1
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Kato D, Aoyama Y, Nishida K, Takahashi Y, Sakamoto T, Takeda I, Tatematsu T, Go S, Saito Y, Kunishima S, Cheng J, Hou L, Tachibana Y, Sugio S, Kondo R, Eto F, Sato S, Moorhouse AJ, Yao I, Kadomatsu K, Setou M, Wake H. Regulation of lipid synthesis in myelin modulates neural activity and is required for motor learning. Glia 2023; 71:2591-2608. [PMID: 37475643 DOI: 10.1002/glia.24441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 06/11/2023] [Accepted: 07/03/2023] [Indexed: 07/22/2023]
Abstract
Brain function relies on both rapid electrical communication in neural circuitry and appropriate patterns or synchrony of neural activity. Rapid communication between neurons is facilitated by wrapping nerve axons with insulation by a myelin sheath composed largely of different lipids. Recent evidence has indicated that the extent of myelination of nerve axons can adapt based on neural activity levels and this adaptive myelination is associated with improved learning of motor tasks, suggesting such plasticity may enhance effective learning. In this study, we examined whether another aspect of myelin plasticity-changes in myelin lipid synthesis and composition-may also be associated with motor learning. We combined a motor learning task in mice with in vivo two-photon imaging of neural activity in the primary motor cortex (M1) to distinguish early and late stages of learning and then probed levels of some key myelin lipids using mass spectrometry analysis. Sphingomyelin levels were elevated in the early stage of motor learning while galactosylceramide levels were elevated in the middle and late stages of motor learning, and these changes were correlated across individual mice with both learning performance and neural activity changes. Targeted inhibition of oligodendrocyte-specific galactosyltransferase expression, the enzyme that synthesizes myelin galactosylceramide, impaired motor learning. Our results suggest regulation of myelin lipid composition could be a novel facet of myelin adaptations associated with learning.
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Affiliation(s)
- Daisuke Kato
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
- Division of Multicellular Circuit Dynamics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan
| | - Yuki Aoyama
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Kazuki Nishida
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yutaka Takahashi
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Takumi Sakamoto
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Ikuko Takeda
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
- Division of Multicellular Circuit Dynamics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan
| | - Tsuyako Tatematsu
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Shiori Go
- Institute for Glyco-core Research, Nagoya University, Nagoya, Japan
| | - Yutaro Saito
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Shiho Kunishima
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Jinlei Cheng
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Lingnan Hou
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yoshihisa Tachibana
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Shouta Sugio
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Reon Kondo
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Fumihiro Eto
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Hamamatsu, Japan
- Department of Biomedical Chemistry, School of Science and Technology, Kwansei Gakuin University, Sanda, Japan
| | - Shumpei Sato
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Andrew J Moorhouse
- School of Medical Sciences, UNSW Sydney, Sydney, New South Wales, Australia
| | - Ikuko Yao
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Hamamatsu, Japan
- Department of Biomedical Chemistry, School of Science and Technology, Kwansei Gakuin University, Sanda, Japan
| | - Kenji Kadomatsu
- Institute for Glyco-core Research, Nagoya University, Nagoya, Japan
| | - Mitsutoshi Setou
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Hiroaki Wake
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
- Division of Multicellular Circuit Dynamics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan
- Center of Optical Scattering Image Science, Kobe University, Kobe, Japan
- Department of Physiological Sciences, Graduate University for Advanced Studies, SOKENDAI, Hayama, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
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2
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Etherington SJ, Moorhouse AJ, Paravicini TM, Towstoless M, Hayes A, Hryciw DH, Lexis L, Tangalakis K. Unpacking and validating the 'Cell Membrane' Core Concept of Physiology by an Australian team. Adv Physiol Educ 2023. [PMID: 37318997 DOI: 10.1152/advan.00143.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 06/07/2023] [Indexed: 06/17/2023]
Abstract
A task force of physiology educators from 25 Australian universities generated an Australia-wide consensus on seven core concepts for physiology curricula. One adopted core concept was 'Cell membrane', defined as 'Cell membranes determine what substances enter or leave the cell and its organelles. They are essential for cell signaling, transport, and other cellular functions'. This concept was unpacked by a team of three Australian physiology educators into four themes and 33 sub-themes arranged in a hierarchical structure up to five levels deep. The four themes related to defining the cell membrane, cell membrane structure, transport across cell membranes and cell membrane potentials. Subsequently, 22 physiology educators with a broad range of teaching experience reviewed and assessed the 37 themes and sub-themes for importance for students to understand and level of difficulty for students on a 5-point Likert scale. The majority (28) of items evaluated were rated as either Essential or Important. Theme 2 (cell membrane structure) was rated as less important than the other 3 themes. Theme 4 (membrane potentials) was rated most difficult, while theme 1 (defining cell membranes) was rated as the easiest. The importance of cell membranes as a key aspect of biomedical education received strong support from Australian educators. The unpacking of the themes and sub-themes within the cell membrane core concept provides guidance in the development of curricula and should facilitate better identification of the more challenging aspects within this core concept and help inform the time and resources required to support student learning.
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Affiliation(s)
- Sarah J Etherington
- College of Science, Health, Engineering and Education, Murdoch University, Perth, Western Australia, Australia
| | - Andrew J Moorhouse
- School of Biomedical Sciences, University of New South Wales, Sydney, Australia
| | - Tamara M Paravicini
- School of Health and Biomedical Sciences, RMIT University, Melbourne, VIC, Australia
| | | | - Alan Hayes
- Institute of Health and Sport, Victoria University, Melbourne, Australia
| | - Deanne H Hryciw
- School of Environment and Science, Griffith University, Nathan, Queensland, Australia
| | - Louise Lexis
- School of Agriculture, Biomedicine and Environment, La Trobe University, Bundoora, VIC, Australia
| | - Kathy Tangalakis
- First Year College, Victoria University, Melbourne, Victoria, Australia
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3
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Hashimoto A, Kawamura N, Tarusawa E, Takeda I, Aoyama Y, Ohno N, Inoue M, Kagamiuchi M, Kato D, Matsumoto M, Hasegawa Y, Nabekura J, Schaefer A, Moorhouse AJ, Yagi T, Wake H. Microglia enable cross-modal plasticity by removing inhibitory synapses. Cell Rep 2023; 42:112383. [PMID: 37086724 DOI: 10.1016/j.celrep.2023.112383] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 02/13/2023] [Accepted: 03/28/2023] [Indexed: 04/24/2023] Open
Abstract
Cross-modal plasticity is the repurposing of brain regions associated with deprived sensory inputs to improve the capacity of other sensory modalities. The functional mechanisms of cross-modal plasticity can indicate how the brain recovers from various forms of injury and how different sensory modalities are integrated. Here, we demonstrate that rewiring of the microglia-mediated local circuit synapse is crucial for cross-modal plasticity induced by visual deprivation (monocular deprivation [MD]). MD relieves the usual inhibition of functional connectivity between the somatosensory cortex and secondary lateral visual cortex (V2L). This results in enhanced excitatory responses in V2L neurons during whisker stimulation and a greater capacity for vibrissae sensory discrimination. The enhanced cross-modal response is mediated by selective removal of inhibitory synapse terminals on pyramidal neurons by the microglia in the V2L via matrix metalloproteinase 9 signaling. Our results provide insights into how cortical circuits integrate different inputs to functionally compensate for neuronal damage.
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Affiliation(s)
- Akari Hashimoto
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Nanami Kawamura
- KOKORO-Biology Group, Laboratories for Integrated Biology, Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
| | - Etsuko Tarusawa
- KOKORO-Biology Group, Laboratories for Integrated Biology, Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
| | - Ikuko Takeda
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Yuki Aoyama
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Nobuhiko Ohno
- Department of Anatomy, Division of Histology and Cell Biology, Jichi Medical University, Shimotsuke 329-0498, Japan; Division of Ultrastructural Research, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
| | - Mio Inoue
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Mai Kagamiuchi
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Daisuke Kato
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Mami Matsumoto
- Section of Electron Microscopy, Supportive Center for Brain Research, National Institute for Physiological Sciences, Okazaki 444-8585, Japan; Department of Developmental and Regenerative Neurobiology, Institute of Brain Science, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
| | - Yoshihiro Hasegawa
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Junichi Nabekura
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki 444-8585, Japan; Department of Physiological Sciences, Graduate University for Advanced Studies, SOKENDAI, Hayama 240-0193, Japan
| | - Anne Schaefer
- Center for Glial Biology, Department of Neuroscience and Psychiatry, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA; Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Andrew J Moorhouse
- School of Biomedical Sciences, The University of New South Wales, Sydney, NSW 2052, Australia
| | - Takeshi Yagi
- KOKORO-Biology Group, Laboratories for Integrated Biology, Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
| | - Hiroaki Wake
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan; Division of Multicellular Circuit Dynamics, National Institute for Physiological Sciences, Okazaki 444-8585, Japan; Center for Optical Scattering Image Science, Kobe University, Kobe 657-8501, Japan; Department of Physiological Sciences, Graduate University for Advanced Studies, SOKENDAI, Hayama 240-0193, Japan; Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama 332-0012, Japan.
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4
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Takeda I, Yoshihara K, Cheung DL, Kobayashi T, Agetsuma M, Tsuda M, Eto K, Koizumi S, Wake H, Moorhouse AJ, Nabekura J. Controlled activation of cortical astrocytes modulates neuropathic pain-like behaviour. Nat Commun 2022; 13:4100. [PMID: 35835747 PMCID: PMC9283422 DOI: 10.1038/s41467-022-31773-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 07/04/2022] [Indexed: 11/20/2022] Open
Abstract
Chronic pain is a major public health problem that currently lacks effective treatment options. Here, a method that can modulate chronic pain-like behaviour induced by nerve injury in mice is described. By combining a transient nerve block to inhibit noxious afferent input from injured peripheral nerves, with concurrent activation of astrocytes in the somatosensory cortex (S1) by either low intensity transcranial direct current stimulation (tDCS) or via the chemogenetic DREADD system, we could reverse allodynia-like behaviour previously established by partial sciatic nerve ligation (PSL). Such activation of astrocytes initiated spine plasticity to reduce those synapses formed shortly after PSL. This reversal from allodynia-like behaviour persisted well beyond the active treatment period. Thus, our study demonstrates a robust and potentially translational approach for modulating pain, that capitalizes on the interplay between noxious afferents, sensitized central neuronal circuits, and astrocyte-activation induced synaptic plasticity. Astrocytes may contribute to synaptic remodelling in the cortex in chronic pain states. Here the authors describe modulation of astrocyte activity to drive circuit reorganization in somatosensory cortex in mice, along with peripheral nerve block, which could be a potential therapeutic approach for the treatment of chronic pain.
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Affiliation(s)
- Ikuko Takeda
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan.,Department of Anatomy and Molecular Cell Biology Graduate School of Medicine, Nagoya University, Nagoya, Japan.,Division of Multicellular Circuit Dynamics, National Institute for Physiological Sciences, Okazaki, Japan
| | - Kohei Yoshihara
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Dennis L Cheung
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan
| | - Tomoko Kobayashi
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan
| | - Masakazu Agetsuma
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan.,Division of Molecular Design, Research Center for Systems Immunology, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
| | - Makoto Tsuda
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Kei Eto
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan.,Department of Physiology, School of Allied Health Sciences, Kitasato University, Sagamihara, Kanagawa, Japan
| | - Schuichi Koizumi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan.,GLIA Center, University of Yamanashi, Yamanashi, Japan
| | - Hiroaki Wake
- Department of Anatomy and Molecular Cell Biology Graduate School of Medicine, Nagoya University, Nagoya, Japan.,Division of Multicellular Circuit Dynamics, National Institute for Physiological Sciences, Okazaki, Japan.,Center of Optical Scattering Image Science Department of Systems Science, Kobe University, Kobe, Japan
| | - Andrew J Moorhouse
- Department of Physiology, School of Medical Sciences, The University of New South Wales, Sydney, Australia
| | - Junichi Nabekura
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan. .,Graduate School of Medicine, Nagoya University, Nagoya, Japan. .,Department of Physiological Sciences, Graduate University for Advanced Studies, SOKENDAI, Hayama, Japan.
