targets represents a real opportunity for developing fresh strategies against pain. Ion channels are interesting targets because they are directly involved in the detection and the transmission of noxious stimuli by sensory fibres of the peripheral nervous system and by neurons of the spinal cord. Acid-Sensing Ion Channels (ASICs) have emerged as important players in the pain pathway. They are neuronal, voltage-independent depolarizing sodium channels activated by extracellular protons. The ASIC family comprises several subunits that need to associate into homo- or hetero-trimers to form a functional channel. The ASIC1 and ASIC3 isoforms are particularly important in sensory neurons, whereas ASIC1a, alone or in association with ASIC2, is essential in the central nervous system. The potent analgesic effects associated with their inhibition in animals (which can be comparable to those of morphine) and data suggesting a role in human pain illustrate the therapeutic potential of these channels.
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Affiliation(s)
- Eric Lingueglia
- CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, UMR 7275, 660 route des Lucioles, Sophia Antipolis, 06560 Valbonne, France - Université de Nice-Sophia Antipolis, 660 route des Lucioles, 06560 Valbonne, France - LabEx Ion Channel Science and Therapeutics, 06560 Valbonne, France
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20
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Noël J, Salinas M, Baron A, Diochot S, Deval E, Lingueglia E. Current perspectives on acid-sensing ion channels: new advances and therapeutic implications. Expert Rev Clin Pharmacol 2014; 3:331-46. [DOI: 10.1586/ecp.10.13] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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21
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Price MP, Gong H, Parsons MG, Kundert JR, Reznikov LR, Bernardinelli L, Chaloner K, Buchanan GF, Wemmie JA, Richerson GB, Cassell MD, Welsh MJ. Localization and behaviors in null mice suggest that ASIC1 and ASIC2 modulate responses to aversive stimuli. GENES BRAIN AND BEHAVIOR 2013; 13:179-94. [PMID: 24256442 DOI: 10.1111/gbb.12108] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 09/25/2013] [Accepted: 11/18/2013] [Indexed: 12/21/2022]
Abstract
Acid-sensing ion channels (ASICs) generate H(+) -gated Na(+) currents that contribute to neuronal function and animal behavior. Like ASIC1, ASIC2 subunits are expressed in the brain and multimerize with ASIC1 to influence acid-evoked currents and facilitate ASIC1 localization to dendritic spines. To better understand how ASIC2 contributes to brain function, we localized the protein and tested the behavioral consequences of ASIC2 gene disruption. For comparison, we also localized ASIC1 and studied ASIC1(-/-) mice. ASIC2 was prominently expressed in areas of high synaptic density, and with a few exceptions, ASIC1 and ASIC2 localization exhibited substantial overlap. Loss of ASIC1 or ASIC2 decreased freezing behavior in contextual and auditory cue fear conditioning assays, in response to predator odor and in response to CO2 inhalation. In addition, loss of ASIC1 or ASIC2 increased activity in a forced swim assay. These data suggest that ASIC2, like ASIC1, plays a key role in determining the defensive response to aversive stimuli. They also raise the question of whether gene variations in both ASIC1 and ASIC2 might affect fear and panic in humans.
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Affiliation(s)
- M P Price
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
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22
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Li X, Wu FR, Xu RS, Hu W, Jiang DL, Ji C, Chen FH, Yuan FL. Acid-sensing ion channel 1a-mediated calcium influx regulates apoptosis of endplate chondrocytes in intervertebral discs. Expert Opin Ther Targets 2013; 18:1-14. [DOI: 10.1517/14728222.2014.859248] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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23
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Chen CC, Wong CW. Neurosensory mechanotransduction through acid-sensing ion channels. J Cell Mol Med 2013; 17:337-49. [PMID: 23490035 PMCID: PMC3823015 DOI: 10.1111/jcmm.12025] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Accepted: 12/28/2012] [Indexed: 02/06/2023] Open
Abstract
Acid-sensing ion channels (ASICs) are voltage-insensitive cation channels responding to extracellular acidification. ASIC proteins have two transmembrane domains and a large extracellular domain. The molecular topology of ASICs is similar to that of the mechanosensory abnormality 4- or 10-proteins expressed in touch receptor neurons and involved in neurosensory mechanotransduction in nematodes. The ASIC proteins are involved in neurosensory mechanotransduction in mammals. The ASIC isoforms are expressed in Merkel cell-neurite complexes, periodontal Ruffini endings and specialized nerve terminals of skin and muscle spindles, so they might participate in mechanosensation. In knockout mouse models, lacking an ASIC isoform produces defects in neurosensory mechanotransduction of tissue such as skin, stomach, colon, aortic arch, venoatrial junction and cochlea. The ASICs are thus implicated in touch, pain, digestive function, baroreception, blood volume control and hearing. However, the role of ASICs in mechanotransduction is still controversial, because we lack evidence that the channels are mechanically sensitive when expressed in heterologous cells. Thus, ASIC channels alone are not sufficient to reconstruct the path of transducing molecules of mechanically activated channels. The mechanotransducers associated with ASICs need further elucidation. In this review, we discuss the expression of ASICs in sensory afferents of mechanoreceptors, findings of knockout studies, technical issues concerning studies of neurosensory mechanotransduction and possible missing links. Also we propose a molecular model and a new approach to disclose the molecular mechanism underlying the neurosensory mechanotransduction.
