1
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Hanke-Gogokhia C, Zapadka TE, Finkelstein S, Klingeborn M, Maugel TK, Singer JH, Arshavsky VY, Demb JB. The Structural and Functional Integrity of Rod Photoreceptor Ribbon Synapses Depends on Redundant Actions of Dynamins 1 and 3. J Neurosci 2024; 44:e1379232024. [PMID: 38641407 PMCID: PMC11209669 DOI: 10.1523/jneurosci.1379-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 04/02/2024] [Accepted: 04/13/2024] [Indexed: 04/21/2024] Open
Abstract
Vertebrate vision begins with light absorption by rod and cone photoreceptors, which transmit signals from their synaptic terminals to second-order neurons: bipolar and horizontal cells. In mouse rods, there is a single presynaptic ribbon-type active zone at which the release of glutamate occurs tonically in the dark. This tonic glutamatergic signaling requires continuous exo- and endocytosis of synaptic vesicles. At conventional synapses, endocytosis commonly requires dynamins: GTPases encoded by three genes (Dnm1-3), which perform membrane scission. Disrupting endocytosis by dynamin deletions impairs transmission at conventional synapses, but the impact of disrupting endocytosis and the role(s) of specific dynamin isoforms at rod ribbon synapses are understood incompletely. Here, we used cell-specific knock-outs (KOs) of the neuron-specific Dnm1 and Dnm3 to investigate the functional roles of dynamin isoforms in rod photoreceptors in mice of either sex. Analysis of synaptic protein expression, synapse ultrastructure, and retinal function via electroretinograms (ERGs) showed that dynamins 1 and 3 act redundantly and are essential for supporting the structural and functional integrity of rod ribbon synapses. Single Dnm3 KO showed no phenotype, and single Dnm1 KO only modestly reduced synaptic vesicle density without affecting vesicle size and overall synapse integrity, whereas double Dnm1/Dnm3 KO impaired vesicle endocytosis profoundly, causing enlarged vesicles, reduced vesicle density, reduced ERG responses, synaptic terminal degeneration, and disassembly and degeneration of postsynaptic processes. Concurrently, cone function remained intact. These results show the fundamental redundancy of dynamins 1 and 3 in regulating the structure and function of rod ribbon synapses.
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Affiliation(s)
- Christin Hanke-Gogokhia
- Departments of Ophthalmology & Visual Science, Yale University, New Haven, Connecticut 06511
| | - Thomas E Zapadka
- Departments of Ophthalmology & Visual Science, Yale University, New Haven, Connecticut 06511
- Cellular & Molecular Physiology, Yale University, New Haven, Connecticut 06511
| | - Stella Finkelstein
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina 27705
| | - Mikael Klingeborn
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina 27705
| | - Timothy K Maugel
- Department of Biology, University of Maryland, College Park, Maryland 20742
| | - Joshua H Singer
- Department of Biology, University of Maryland, College Park, Maryland 20742
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina 27705
| | - Jonathan B Demb
- Departments of Ophthalmology & Visual Science, Yale University, New Haven, Connecticut 06511
- Cellular & Molecular Physiology, Yale University, New Haven, Connecticut 06511
- Department of Neuroscience, Yale University, New Haven, Connecticut 06511
- Wu Tsai Institute, Yale University, New Haven, Connecticut 06511
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2
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Gierke K, Lux UT, Regus-Leidig H, Brandstätter JH. The first synapse in vision in the aging mouse retina. Front Cell Neurosci 2023; 17:1291054. [PMID: 38026697 PMCID: PMC10654782 DOI: 10.3389/fncel.2023.1291054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 10/20/2023] [Indexed: 12/01/2023] Open
Abstract
Vision is our primary sense, and maintaining it throughout our lifespan is crucial for our well-being. However, the retina, which initiates vision, suffers from an age-related, irreversible functional decline. What causes this functional decline, and how it might be treated, is still unclear. Synapses are the functional hub for signal transmission between neurons, and studies have shown that aging is widely associated with synaptic dysfunction. In this study, we examined the first synapse of the visual system - the rod and cone photoreceptor ribbon synapse - in the mouse retina using light and electron microscopy at 2-3 months, ~1 year, and >2 years of age. We asked, whether age-related changes in key synaptic components might be a driver of synaptic dysfunction and ultimately age-related functional decline during normal aging. We found sprouting of horizontal and bipolar cells, formation of ectopic photoreceptor ribbon synapses, and a decrease in the number of rod photoreceptors and photoreceptor ribbon synapses in the aged retina. However, the majority of the photoreceptors did not show obvious changes in the structural components and protein composition of their ribbon synapses. Noteworthy is the increase in mitochondrial size in rod photoreceptor terminals in the aged retina.