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5
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Cheung DL, Cooke MJ, Goulton CS, Chaichim C, Cheung LF, Khoshaba A, Nabekura J, Moorhouse AJ. Global transgenic upregulation of KCC2 confers enhanced diazepam efficacy in treating sustained seizures. Epilepsia 2021; 63:e15-e22. [PMID: 34791657 DOI: 10.1111/epi.17097] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Revised: 09/25/2021] [Accepted: 09/29/2021] [Indexed: 11/30/2022]
Abstract
Reduced anticonvulsant efficacy of benzodiazepines is a problem in the treatment of status epilepticus, with up to 50% of patients failing to respond to their first dose. KCC2 is a neuronal K+ -Cl- co-transporter that helps set and maintain intracellular Cl- concentrations. KCC2 functional downregulation is a potential contributor to benzodiazepine resistance. We tested this idea using male and female doxycycline-inducible, conditional transgenic mice to increase the functional expression of KCC2 in pyramidal neurons. We administered mice with two doses of the chemoconvulsant kainic acid (5 mg/kg, i.p.) 60 min apart and quantified the resultant seizures with electroencephalography (EEG) recordings. Overexpression of KCC2 prior to the chemoconvulsant challenge did not affect seizure latency or other measures of seizure severity, but it did increase diazepam's efficacy in stopping EEG seizures. Spike rate, time in seizure, and EEG spectral power following diazepam (5 mg/kg, i.p) were all significantly lower in KCC2 overexpression mice as compared to control mice. Our results indicate that, in the context of benzodiazepine resistance during sustained seizures, addressing impaired Cl- homeostasis alone appreciably improves the efficacy of γ-aminobutyric acid (GABA)ergic inhibition. We therefore suggest the simultaneous targeting of KCC2 and GABAA receptors as a pathway for improving current anticonvulsant therapeutic strategies.
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Affiliation(s)
- Dennis L Cheung
- Department of Physiology, School of Medical Sciences, Faculty of Medicine, UNSW Sydney, Sydney, New South Wales, Australia.,Division of Homeostatic Development, Department of Fundamental Neuroscience, National Institute for Physiological Sciences, Okazaki, Japan
| | - Matthew J Cooke
- School of Electrical Engineering and Telecommunications, Faculty of Engineering, UNSW Sydney, Sydney, New South Wales, Australia
| | - Chelsea S Goulton
- Department of Physiology, School of Medical Sciences, Faculty of Medicine, UNSW Sydney, Sydney, New South Wales, Australia.,School of Psychology, Faculty of Science, UNSW Sydney, Sydney, New South Wales, Australia
| | - Chanchanok Chaichim
- Department of Physiology, School of Medical Sciences, Faculty of Medicine, UNSW Sydney, Sydney, New South Wales, Australia
| | - Louis F Cheung
- School of Computer Science and Engineering, Faculty of Engineering, University of New South Wales, Sydney, New South Wales, Australia
| | - Ashor Khoshaba
- Department of Physiology, School of Medical Sciences, Faculty of Medicine, UNSW Sydney, Sydney, New South Wales, Australia
| | - Junichi Nabekura
- Division of Homeostatic Development, Department of Fundamental Neuroscience, National Institute for Physiological Sciences, Okazaki, Japan
| | - Andrew J Moorhouse
- Department of Physiology, School of Medical Sciences, Faculty of Medicine, UNSW Sydney, Sydney, New South Wales, Australia
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6
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Okada T, Kato D, Nomura Y, Obata N, Quan X, Morinaga A, Yano H, Guo Z, Aoyama Y, Tachibana Y, Moorhouse AJ, Matoba O, Takiguchi T, Mizobuchi S, Wake H. Pain induces stable, active microcircuits in the somatosensory cortex that provide a therapeutic target. Sci Adv 2021; 7:7/12/eabd8261. [PMID: 33741588 PMCID: PMC7978434 DOI: 10.1126/sciadv.abd8261] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 02/03/2021] [Indexed: 05/23/2023]
Abstract
Sustained neuropathic pain from injury or inflammation remains a major burden for society. Rodent pain models have informed some cellular mechanisms increasing neuronal excitability within the spinal cord and primary somatosensory cortex (S1), but how activity patterns within these circuits change during pain remains unclear. We have applied multiphoton in vivo imaging and holographic stimulation to examine single S1 neuron activity patterns and connectivity during sustained pain. Following pain induction, there is an increase in synchronized neuronal activity and connectivity within S1, indicating the formation of pain circuits. Artificially increasing neuronal activity and synchrony using DREADDs reduced pain thresholds. The expression of N-type voltage-dependent Ca2+ channel subunits in S1 was increased after pain induction, and locally blocking these channels reduced both the synchrony and allodynia associated with inflammatory pain. Targeting these S1 pain circuits, via inhibiting N-type Ca2+ channels or other approaches, may provide ways to reduce inflammatory pain.
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Affiliation(s)
- Takuya Okada
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
- Division of Anesthesiology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Daisuke Kato
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yuki Nomura
- Division of Anesthesiology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Norihiko Obata
- Division of Anesthesiology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Xiangyu Quan
- Department of System Science, Kobe University Graduate School of System Informatics, Kobe, Japan
| | - Akihito Morinaga
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Hajime Yano
- Department of Information Science, Kobe University Graduate School of System Informatics, Kobe, Japan
| | - Zhongtian Guo
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yuki Aoyama
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yoshihisa Tachibana
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
| | | | - Osamu Matoba
- Department of System Science, Kobe University Graduate School of System Informatics, Kobe, Japan
| | - Tetsuya Takiguchi
- Department of Information Science, Kobe University Graduate School of System Informatics, Kobe, Japan
| | - Satoshi Mizobuchi
- Division of Anesthesiology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroaki Wake
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan.
- Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
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7
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Haruwaka K, Ikegami A, Tachibana Y, Ohno N, Konishi H, Hashimoto A, Matsumoto M, Kato D, Ono R, Kiyama H, Moorhouse AJ, Nabekura J, Wake H. Dual microglia effects on blood brain barrier permeability induced by systemic inflammation. Nat Commun 2019; 10:5816. [PMID: 31862977 PMCID: PMC6925219 DOI: 10.1038/s41467-019-13812-z] [Citation(s) in RCA: 439] [Impact Index Per Article: 87.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 11/26/2019] [Indexed: 12/12/2022] Open
Abstract
Microglia survey brain parenchyma, responding to injury and infections. Microglia also respond to systemic disease, but the role of blood-brain barrier (BBB) integrity in this process remains unclear. Using simultaneous in vivo imaging, we demonstrated that systemic inflammation induces CCR5-dependent migration of brain resident microglia to the cerebral vasculature. Vessel-associated microglia initially maintain BBB integrity via expression of the tight-junction protein Claudin-5 and make physical contact with endothelial cells. During sustained inflammation, microglia phagocytose astrocytic end-feet and impair BBB function. Our results show microglia play a dual role in maintaining BBB integrity with implications for elucidating how systemic immune-activation impacts neural functions.
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Affiliation(s)
- Koichiro Haruwaka
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan.,Division of Homeostatic Development, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan.,Department of Physiological Sciences, The Graduate School for Advanced Study, Hayama, Japan
| | - Ako Ikegami
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yoshihisa Tachibana
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Nobuhiko Ohno
- Department of Anatomy, Division of Histology and Cell Biology, Jichi Medical University, Tochigi, Japan.,Division of Ultrastructural Research, National Institute for Physiological Sciences, Okazaki, Japan
| | - Hiroyuki Konishi
- Department of Functional Anatomy and Neuroscience, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Akari Hashimoto
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Mami Matsumoto
- Section of Electron Microscopy, Supportive Center for Brain Research, National Institute for Physiological Sciences, Okazaki, Japan.,Department of Developmental and Regenerative Biology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | - Daisuke Kato
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan.,Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Riho Ono
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroshi Kiyama
- Department of Functional Anatomy and Neuroscience, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Andrew J Moorhouse
- School of Medical Sciences, The University of New South Wales, Sydney, NSW, Australia
| | - Junichi Nabekura
- Division of Homeostatic Development, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan.,Department of Physiological Sciences, The Graduate School for Advanced Study, Hayama, Japan
| | - Hiroaki Wake
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan. .,Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan. .,Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan. .,Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Saitama, Japan.
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8
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Kato D, Wake H, Lee PR, Tachibana Y, Ono R, Sugio S, Tsuji Y, Tanaka YH, Tanaka YR, Masamizu Y, Hira R, Moorhouse AJ, Tamamaki N, Ikenaka K, Matsukawa N, Fields RD, Nabekura J, Matsuzaki M. Motor learning requires myelination to reduce asynchrony and spontaneity in neural activity. Glia 2019; 68:193-210. [PMID: 31465122 PMCID: PMC6899965 DOI: 10.1002/glia.23713] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 07/23/2019] [Accepted: 08/12/2019] [Indexed: 12/21/2022]
Abstract
Myelination increases the conduction velocity in long‐range axons and is prerequisite for many brain functions. Impaired myelin regulation or impairment of myelin itself is frequently associated with deficits in learning and cognition in neurological and psychiatric disorders. However, it has not been revealed what perturbation of neural activity induced by myelin impairment causes learning deficits. Here, we measured neural activity in the motor cortex during motor learning in transgenic mice with a subtle impairment of their myelin. This deficit in myelin impaired motor learning, and was accompanied by a decrease in the amplitude of movement‐related activity and an increase in the frequency of spontaneous activity. Thalamocortical axons showed variability in axonal conduction with a large spread in the timing of postsynaptic cortical responses. Repetitive pairing of forelimb movements with optogenetic stimulation of thalamocortical axon terminals restored motor learning. Thus, myelin regulation helps to maintain the synchrony of cortical spike‐time arrivals through long‐range axons, facilitating the propagation of the information required for learning. Our results revealed the pathological neuronal circuit activity with impaired myelin and suggest the possibility that pairing of noninvasive brain stimulation with relevant behaviors may ameliorate cognitive and behavioral abnormalities in diseases with impaired myelination.
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Affiliation(s)
- Daisuke Kato
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan.,Division of Brain Circuits, National Institute for Basic Biology, Okazaki, Aichi, Japan.,Department of Neurology, Graduate School of Medicine, Nagoya City University, Nagoya, Japan.,Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroaki Wake
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan.,Division of Brain Circuits, National Institute for Basic Biology, Okazaki, Aichi, Japan.,Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan.,Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Saitama, Japan.,Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
| | - Philip R Lee
- Section on Nervous System Development and Plasticity, National Institutes of Health, National Institute of Child Health and Human Development, Bethesda, Maryland
| | - Yoshihisa Tachibana
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Riho Ono
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Shouta Sugio
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yukio Tsuji
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yasuyo H Tanaka
- Division of Brain Circuits, National Institute for Basic Biology, Okazaki, Aichi, Japan.,Department of Physiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Yasuhiro R Tanaka
- Division of Brain Circuits, National Institute for Basic Biology, Okazaki, Aichi, Japan.,Department of Physiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Yoshito Masamizu
- Division of Brain Circuits, National Institute for Basic Biology, Okazaki, Aichi, Japan.,Department of Physiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Riichiro Hira
- Division of Brain Circuits, National Institute for Basic Biology, Okazaki, Aichi, Japan
| | - Andrew J Moorhouse
- Department of Physiology, School of Medical Sciences, The University of New South Wales, Sydney, Australia
| | - Nobuaki Tamamaki
- Department of Morphological Neural Science, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan
| | - Kazuhiro Ikenaka
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, Okazaki, Japan
| | - Noriyuki Matsukawa
- Department of Neurology, Graduate School of Medicine, Nagoya City University, Nagoya, Japan
| | - R Douglas Fields
- Section on Nervous System Development and Plasticity, National Institutes of Health, National Institute of Child Health and Human Development, Bethesda, Maryland
| | - Junichi Nabekura
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan.,Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan.,School of Life Science, The Graduate School for Advanced Study, Hayama, Japan
| | - Masanori Matsuzaki
- Division of Brain Circuits, National Institute for Basic Biology, Okazaki, Aichi, Japan.,Department of Physiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.,Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan.,School of Life Science, The Graduate School for Advanced Study, Hayama, Japan
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9
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Moorhouse AJ, Power JM. Making light work of fine-tuning channelrhodopsins. J Biol Chem 2019; 294:3822-3823. [PMID: 30877261 DOI: 10.1074/jbc.h119.007749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The development of genetically engineered proteins that can control cell excitability with light have revolutionized our understanding of the nervous system. The most widely used of these optogenetic tools is the light-gated ion channel, channelrhodopsin 2 (ChR2). A new study by Cho et al. describes the development of ChR2 variants with improved photocurrents and more selective ion permeability using an automated multifaceted fluorescence-based screening. This methodological framework holds promise not only in refining features of ChR2, but also for other proteins in which fluorescence phenotyping is possible.