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Affiliation(s)
- Chih-Cheng Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
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24
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Abstract
Acid-sensing ion channels (ASICs) are present in neurons and may contribute to chemoreception. Among six subunits of ASICs, ASIC1 is mainly expressed in the central nervous system. Recently, multiple sites in the brain including the lateral hypothalamus (LH) have been found to be sensitive to extracellular acidification. Since LH contains orexin neurons and innervates the medulla respiratory center, we hypothesize that ASIC1 is expressed on the orexin neuron and contributes to acid-induced increase in respiratory drive. To test this hypothesis, we used double immunofluorescence to determine whether ASIC1 is expressed on orexin neurons in the LH, and assessed integrated phrenic nerve discharge (iPND) in intact rats in response to acidification of the LH. We found that ASIC1 was co-localized with orexinA in the LH. Microinjection of acidified artificial cerebrospinal fluid increased the amplitude of iPND by 70% (pH 7.4 v.s. pH 6.5:1.05±0.12 v.s. 1.70±0.10, n = 6, P<0.001) and increased the respiratory drive (peak amplitude of iPND/inspiratory time, PA/Ti) by 40% (1.10±0.23 v.s. 1.50±0.38, P<0.05). This stimulatory effect was abolished by blocking ASIC1 with a nonselective inhibitor (amiloride 10 mM), a selective inhibitor (PcTX1, 10 nM) or by damaging orexin neurons in the LH. Current results support our hypothesis that the orexin neuron in the LH can exert an excitation on respiration via ASIC1 during local acidosis. Since central acidification is involved in breathing dysfunction in a variety of pulmonary diseases, understanding its underlying mechanism may improve patient management.
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25
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Song N, Zhang G, Geng W, Liu Z, Jin W, Li L, Cao Y, Zhu D, Yu J, Shen L. Acid sensing ion channel 1 in lateral hypothalamus contributes to breathing control. PLoS One 2012; 7:e39982. [PMID: 22792205 PMCID: PMC3391217 DOI: 10.1371/journal.pone.0039982] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Accepted: 05/30/2012] [Indexed: 12/20/2022] Open
Abstract
Acid-sensing ion channels (ASICs) are present in neurons and may contribute to chemoreception. Among six subunits of ASICs, ASIC1 is mainly expressed in the central nervous system. Recently, multiple sites in the brain including the lateral hypothalamus (LH) have been found to be sensitive to extracellular acidification. Since LH contains orexin neurons and innervates the medulla respiratory center, we hypothesize that ASIC1 is expressed on the orexin neuron and contributes to acid-induced increase in respiratory drive. To test this hypothesis, we used double immunofluorescence to determine whether ASIC1 is expressed on orexin neurons in the LH, and assessed integrated phrenic nerve discharge (iPND) in intact rats in response to acidification of the LH. We found that ASIC1 was co-localized with orexinA in the LH. Microinjection of acidified artificial cerebrospinal fluid increased the amplitude of iPND by 70% (pH 7.4 v.s. pH 6.5:1.05±0.12 v.s. 1.70±0.10, n = 6, P<0.001) and increased the respiratory drive (peak amplitude of iPND/inspiratory time, PA/Ti) by 40% (1.10±0.23 v.s. 1.50±0.38, P<0.05). This stimulatory effect was abolished by blocking ASIC1 with a nonselective inhibitor (amiloride 10 mM), a selective inhibitor (PcTX1, 10 nM) or by damaging orexin neurons in the LH. Current results support our hypothesis that the orexin neuron in the LH can exert an excitation on respiration via ASIC1 during local acidosis. Since central acidification is involved in breathing dysfunction in a variety of pulmonary diseases, understanding its underlying mechanism may improve patient management.
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Affiliation(s)
- Nana Song
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Guihong Zhang
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Wenye Geng
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Zibing Liu
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Weizhong Jin
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Li Li
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Yinxiang Cao
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Danian Zhu
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Jerry Yu
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
- Department of Pulmonary Medicine, University of Louisville, Louisville, Kentucky, United States of America
| | - Linlin Shen
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
- * E-mail:
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26
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Abstract
The epithelial Na(+) channel (ENaC) and acid-sensitive ion channel (ASIC) branches of the ENaC/degenerin superfamily of cation channels have drawn increasing attention as potential therapeutic targets in a variety of diseases and conditions. Originally thought to be solely expressed in fluid absorptive epithelia and in neurons, it has become apparent that members of this family exhibit nearly ubiquitous expression. Therapeutic opportunities range from hypertension, due to the role of ENaC in maintaining whole body salt and water homeostasis, to anxiety disorders and pain associated with ASIC activity. As a physiologist intrigued by the fundamental mechanics of salt and water transport, it was natural that Dale Benos, to whom this series of reviews is dedicated, should have been at the forefront of research into the amiloride-sensitive sodium channel. The cloning of ENaC and subsequently the ASIC channels has revealed a far wider role for this channel family than was previously imagined. In this review, we will discuss the known and potential roles of ENaC and ASIC subunits in the wide variety of pathologies in which these channels have been implicated. Some of these, such as the role of ENaC in Liddle's syndrome are well established, others less so; however, all are related in that the fundamental defect is due to inappropriate channel activity.
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Affiliation(s)
- Yawar J Qadri
- Department of Physiology and Biophysics, University of Alabama at Birmingham, AL 35294, USA
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27
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Abstract
Central to our ability to hear and sense gravity is a cellular process known as mechanotransduction, which is initiated by the opening of mechanosensitive cation channels located near the tips of the stereocilia of auditory and vestibular inner ear hair cells. The molecular identity of the mechanotransduction channels has eluded researchers despite intensive investigations over the years. In this issue of the JCI, Kawashima et al. report their results obtained using mice with targeted deletion of both transmembrane channel-like 1 (Tmc1) and Tmc2. The use of inner ear hair cells isolated from these mice provided a nearly perfect system for testing the mechanotransduction channels without disrupting functions of other accessory proteins needed in the complicated molecular apparatus, and it allowed the authors to show that the proteins encoded by these genes are integral components of the mechanotransduction complex.
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Affiliation(s)
- Xi Lin
- Department of Otolaryngology, Emory University School of Medicine, Atlanta, Georgia 30322-3030, USA.