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Affiliation(s)
| | | | | | - Johann Helmut Brandstätter
- Animal Physiology/Neurobiology, Department of Biology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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3
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Abstract
Because the central nervous system is largely nonrenewing, neurons and their synapses must be maintained over the lifetime of an individual to ensure circuit function. Age is a dominant risk factor for neural diseases, and declines in nervous system function are a common feature of aging even in the absence of disease. These alterations extend to the visual system and, in particular, to the retina. The retina is a site of clinically relevant age-related alterations but has also proven to be a uniquely approachable system for discovering principles that govern neural aging because it is well mapped, contains diverse neuron types, and is experimentally accessible. In this article, we review the structural and molecular impacts of aging on neurons within the inner and outer retina circuits. We further discuss the contribution of non-neuronal cell types and systems to retinal aging outcomes. Understanding how and why the retina ages is critical to efforts aimed at preventing age-related neural decline and restoring neural function.
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Affiliation(s)
- Jeffrey D Zhu
- Department of Neuroscience, Huffington Center on Aging, Baylor College of Medicine, Houston, Texas, USA;
| | - Sharma Pooja Tarachand
- Department of Neuroscience, Huffington Center on Aging, Baylor College of Medicine, Houston, Texas, USA;
| | - Qudrat Abdulwahab
- Department of Neuroscience, Huffington Center on Aging, Baylor College of Medicine, Houston, Texas, USA;
| | - Melanie A Samuel
- Department of Neuroscience, Huffington Center on Aging, Baylor College of Medicine, Houston, Texas, USA;
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4
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Hagiwara A, Mizutani A, Kawamura S, Abe M, Hida Y, Sakimura K, Ohtsuka T. Critical Role of the Presynaptic Protein CAST in Maintaining the Photoreceptor Ribbon Synapse Triad. Int J Mol Sci 2023; 24:ijms24087251. [PMID: 37108413 PMCID: PMC10138387 DOI: 10.3390/ijms24087251] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 04/08/2023] [Accepted: 04/12/2023] [Indexed: 04/29/2023] Open
Abstract
The cytomatrix at the active zone-associated structural protein (CAST) and its homologue, named ELKS, being rich in glutamate (E), leucine (L), lysine (K), and serine (S), belong to a family of proteins that organize presynaptic active zones at nerve terminals. These proteins interact with other active zone proteins, including RIMs, Munc13s, Bassoon, and the β subunit of Ca2+ channels, and have various roles in neurotransmitter release. A previous study showed that depletion of CAST/ELKS in the retina causes morphological changes and functional impairment of this structure. In this study, we investigated the roles of CAST and ELKS in ectopic synapse localization. We found that the involvement of these proteins in ribbon synapse distribution is complex. Unexpectedly, CAST and ELKS, in photoreceptors or in horizontal cells, did not play a major role in ribbon synapse ectopic localization. However, depletion of CAST and ELKS in the mature retina resulted in degeneration of the photoreceptors. These findings suggest that CAST and ELKS play critical roles in maintaining neural signal transduction in the retina, but the regulation of photoreceptor triad synapse distribution is not solely dependent on their actions within photoreceptors and horizontal cells.
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Affiliation(s)
- Akari Hagiwara
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba 278-8510, Japan
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, Yamanashi 409-3898, Japan
| | - Ayako Mizutani
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba 278-8510, Japan
| | - Saki Kawamura
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba 278-8510, Japan
| | - Manabu Abe
- Department of Animal Model Development, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Yamato Hida
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, Yamanashi 409-3898, Japan
| | - Kenji Sakimura
- Department of Animal Model Development, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Toshihisa Ohtsuka
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, Yamanashi 409-3898, Japan
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5
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Cao Y, Fajardo D, Guerrero-Given D, Samuel MA, Ohtsuka T, Boye SE, Kamasawa N, Martemyanov KA. Post-developmental plasticity of the primary rod pathway allows restoration of visually guided behaviors. Curr Biol 2022; 32:4783-4796.e3. [PMID: 36179691 PMCID: PMC9691582 DOI: 10.1016/j.cub.2022.09.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 08/17/2022] [Accepted: 09/08/2022] [Indexed: 01/24/2023]
Abstract
The formation of neural circuits occurs in a programmed fashion, but proper activity in the circuit is essential for refining the organization necessary for driving complex behavioral tasks. In the retina, sensory deprivation during the critical period of development is well known to perturb the organization of the visual circuit making the animals unable to use vision for behavior. However, the extent of plasticity, molecular factors involved, and malleability of individual channels in the circuit to manipulations outside of the critical period are not well understood. In this study, we selectively disconnected and reconnected rod photoreceptors in mature animals after completion of the retina circuit development. We found that introducing synaptic rod photoreceptor input post-developmentally allowed their integration into the circuit both anatomically and functionally. Remarkably, adult mice with newly integrated rod photoreceptors gained high-sensitivity vision, even when it was absent from birth. These observations reveal plasticity of the retina circuit organization after closure of the critical period and encourage the development of vision restoration strategies for congenital blinding disorders.