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Affiliation(s)
- Andrew J Moorhouse
- From the School of Medical Sciences, UNSW Sydney, New South Wales, 2052, Australia
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10
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Abstract
Microglia are the sole immune responding cells in the central nervous system. Their role as neuroimmune cells in the pathogenesis of various neurodegenerative and infectious diseases of the brain have been extensively studied. Upon brain disease and infection, they adopt an activated phenotype associated with the release of cytokines and neurotrophic factors and resulting in neuroprotective or neurotoxic outcomes. However, microglia are resident also in the healthy or physiological brain, but much less is known about their role(s) in the healthy brain, partly due to technical limitations regarding investigation of these highly reactive cells in the intact brain. Recent developments in molecular probes and in vivo optical imaging techniques has now helped to characterize microglia in the physiological or healthy brain. In vivo two-photon imaging of fluorescently labeled microglia have revealed that they are highly motile cells in the healthy brain, extending and retracting their processes that extend from a largely stationary cell soma. In this chapter, we briefly summarize some of the physiological functions of microglia in the uninjured brain, with a focus on interactions they have with synapses.
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Affiliation(s)
- Hiroaki Wake
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan.,Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Saitama, Japan.,Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
| | - Hiroshi Horiuchi
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan.,Department of Physiological Sciences, The Graduate School for Advanced Study, Hayama, Japan
| | - Daisuke Kato
- Division of System Neuroscience, Kobe University Graduate School of Medicine, Kobe, Japan.,Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan
| | - Andrew J Moorhouse
- School of Medical Sciences, The University of New South Wales, Sydney, NSW, Australia
| | - Junichi Nabekura
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan. .,Department of Physiological Sciences, The Graduate School for Advanced Study, Hayama, Japan.
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11
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Nakahata Y, Eto K, Murakoshi H, Watanabe M, Kuriu T, Hirata H, Moorhouse AJ, Ishibashi H, Nabekura J. Activation-Dependent Rapid Postsynaptic Clustering of Glycine Receptors in Mature Spinal Cord Neurons. eNeuro 2017; 4:ENEURO.0194-16.2017. [PMID: 28197549 PMCID: PMC5292596 DOI: 10.1523/eneuro.0194-16.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 01/05/2017] [Accepted: 01/17/2017] [Indexed: 12/02/2022] Open
Abstract
Inhibitory synapses are established during development but continue to be generated and modulated in strength in the mature nervous system. In the spinal cord and brainstem, presynaptically released inhibitory neurotransmitter dominantly switches from GABA to glycine during normal development in vivo. While presynaptic mechanisms of the shift of inhibitory neurotransmission are well investigated, the contribution of postsynaptic neurotransmitter receptors to this shift is not fully elucidated. Synaptic clustering of glycine receptors (GlyRs) is regulated by activation-dependent depolarization in early development. However, GlyR activation induces hyperpolarization after the first postnatal week, and little is known whether and how presynaptically released glycine regulates postsynaptic receptors in a depolarization-independent manner in mature developmental stage. Here we developed spinal cord neuronal culture of rodents using chronic strychnine application to investigate whether initial activation of GlyRs in mature stage could change postsynaptic localization of GlyRs. Immunocytochemical analyses demonstrate that chronic blockade of GlyR activation until mature developmental stage resulted in smaller clusters of postsynaptic GlyRs that could be enlarged upon receptor activation for 1 h in the mature stage. Furthermore, live cell-imaging techniques show that GlyR activation decreases its lateral diffusion at synapses, and this phenomenon is dependent on PKC, but neither Ca2+ nor CaMKII activity. These results suggest that the GlyR activation can regulate receptor diffusion and cluster size at inhibitory synapses in mature stage, providing not only new insights into the postsynaptic mechanism of shifting inhibitory neurotransmission but also the inhibitory synaptic plasticity in mature nervous system.
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Affiliation(s)
- Yoshihisa Nakahata
- Division of Homeostatic Development, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
| | - Kei Eto
- Division of Homeostatic Development, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
| | - Hideji Murakoshi
- Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
- Supportive Center for Brain Research, National Institute for Physiological Science, Okazaki 444-8585, Japan
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi 332-0012, Japan
| | - Miho Watanabe
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Toshihiko Kuriu
- Department of Neurophysiology, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Tokushima 769-2193, Japan
| | - Hiromi Hirata
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi 332-0012, Japan
- Division of Molecular and Developmental Biology, National Institute of Genetics, Mishima 411-8540, Japan
- Department of Genetics, The Graduate University for Advanced Studies (SOKENDAI), Mishima 411-8540, Japan
- Department of Chemistry and Biological Science, Graduate School of Science and Engineering, Aoyama Gakuin University, Sagamihara 252-5258, Japan
| | - Andrew J. Moorhouse
- Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney 2052, Australia
| | - Hitoshi Ishibashi
- Division of Homeostatic Development, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
- Department of Physiology, Kitasato University School of Allied Health Sciences, Sagamihara 252-0373, Japan
| | - Junichi Nabekura
- Division of Homeostatic Development, Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
- CREST, Japan Science and Technology Agency (JST), Kawaguchi 332-0012, Japan
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12
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Miyamoto A, Wake H, Ishikawa AW, Eto K, Shibata K, Murakoshi H, Koizumi S, Moorhouse AJ, Yoshimura Y, Nabekura J. Microglia contact induces synapse formation in developing somatosensory cortex. Nat Commun 2016; 7:12540. [PMID: 27558646 PMCID: PMC5007295 DOI: 10.1038/ncomms12540] [Citation(s) in RCA: 416] [Impact Index Per Article: 52.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 07/12/2016] [Indexed: 01/17/2023] Open
Abstract
Microglia are the immune cells of the central nervous system that play important roles in brain pathologies. Microglia also help shape neuronal circuits during development, via phagocytosing weak synapses and regulating neurogenesis. Using in vivo multiphoton imaging of layer 2/3 pyramidal neurons in the developing somatosensory cortex, we demonstrate here that microglial contact with dendrites directly induces filopodia formation. This filopodia formation occurs only around postnatal day 8-10, a period of intense synaptogenesis and when microglia have an activated phenotype. Filopodia formation is preceded by contact-induced Ca(2+) transients and actin accumulation. Inhibition of microglia by genetic ablation decreases subsequent spine density, functional excitatory synapses and reduces the relative connectivity from layer 4 neurons. Our data provide the direct demonstration of microglial-induced spine formation and provide further insights into immune system regulation of neuronal circuit development, with potential implications for developmental disorders of immune and brain dysfunction.
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Affiliation(s)
- Akiko Miyamoto
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Core Research for Evolutional Science and Technology, Japan Agency for Medical Research and Development, Tokyo 100-0004, Japan
| | - Hiroaki Wake
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Core Research for Evolutional Science and Technology, Japan Agency for Medical Research and Development, Tokyo 100-0004, Japan
- Department of Physiological Sciences, The Graduate School for Advanced Study, Hayama 240-0193, Japan
- Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Saitama 102-0076, Japan
| | - Ayako Wendy Ishikawa
- Department of Physiological Sciences, The Graduate School for Advanced Study, Hayama 240-0193, Japan
- Division of Visual Information Processing, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
| | - Kei Eto
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Core Research for Evolutional Science and Technology, Japan Agency for Medical Research and Development, Tokyo 100-0004, Japan
- Department of Physiological Sciences, The Graduate School for Advanced Study, Hayama 240-0193, Japan
| | - Keisuke Shibata
- Core Research for Evolutional Science and Technology, Japan Agency for Medical Research and Development, Tokyo 100-0004, Japan
- Department of Pharmacology, Graduated School of Medical and Engineering, Yamanashi University, Chuo 409-3898, Japan
| | - Hideji Murakoshi
- Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Saitama 102-0076, Japan
- Section of Multiphoton Neuroimaging, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
| | - Schuichi Koizumi
- Core Research for Evolutional Science and Technology, Japan Agency for Medical Research and Development, Tokyo 100-0004, Japan
- Department of Pharmacology, Graduated School of Medical and Engineering, Yamanashi University, Chuo 409-3898, Japan
| | - Andrew J. Moorhouse
- School of Medical Sciences, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Yumiko Yoshimura
- Department of Physiological Sciences, The Graduate School for Advanced Study, Hayama 240-0193, Japan
- Division of Visual Information Processing, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
| | - Junichi Nabekura
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Core Research for Evolutional Science and Technology, Japan Agency for Medical Research and Development, Tokyo 100-0004, Japan
- Department of Physiological Sciences, The Graduate School for Advanced Study, Hayama 240-0193, Japan
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13
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Kim SK, Hayashi H, Ishikawa T, Shibata K, Shigetomi E, Shinozaki Y, Inada H, Roh SE, Kim SJ, Lee G, Bae H, Moorhouse AJ, Mikoshiba K, Fukazawa Y, Koizumi S, Nabekura J. Cortical astrocytes rewire somatosensory cortical circuits for peripheral neuropathic pain. J Clin Invest 2016; 126:1983-97. [PMID: 27064281 PMCID: PMC4855913 DOI: 10.1172/jci82859] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 02/25/2016] [Indexed: 01/09/2023] Open
Abstract
Long-term treatments to ameliorate peripheral neuropathic pain that includes mechanical allodynia are limited. While glial activation and altered nociceptive transmission within the spinal cord are associated with the pathogenesis of mechanical allodynia, changes in cortical circuits also accompany peripheral nerve injury and may represent additional therapeutic targets. Dendritic spine plasticity in the S1 cortex appears within days following nerve injury; however, the underlying cellular mechanisms of this plasticity and whether it has a causal relationship to allodynia remain unsolved. Furthermore, it is not known whether glial activation occurs within the S1 cortex following injury or whether it contributes to this S1 synaptic plasticity. Using in vivo 2-photon imaging with genetic and pharmacological manipulations of murine models, we have shown that sciatic nerve ligation induces a re-emergence of immature metabotropic glutamate receptor 5 (mGluR5) signaling in S1 astroglia, which elicits spontaneous somatic Ca2+ transients, synaptogenic thrombospondin 1 (TSP-1) release, and synapse formation. This S1 astrocyte reactivation was evident only during the first week after injury and correlated with the temporal changes in S1 extracellular glutamate levels and dendritic spine turnover. Blocking the astrocytic mGluR5-signaling pathway suppressed mechanical allodynia, while activating this pathway in the absence of any peripheral injury induced long-lasting (>1 month) allodynia. We conclude that reawakened astrocytes are a key trigger for S1 circuit rewiring and that this contributes to neuropathic mechanical allodynia.
