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Niklaus S, Glasauer SMK, Kovermann P, Farshori KF, Cadetti L, Früh S, Rieser NN, Gesemann M, Zang J, Fahlke C, Neuhauss SCF. Glutamate transporters are involved in direct inhibitory synaptic transmission in the vertebrate retina. Open Biol 2024; 14:240140. [PMID: 39079673 PMCID: PMC11288666 DOI: 10.1098/rsob.240140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Accepted: 06/12/2024] [Indexed: 08/03/2024] Open
Abstract
In the central nervous system of vertebrates, glutamate serves as the primary excitatory neurotransmitter. However, in the retina, glutamate released from photoreceptors causes hyperpolarization in post-synaptic ON-bipolar cells through a glutamate-gated chloride current, which seems paradoxical. Our research reveals that this current is modulated by two excitatory glutamate transporters, EAAT5b and EAAT7. In the zebrafish retina, these transporters are located at the dendritic tips of ON-bipolar cells and interact with all four types of cone photoreceptors. The absence of these transporters leads to a decrease in ON-bipolar cell responses, with eaat5b mutants being less severely affected than eaat5b/eaat7 double mutants, which also exhibit altered response kinetics. Biophysical investigations establish that EAAT7 is an active glutamate transporter with a predominant anion conductance. Our study is the first to demonstrate the direct involvement of post-synaptic glutamate transporters in inhibitory direct synaptic transmission at a central nervous system synapse.
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Affiliation(s)
- Stephanie Niklaus
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Stella M. K. Glasauer
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Peter Kovermann
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, Leo-Brandt-Strasse, 52425 Jülich, Germany
| | - Kulsum F. Farshori
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Lucia Cadetti
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Simon Früh
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Nicolas N. Rieser
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Matthias Gesemann
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Jingjing Zang
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Christoph Fahlke
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, Leo-Brandt-Strasse, 52425 Jülich, Germany
| | - Stephan C. F. Neuhauss
- Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Excitatory Amino Acid Transporter EAAT5 Improves Temporal Resolution in the Retina. eNeuro 2021; 8:ENEURO.0406-21.2021. [PMID: 34772693 PMCID: PMC8670604 DOI: 10.1523/eneuro.0406-21.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 10/16/2021] [Indexed: 11/21/2022] Open
Abstract
Excitatory amino acid transporters (EAATs) remove glutamate from the synaptic cleft. In the retina, EAAT1 and EAAT2 are considered the major glutamate transporters. However, it has not yet been possible to determine how EAAT5 shapes the retinal light responses because of the lack of a selective EAAT5 blocker or EAAT5 knock-out (KO) animal model. In this study, EAAT5 was found to be expressed in a punctate manner close to release sites of glutamatergic synapses in the mouse retina. Light responses from retinae of wild-type (WT) and of a newly generated model with a targeted deletion of EAAT5 (EAAT5-/-) were recorded in vitro using multielectrode arrays (MEAs). Flicker resolution was considerably lower in EAAT5-/- retinae than in WT retinae. The close proximity to the glutamate release site makes EAAT5 an ideal tool to improve temporal information processing in the retina by controlling information transfer at glutamatergic synapses.
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Lukasiewcz PD, Bligard GW, DeBrecht JD. EAAT5 Glutamate Transporter-Mediated Inhibition in the Vertebrate Retina. Front Cell Neurosci 2021; 15:662859. [PMID: 34025361 PMCID: PMC8134652 DOI: 10.3389/fncel.2021.662859] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 03/19/2021] [Indexed: 12/29/2022] Open
Abstract
Glutamate transporters typically remove glutamate from the synaptic cleft. In addition, all glutamate transporters have a chloride channel, which is opened upon glutamate binding to the transporter. There are five types of glutamate transporter (EAATs 1–5, excitatory amino acid transporters), which have distinct chloride conductances. Some EAATs that have low chloride conductances, remove glutamate from the synaptic cleft most effectively (e.g., EAAT1). By contrast, EAATs that have high chloride conductances, remove glutamate less effectively (e.g., EAAT5). We have studied EAAT5 in the retina. In the retina, light activates a chloride current, mediated by the glutamate activation of EAAT5. EAAT5 is not a significant contributor to lateral inhibition in the retina. Instead, it is the main source of autoinhibition to rod bipolar cells (RBCs). EAAT5-mediated inhibition has a substantial effect on synaptic transmission from RBCs to downstream retinal neurons.