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Affiliation(s)
- Yan Cao
- Department of Neuroscience, UF Scripps Biomedical Research, Jupiter, FL 33458, USA
| | - Diego Fajardo
- Division of Cellular and Molecular Therapy, Department of Pediatrics, University of Florida, Gainesville, FL, USA
| | - Debbie Guerrero-Given
- The Imaging Center, Electron Microscopy Core Facility, Max Planck Florida Institute, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Melanie A Samuel
- Department of Neuroscience, Huffington Center on Aging, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Toshihisa Ohtsuka
- Department of Biochemistry, Graduate School of Medicine, Faculty of Medicine, University of Yamanashi, Yamanashi 409-3898, Japan
| | - Shannon E Boye
- Division of Cellular and Molecular Therapy, Department of Pediatrics, University of Florida, Gainesville, FL, USA
| | - Naomi Kamasawa
- The Imaging Center, Electron Microscopy Core Facility, Max Planck Florida Institute, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Kirill A Martemyanov
- Department of Neuroscience, UF Scripps Biomedical Research, Jupiter, FL 33458, USA.
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6
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Mochida S. Mechanisms of Synaptic Vesicle Exo- and Endocytosis. Biomedicines 2022; 10:1593. [PMID: 35884898 PMCID: PMC9313035 DOI: 10.3390/biomedicines10071593] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 06/21/2022] [Accepted: 06/22/2022] [Indexed: 01/05/2023] Open
Abstract
Within 1 millisecond of action potential arrival at presynaptic terminals voltage-gated Ca2+ channels open. The Ca2+ channels are linked to synaptic vesicles which are tethered by active zone proteins. Ca2+ entrance into the active zone triggers: (1) the fusion of the vesicle and exocytosis, (2) the replenishment of the active zone with vesicles for incoming exocytosis, and (3) various types of endocytosis for vesicle reuse, dependent on the pattern of firing. These time-dependent vesicle dynamics are controlled by presynaptic Ca2+ sensor proteins, regulating active zone scaffold proteins, fusion machinery proteins, motor proteins, endocytic proteins, several enzymes, and even Ca2+ channels, following the decay of Ca2+ concentration after the action potential. Here, I summarize the Ca2+-dependent protein controls of synchronous and asynchronous vesicle release, rapid replenishment of the active zone, endocytosis, and short-term plasticity within 100 msec after the action potential. Furthermore, I discuss the contribution of active zone proteins to presynaptic plasticity and to homeostatic readjustment during and after intense activity, in addition to activity-dependent endocytosis.
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Affiliation(s)
- Sumiko Mochida
- Department of Physiology, Tokyo Medical University, Tokyo 160-8402, Japan
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7
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Buscham TJ, Eichel-Vogel MA, Steyer AM, Jahn O, Strenzke N, Dardawal R, Memhave TR, Siems SB, Müller C, Meschkat M, Sun T, Ruhwedel T, Möbius W, Krämer-Albers EM, Boretius S, Nave KA, Werner HB. Progressive axonopathy when oligodendrocytes lack the myelin protein CMTM5. eLife 2022; 11:75523. [PMID: 35274615 PMCID: PMC8916772 DOI: 10.7554/elife.75523] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 02/27/2022] [Indexed: 11/26/2022] Open
Abstract
Oligodendrocytes facilitate rapid impulse propagation along the axons they myelinate and support their long-term integrity. However, the functional relevance of many myelin proteins has remained unknown. Here, we find that expression of the tetraspan-transmembrane protein CMTM5 (chemokine-like factor-like MARVEL-transmembrane domain containing protein 5) is highly enriched in oligodendrocytes and central nervous system (CNS) myelin. Genetic disruption of the Cmtm5 gene in oligodendrocytes of mice does not impair the development or ultrastructure of CNS myelin. However, oligodendroglial Cmtm5 deficiency causes an early-onset progressive axonopathy, which we also observe in global and tamoxifen-induced oligodendroglial Cmtm5 mutants. Presence of the WldS mutation ameliorates the axonopathy, implying a Wallerian degeneration-like pathomechanism. These results indicate that CMTM5 is involved in the function of oligodendrocytes to maintain axonal integrity rather than myelin biogenesis.