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Affiliation(s)
- Sun Kwang Kim
- Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul, South Korea
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
| | - Hideaki Hayashi
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Tatsuya Ishikawa
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
- Department of Physiological Sciences, The Graduate School for Advanced Study, Hayama, Japan
| | - Keisuke Shibata
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Eiji Shigetomi
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Youichi Shinozaki
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Hiroyuki Inada
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
| | - Seung Eon Roh
- Department of Physiology, College of Medicine, Seoul National University, Seoul, South Korea
| | - Sang Jeong Kim
- Department of Physiology, College of Medicine, Seoul National University, Seoul, South Korea
| | - Gihyun Lee
- Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul, South Korea
| | - Hyunsu Bae
- Department of Physiology, College of Korean Medicine, Kyung Hee University, Seoul, South Korea
| | - Andrew J. Moorhouse
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, Brain Science Institute, RIKEN, Saitama, Japan
| | - Yugo Fukazawa
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
- Division of Cell Biology and Neuroscience, Department of Histological and Physiological Sciences, Faculty of Medical Science, University of Fukui, Fukui, Japan
| | - Schuichi Koizumi
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Junichi Nabekura
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan
- Department of Physiological Sciences, The Graduate School for Advanced Study, Hayama, Japan
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14
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Barry PH, Sugiharto S, Lewis TM, Moorhouse AJ. Further analysis of counterion permeation through anion-selective glycine receptor channels. Channels (Austin) 2014; 4:142-9. [DOI: 10.4161/chan.4.3.11020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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15
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Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, McGrath JC, Catterall WA, Spedding M, Peters JA, Harmar AJ, Abul-Hasn N, Anderson CM, Anderson CMH, Araiksinen MS, Arita M, Arthofer E, Barker EL, Barratt C, Barnes NM, Bathgate R, Beart PM, Belelli D, Bennett AJ, Birdsall NJM, Boison D, Bonner TI, Brailsford L, Bröer S, Brown P, Calo G, Carter WG, Catterall WA, Chan SLF, Chao MV, Chiang N, Christopoulos A, Chun JJ, Cidlowski J, Clapham DE, Cockcroft S, Connor MA, Cox HM, Cuthbert A, Dautzenberg FM, Davenport AP, Dawson PA, Dent G, Dijksterhuis JP, Dollery CT, Dolphin AC, Donowitz M, Dubocovich ML, Eiden L, Eidne K, Evans BA, Fabbro D, Fahlke C, Farndale R, Fitzgerald GA, Fong TM, Fowler CJ, Fry JR, Funk CD, Futerman AH, Ganapathy V, Gaisnier B, Gershengorn MA, Goldin A, Goldman ID, Gundlach AL, Hagenbuch B, Hales TG, Hammond JR, Hamon M, Hancox JC, Hauger RL, Hay DL, Hobbs AJ, Hollenberg MD, Holliday ND, Hoyer D, Hynes NA, Inui KI, Ishii S, Jacobson KA, Jarvis GE, Jarvis MF, Jensen R, Jones CE, Jones RL, Kaibuchi K, Kanai Y, Kennedy C, Kerr ID, Khan AA, Klienz MJ, Kukkonen JP, Lapoint JY, Leurs R, Lingueglia E, Lippiat J, Lolait SJ, Lummis SCR, Lynch JW, MacEwan D, Maguire JJ, Marshall IL, May JM, McArdle CA, McGrath JC, Michel MC, Millar NS, Miller LJ, Mitolo V, Monk PN, Moore PK, Moorhouse AJ, Mouillac B, Murphy PM, Neubig RR, Neumaier J, Niesler B, Obaidat A, Offermanns S, Ohlstein E, Panaro MA, Parsons S, Pwrtwee RG, Petersen J, Pin JP, Poyner DR, Prigent S, Prossnitz ER, Pyne NJ, Pyne S, Quigley JG, Ramachandran R, Richelson EL, Roberts RE, Roskoski R, Ross RA, Roth M, Rudnick G, Ryan RM, Said SI, Schild L, Sanger GJ, Scholich K, Schousboe A, Schulte G, Schulz S, Serhan CN, Sexton PM, Sibley DR, Siegel JM, Singh G, Sitsapesan R, Smart TG, Smith DM, Soga T, Stahl A, Stewart G, Stoddart LA, Summers RJ, Thorens B, Thwaites DT, Toll L, Traynor JR, Usdin TB, Vandenberg RJ, Villalon C, Vore M, Waldman SA, Ward DT, Willars GB, Wonnacott SJ, Wright E, Ye RD, Yonezawa A, Zimmermann M. The Concise Guide to PHARMACOLOGY 2013/14: overview. Br J Pharmacol 2014; 170:1449-58. [PMID: 24528237 DOI: 10.1111/bph.12444] [Citation(s) in RCA: 146] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties from the IUPHAR database. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. This compilation of the major pharmacological targets is divided into seven areas of focus: G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors & Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and GRAC and provides a permanent, citable, point-in-time record that will survive database updates.
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Affiliation(s)
- Stephen P H Alexander
- School of Life Sciences, University of Nottingham Medical School, Nottingham, NG7 2UH, UK
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16
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Barry PH, Lewis TM, Moorhouse AJ. An optimised 3 M KCl salt-bridge technique used to measure and validate theoretical liquid junction potential values in patch-clamping and electrophysiology. Eur Biophys J 2013; 42:631-46. [PMID: 23794083 DOI: 10.1007/s00249-013-0911-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 05/09/2013] [Indexed: 11/30/2022]
Abstract
Accurate potential measurements in electrophysiological experiments require correction for liquid junction potentials (LJPs), and, in patch-clamping especially, these can often be ~5-10 mV or more. They can be either calculated, if ion mobilities are known, or measured directly. We describe an optimised system to directly measure LJPs with a patch-clamp amplifier, using as a reference electrode, a freshly-cut 3 M KCl-agar salt-bridge (in polyethylene tubing) with its tip cut off by at least 5 mm during solution changes to eliminate its solution-history-dependent effects. We quantify such history-dependent effects and complement this with a de-novo theoretical analysis of salt diffusion to and from the salt-bridge. Our analysis and experimental results validate the optimised methodology for measuring LJPs, and the use of the Henderson equation for accurately calculating them. The use of this equation is also assessed and generally validated in the light of rigorous Nernst-Planck-Poisson and other numerical simulations and analytical studies of LJPs over recent decades. Digitizing, recording and amplifying the measured potentials increases their accuracy. The measured potentials still need correction for small, well-defined calculable, shifts in LJPs at the 3 M KCl-agar reference. Using this technique, we have measured changes in LJPs for diluted solutions of NaCl, LiCl, KCl, CsCl and NaF, obtaining excellent agreement within ±0.1 mV of predicted values, calculated using ion activities. Our de novo LJP measurements of biionic combinations of the above undiluted salts, and NaI and NaF (with halide anions I⁻ and F⁻), generally also gave excellent agreement with predicted values.
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Affiliation(s)
- Peter H Barry
- Department of Physiology, School of Medical Sciences, University of New South Wales-UNSW, Sydney, NSW 2052, Australia.
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17
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Miyamoto A, Wake H, Moorhouse AJ, Nabekura J. Microglia and synapse interactions: fine tuning neural circuits and candidate molecules. Front Cell Neurosci 2013; 7:70. [PMID: 23720611 PMCID: PMC3654203 DOI: 10.3389/fncel.2013.00070] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 04/26/2013] [Indexed: 11/13/2022] Open
Abstract
Brain function depends critically on the interactions among the underlying components that comprise neural circuits. This includes coordinated activity in pre-synaptic and postsynaptic neuronal elements, but also in the non-neuronal elements such as glial cells. Microglia are glial cells in the central nervous system (CNS) that have well-known roles in neuronal immune function, responding to infections and brain injury and influencing the progress of neurodegenerative disorders. However, microglia are also surveyors of the healthy brain, continuously extending and retracting their processes and making contacts with pre- and postsynaptic elements of neural circuits, a process that clearly consumes considerable energy. Pruning of synapses during development and in response to injury has also been documented, and we propose that this extensive surveillance of the brain parenchyma in adult healthy brain results in similar “fine-tuning” of neural circuits. A reasonable extension is that a dysfunction of such a homeostatic role of microglia could be a primary cause of neuronal disease. Indeed, neuronal functions including cognition, personality, and information processing are affected by immune status. In this review we focus on the interactions between microglia and synapses, the possible cellular and molecular mechanisms that mediate such contacts, and the possible implications these interactions may have in the fine tuning of neural circuits that is so important for physiological brain function.
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Affiliation(s)
- Akiko Miyamoto
- Division of Homeostatic Development, National Institute for Physiological Sciences Okazaki, Japan ; Department of Physiological Sciences, The Graduate School for Advanced Study Hayama, Japan
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Eto K, Ishibashi H, Yoshimura T, Watanabe M, Miyamoto A, Ikenaka K, Moorhouse AJ, Nabekura J. Enhanced GABAergic activity in the mouse primary somatosensory cortex is insufficient to alleviate chronic pain behavior with reduced expression of neuronal potassium-chloride cotransporter. J Neurosci 2012; 32:16552-9. [PMID: 23175811 PMCID: PMC6621771 DOI: 10.1523/jneurosci.2104-12.2012] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 09/10/2012] [Accepted: 09/17/2012] [Indexed: 01/22/2023] Open
Abstract
The correct balance between excitation and inhibition is crucial for brain function and disrupted in several pathological conditions. Excitatory neuronal circuits in the primary somatosensory cortex (S1) are modulated by local inhibitory neurons with the balance of this excitatory and inhibitory activity important for function. The activity of excitatory layer 2/3 neurons (L2/3) in the S1 cortex is increased in chronic pain, but it is not known how the local interneurons, nor the balance between excitation and inhibition, may change in chronic pain. Using in vivo two-photon calcium imaging and electrophysiology, we report here that the response of L2/3 local inhibitory neurons to both sensory stimulation and to layer 4 electrical stimulation increases in inflammatory chronic pain. Local application into L2/3 of a GABA(A) receptor blocker further enhanced the activity of S1 excitatory neurons and reduced pain thresholds, whereas local application of the GABA(A) receptor modulators (muscimol and diazepam) transiently alleviated the allodynia. This illustrates the importance of the local inhibitory pathways in chronic pain sensation. A reduction in the expression and function of the potassium-chloride cotransporter 2 occurred during chronic pain, which reduces the efficacy of the inhibitory inputs to L2/3 excitatory neurons. In summary, both excitatory and inhibitory neuronal activities in the S1 are enhanced in the chronic pain model, but the increased inhibition is insufficient to completely counterbalance the increased excitation and alleviate the symptoms of chronic pain.
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Affiliation(s)
- Kei Eto
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
| | - Hitoshi Ishibashi
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan
| | - Takeshi Yoshimura
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, Okazaki 444-8787, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan
| | - Miho Watanabe
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
| | - Akiko Miyamoto
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan
| | - Kazuhiro Ikenaka
- Division of Neurobiology and Bioinformatics, National Institute for Physiological Sciences, Okazaki 444-8787, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan
| | - Andrew J. Moorhouse
- Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia, and
| | - Junichi Nabekura
- Division of Homeostatic Development, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama 332-0012, Japan
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19
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Nakahata Y, Miyamoto A, Watanabe M, Moorhouse AJ, Nabekura J, Ishibashi H. Depolarizing shift in the GABA-induced current reversal potential by lidocaine hydrochloride. Brain Res 2010; 1345:19-27. [PMID: 20580693 DOI: 10.1016/j.brainres.2010.05.052] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 05/06/2010] [Accepted: 05/16/2010] [Indexed: 11/23/2022]
Abstract
Lidocaine hydrochloride (LC-HCl) is widely used as a local anesthetic, while various adverse effects of LC-HCl, such as seizures have also been reported. Lidocaine is reported to inhibit various channels and receptors including GABA(A) receptors. Although the GABA(A) receptor-mediated response depends on Cl(-) equilibrium potential (E(Cl)), little is known about the effect of LC-HCl on E(Cl). In the present study, we investigated the effect of LC-HCl on GABA-induced currents in cultured rat hippocampal neurons with gramicidin-perforated patch-clamp recording which is known to keep the intracellular Cl(-) concentration intact. LC-HCl inhibited outward GABA-induced currents with depolarizing shift of the GABA reversal potential (E(GABA)). The LC-HCl-induced positive E(GABA) shift was not observed with conventional whole-cell patch-clamp method which cannot retain intact intracellular Cl(-) concentration. The LC-HCl action on E(GABA) was inhibited by either furosemide, a blocker of both Na(+)-K(+)-Cl(-) cotransporter (NKCC) and K(+)-Cl(-) cotransporter (KCC), or an increase in extracellular K(+) concentrations. Neither bumetanide, a specific inhibitor of NKCC, nor Na(+)-free external solution had any effect on the LC-HCl-induced E(GABA) shift. QX-314, a membrane impermeable lidocaine derivative, failed to shift E(GABA) to positive potential. Furthermore, LC-HCl caused a depolarizing shift of E(GABA) in cultured GT1-7 cells expressing KCC2 but failed to change E(GABA) in GT1-7 cells without expression of KCC2. These results suggest that the LC-HCl-induced positive E(GABA) shift is due to a blockade of KCC2. Together with the direct LC-HCl action to GABA(A) receptors, the positive E(GABA) shift induced by LC-HCl reduces the GABAergic inhibition in the central nervous system.