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Affiliation(s)
- Peter D Lukasiewcz
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine in St. Louis, St. Louis, MO, United States.,Department of Neuroscience, Washington University School of Medicine in St. Louis, St. Louis, MO, United States
| | - Gregory W Bligard
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine in St. Louis, St. Louis, MO, United States
| | - James D DeBrecht
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine in St. Louis, St. Louis, MO, United States
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Todd AC, Hardingham GE. The Regulation of Astrocytic Glutamate Transporters in Health and Neurodegenerative Diseases. Int J Mol Sci 2020; 21:E9607. [PMID: 33348528 PMCID: PMC7766851 DOI: 10.3390/ijms21249607] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Revised: 12/04/2020] [Accepted: 12/11/2020] [Indexed: 12/24/2022] Open
Abstract
The astrocytic glutamate transporters excitatory amino acid transporters 1 and 2 (EAAT1 and EAAT2) play a key role in nervous system function to maintain extracellular glutamate levels at low levels. In physiology, this is essential for the rapid uptake of synaptically released glutamate, maintaining the temporal fidelity of synaptic transmission. However, EAAT1/2 hypo-expression or hypo-function are implicated in several disorders, including epilepsy and neurodegenerative diseases, as well as being observed naturally with aging. This not only disrupts synaptic information transmission, but in extremis leads to extracellular glutamate accumulation and excitotoxicity. A key facet of EAAT1/2 expression in astrocytes is a requirement for signals from other brain cell types in order to maintain their expression. Recent evidence has shown a prominent role for contact-dependent neuron-to-astrocyte and/or endothelial cell-to-astrocyte Notch signalling for inducing and maintaining the expression of these astrocytic glutamate transporters. The relevance of this non-cell-autonomous dependence to age- and neurodegenerative disease-associated decline in astrocytic EAAT expression is discussed, plus the implications for disease progression and putative therapeutic strategies.
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Affiliation(s)
- Alison C. Todd
- UK Dementia Research Institute at the University of Edinburgh, Chancellor’s Building, Edinburgh Medical School, Edinburgh EH16 4SB, UK;
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK
| | - Giles E. Hardingham
- UK Dementia Research Institute at the University of Edinburgh, Chancellor’s Building, Edinburgh Medical School, Edinburgh EH16 4SB, UK;
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK
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Musilova Z, Indermaur A, Bitja‐Nyom AR, Omelchenko D, Kłodawska M, Albergati L, Remišová K, Salzburger W. Evolution of the visual sensory system in cichlid fishes from crater lake Barombi Mbo in Cameroon. Mol Ecol 2019; 28:5010-5031. [DOI: 10.1111/mec.15217] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 08/09/2019] [Accepted: 08/13/2019] [Indexed: 01/09/2023]
Affiliation(s)
- Zuzana Musilova
- Department of Zoology Charles University in Prague Prague Czech Republic
- Zoological Institute University of Basel Basel Switzerland
| | | | - Arnold Roger Bitja‐Nyom
- Department of Biological Sciences University of Ngaoundéré Ngaoundéré Cameroon
- Department of Management of Fisheries and Aquatic Ecosystems University of Douala Douala Cameroon
| | - Dmytro Omelchenko
- Department of Zoology Charles University in Prague Prague Czech Republic
| | - Monika Kłodawska
- Department of Zoology Charles University in Prague Prague Czech Republic
| | - Lia Albergati
- Zoological Institute University of Basel Basel Switzerland
| | - Kateřina Remišová
- Department of Physiology Charles University in Prague Prague Czech Republic
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Dai J, Fu Y, Zeng Y, Li S, Qin Yin Z. Improved retinal function in RCS rats after suppressing the over-activation of mGluR5. Sci Rep 2017; 7:3546. [PMID: 28615682 PMCID: PMC5471183 DOI: 10.1038/s41598-017-03702-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 05/03/2017] [Indexed: 01/09/2023] Open
Abstract
Müller cells maintain retinal synaptic homeostasis by taking up glutamate from the synaptic cleft and transporting glutamine back to the neurons. To study the interaction between Müller cells and photoreceptors, we injected either DL-α-aminoadipate or L-methionine sulfoximine–both inhibitors of glutamine synthetase–subretinally in rats. Following injection, the a-wave of the electroretinogram (ERG) was attenuated, and metabotropic glutamate receptor 5 (mGluR5) was activated. Selective antagonism of mGluR5 by 2-methyl-6-(phenylethynyl)-pyridine increased the ERG a-wave amplitude and also increased rhodopsin expression. Conversely, activation of mGluR5 by the agonist, (R,S)-2-chloro-5-hydroxyphenylglycine, decreased both the a-wave amplitude and rhodopsin expression, but upregulated expression of Gq alpha subunit and phospholipase C βIII. Overexpression of mGluR5 reduced the inward-rectifying potassium ion channel (Kir) current and decreased the expression of Kir4.1 and aquaporin-4 (AQP4). Further experiments indicated that mGluR5 formed a macromolecular complex with these two membrane channels. Lastly, increased expression of mGluR5 was found in Royal College of Surgeons rats–a model of retinitis pigmentosa (RP). Inhibition of mGluR5 in this model restored the amplitude of ERG features, and reduced the expression of glial fibrillary acidic protein. These results suggest that mGluR5 may be worth considering as a potential therapeutic target in RP.