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28
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Kikuchi S, Ninomiya T, Kawamata T, Ogasawara N, Kojima T, Tachi N, Tatsumi H. The acid-sensing ion channel 2 (ASIC2) of ciliated cells in the developing rat nasal septum. ACTA ACUST UNITED AC 2011; 73:81-9. [PMID: 21566334 DOI: 10.1679/aohc.73.81] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The airway epithelium is exposed to an acidic environment in certain conditions. The acid-sensing ion channel 2 (ASIC2) belongs to the epithelial amiloride-sensitive sodium channel and degenerin (ENaC/DEG) family and is expressed on cilia of the respiratory epithelium. The aim of this study was to detect the expression of ASIC2 in the nasal septum in the embryonic stage of the rat. ASIC2 expression was not observed in the primary cilium but was found in some cilia on embryonic day 17 (E17). After E18, all cilia showed ASIC2 immunoreactivity. RT-PCR analysis revealed that ASIC2b, a subtype of ASIC2, was expressed in the nasal septum while ASIC2a was not. Quantitative Real-time RT-PCR studies indicated that the expression level of ASIC2 mRNA was highest on E21, just before birth. These results imply that ASIC2 plays little part in the development of the nasal septum epithelium. On the other hand, ASIC2, especially ASIC2b, may function for the survival and retention of ciliated cells of the nasal septum against dynamic changes in the pH environment at birth.
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Affiliation(s)
- Shin Kikuchi
- Department of Anatomy, Sapporo Medical University School of Medicine, Japan.
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Heteromeric acid-sensing ion channels (ASICs) composed of ASIC2b and ASIC1a display novel channel properties and contribute to acidosis-induced neuronal death. J Neurosci 2011; 31:9723-34. [PMID: 21715637 DOI: 10.1523/jneurosci.1665-11.2011] [Citation(s) in RCA: 175] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Acid-sensing ion channel (ASIC) subunits associate to form homomeric or heteromeric proton-gated ion channels in neurons throughout the nervous system. The ASIC1a subunit plays an important role in establishing the kinetics of proton-gated currents in the CNS, and activation of ASIC1a homomeric channels induces neuronal death after local acidosis that accompanies cerebral ischemia. The ASIC2b subunit is expressed in the brain in a pattern that overlaps ASIC1a, yet the contribution of ASIC2b has remained elusive. We find that coexpression of ASIC2b with ASIC1a in Xenopus oocytes results in novel proton-gated currents with properties distinct from ASIC1a homomeric channels. In particular, ASIC2b/1a heteromeric channels are inhibited by the nonselective potassium channel blockers tetraethylammonium and barium. In addition, steady-state desensitization is induced at more basic pH values, and Big Dynorphin sensitivity is enhanced in these unique heteromeric channels. Cultured hippocampal neurons show proton-gated currents consistent with ASIC2b contribution, and these currents are lacking in neurons from mice with an ACCN1 (ASIC2) gene disruption. Finally, we find that these ASIC2b/1a heteromeric channels contribute to acidosis-induced neuronal death. Together, our results show that ASIC2b confers unique properties to heteromeric channels in central neurons. Furthermore, these data indicate that ASIC2, like ASIC1, plays a role in acidosis-induced neuronal death and implicate the ASIC2b/1a subtype as a novel pharmacological target to prevent neuronal injury after stroke.
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Abstract
All animals use a sophisticated array of receptor proteins to sense their external and internal environments. Major advances have been made in recent years in understanding the molecular and genetic bases for sensory transduction in diverse modalities, indicating that both metabotropic and ionotropic pathways are important in sensory functions. Here, I review the historical background and recent advances in understanding the roles of a relatively newly discovered family of receptors, the degenerin/epithelial sodium channels (DEG/ENaC). These animal-specific cation channels show a remarkable sequence and functional diversity in different species and seem to exert their functions in diverse sensory modalities. Functions for DEG/ENaC channels have been implicated in mechanosensation as well as chemosensory transduction pathways. In spite of overall sequence diversity, all family members share a unique protein topology that includes just two transmembrane domains and an unusually large and highly structured extracellular domain, that seem to be essential for both their mechanical and chemical sensory functions. This review will discuss many of the recent discoveries and controversies associated with sensory function of DEG/ENaC channels in both vertebrate and invertebrate model systems, covering the role of family members in taste, mechanosensation, and pain.
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Deval E, Gasull X, Noël J, Salinas M, Baron A, Diochot S, Lingueglia E. Acid-sensing ion channels (ASICs): pharmacology and implication in pain. Pharmacol Ther 2010; 128:549-58. [PMID: 20807551 DOI: 10.1016/j.pharmthera.2010.08.006] [Citation(s) in RCA: 241] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Tissue acidosis is a common feature of many painful conditions. Protons are indeed among the first factors released by injured tissues, inducing a local pH fall that depolarizes peripheral free terminals of nociceptors and leads to pain. ASICs are excitatory cation channels directly gated by extracellular protons that are expressed in the nervous system. In sensory neurons, they act as "chemo-electrical" transducers and are involved in somatic and visceral nociception. Two highly specific inhibitory peptides isolated from animal venoms have considerably helped in the understanding of the physiological roles of these channels in pain. At the peripheral level, ASIC3 is important for inflammatory pain. Its expression and its activity are potentiated by several pain mediators present in the "inflammatory soup" that sensitize nociceptors. ASICs have also been involved in some aspects of mechanosensation and mechanonociception, notably in the gastrointestinal tract, but the underlying mechanisms remain to be determined. At the central level, ASIC1a is largely expressed in spinal cord neurons where it has been proposed to participate in the processing of noxious stimuli and in central sensitization. Blocking ASIC1a in the spinal cord also produces a potent analgesia in a broad range of pain conditions through activation of the opiate system. Targeting ASIC channels at different levels of the nervous system could therefore be an interesting strategy for the relief of pain.
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Affiliation(s)
- Emmanuel Deval
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), UMR 6097 CNRS/Université de Nice-Sophia Antipolis (UNS), 660, route des Lucioles, 06560 Valbonne, France.