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Affiliation(s)
- Yoshihisa Nakahata
- Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki, Japan
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Sugiharto S, Carland JE, Lewis TM, Moorhouse AJ, Barry PH. External divalent cations increase anion-cation permeability ratio in glycine receptor channels. Pflugers Arch 2010; 460:131-52. [PMID: 20198385 DOI: 10.1007/s00424-010-0792-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2009] [Revised: 01/15/2010] [Accepted: 01/22/2010] [Indexed: 11/24/2022]
Abstract
The functional role of ligand-gated ion channels in the central nervous system depends on their relative anion-cation permeability. Using standard whole-cell patch clamp measurements and NaCl dilution potential measurements, we explored the effect of external divalent ions on anion-cation selectivity in alpha1-homomeric wild-type glycine receptor channels. We show that increasing external Ca(2+) from 0 to 4 mM resulted in a sigmoidal increase in anion-cation permeability by 37%, reaching a maximum above about 2 mM. Our accurate quantification of this effect required rigorous correction for liquid junction potentials (LJPs) using ion activities, and allowing for an initial offset potential. Failure to do this results in a considerable overestimation of the Ca(2+)-induced increase in anion-cation permeability by almost three-fold at 4 mM external Ca(2+). Calculations of LJPs (using activities)_ were validated by precise agreement with direct experimental measurements. External SO (4) (2-) was found to decrease anion-cation permeability. Single-channel conductance measurements indicated that external Ca(2+) both decreased Na(+) permeability and increased Cl(-) permeability. There was no evidence of Ca(2+) changing channel pore diameter. Theoretical modeling indicates that the effect is not surface charge related. Rather, we propose that, under dilution conditions, the presence of an impermeant Ca(2+) ion in the channel pore region just external to the selectivity filter tends to electrostatically retard outward movement of Na(+) ions and to enhance movement of Cl(-) ions down their energy gradients.
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Affiliation(s)
- Silas Sugiharto
- Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, NSW, 2052, Australia
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22
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Watanabe M, Wake H, Moorhouse AJ, Nabekura J. Clustering of neuronal K+-Cl- cotransporters in lipid rafts by tyrosine phosphorylation. J Biol Chem 2009; 284:27980-27988. [PMID: 19679663 PMCID: PMC2788850 DOI: 10.1074/jbc.m109.043620] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 08/11/2009] [Indexed: 02/02/2023] Open
Abstract
The neuronal K(+)-Cl(-) cotransporter (KCC2) is a membrane transport protein that extrudes Cl(-) from neurons and helps maintain low intracellular [Cl(-)] and hyperpolarizing GABAergic synaptic potentials. Depolarizing gamma-aminobutyric acid (GABA) responses in neonatal neurons and following various forms of neuronal injury are associated with reduced levels of KCC2 expression. Despite the importance for plasticity of inhibitory transmission, less is known about cellular mechanisms involved in more dynamic changes in KCC2 function. In this study, we investigated the role of tyrosine phosphorylation in KCC2 localization and function in hippocampal neurons and in cultured GT1-7 cells. Mutation to the putative tyrosine phosphorylation site within the long intracellular carboxyl terminus of KCC2(Y1087D) or application of the tyrosine kinase inhibitor genistein shifted the GABA reversal potential (E(GABA)) to more depolarized values, indicating reduced KCC2 function. This was associated with a change in the expression pattern of KCC2 from a punctate distribution to a more uniform distribution, suggesting that functional tyrosine-phosphorylated KCC2 forms clusters in restricted membrane domains. Sodium vanadate, a tyrosine phosphatase inhibitor, increased the proportion of KCC2 associated with lipid rafts membrane domains. Loss of tyrosine phosphorylation also reduced oligomerization of KCC2. A loss of the punctuate distribution and oligomerization of KCC2 and a more depolarized E(GABA) were seen when the 28-amino-acid carboxyl terminus of KCC2 was deleted. These results indicate that direct tyrosine phosphorylation of KCC2 results in membrane clusters and functional transport activity, suggesting a mechanism by which intracellular Cl(-) concentrations and GABA responses can be rapidly modulated.
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Affiliation(s)
- Miho Watanabe
- Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
| | - Hiroaki Wake
- Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan; Core Research for the Evolutionary Science and Technology, Japan Science and Technology Corporation, Saitama 333-0012, Japan
| | - Andrew J Moorhouse
- Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Junichi Nabekura
- Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan; Core Research for the Evolutionary Science and Technology, Japan Science and Technology Corporation, Saitama 333-0012, Japan; Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDAI), Hayama 240-0193, Japan.
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Carland JE, Cooper MA, Sugiharto S, Jeong HJ, Lewis TM, Barry PH, Peters JA, Lambert JJ, Moorhouse AJ. Characterization of the effects of charged residues in the intracellular loop on ion permeation in alpha1 glycine receptor channels. J Biol Chem 2008; 284:2023-30. [PMID: 19049967 DOI: 10.1074/jbc.m806618200] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Cys loop receptor channels mediate fast synaptic transmission in the nervous system. The M2-demarcated transmembrane pore is an important determinant of their ion permeation properties. Portals within the intracellular domain are also part of the permeation pathway in cationic Cys loop receptors, with charged residues in a helical MA stretch partially lining these openings profoundly affecting channel conductance. It is unknown whether analogous portals contribute to the permeation pathway in anionic Cys loop receptors. We therefore investigated the influence of charged residues within the proposed MA stretch on functional properties of the homomeric glycine alpha1 receptor. Up to eight basic residues in the MA stretch were concurrently mutated to a negatively charged glutamate, and wild-type and mutant subunits were expressed in HEK-293 cells. Mutation of all eight residues produced a non-functional receptor. The greatest reduction in conductance at negative membrane potentials (from 92.2+/-2.8 to 60.0+/-2.2 picosiemens) was observed with glutamate present at the 377, 378, 385, and 386 positions (the 4E subunit). Inclusion of additional glutamate residues within this subunit did not decrease conductance further. Neutralizing these residues (the 4A subunit) caused a modest decrease in conductance (80.5+/-2.3 picosiemens). Outward conductance at positive potentials was not markedly affected. Anion to cation selectivity and concentration-response relationships were unaffected by the 4A or 4E mutations. Our results identify basic residues affecting conductance in the glycine receptor, suggesting that portals are part of the extended permeation pathway but that the M2-demarcated channel pore is the dominant determinant of permeation properties in glycine receptors.
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Affiliation(s)
- Jane E Carland
- School of Medical Sciences, University of New South Wales, Sydney, 2052, Australia
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Park EJ, Choi IS, Cho JH, Nakamura M, Lee JJ, Lee MG, Choi BJ, Moorhouse AJ, Jang IS. Zinc modulation of glycine receptors in acutely isolated rat CA3 neurons. Life Sci 2008; 83:149-54. [DOI: 10.1016/j.lfs.2008.04.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2007] [Revised: 04/25/2008] [Accepted: 04/25/2008] [Indexed: 10/21/2022]
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Wake H, Watanabe M, Moorhouse AJ, Kanematsu T, Horibe S, Matsukawa N, Asai K, Ojika K, Hirata M, Nabekura J. Early changes in KCC2 phosphorylation in response to neuronal stress result in functional downregulation. J Neurosci 2007; 27:1642-50. [PMID: 17301172 PMCID: PMC6673731 DOI: 10.1523/jneurosci.3104-06.2007] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Revised: 01/04/2007] [Accepted: 01/05/2007] [Indexed: 01/26/2023] Open
Abstract
The K+ Cl- cotransporter KCC2 plays an important role in chloride homeostasis and in neuronal responses mediated by ionotropic GABA and glycine receptors. The expression levels of KCC2 in neurons determine whether neurotransmitter responses are inhibitory or excitatory. KCC2 expression is decreased in developing neurons, as well as in response to various models of neuronal injury and epilepsy. We investigated whether there is also direct modulation of KCC2 activity by changes in phosphorylation during such neuronal stressors. We examined tyrosine phosphorylation of KCC2 in rat hippocampal neurons under different conditions of in vitro neuronal stress and the functional consequences of changes in tyrosine phosphorylation. Oxidative stress (H2O2) and the induction of seizure activity (BDNF) and hyperexcitability (0 Mg2+) resulted in a rapid dephosphorylation of KCC2 that preceded the decreases in KCC2 protein or mRNA expression. Dephosphorylation of KCC2 is correlated with a reduction of transport activity and a decrease in [Cl-]i, as well as a reduction in KCC2 surface expression. Manipulation of KCC2 tyrosine phosphorylation resulted in altered neuronal viability in response to in vitro oxidative stress. During continued neuronal stress, a second phase of functional KCC2 downregulation occurs that corresponds to decreases in KCC2 protein expression levels. We propose that neuronal stress induces a rapid loss of tyrosine phosphorylation of KCC2 that results in translocation of the protein and functional loss of transport activity. Additional understanding of the mechanisms involved may provide means for manipulating the extent of irreversible injury resulting from different neuronal stressors.