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Affiliation(s)
- Tobias J Buscham
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Maria A Eichel-Vogel
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Anna M Steyer
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Olaf Jahn
- Proteomics Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Translational Neuroproteomics Group, Department of Psychiatry and Psychotherapy, University Medical Center Göttingen, Georg-August-University, Göttingen, Germany
| | - Nicola Strenzke
- Institute for Auditory Neuroscience, University Medicine Göttingen, Göttingen, Germany
| | - Rakshit Dardawal
- Functional Imaging Laboratory, German Primate Center, Leibniz Institute for Primate Research, Göttingen, Germany
| | - Tor R Memhave
- Functional Imaging Laboratory, German Primate Center, Leibniz Institute for Primate Research, Göttingen, Germany
| | - Sophie B Siems
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Christina Müller
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University, Mainz, Germany
| | - Martin Meschkat
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Abberior Instruments Gmbh, Göttingen, Germany
| | - Ting Sun
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Torben Ruhwedel
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Wiebke Möbius
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Eva-Maria Krämer-Albers
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University, Mainz, Germany
| | - Susann Boretius
- Functional Imaging Laboratory, German Primate Center, Leibniz Institute for Primate Research, Göttingen, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Göttingen, Germany
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8
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Mochida S. Stable and Flexible Synaptic Transmission Controlled by the Active Zone Protein Interactions. Int J Mol Sci 2021; 22:ijms222111775. [PMID: 34769208 PMCID: PMC8583982 DOI: 10.3390/ijms222111775] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/24/2021] [Accepted: 10/25/2021] [Indexed: 12/28/2022] Open
Abstract
An action potential triggers neurotransmitter release from synaptic vesicles docking to a specialized release site of the presynaptic plasma membrane, the active zone. The active zone is a highly organized structure with proteins that serves as a platform for synaptic vesicle exocytosis, mediated by SNAREs complex and Ca2+ sensor proteins, within a sub-millisecond opening of nearby Ca2+ channels with the membrane depolarization. In response to incoming neuronal signals, each active zone protein plays a role in the release-ready site replenishment with synaptic vesicles for sustainable synaptic transmission. The active zone release apparatus provides a possible link between neuronal activity and plasticity. This review summarizes the mostly physiological role of active zone protein interactions that control synaptic strength, presynaptic short-term plasticity, and homeostatic synaptic plasticity.
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Affiliation(s)
- Sumiko Mochida
- Department of Physiology, Tokyo Medical University, Tokyo 160-8402, Japan
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9
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Grabner CP, Moser T. The mammalian rod synaptic ribbon is essential for Ca v channel facilitation and ultrafast synaptic vesicle fusion. eLife 2021; 10:63844. [PMID: 34617508 PMCID: PMC8594941 DOI: 10.7554/elife.63844] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 10/06/2021] [Indexed: 12/19/2022] Open
Abstract
Rod photoreceptors (PRs) use ribbon synapses to transmit visual information. To signal ‘no light detected’ they release glutamate continually to activate post-synaptic receptors. When light is detected glutamate release pauses. How a rod’s individual ribbon enables this process was studied here by recording evoked changes in whole-cell membrane capacitance from wild-type and ribbonless (Ribeye-ko) mice. Wild-type rods filled with high (10 mM) or low (0.5 mM) concentrations of the Ca2+-buffer EGTA created a readily releasable pool (RRP) of 87 synaptic vesicles (SVs) that emptied as a single kinetic phase with a τ<0.4 ms. The lower concentration of EGTA accelerated Cav channel opening and facilitated release kinetics. In contrast, ribbonless rods created a much smaller RRP of 22 SVs, and they lacked Cav channel facilitation; however, Ca2+ channel-release coupling remained tight. These release deficits caused a sharp attenuation of rod-driven scotopic light responses. We conclude that the synaptic ribbon facilitates Ca2+-influx and establishes a large RRP of SVs.