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Simon A, Shenton F, Hunter I, Banks RW, Bewick GS. Amiloride-sensitive channels are a major contributor to mechanotransduction in mammalian muscle spindles. J Physiol 2009; 588:171-85. [PMID: 19917568 DOI: 10.1113/jphysiol.2009.182683] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
We investigated whether channels of the epithelial sodium/amiloride-sensitive degenerin (ENaC/DEG) family are a major contributor to mechanosensory transduction in primary mechanosensory afferents, using adult rat muscle spindles as a model system. Stretch-evoked afferent discharge was reduced in a dose-dependent manner by amiloride and three analogues - benzamil, 5-(N-ethyl-N-isopropyl) amiloride (EIPA) and hexamethyleneamiloride (HMA), reaching > or = 85% inhibition at 1 mm. Moreover, firing was slightly but significantly increased by ENaC delta subunit agonists (icilin and capsazepine). HMA's profile of effects was distinct from that of the other drugs. Amiloride, benzamil and EIPA significantly decreased firing (P < 0.01 each) at 1 microm, while 10 microm HMA was required for highly significant inhibition (P < 0.0001). Conversely, amiloride, benzamil and EIPA rarely blocked firing entirely at 1 mm, whereas 1 mm HMA blocked 12 of 16 preparations. This pharmacology suggests low-affinity ENaCs are the important spindle mechanotransducer. In agreement with this, immunoreactivity to ENaC alpha, beta and gamma subunits was detected both by Western blot and immunocytochemistry. Immunofluorescence intensity ratios for ENaC alpha, beta or gamma relative to the vesicle marker synaptophysin in the same spindle all significantly exceeded controls (P < 0.001). Ratios for the related brain sodium channel ASIC2 (BNaC1alpha) were also highly significantly greater (P < 0.005). Analysis of confocal images showed strong colocalisation within the terminal of ENaC/ASIC2 subunits and synaptophysin. This study implicates ENaC and ASIC2 in mammalian mechanotransduction. Moreover, within the terminals they colocalise with synaptophysin, a marker for the synaptic-like vesicles which regulate afferent excitability in these mechanosensitive endings.
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Affiliation(s)
- Anna Simon
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
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Wu WL, Wang CH, Huang EYK, Chen CC. Asic3(-/-) female mice with hearing deficit affects social development of pups. PLoS One 2009; 4:e6508. [PMID: 19652708 PMCID: PMC2714966 DOI: 10.1371/journal.pone.0006508] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Accepted: 07/01/2009] [Indexed: 12/17/2022] Open
Abstract
Background Infant crying is an important cue for mothers to respond adequately. Inappropriate response to infant crying can hinder social development in infants. In rodents, the pup-mother interaction largely depends on pup's calls. Mouse pups emit high frequency to ultrasonic vocalization (2–90 kHz) to communicate with their dam for maternal care. However, little is known about how the maternal response to infant crying or pup calls affects social development over the long term. Methodology/Principal Findings Here we used mice lacking acid-sensing ion channel 3 (Asic3−/−) to create a hearing deficit to probe the effect of caregiver hearing on maternal care and adolescent social development. Female Asic3−/− mice showed elevated hearing thresholds for low to ultrasonic frequency (4–32 kHz) on auditory brain stem response, which thus hindered their response to their pups' wriggling calls and ultrasonic vocalization, as well as their retrieval of pups. In adolescence, pups reared by Asic3−/− mice showed a social deficit in juvenile social behaviors as compared with those reared by wild-type or heterozygous dams. The social-deficit phenotype in juvenile mice reared by Asic3−/− mice was associated with the reduced serotonin transmission of the brain. However, Asic3−/− pups cross-fostered to wild-type dams showed rescued social deficit. Conclusions/Significance Inadequate response to pups' calls as a result of ASIC3-dependent hearing loss confers maternal deficits in caregivers and social development deficits in their young.
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Affiliation(s)
- Wei-Li Wu
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan, Republic of China
- Institute of Biomedical Sciences, Academia Sinica, Nankang, Taipei, Taiwan, Republic of China
| | - Chih-Hung Wang
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan, Republic of China
- Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital, Taipei, Taiwan, Republic of China
| | - Eagle Yi-Kung Huang
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan, Republic of China
- Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan, Republic of China
| | - Chih-Cheng Chen
- Institute of Biomedical Sciences, Academia Sinica, Nankang, Taipei, Taiwan, Republic of China
- * E-mail:
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Light AR, White AT, Hughen RW, Light KC. Moderate exercise increases expression for sensory, adrenergic, and immune genes in chronic fatigue syndrome patients but not in normal subjects. THE JOURNAL OF PAIN 2009; 10:1099-112. [PMID: 19647494 DOI: 10.1016/j.jpain.2009.06.003] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Revised: 05/10/2009] [Accepted: 06/01/2009] [Indexed: 01/23/2023]
Abstract
UNLABELLED Chronic fatigue syndrome (CFS) is characterized by debilitating fatigue, often accompanied by widespread muscle pain that meets criteria for fibromyalgia syndrome (FMS). Symptoms become markedly worse after exercise. Previous studies implicated dysregulation of the sympathetic nervous system (SNS), and immune system (IS) in CFS and FMS. We recently demonstrated that acid sensing ion channel (probably ASIC3), purinergic type 2X receptors (probably P2X4 and P2X5) and the transient receptor potential vanilloid type 1 (TRPV1) are molecular receptors in mouse sensory neurons detecting metabolites that cause acute muscle pain and possibly muscle fatigue. These molecular receptors are found on human leukocytes along with SNS and IS genes. Real-time, quantitative PCR showed that 19 CFS patients had lower expression of beta-2 adrenergic receptors but otherwise did not differ from 16 control subjects before exercise. After a sustained moderate exercise test, CFS patients showed greater increases than control subjects in gene expression for metabolite detecting receptors ASIC3, P2X4, and P2X5, for SNS receptors alpha-2A, beta-1, beta-2, and COMT and IS genes for IL10 and TLR4 lasting from 0.5 to 48 hours (P < .05). These increases were also seen in the CFS subgroup with comorbid FMS and were highly correlated with symptoms of physical fatigue, mental fatigue, and pain. These new findings suggest dysregulation of metabolite detecting receptors as well as SNS and IS in CFS and CFS-FMS. PERSPECTIVE Muscle fatigue and pain are major symptoms of CFS. After moderate exercise, CFS and CFS-FMS patients show enhanced gene expression for receptors detecting muscle metabolites and for SNS and IS, which correlate with these symptoms. These findings suggest possible new causes, points for intervention, and objective biomarkers for these disorders.