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Affiliation(s)
- Hiroaki Wake
- Division of Homeostatic Development, National Institute of Physiological Sciences, Okazaki 444-8585, Japan
- Department of Neurology and Neuroscience, Nagoya City University Graduate School of Medical Sciences, Mizuho-ku, Nagoya 467-8601, Japan
| | - Miho Watanabe
- Division of Homeostatic Development, National Institute of Physiological Sciences, Okazaki 444-8585, Japan
| | - Andrew J. Moorhouse
- Department of Physiology and Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Takashi Kanematsu
- Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Shoko Horibe
- Division of Homeostatic Development, National Institute of Physiological Sciences, Okazaki 444-8585, Japan
- School of Life Science, The Graduate University for Advanced Studies, Hayama 240-0193, Japan, and
| | - Noriyuki Matsukawa
- Department of Neurology and Neuroscience, Nagoya City University Graduate School of Medical Sciences, Mizuho-ku, Nagoya 467-8601, Japan
| | - Kiyofumi Asai
- Department of Molecular Neurobiology, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
| | - Kosei Ojika
- Department of Neurology and Neuroscience, Nagoya City University Graduate School of Medical Sciences, Mizuho-ku, Nagoya 467-8601, Japan
| | - Masato Hirata
- Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan
| | - Junichi Nabekura
- Division of Homeostatic Development, National Institute of Physiological Sciences, Okazaki 444-8585, Japan
- School of Life Science, The Graduate University for Advanced Studies, Hayama 240-0193, Japan, and
- Core Research for the Evolutionary Science and Technology, Japan Science and Technology Corporation, Saitama 332-0012, Japan
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Qu W, Moorhouse AJ, Chandra M, Pierce KD, Lewis TM, Barry PH. A single P-loop glutamate point mutation to either lysine or arginine switches the cation-anion selectivity of the CNGA2 channel. ACTA ACUST UNITED AC 2006; 127:375-89. [PMID: 16533895 PMCID: PMC2151509 DOI: 10.1085/jgp.200509378] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cyclic nucleotide-gated (CNG) channels play a critical role in olfactory and visual transduction. Site-directed mutagenesis and inside-out patch-clamp recordings were used to investigate ion permeation and selectivity in two mutant homomeric rat olfactory CNGA2 channels expressed in HEK293 cells. A single point mutation of the negatively charged pore loop (P-loop) glutamate (E342) to either a positively charged lysine or arginine resulted in functional channels, which consistently responded to cGMP, although the currents were generally extremely small. The concentration–response curve of the lysine mutant channel was very similar to that of wild-type (WT) channels, suggesting no major structural alteration to the mutant channels. Reversal potential measurements, during cytoplasmic NaCl dilutions, showed that the lysine and the arginine mutations switched the selectivity of the channel from cations (PCl/PNa = 0.07 [WT]) to anions (PCl/PNa = 14 [Lys] or 10 [Arg]). Relative anion permeability sequences for the two mutant channels, measured with bi-ionic substitutions, were NO3− > I− > Br− > Cl− > F− > acetate−, the same as those obtained for anion-selective GABA and glycine channels. The mutant channels also seem to have an extremely small single-channel conductance, measured using noise analysis of about 1–2 pS, compared to a WT value of about 29 pS. The results showed that it is predominantly the charge of the E342 residue in the P-loop, rather than the pore helix dipoles, which controls the cation–anion selectivity of this channel. However, the outward rectification displayed by both mutant channels in symmetrical NaCl solutions suggests that the negative ends of the pore helix dipoles may play a role in reducing the outward movement of Cl− ions through these anion-selective channels. These results have potential implications for the determinants of anion–cation selectivity in the large family of P-loop–containing channels.
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Affiliation(s)
- Wei Qu
- Department of Physiology and Pharmacology, School of Medical Sciences, The University of New South Wales, UNSW Sydney, Australia
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27
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Qu W, Moorhouse AJ, Lewis TM, Pierce KD, Barry PH. Mutation of the pore glutamate affects both cytoplasmic and external dequalinium block in the rat olfactory CNGA2 channel. Eur Biophys J 2005; 34:442-53. [PMID: 15928936 DOI: 10.1007/s00249-005-0479-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Revised: 02/21/2005] [Accepted: 02/28/2005] [Indexed: 10/25/2022]
Abstract
Dequalinium has recently been reported to block CNGA1 and CNGA2 channels expressed in Xenopus laevis. Using the inside-out configuration of the patch-clamp technique, we examined the effects of dequalinium on rat olfactory CNGA2 channels expressed in human embryonic kidney (HEK293) cells and studied aspects of its molecular mechanism of action. We found that cytoplasmic dequalinium blocked wild-type (WT) CNGA2 channels in a voltage-dependent manner with an IC(50) of approximately 1.3 muM at a V(m) of + 60 mV, and an effective fractional charge, zdelta, of +0.8 (z=2, delta=+0.4), suggesting that cytoplasmic dequalinium interacts with a binding site that is about two fifths of the way along the membrane electric field (from the intracellular side). Neutralizing the negatively charged pore lining glutamate acid residue (E342Q) still allows effective channel block by cytoplasmic dequalinium with an IC(50) of approximately 2.2 muM at a V(m) of +60 mV but now having a zdelta of +0.1 (delta=+0.05), indicating a profoundly decreased level of voltage-dependence. In addition, by comparing the extent of block under different levels of channel activation, we show that the block by cytoplasmic dequalinium displayed clear state-dependence in WT channels by interacting predominantly with the closed channel, whereas the block in E342Q channels was state-independent. Application of dequalinium to the external membrane surface also blocked currents through WT channels and the E342Q mutation significantly increased the IC(50) for external block approximately fivefold. These results confirm dequalinium as a potent, voltage-dependent and state-dependent blocker of cyclic-nucleotide-gated channels, and show that neutralization of the E342 residue profoundly affects the block by both cytoplasmic and external application of dequalinium.
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Affiliation(s)
- Wei Qu
- School of Medical Sciences, The University of New South Wales, Sydney, NSW 2052, Australia
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28
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Katsurabayashi S, Kubota H, Moorhouse AJ, Akaike N. Differential modulation of evoked and spontaneous glycine release from rat spinal cord glycinergic terminals by the cyclic AMP/protein kinase A transduction cascade. J Neurochem 2005; 91:657-66. [PMID: 15485496 DOI: 10.1111/j.1471-4159.2004.02741.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mechanisms underlying cyclic AMP modulation of action potential-dependent and -independent (spontaneous) release of glycine from terminals synapsing onto sacral dorsal commissural nucleus neurons of lamina X were studied in spinal cord slices using conventional patch-clamp recordings. 3-Isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor, and forskolin increased the amplitude of evoked inhibitory postsynaptic currents (eIPSCs) in a sensitive manner to protein kinase A (PKA) inhibition (with KT-5720). Direct activation (with adenosine 3',5'-cyclic-monophosphothioate, Sp-isomer) and inhibition (with adenosine 3',5'-cyclic-monophosphothioate, Rp-isomer) of PKA increased and decreased the eIPSC amplitude, respectively. Paired pulse experiments and direct injection of PKA inhibitor fragment 6-22 amide (PKI(6-22)) into the recording neuron revealed that these effects on eIPSC amplitude occurred presynaptically, indicating that evoked glycine release is regulated by presynaptic cAMP via changes in PKA activity. Increasing cAMP also increased spontaneous release of glycine, causing an increased frequency of miniature IPSCs (mIPSCs). In contrast to the effects on evoked release, this response was not solely mediated via PKA, as it was not occluded by PKA inhibition, and both direct inhibition and direct activation of PKA actually enhanced mIPSC frequency. Direct inhibition of cAMP (with SQ 22536) did, however, reduce mIPSC frequency. These results suggest cAMP modulation of evoked and spontaneous release involves different presynaptic mechanisms and proteins.
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Affiliation(s)
- Shutaro Katsurabayashi
- Cellular and System Physiology, Graduate School of Medical Studies, Kyushu University, Fukuoka, Japan
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Carland JE, Moorhouse AJ, Barry PH, Johnston GAR, Chebib M. Charged Residues at the 2′ Position of Human GABAC ρ1 Receptors Invert Ion Selectivity and Influence Open State Probability. J Biol Chem 2004; 279:54153-60. [PMID: 15485818 DOI: 10.1074/jbc.m410625200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ability of members of the nicotinicoid superfamily of ligand-gated ion channels to selectively conduct anions or cations is critical to their function within the central nervous system. Recent work has demonstrated that residues at the intracellular end of the second transmembrane domain, between the -3' and 2' positions, form the ion selectivity filter of these receptors. In this study, the proline residue at the 2' position (Pro-2') at the intracellular end of the second transmembrane domain of the gamma-aminobutyric acid type C rho 1 subunit was mutated to glutamate (rho 1P2'E) and arginine (rho 1P2'R). Dilution potential experiments indicated that the charge selectivity of the rho 1P2'E receptor channels had been inverted, with the channels now becoming predominantly cation selective, indicating the ability of negatively charged residues at this 2' position to control charge selectivity. The mutation was also seen to have significantly decreased agonist potency and intrinsic efficacy. In contrast, the rho 1P2'R receptor channels were anion-selective but were now found to be constitutively open with high holding currents (inhibited by low gamma-aminobutyric acid doses and the competitive antagonist, 1,2,5,6-tetrahydropyridine-4-yl)methylphosphinic acid alone) and increased agonist activity. Hill coefficients of both mutants were decreased, but competitive antagonist studies indicated that their binding sites were not significantly affected.
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Affiliation(s)
- Jane E Carland
- Faculty of Pharmacy, University of Sydney, New South Wales 2006, Australia
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30
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Keramidas A, Moorhouse AJ, Schofield PR, Barry PH. Ligand-gated ion channels: mechanisms underlying ion selectivity. Progress in Biophysics and Molecular Biology 2004; 86:161-204. [PMID: 15288758 DOI: 10.1016/j.pbiomolbio.2003.09.002] [Citation(s) in RCA: 162] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Anion/cation selectivity is a critical property of ion channels and underpins their physiological function. Recently, there have been numerous mutagenesis studies, which have mapped sites within the ion channel-forming segments of ligand-gated ion channels that are determinants of the ion selectivity. Site-directed mutations to specific amino acids within or flanking the M2 transmembrane segments of the anion-selective glycine, GABA(A) and GABA(C) receptors and the cation-selective nicotinic acetylcholine and serotonin (type 3) receptors have revealed discrete, equivalent regions within the ion channel that form the principal selectivity filter, leading to plausible molecular mechanisms and mathematical models to describe how ions preferentially permeate these channels. In particular, the dominant factor determining anion/cation selectivity seems to be the sign and exposure of charged amino acids lining the selectivity filter region of the open channel. In addition, the minimum pore diameter, which can be influenced by the presence of a local proline residue, also makes a contribution to such ion selectivity in LGICs with smaller diameters increasing anion/cation selectivity and larger ones decreasing it.
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Affiliation(s)
- Angelo Keramidas
- Department of Physiology and Pharmacology, School of Medical Sciences, The University of New South Wales, UNSW Sydney, NSW 2052, Australia
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Moorhouse AJ, Li S, Vickery RM, Hill MA, Morley JW. A patch-clamp investigation of membrane currents in a novel mammalian retinal ganglion cell line. Brain Res 2004; 1003:205-8. [PMID: 15019582 DOI: 10.1016/j.brainres.2004.01.027] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/27/2004] [Indexed: 10/26/2022]
Abstract
We characterised membrane currents in undifferentiated RGC-5 cells, a cell line used in in vitro models of apoptosis and glaucoma. The cells were inexcitable, with no voltage-dependent Na(+) currents or action potentials. Some novel currents were observed including basal Cl(-) currents, inwardly rectifiying K(+) currents and Gd(3+) insensitive stretch-activated currents. Our results highlight the differences between the electrophysiological properties of undifferentiated RGC-5 cells and retinal ganglion cells.
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Affiliation(s)
- Andrew J Moorhouse
- School of Medical Sciences, The University of New South Wales, Sydney, 2052, Australia
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Lee DJS, Keramidas A, Moorhouse AJ, Schofield PR, Barry PH. The contribution of proline 250 (P-2') to pore diameter and ion selectivity in the human glycine receptor channel. Neurosci Lett 2004; 351:196-200. [PMID: 14623139 DOI: 10.1016/j.neulet.2003.08.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The glycine receptor-channel (GlyR) mediates neuronal inhibition by selectively allowing the passage of Cl(-) ions through its channel. The pore region for ion selectivity is localised to the constricted internal end of the M2 transmembrane domain. This paper investigates the contribution of the P-2' residue in determining pore diameter and ion charge selectivity of the GlyR. The deletion of this proline has been shown to decrease the anion/cation permeability ratio, with P(Cl)/P(Na) decreasing from approximately 27 to approximately 4. We show that the P-2' deletion by itself produces a GlyR with a larger pore diameter ( approximately 0.69 nm) than the wild type value ( approximately 0.54 nm). This confirms that the P-2' residue reduces pore size, which suggests that, in addition to electrostatic effects, pore size also contributes to ion-charge selectivity.