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Affiliation(s)
- Jiaman Dai
- Bioengineering College, Chongqing University, Chongqing, 400040, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, 400038, China
| | - Yan Fu
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University, Chongqing, 400038, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, 400038, China
| | - Yuxiao Zeng
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University, Chongqing, 400038, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, 400038, China
| | - Shiying Li
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University, Chongqing, 400038, China. .,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, 400038, China.
| | - Zheng Qin Yin
- Bioengineering College, Chongqing University, Chongqing, 400040, China. .,Southwest Hospital/Southwest Eye Hospital, Third Military Medical University, Chongqing, 400038, China. .,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, 400038, China.
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Chapot CA, Euler T, Schubert T. How do horizontal cells 'talk' to cone photoreceptors? Different levels of complexity at the cone-horizontal cell synapse. J Physiol 2017; 595:5495-5506. [PMID: 28378516 DOI: 10.1113/jp274177] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 03/27/2017] [Indexed: 11/08/2022] Open
Abstract
The first synapse of the retina plays a fundamental role in the visual system. Due to its importance, it is critical that it encodes information from the outside world with the greatest accuracy and precision possible. Cone photoreceptor axon terminals contain many individual synaptic sites, each represented by a presynaptic structure called a 'ribbon'. These synapses are both highly sophisticated and conserved. Each ribbon relays the light signal to one ON cone bipolar cell and several OFF cone bipolar cells, while two dendritic processes from a GABAergic interneuron, the horizontal cell, modulate the cone output via parallel feedback mechanisms. The presence of these three partners within a single synapse has raised numerous questions, and its anatomical and functional complexity is still only partially understood. However, the understanding of this synapse has recently evolved, as a consequence of progress in understanding dendritic signal processing and its role in facilitating global versus local signalling. Indeed, for the downstream retinal network, dendritic processing in horizontal cells may be essential, as they must support important functional operations such as contrast enhancement, which requires spatial averaging of the photoreceptor array, while at the same time preserving accurate spatial information. Here, we review recent progress made towards a better understanding of the cone synapse, with an emphasis on horizontal cell function, and discuss why such complexity might be necessary for early visual processing.
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Affiliation(s)
- Camille A Chapot
- Institute for Ophthalmic Research, University of Tübingen, 72076, Tübingen, Germany.,Centre for Integrative Neuroscience, University of Tübingen, 72076, Tübingen, Germany.,Graduate Training Centre of Neuroscience, University of Tübingen, 72076, Tübingen, Germany
| | - Thomas Euler
- Institute for Ophthalmic Research, University of Tübingen, 72076, Tübingen, Germany.,Centre for Integrative Neuroscience, University of Tübingen, 72076, Tübingen, Germany.,Bernstein Centre for Computational Neuroscience, University of Tübingen, 72076, Tübingen, Germany
| | - Timm Schubert
- Institute for Ophthalmic Research, University of Tübingen, 72076, Tübingen, Germany.,Centre for Integrative Neuroscience, University of Tübingen, 72076, Tübingen, Germany
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Popova E. ON-OFF Interactions in the Retina: Role of Glycine and GABA. Curr Neuropharmacol 2014; 12:509-26. [PMID: 25977678 PMCID: PMC4428025 DOI: 10.2174/1570159x13999150122165018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 12/19/2014] [Accepted: 12/22/2014] [Indexed: 01/03/2023] Open
Abstract
In the vertebrate retina, visual signals are segregated into parallel ON and OFF pathways, which provide information for light increments and decrements. The segregation is first evident at the level of the ON and OFF bipolar cells and it apparently remains as signals propagate to higher brain visual centers. A fundamental question in visual neuroscience is how these two parallel pathways function: are they independent from each other or do they interact somehow? In the latter case, what kinds of mechanisms are involved and what are the consequences from this cross-talk? This review summarizes current knowledge about the types of interactions between the ON and OFF channels in nonmammalian and mammalian retina. Data concerning the ON-OFF interactions in distal retina revealed by recording of single bipolar cell activity and electroretinographic ON (b-wave) and OFF (d-wave) responses are presented. Special emphasis is put on the ON-OFF interactions in proximal retina and their dependence on the state of light adaptation in mammalian retina. The involvement of the GABAergic and glycinergic systems in the ON-OFF crosstalk is also discussed.
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Affiliation(s)
- Elka Popova
- Department of Physiology, Medical Phaculty, Medical University, 1431 Sofia, Country Bulgaria
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