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Affiliation(s)
- Alan R Light
- Department of Anesthesiology, University of Utah, Salt Lake City, Utah 84132-2304, USA.
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Rusznák Z, Szucs G. Spiral ganglion neurones: an overview of morphology, firing behaviour, ionic channels and function. Pflugers Arch 2008; 457:1303-25. [PMID: 18777041 DOI: 10.1007/s00424-008-0586-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 08/22/2008] [Accepted: 08/26/2008] [Indexed: 11/29/2022]
Abstract
The spiral ganglion cells provide the afferent innervation of the hair cells of the organ of Corti. Ninety-five percent of these cells (termed type I spiral ganglion neurones) are in synaptic contact with the inner hair cells, whereas about 5% of them are type II cells, which are responsible for the sensory innervation of the outer hair cells. To understand the function of the spiral ganglion neurones, it is important to explore their membrane properties, understand their activity patterns and describe the variety of ionic channels determining their behaviour. In this review, a brief description is given of the various experimental methods that allow the investigation of the spiral ganglion cells, followed by the discussion of their action potential firing patterns and ionic conductances. The presence, distribution and significance of the K(+) currents of the spiral ganglion cells are specifically addressed, along with the introduction of the putative subunit compositions of the relevant voltage-gated K(+) channels.
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Affiliation(s)
- Zoltán Rusznák
- Department of Physiology, Medical and Health Science Centre, University of Debrecen, Debrecen, P O Box 22, H-4012, Hungary.
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Functional characterization of acid-sensing ion channels in cultured neurons of rat inferior colliculus. Neuroscience 2008; 154:461-72. [DOI: 10.1016/j.neuroscience.2008.03.040] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 03/12/2008] [Accepted: 03/13/2008] [Indexed: 11/22/2022]
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Eatock RA, Xue J, Kalluri R. Ion channels in mammalian vestibular afferents may set regularity of firing. J Exp Biol 2008; 211:1764-74. [PMID: 18490392 PMCID: PMC3311106 DOI: 10.1242/jeb.017350] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Rodent vestibular afferent neurons offer several advantages as a model system for investigating the significance and origins of regularity in neuronal firing interval. Their regularity has a bimodal distribution that defines regular and irregular afferent classes. Factors likely to be involved in setting firing regularity include the morphology and physiology of the afferents' contacts with hair cells, which may influence the averaging of synaptic noise and the afferents' intrinsic electrical properties. In vitro patch clamp studies on the cell bodies of primary vestibular afferents reveal a rich diversity of ion channels, with indications of at least two neuronal populations. Here we suggest that firing patterns of isolated vestibular ganglion somata reflect intrinsic ion channel properties, which in vivo combine with hair cell synaptic drive to produce regular and irregular firing.
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Affiliation(s)
- Ruth Anne Eatock
- Otology and Laryngology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114, USA.
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Ugawa S, Ishida Y, Ueda T, Yu Y, Shimada S. Hypotonic stimuli enhance proton-gated currents of acid-sensing ion channel-1b. Biochem Biophys Res Commun 2007; 367:530-4. [PMID: 18158916 DOI: 10.1016/j.bbrc.2007.12.096] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Accepted: 12/12/2007] [Indexed: 11/19/2022]
Abstract
Acid-sensing ion channels (ASICs) are strong candidates for mammalian mechanoreceptors. We investigated whether mouse acid-sensing ion channel-1b (ASIC1b) is sensitive to mechanical stimuli using oocyte electrophysiology, because ASIC1b is located in the mechanosensory stereocilia of cochlear hair cells. Hypotonic stimuli that induced membrane stretch of oocytes evoked no significant current in ASIC1b-expressing oocytes at pH 7.5. However, acid (pH 4.0 or 5.0)-evoked currents in the oocytes were substantially enhanced by the hypotonicity, showing mechanosensitivity of ASIC1b and possible mechanogating of the channel in the presence of other components. Interestingly, the ASIC1b channel was permeable to K(+) (a principal charge carrier for cochlear sensory transduction) and the affinity of the channel for amiloride (IC(50) (inhibition constant)=approximately 48.3 microM) was quite similar to that described for the mouse hair cell mechanotransducer current. Taken together, these data raise the possibility that ASIC1b participates in cochlear mechanoelectrical transduction.
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Affiliation(s)
- Shinya Ugawa
- Department of Neurobiology and Anatomy, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
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Characterization of human ASIC2a homomeric channels stably expressed in murine Ltk- cells. Life Sci 2007; 82:30-40. [PMID: 18054963 DOI: 10.1016/j.lfs.2007.10.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Revised: 10/16/2007] [Accepted: 10/18/2007] [Indexed: 11/23/2022]
Abstract
ASIC2a (BNaC1 or MDEG) is distributed throughout the nervous system and potentially involved in mechanosensation, hearing, vision, and taste functions. However, pharmacological properties of ASIC2 homomers including the mechanism of inhibition by amiloride remain unclear. In this study, we describe the properties of hASIC2a stably expressed in Ltk(-) cells, the first reported stable cell line expressing any ASICs subunit, by standard whole cell voltage clamp method. In response to pH 4.0, at -80 mV, hASIC2a cells exhibited rapidly activating fast transient inward current ( approximately 100 pA/pF) that was followed by a sustained current ( approximately 13 pA/pF). In contrast, untransfected Ltk(-) cells showed only a very small rapidly activating non-inactivating inward current ( approximately 4 pA/pF). The magnitude of hASIC2a transient current was pH dependent with pH(50) values for activation and inactivation of approximately 4.2 and approximately 5.5, respectively. Ion substitution experiments revealed the following rank order of permeability: Na(+)>K(+)>Ca(2+) for the transient current. Amiloride reversibly inhibited the pH 4.0 evoked transient current with IC(50) values of approximately 20 microM at both -30 and -80 mV holding potentials, indicating that the interactions are voltage independent when nearly all amiloride is protonated. Amiloride (100 microM) did not inhibit ASIC2a transient current when pre-applied in pH 7.4 and pH 4.0 currents obtained in absence of amiloride, but it did inhibit currents when co-applied at pH 4.0 suggesting open channel blockade. In summary, ASIC2a stable cell line serves as a useful model system to study the pharmacological properties of ASIC2a currents, potentially contributing to pH-evoked responses in cells of the dorsal root ganglion and the central nervous system.