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Affiliation(s)
- David J-S Lee
- Department of Physiology and Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia
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Kubota H, Katsurabayashi S, Moorhouse AJ, Murakami N, Koga H, Akaike N. GABAB receptor transduction mechanisms, and cross-talk between protein kinases A and C, in GABAergic terminals synapsing onto neurons of the rat nucleus basalis of Meynert. J Physiol 2003; 551:263-76. [PMID: 12815184 PMCID: PMC2343138 DOI: 10.1113/jphysiol.2003.046524] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The transduction mechanisms underlying presynaptic GABAB receptor-mediated inhibition of transmitter release have been characterized for a variety of synapses in the central nervous system (CNS). These studies have suggested a range of transduction mechanisms, including a role for second messengers such as protein kinases A (PKA) and C (PKC). In the present study, we have examined the intracellular signalling pathways underlying baclofen-induced inhibition of GABA release from terminals synapsing onto rat basalis of Meynert neurons using patch-clamp recordings. Baclofen, a selective GABAB receptor agonist, reversibly decreased both evoked and spontaneous, miniature, GABAergic inhibitory postsynaptic currents (eIPSCs and mIPSCs, respectively). Such baclofen actions were completely abolished by CGP55845A, a selective GABAB receptor antagonist, and by staurosporine, a non-selective PKA and PKC inhibitor. The mIPSC frequency was still decreased by baclofen even in the presence of 4 AP, a K+ channel blocker, and Cd2+, a voltage-dependent calcium channel blocker. Pharmacological activation or inhibition of PKC activity affected basal GABA release and mildly affected the response to baclofen. Inhibition of the cAMP/PKA cascade also affected basal GABA release and, in a subset of neurons, occluded the effects of baclofen, suggesting that the GABAB receptor-mediated inhibitory action on GABA release was mediated via decreases in PKA activity. In addition, PKA inhibition occluded the effects of PKC modulation on both basal GABA release and on the response to baclofen. Our results characterize the transduction pathway of baclofen at these nucleus basalis of Maynert (nBM) synapses and show, for the first time, some cross-talk between the cAMP/PKA and PKC pathways in mammalian presynaptic nerve terminals.
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Affiliation(s)
- Hisahiko Kubota
- Cellular and System Physiology, Graduate School of Medical Sciences, Kyushu University, Maidashi 3-1-1, Fukuoka 812-8582, Japan
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Jeong HJ, Jang IS, Moorhouse AJ, Akaike N. Activation of presynaptic glycine receptors facilitates glycine release from presynaptic terminals synapsing onto rat spinal sacral dorsal commissural nucleus neurons. J Physiol 2003; 550:373-83. [PMID: 12754315 PMCID: PMC2343048 DOI: 10.1113/jphysiol.2003.041053] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Glycine is a major inhibitory neurotransmitter in the spinal cord and brainstem. Here we report the novel finding that presynaptic glycine autoreceptors modulate release from terminals synapsing onto rat spinal sacral dorsal commissural nucleus (SDCN) neurons. In mechanically dissociated SDCN neurons, in which functional presynaptic nerve terminals remain adherent to the isolated neurons, exogenously applied glycine (3 microM) increased the frequency of glycinergic spontaneous inhibitory postsynaptic currents (sIPSCs) without affecting their amplitudes or decay times. This suggests that glycine acts presynaptically to increase glycine release probability. Picrotoxin, at a concentration that had little direct effect on sIPSC frequency and amplitude (30 microM), significantly attenuated glycine-induced presynaptic sIPSC facilitation. The glycine-induced sIPSC frequency facilitation was completely abolished either in a Ca(2+)-free external solution or in the presence of 100 microM Cd2+, suggesting the involvement of extracellular Ca2+ influx into the nerve terminals. The glycine action was also completely occluded in the presence of 300 nM tetrodotoxin. In recordings from SDCN neurons in spinal cord slices, glycine (10 microM) increased evoked IPSC (eIPSC) amplitude and decreased the extent of paired-pulse facilitation. In response to brief high frequency stimulus trains the eIPSCs displayed a profound frequency-dependent facilitation that was greatly reduced by picrotoxin (30 microM). These results indicate that glycine acts at presynaptic autoreceptors, causing depolarization of the glycinergic nerve terminals, the subsequent activation of voltage-dependent Na+ and Ca2+ channels, and facilitation of glycine release. Furthermore, this presynaptic facilitation was observed under more physiological conditions, suggesting that these glycinergic autoreceptors may contribute to the integration of local inhibitory inputs to SDCN neurons.
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Affiliation(s)
- Hyo-Jin Jeong
- Cellular and System Physiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
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Abstract
Single mammalian neurons can be isolated with adherent functional synaptic terminals using an enzyme-free, mechanical dissociation procedure. This allows investigations of the effects of presynaptic modulators of synaptic transmission with unprecedented ease and accuracy. Furthermore, single presynaptic terminals and boutons can be visualized using fluorescent markers and can also be focally stimulated with electrical pulses. In this article, the isolated-nerve-adherent-synaptic-bouton preparation and some examples of its general properties and uses are discussed.
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Affiliation(s)
- Norio Akaike
- Cellular and Systems Physiology, Graduate School of Medical Sciences, Kyushu University, Maidashi 3-1-1, Higashi-ku, 812-8582, Fukuoka, Japan.
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Keramidas A, Moorhouse AJ, Pierce KD, Schofield PR, Barry PH. Cation-selective mutations in the M2 domain of the inhibitory glycine receptor channel reveal determinants of ion-charge selectivity. J Gen Physiol 2002; 119:393-410. [PMID: 11981020 PMCID: PMC2233820 DOI: 10.1085/jgp.20028552] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2001] [Revised: 03/22/2002] [Accepted: 03/22/2002] [Indexed: 11/20/2022] Open
Abstract
Ligand-gated ion channel receptors mediate neuronal inhibition or excitation depending on their ion charge selectivity. An investigation into the determinants of ion charge selectivity of the anion-selective alpha1 homomeric glycine receptor (alpha1 glycine receptor [GlyR]) was undertaken using point mutations to residues lining the extra- and intracellular ends of the ion channel. Five mutant GlyRs were studied. A single substitution at the intracellular mouth of the channel (A-1'E GlyR) was sufficient to convert the channels to select cations over anions with P(Cl)/P(Na) = 0.34. This result delimits the selectivity filter and provides evidence that electrostatic interactions between permeating ions and pore residues are a critical factor in ion charge selectivity. The P-2'Delta mutant GlyR retained its anion selectivity (P(Cl)/P(Na) = 3.81), but it was much reduced compared with the wild-type (WT) GlyR (P(Cl)/P(Na) = 27.9). When the A-1'E and the P-2'Delta mutations were combined (selectivity double mutant [SDM] GlyR), the relative cation permeability was enhanced (P(Cl)/P(Na) = 0.13). The SDM GlyR was also Ca(2+) permeable (P(Ca)/P(Na) = 0.29). Neutralizing the extracellular mouth of the SDM GlyR ion channel (SDM+R19'A GlyR) produced a more Ca(2+)-permeable channel (P(Ca)/P(Na) = 0.73), without drastically altering monovalent charge selectivity (P(Cl)/P(Na) = 0.23). The SDM+R19'E GlyR, which introduces a negatively charged ring at the extracellular mouth of the channel, further enhanced Ca(2+) permeability (P(Ca)/P(Na) = 0.92), with little effect on monovalent selectivity (P(Cl)/P(Na) = 0.19). Estimates of the minimum pore diameter of the A-1'E, SDM, SDM+R19'A, and SDM+R19'E GlyRs revealed that these pores are larger than the alpha1 GlyR, with the SDM-based GlyRs being comparable in diameter to the cation-selective nicotinic acetylcholine receptors. This result provides evidence that the diameter of the ion channel is also an important factor in ion charge selectivity.
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Affiliation(s)
- Angelo Keramidas
- Department of Physiology and Pharmacology, University of New South Wales, Sydney 2052, Australia
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Moorhouse AJ, Keramidas A, Zaykin A, Schofield PR, Barry PH. Single channel analysis of conductance and rectification in cation-selective, mutant glycine receptor channels. J Gen Physiol 2002; 119:411-25. [PMID: 11981021 PMCID: PMC2233819 DOI: 10.1085/jgp.20028553] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Members of the ligand-gated ion channel superfamily mediate fast synaptic transmission in the nervous system. In this study, we investigate the molecular determinants and mechanisms of ion permeation and ion charge selectivity in this family of channels by characterizing the single channel conductance and rectification of alpha1 homomeric human glycine receptor channels (GlyRs) containing pore mutations that impart cation selectivity. The A-1'E mutant GlyR and the selectivity double mutant ([SDM], A-1'E, P-2' Delta) GlyR, had mean inward chord conductances (at -60 mV) of 7 pS and mean outward conductances of 11 and 12 pS (60 mV), respectively. This indicates that the mutations have not simply reduced anion permeability, but have replaced the previous anion conductance with a cation one. An additional mutation to neutralize the ring of positive charge at the extracellular mouth of the channel (SDM+R19'A GlyR) made the conductance-voltage relationship linear (14 pS at both 60 and -60 mV). When this external charged ring was made negative (SDM+R19'E GlyR), the inward conductance was further increased (to 22 pS) and now became sensitive to external divalent cations (being 32 pS in their absence). The effects of the mutations to the external ring of charge on conductance and rectification could be fit to a model where only the main external energy barrier height for permeation was changed. Mean outward conductances in the SDM+R19'A and SDM+R19'E GlyRs were increased when internal divalent cations were absent, consistent with the intracellular end of the pore being flanked by fixed negative charges. This supports our hypothesis that the ion charge selectivity mutations have inverted the electrostatic profile of the pore by introducing a negatively charged ring at the putative selectivity filter. These results also further confirm the role of external pore vestibule electrostatics in determining the conductance and rectification properties of the ligand-gated ion channels.
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Affiliation(s)
- Andrew J Moorhouse
- Department of Physiology and Pharmacology, University of New South Wales, Sydney 2052, Australia
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Qu W, Moorhouse AJ, Cunningham AM, Barry PH. Anomalous mole-fraction effects in recombinant and native cyclic nucleotide-gated channels in rat olfactory receptor neurons. Proc Biol Sci 2001; 268:1395-403. [PMID: 11429140 PMCID: PMC1088754 DOI: 10.1098/rspb.2001.1663] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Anomalous mole-fraction effects (AMFE) were studied, using the inside-out configuration of the patchclamp technique, in both recombinant wild-type alpha-homomeric rat olfactory adenosine 3',5'-cyclic monophosphate (cAMP)-gated channels (rOCNC1) expressed in human embryonic kidney cells (HEK 293) and native cyclic nucleotide-gated (CNG) channels in acutely isolated rat olfactory receptor neurons. Single-channel and macroscopic currents were activated by 200 microM and 500 microM cAMP, respectively. Macroscopic currents, measured with mixtures of Na(+)-NH(4)(+) or Cs(+)-Li(+) in the cytoplasmic bathing solution, displayed AMFE in the rOCNC1 channels at both positive and negative membrane potentials. The rOCNC1 single-channel conductance showed a distinct minimum (or maximum) in an 80% Na(+)-20% NH(4)(+) mixture (or a 60% Cs(+)-40% Li(+) mixture), but only at positive membrane potentials. Macroscopic measurements in native olfactory CNG channels with mixtures of Na(+)-NH(4)(+) indicated similar AMFE. These results suggest that both native CNG channels and recombinant alpha-homomeric channels allow several ions to be present simultaneously within the channel pore. They also further validate the dominant role of the alpha-subunit in permeation through these channels, provide the first evidence to suggest that rOCNC1 channels have multi-ion properties and further justify the use of the rOCNC1 channel as an effective model for structure-function studies of ion permeation and selectivity in olfactory CNG channels.