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Lang F, Vallon V, Knipper M, Wangemann P. Functional significance of channels and transporters expressed in the inner ear and kidney. Am J Physiol Cell Physiol 2007; 293:C1187-208. [PMID: 17670895 DOI: 10.1152/ajpcell.00024.2007] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A number of ion channels and transporters are expressed in both the inner ear and kidney. In the inner ear, K+cycling and endolymphatic K+, Na+, Ca2+, and pH homeostasis are critical for normal organ function. Ion channels and transporters involved in K+cycling include K+channels, Na+-2Cl−-K+cotransporter, Na+/K+-ATPase, Cl−channels, connexins, and K+/Cl−cotransporters. Furthermore, endolymphatic Na+and Ca2+homeostasis depends on Ca2+-ATPase, Ca2+channels, Na+channels, and a purinergic receptor channel. Endolymphatic pH homeostasis involves H+-ATPase and Cl−/HCO3−exchangers including pendrin. Defective connexins (GJB2 and GJB6), pendrin (SLC26A4), K+channels (KCNJ10, KCNQ1, KCNE1, and KCNMA1), Na+-2Cl−-K+cotransporter (SLC12A2), K+/Cl−cotransporters (KCC3 and KCC4), Cl−channels (BSND and CLCNKA + CLCNKB), and H+-ATPase (ATP6V1B1 and ATPV0A4) cause hearing loss. All these channels and transporters are also expressed in the kidney and support renal tubular transport or signaling. The hearing loss may thus be paralleled by various renal phenotypes including a subtle decrease of proximal Na+-coupled transport (KCNE1/KCNQ1), impaired K+secretion (KCNMA1), limited HCO3−elimination (SLC26A4), NaCl wasting (BSND and CLCNKB), renal tubular acidosis (ATP6V1B1, ATPV0A4, and KCC4), or impaired urinary concentration (CLCNKA). Thus, defects of channels and transporters expressed in the kidney and inner ear result in simultaneous dysfunctions of these seemingly unrelated organs.
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Affiliation(s)
- Florian Lang
- Department of Physiology, Eberhard-Karls-University of Tübingen, Gmelinstrasse 5, Tübingen, Germany.
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Gabashvili IS, Sokolowski BHA, Morton CC, Giersch ABS. Ion channel gene expression in the inner ear. J Assoc Res Otolaryngol 2007; 8:305-28. [PMID: 17541769 PMCID: PMC2538437 DOI: 10.1007/s10162-007-0082-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Accepted: 04/23/2007] [Indexed: 12/13/2022] Open
Abstract
The ion channel genome is still being defined despite numerous publications on the subject. The ion channel transcriptome is even more difficult to assess. Using high-throughput computational tools, we surveyed all available inner ear cDNA libraries to identify genes coding for ion channels. We mapped over 100,000 expressed sequence tags (ESTs) derived from human cochlea, mouse organ of Corti, mouse and zebrafish inner ear, and rat vestibular end organs to Homo sapiens, Mus musculus, Danio rerio, and Rattus norvegicus genomes. A survey of EST data alone reveals that at least a third of the ion channel genome is expressed in the inner ear, with highest expression occurring in hair cell-enriched mouse organ of Corti and rat vestibule. Our data and comparisons with other experimental techniques that measure gene expression show that every method has its limitations and does not per se provide a complete coverage of the inner ear ion channelome. In addition, the data show that most genes produce alternative transcripts with the same spectrum across multiple organisms, no ion channel gene variants are unique to the inner ear, and many splice variants have yet to be annotated. Our high-throughput approach offers a qualitative computational and experimental analysis of ion channel genes in inner ear cDNA collections. A lack of data and incomplete gene annotations prevent both rigorous statistical analyses and comparisons of entire ion channelomes derived from different tissues and organisms.
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Chai S, Li M, Lan J, Xiong ZG, Saugstad JA, Simon RP. A kinase-anchoring protein 150 and calcineurin are involved in regulation of acid-sensing ion channels ASIC1a and ASIC2a. J Biol Chem 2007; 282:22668-77. [PMID: 17548344 PMCID: PMC3799797 DOI: 10.1074/jbc.m703624200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Acid-sensing ion channel (ASIC) 1a and ASIC2a are acid-sensing ion channels in central and peripheral neurons. ASIC1a has been implicated in long-term potentiation of synaptic transmission and ischemic brain injury, whereas ASIC2a is involved in mechanosensation. Although the biological role and distribution of ASIC1a and ASIC2a subunits in brain have been well characterized, little is known about the intracellular regulation of these ion channels that modulates their function. Using pulldown assays and mass spectrometry, we have identified A kinase-anchoring protein (AKAP)150 and the protein phosphatase calcineurin as binding proteins to ASIC2a. Extended pulldown and co-immunoprecipitation assays showed that these regulatory proteins also interact with ASIC1a. Transfection of rat cortical neurons with constructs encoding green fluorescent protein- or hemagglutinin-tagged channels showed expression of ASIC1a and ASIC2a in punctate and clustering patterns in dendrites that co-localized with AKAP150. Inhibition of protein kinase A binding to AKAPs by Ht-31 peptide reduces ASIC currents in cortical neurons and Chinese hamster ovary cells, suggesting a role of AKAP150 in association with protein kinase A in ASIC function. We also demonstrated a regulatory function of calcineurin in ASIC1a and ASIC2a activity. Cyclosporin A, an inhibitor of calcineurin, increased ASIC currents in Chinese hamster ovary cells and in cortical neurons, suggesting that activity of ASICs is inhibited by calcineurin-dependent dephosphorylation. These data imply that ASIC down-regulation by calcineurin could play an important role under pathological conditions accompanying intracellular Ca(2+) overload and tissue acidosis to circumvent harmful activities mediated by these channels.