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Affiliation(s)
- W Qu
- Schools of Physiology and Pharmacology, The University of New South Wales, Sydney 2052, Australia
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Kaur R, Zhu XO, Moorhouse AJ, Barry PH. IP3-gated channels and their occurrence relative to CNG channels in the soma and dendritic knob of rat olfactory receptor neurons. J Membr Biol 2001; 181:91-105. [PMID: 11420596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2000] [Indexed: 02/20/2023]
Abstract
Olfactory receptor neurons respond to odorants with G protein-mediated increases in the concentrations of cyclic adenosine 3',5'-monophosphate (cAMP) and/or inositol-1,4,5-trisphosphate (IP3). This study provides evidence that both second messengers can directly activate distinct ion channels in excised inside-out patches from the dendritic knob and soma membrane of rat olfactory receptor neurons (ORNs). The IP3-gated channels in the dendritic knob and soma membranes could be classified into two types, with conductances of 40 +/- 7 pS (n = 5) and 14 +/- 3 pS (n = 4), with the former having longer open dwell times. Estimated values of the densities of both channels from the same inside-out membrane patches were very much smaller for IP3-gated than for CNG channels. For example, in the dendritic knob membrane there were about 1000 CNG channels x microm(-2) compared to about 85 IP3-gated channels x microm(-2). Furthermore, only about 36% of the dendritic knob patches responded to IP3, whereas 83% of the same patches responded to cAMP. In the soma, both channel densities were lower, with the CNG channel density again being larger ( approximately 57 channels x microm(-2)) than that of the IP3-gated channels ( approximately 13 channels x microm(-2)), with again a much smaller fraction of patches responding to IP3 than to cAMP. These results were consistent with other evidence suggesting that the cAMP-pathway dominates the IP3 pathway in mammalian olfactory transduction.
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Affiliation(s)
- R Kaur
- School of Physiology and Pharmacology, The University of New South Wales, Sydney 2052, Australia
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Qu W, Zhu XO, Moorhouse AJ, Bieri S, Cunningham AM, Barry PH. Ion permeation and selectivity of wild-type recombinant rat CNG (rOCNC1) channels expressed in HEK293 cells. J Membr Biol 2000; 178:137-50. [PMID: 11083902 DOI: 10.1007/s002320010021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The permeation properties of adenosine 3', 5'-cyclic monophosphate (cAMP)-activated recombinant rat olfactory cyclic nucleotide-gated channels (rOCNC1) in human embryonic kidney (HEK 293) cells were investigated using inside-out excised membrane patches. The relative permeability of these rOCNC1 channels to monovalent alkali cations and organic cations was determined from measurements of the changes in reversal potential upon replacing sodium in the bathing solution with different test cations. The permeability ratio of Cl(-) relative to Na(+) (P(Cl)/P(Na)) was about 0.14, confirming that these channels are mainly permeable to cations. The sequence of relative permeabilities of monovalent alkali metal ions in these channels was P(Na) > or = P(K) > P(Li) > P(Cs) > or = P(Rb), which closely corresponds to a high-strength field sequence as previously determined for native rat olfactory receptor neurons (ORNs). The permeability sequence for organic cations relative to sodium was P(NH3OH) > P(NH4) > P(Na) > P(Tris) > P(Choline) > P(TEA), again in good agreement with previous permeability ratios obtained in native rat ORNs. Single-channel conductance sequences agreed surprisingly well with permeability sequences. These conductance measurements also indicated that, even in asymmetric bi-ionic cation solutions, the conductance was somewhat independent of current direction and dependent on the composition of both solutions. These results indicate that the permeability properties of rOCNC1 channels are similar to those of native rat CNG channels, and provide a suitable reference point for exploring the molecular basis of ion selectivity in recombinant rOCNC1 channels using site-directed mutagenesis.
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Affiliation(s)
- W Qu
- School of Physiology and Pharmacology, The University of New South Wales, Sydney 2052, Australia
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Keramidas A, Moorhouse AJ, French CR, Schofield PR, Barry PH. M2 pore mutations convert the glycine receptor channel from being anion- to cation-selective. Biophys J 2000; 79:247-59. [PMID: 10866951 PMCID: PMC1300929 DOI: 10.1016/s0006-3495(00)76287-4] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Three mutations in the M2 transmembrane domains of the chloride-conducting alpha1 homomeric glycine receptor (P250Delta, A251E, and T265V), which normally mediate fast inhibitory neurotransmission, produced a cation-selective channel with P(Cl)/P(Na), = 0.27 (wild-type P(Cl)/P(Na) = 25), a permeability sequence P(Cs) > P(K) > P(Na) > P(Li), an impermeability to Ca(2+), and a reduced glycine sensitivity. Outside-out patch measurements indicated reversed and accentuated rectification with extremely low mean single channel conductances of 3 pS (inward current) and 11 pS (outward current). The three inverse mutations, to those analyzed in this study, have previously been shown to make the alpha7 acetylcholine receptor channel anion-selective, indicating a common location for determinants of charge selectivity of inhibitory and excitatory ligand-gated ion channels.
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Affiliation(s)
- A Keramidas
- School of Physiology and Pharmacology, University of New South Wales, Sydney 2052, Australia
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Qu W, Moorhouse AJ, Rajendra S, Barry PH. Very negative potential for half-inactivation of, and effects of anions on, voltage-dependent sodium currents in acutely isolated rat olfactory receptor neurons. J Membr Biol 2000; 175:123-38. [PMID: 10811974 DOI: 10.1007/s002320001061] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Previous measurements with CsF pipette solutions using whole-cell patch-clamp techniques in dissociated rat olfactory receptor neurons (ORNs) indicated that the sodium currents had very negative inactivation characteristics with the implication that the cell resting potential must also normally have a very negative value. This study supports the conclusions that such an effect was real and not dependent on either the nature of the pipette anions or the recording situation previously used. For all pipette solutions, sodium currents showed a threshold activation approximately -80 mV and half-maximal activation voltages approximately -55 with half-inactivation potential < or =-100 mV, without being significantly affected by the replacement of F(-) by other pipette anions (H(2)PO(-)(4) and acetate(-)) or the addition of nucleotides and glutathione (which did cause a very slight positive shift). F(-), followed by H(2)PO(-)(4) and to a much lesser extent by acetate(-), was the most favorable pipette anion for obtaining good seals and whole-cell sodium currents in these extremely small ORNs. These results implied that resting potentials, for viable responsive cells, should be more negative than about -90 mV, as supported by the observation that action potentials could only be evoked from holding potentials more negative than -90 mV.
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Affiliation(s)
- W Qu
- School of Physiology and Pharmacology, The University of New South Wales, Sydney 2052, Australia
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Abstract
1. The glycine receptor channel (GlyR), a member of the ligand-gated ion channel superfamily, shares many similar permeation properties with the GABAA receptor channel. 2. The GlyR is anion permeable, with PK/PCl < 0.05, has a 5-6 A minimum pore diameter and a permeation selectivity sequence dominated by hydration energies. 3. The channels, which display multiple subconductance states, can be multiply occupied. 4. Two positive arginine rings at the ends of the pore region may contribute to the anion selectivity of the GlyR. 5. Mutation of the extracellular charged arginine ring can impair channel function by decreasing the sensitivity of glycine activation, reducing channel conductance, shifting the normal multi-subconductance states to lower values and by decoupling the link between ligand binding and channel gating. 6. These and other site-directed mutagenesis studies of recombinant GlyR, together with studies of native GlyR, are providing further insights into what controls gating and ion permeation and selectivity through this channel.
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Affiliation(s)
- P H Barry
- School of Physiology and Pharmacology, University of New South Wales, Australia.
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Keramidas A, Kuhlmann L, Moorhouse AJ, Barry PH. Measurement of the limiting equivalent conductivities and mobilities of the most prevalent ionic species of EGTA (EGTA2- and EGTA3-) for use in electrophysiological experiments. J Neurosci Methods 1999; 89:41-7. [PMID: 10476682 DOI: 10.1016/s0165-0270(99)00036-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In many experimental biological situations, chelating agents like EGTA (ethylene glycol-bis-(beta-amino-ethyl ether) N,N,N',N'-tetra-acetic acid) are commonly used to control or suppress the concentration of divalent ions like Ca2+. The evaluation of liquid junction potentials in electrophysiological measurements, and particularly in patch-clamp situations, requires information about the ions within the solution. Where there is a significant concentration of EGTA present, it is necessary to know the values of the relative mobility of at least the most predominant ionic species of EGTA in order to complete these calculations. EGTA, with four negative charges with different pKas, can therefore exist as four differently charged ions in solution (EGTA-, EGTA2-, EGTA3- and EGTA4-) or as uncharged, although between pH 5.5 and 8 it is almost exclusively EGTA2-. We have measured limiting equivalent conductivities of the most common ionic forms of EGTA (EGTA2- and EGTA3-) encountered at physiological pHs. These were 35.9 +/- 0.7 and 56 +/- 2.5 S cm2 equiv(-1) respectively. Their mobilities relative to K+ were 0.24 +/- 0.01 for EGTA2- and 0.25 +/- 0.01 for EGTA3-. Thus for typical electrophysiological solutions, the contribution of EGTA to the liquid junction potential should be small (e.g. approximately 0.4 mV).
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Affiliation(s)
- A Keramidas
- School of Physiology and Pharmacology, University of New South Wales, Sydney, Australia
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Moorhouse AJ, Jacques P, Barry PH, Schofield PR. The startle disease mutation Q266H, in the second transmembrane domain of the human glycine receptor, impairs channel gating. Mol Pharmacol 1999; 55:386-95. [PMID: 9927632 DOI: 10.1124/mol.55.2.386] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hyperekplexia (startle disease) results from mutations in the glycine receptor chloride channel that disrupt inhibitory synaptic transmission. The Q266H missense mutation is the only hyperekplexia mutation located in the transmembrane domains of the receptor. Using recombinant expression and patch-clamping techniques, we have investigated the functional properties of this mutation. The ability of glycine and taurine to open the channel was reduced in the mutated channel, as shown by a 6-fold shift in the concentration-response curve for both agonists. This was not accompanied by similar changes in agonist displacement of strychnine binding, suggesting that the mutation affects functions subsequent to ligand binding. Taurine was also converted to a weak partial agonist and antagonized the actions of glycine, consistent with changes in its channel gating efficacy. Because the Q266H mutation is within the pore-forming second transmembrane domain, we tested for a direct interaction with permeating ions. No change in either the cation/anion selectivity ratio or in single channel conductance levels was observed. No differential effects of Zn++, pH, and diethylpyrocarbonate were observed, implying that the histidine side chain is not exposed to the channel lumen. Single-channel recordings revealed a significant reduction in open times in the mutant receptors, at both high and low agonist concentrations, consistent with the open state of the channel being less stable. This study demonstrates that residues within the second transmembrane domain of ligand-gated ion channel receptors, even those whose side chains do not directly interact with permeating ions, can affect the kinetics of channel gating.
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Affiliation(s)
- A J Moorhouse
- School of Physiology and Pharmacology, University of New South Wales, Sydney, Australia
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Tucker SJ, Pessia M, Moorhouse AJ, Gribble F, Ashcroft FM, Maylie J, Adelman JP. Heteromeric channel formation and Ca(2+)-free media reduce the toxic effect of the weaver Kir 3.2 allele. FEBS Lett 1996; 390:253-7. [PMID: 8706871 DOI: 10.1016/0014-5793(96)00635-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Weaver mice have a severe hypoplasia of the cerebellum with an almost complete loss of the midline granule cells. Recent genetic studies of weaver mice have identified a mutation resulting in an amino acid substitution (G156S) in the pore of the inwardly rectifying potassium channel subunit Kir 3.2. When expressed in Xenopus oocytes the weaver mutation alters channel selectivity from a potassium-selective to a nonspecific cation-selective pore. In this study we confirm by cell-attached patch-clamp recording that the mutation produces a non-selective cation channel. We also demonstrate that the cell death induced by weaver expression may be prevented by elimination of calcium from the extracellular solution as well as by coexpression with the wild-type Kir 3.2 allele, or other members of the Kir 3.0 subfamily. These results suggest that the weaver defect in Kir 3.2 may cause cerebellar cell death by cell swelling and calcium overload. Cells which express the weaver subunit, but which normally survive, may do so because of heteromeric subunit assembly with wild-type subunits of the Kir 3.0 subfamily.
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Affiliation(s)
- S J Tucker
- Vollum Institute, Oregon Health Sciences University, Portland 97201, USA
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