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Affiliation(s)
- Sunghee Chai
- Robert S. Dow Neurobiology Laboratories, Legacy Research, Portland, Oregon 97232, USA.
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Affiliation(s)
- Eric Lingueglia
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-Université de Nice-Sophia Antipolis UMR 6097, 660 route des Lucioles, Sophia Antipolis, 06560 Valbonne, France.
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Ahmad S, Tang W, Chang Q, Qu Y, Hibshman J, Li Y, Söhl G, Willecke K, Chen P, Lin X. Restoration of connexin26 protein level in the cochlea completely rescues hearing in a mouse model of human connexin30-linked deafness. Proc Natl Acad Sci U S A 2007; 104:1337-41. [PMID: 17227867 PMCID: PMC1783143 DOI: 10.1073/pnas.0606855104] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mutations in genes coding for connexin26 (Cx26) and/or Cx30 are linked to approximately half of all cases of human autosomal nonsyndromic prelingual deafness. Cx26 and Cx30 are the two major Cx isoforms found in the cochlea, and they coassemble to form hybrid (heteromeric and heterotypic) gap junctions (GJs). This molecular arrangement implies that homomeric GJs would remain in the cochlea if one of the coassembly partners were mutated resulting in null expression. We generated mice in which extra copies of the Cx26 gene were transgenically expressed from a modified bacterial artificial chromosome in a Cx30-/- background. In the absence of the Cx30 gene, Cx26 expressed from extra alleles completely restored hearing sensitivity and prevented hair cell death in deaf Cx30-/- mice. The results indicated that hybrid GJs consisting of Cx26 and Cx30 were not essential for normal hearing in mice and suggested that up-regulation of Cx26 or slowing down its protein degradation might be a therapeutic strategy to prevent and treat deafness caused by Cx30 mutations.
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Affiliation(s)
| | | | | | - Yan Qu
- Departments of *Otolaryngology and
| | | | - Yuhua Li
- Yerkes Microarray Core, Emory University School of Medicine, 615 Michael Street, Atlanta, GA 30322-3030; and
| | - Goran Söhl
- Institute of Genetics, University of Bonn, 53117 Bonn, Germany
| | - Klaus Willecke
- Institute of Genetics, University of Bonn, 53117 Bonn, Germany
| | - Ping Chen
- Departments of *Otolaryngology and
- Cell Biology
| | - Xi Lin
- Departments of *Otolaryngology and
- Cell Biology
- To whom correspondence should be addressed. E-mail:
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Abstract
The distribution of ion channels in neurons associated with pain pathways is becoming better understood. In particular, we now have insights into the molecular nature of the channels that are activated by tissue-damaging stimuli, as well as the mechanisms by which voltage-gated channels alter the sensitivity of peripheral neurons to change pain thresholds. This chapter details the evidence that individual channels may be associated with particular pain states, and describes genetic approaches to test the possible utility of targeting individual channels to treat pain.
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Affiliation(s)
- Tamara Rosenbaum
- Departamento de Biofísica, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México
- Correspondence should be addressed to León D. Islas or Tamara Rosenbaum, León D. Islas, Departamento de Fisiología, Facultad de Medicina, Apartado Postal 70-600. Circuito Escolar S/N; Ciudad Universitaria, Universidad Nacional Autónoma de México, México, D.F., 04510, México, Phone +(52) 55 5623 2132; Fax +(52) 55 5623 2241, , Tamara Rosenbaum, Departamento de Biofísica, Instituto de Fisiología Celular, Apartado Postal 70-600. Circuito Exterior S/N, Ciudad Universitaria, Universidad Nacional Autónoma de México, México, D.F., 04510, México. Phone +(52) 55 5622 5624; Fax +(52) 55 5622 5607,
| | - Sidney A. Simon
- Department of Neurobiology and Center of Neuroengineering Duke University Medical Center, Durham, NC 27710, USA
| | - Leon D. Islas
- Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, México
- Correspondence should be addressed to León D. Islas or Tamara Rosenbaum, León D. Islas, Departamento de Fisiología, Facultad de Medicina, Apartado Postal 70-600. Circuito Escolar S/N; Ciudad Universitaria, Universidad Nacional Autónoma de México, México, D.F., 04510, México, Phone +(52) 55 5623 2132; Fax +(52) 55 5623 2241, , Tamara Rosenbaum, Departamento de Biofísica, Instituto de Fisiología Celular, Apartado Postal 70-600. Circuito Exterior S/N, Ciudad Universitaria, Universidad Nacional Autónoma de México, México, D.F., 04510, México. Phone +(52) 55 5622 5624; Fax +(52) 55 5622 5607,
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Zha XM, Wemmie JA, Green SH, Welsh MJ. Acid-sensing ion channel 1a is a postsynaptic proton receptor that affects the density of dendritic spines. Proc Natl Acad Sci U S A 2006; 103:16556-61. [PMID: 17060608 PMCID: PMC1621052 DOI: 10.1073/pnas.0608018103] [Citation(s) in RCA: 155] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Extracellular proton concentrations in the brain may be an important signal for neuron function. Proton concentrations change both acutely when synaptic vesicles release their acidic contents into the synaptic cleft and chronically during ischemia and seizures. However, the brain receptors that detect protons and their physiologic importance remain uncertain. Using organotypic hippocampal slices and biolistic transfection, we found the acid-sensing ion channel 1a (ASIC1a), localized in dendritic spines where it functioned as a proton receptor. ASIC1a also affected the density of spines, the postsynaptic site of most excitatory synapses. Decreasing ASIC1a reduced the number of spines, whereas overexpressing ASIC1a had the opposite effect. Ca(2+)-mediated Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) signaling was probably responsible, because acid evoked an ASIC1a-dependent elevation of spine intracellular Ca(2+) concentration, and reducing or increasing ASIC1a levels caused parallel changes in CaMKII phosphorylation in vivo. Moreover, inhibiting CaMKII prevented ASIC1a from increasing spine density. These data indicate that ASIC1a functions as a postsynaptic proton receptor that influences intracellular Ca(2+) concentration and CaMKII phosphorylation and thereby the density of dendritic spines. The results provide insight into how protons influence brain function and how they may contribute to pathophysiology.
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Affiliation(s)
- Xiang-ming Zha
- *Howard Hughes Medical Institute, and
- Departments of Internal Medicine
| | - John A. Wemmie
- Psychiatry
- Veterans Affairs Medical Center, Iowa City, IA 52242
| | | | - Michael J. Welsh
- *Howard Hughes Medical Institute, and
- Departments of Internal Medicine
- Physiology and Biophysics, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242; and
- **To whom correspondence should be addressed. E-mail:
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Ugawa S, Inagaki A, Yamamura H, Ueda T, Ishida Y, Kajita K, Shimizu H, Shimada S. Acid-sensing ion channel-1b in the stereocilia of mammalian cochlear hair cells. Neuroreport 2006; 17:1235-9. [PMID: 16951561 DOI: 10.1097/01.wnr.0000233093.67289.66] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We investigated whether amiloride-blockable proton-gated cation channels ASIC1a (acid-sensing ion channel-1a) and ASIC1b are expressed in the stereocilia of mouse cochlear hair cells. In-situ hybridization studies showed that ASIC1b transcripts, but not ASIC1a transcripts, were expressed in the inner and outer hair cells. Fluorescent immunohistochemical and immunogold electron microscopic analyses revealed that the ASIC1b channels were located at the insertions of the stereocilia into the hair cells. Our findings provide a novel molecular key to the understanding of cochlear physiology and pathophysiology.
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Affiliation(s)
- Shinya Ugawa
- Department of Molecular Morphology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Aichi, Japan.
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48
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Abstract
In contrast to nearly all other sensory systems, the mechanically sensitive ion channel carrying the receptor current into hair cells of the inner ear has not been identified in molecular terms. A number of candidates from at least two different ion channel families have been considered: these include the epithelial sodium channel (ENaC) and acid-sensing ion channel (ASIC) members of the DEG/ENaC superfamily of amiloride-sensitive sodium channels, as well as the TRP channels TRPN1, TRPV4, TRPML3 and TRPA1. For each, initial supportive results were followed by further studies that cast doubts on their involvement. No promising candidates have recently emerged, but the TRP family continues to be attractive in general.
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Affiliation(s)
- David P Corey
- Howard Hughes Medical Institute and Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA.
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Wemmie JA, Price MP, Welsh MJ. Acid-sensing ion channels: advances, questions and therapeutic opportunities. Trends Neurosci 2006; 29:578-86. [PMID: 16891000 DOI: 10.1016/j.tins.2006.06.014] [Citation(s) in RCA: 422] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Revised: 06/08/2006] [Accepted: 06/24/2006] [Indexed: 12/11/2022]
Abstract
Extracellular acid can have important effects on neuron function. In central and peripheral neurons, acid-sensing ion channels (ASICs) have emerged as key receptors for extracellular protons, and recent studies suggest diverse roles for these channels in the pathophysiology of pain, ischemic stroke and psychiatric disease. ASICs have also been implicated in mechanosensation in the peripheral nervous system and in neurotransmission in the central nervous system. Here, we briefly review advances in our understanding of ASICs, their potential contributions to disease, and the possibility for their therapeutic modification.
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Affiliation(s)
- John A Wemmie
- Department of Psychiatry, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
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Mercado F, López IA, Acuna D, Vega R, Soto E. Acid-sensing ionic channels in the rat vestibular endorgans and ganglia. J Neurophysiol 2006; 96:1615-24. [PMID: 16790596 DOI: 10.1152/jn.00378.2006] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Acid-sensing ionic channels (ASICs) are members of the epithelial Na+ channel/degenerin (ENaC/DEG) superfamily. ASICs are widely distributed in the central and peripheral nervous system. They have been implicated in synaptic transmission, pain perception, and the mechanoreception in peripheral tissues. Our objective was to characterize proton-gated currents mediated by ASICs and to determine their immunolocation in the rat vestibular periphery. Voltage clamp of cultured afferent neurons from P7 to P10 rats showed a proton-gated current with rapid activation and complete desensitization, which was carried almost exclusively by sodium ions. The current response to protons (H+) has a pH0.5 of 6.2. This current was reversibly decreased by amiloride, gadolinium, lead, acetylsalicylic acid, and enhanced by FMRFamide and zinc, and negatively modulated by raising the extracellular calcium concentration. Functional expression of the current was correlated with smaller-capacitance neurons. Acidification of the extracellular pH generated action potentials in vestibular neurons, suggesting a functional role of ASICs in their excitability. Immunoreactivity to ASIC1a and ASIC2a subunits was found in small vestibular ganglion neurons and afferent fibers that run throughout the macula utricle and crista stroma. ASIC2b, ASIC3, and ASIC4 were expressed to a lesser degree in vestibular ganglion neurons. The ASIC1b subunit was not detected in the vestibular endorgans. No acid-pH-sensitive currents or ASIC immunoreactivity was found in hair cells. Our results indicate that proton-gated current is carried through ASICs and that ionic current activated by H+ contributes to shape the vestibular afferent neurons' response to its synaptic input.
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Affiliation(s)
- Francisco Mercado
- Instituto de Fisiología, Universidad Autónoma de Pubela, Puebla, Mexico.
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