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Affiliation(s)
- Chad Paul Grabner
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute of Biophysical Chemistry, Göttingen, Germany.,Collaborative Research Center 1286 'Quantitative Synaptology', University of Göttingen, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute of Biophysical Chemistry, Göttingen, Germany.,Collaborative Research Center 1286 'Quantitative Synaptology', University of Göttingen, Göttingen, Germany.,Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, Göttingen, Germany
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10
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Ryl M, Urbasik A, Gierke K, Babai N, Joachimsthaler A, Feigenspan A, Frischknecht R, Stallwitz N, Fejtová A, Kremers J, von Wittgenstein J, Brandstätter JH. Genetic disruption of bassoon in two mutant mouse lines causes divergent retinal phenotypes. FASEB J 2021; 35:e21520. [PMID: 33811381 DOI: 10.1096/fj.202001962r] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 02/19/2021] [Accepted: 02/26/2021] [Indexed: 11/11/2022]
Abstract
Bassoon (BSN) is a presynaptic cytomatrix protein ubiquitously present at chemical synapses of the central nervous system, where it regulates synaptic vesicle replenishment and organizes voltage-gated Ca2+ channels. In sensory photoreceptor synapses, BSN additionally plays a decisive role in anchoring the synaptic ribbon, a presynaptic organelle and functional extension of the active zone, to the presynaptic membrane. In this study, we functionally and structurally analyzed two mutant mouse lines with a genetic disruption of Bsn-Bsngt and Bsnko -using electrophysiology and high-resolution microscopy. In both Bsn mutant mouse lines, full-length BSN was abolished, and photoreceptor synaptic function was similarly impaired, yet synapse structure was more severely affected in Bsngt/gt than in Bsnko/ko photoreceptors. The synaptic defects in Bsngt/gt retina coincide with remodeling of the outer retina-rod bipolar and horizontal cell sprouting, formation of ectopic ribbon synaptic sites-and death of cone photoreceptors, processes that did not occur in Bsnko/ko retina. An analysis of Bsngt/ko hybrid mice revealed that the divergent retinal phenotypes of Bsngt/gt and Bsnko/ko mice can be attributed to the expression of the Bsngt allele, which triggers cone photoreceptor death and neurite sprouting in the outer retina. These findings shed new light on the existing Bsn mutant mouse models and might help to understand mechanisms that drive photoreceptor death.
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Affiliation(s)
- Miriam Ryl
- Department of Biology, Animal Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Alexander Urbasik
- Department of Biology, Animal Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Kaspar Gierke
- Department of Biology, Animal Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Norbert Babai
- Department of Biology, Animal Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Anneka Joachimsthaler
- Department of Ophthalmology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Andreas Feigenspan
- Department of Biology, Animal Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Renato Frischknecht
- Department of Biology, Animal Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Nina Stallwitz
- Department of Ophthalmology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Anna Fejtová
- Department of Psychiatry and Psychotherapy, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Jan Kremers
- Department of Ophthalmology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Julia von Wittgenstein
- Department of Biology, Animal Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Johann Helmut Brandstätter
- Department of Biology, Animal Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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11
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Nemitz L, Dedek K, Janssen-Bienhold U. Synaptic Remodeling in the Cone Pathway After Early Postnatal Horizontal Cell Ablation. Front Cell Neurosci 2021; 15:657594. [PMID: 34122012 PMCID: PMC8187617 DOI: 10.3389/fncel.2021.657594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Accepted: 05/03/2021] [Indexed: 11/30/2022] Open
Abstract
The first synapse of the visual pathway is formed by photoreceptors, horizontal cells and bipolar cells. While ON bipolar cells invaginate into the photoreceptor terminal and form synaptic triads together with invaginating horizontal cell processes, OFF bipolar cells make flat contacts at the base of the terminal. When horizontal cells are ablated during retina development, no invaginating synapses are formed in rod photoreceptors. However, how cone photoreceptors and their synaptic connections with bipolar cells react to this insult, is unclear so far. To answer this question, we specifically ablated horizontal cells from the developing mouse retina. Following ablation around postnatal day 4 (P4)/P5, cones initially exhibited a normal morphology and formed flat contacts with OFF bipolar cells, but only few invaginating contacts with ON bipolar cells. From P15 on, synaptic remodeling became obvious with clustering of cone terminals and mislocalized cone somata in the OPL. Adult cones (P56) finally displayed highly branched axons with numerous terminals which contained ribbons and vesicular glutamate transporters. Furthermore, type 3a, 3b, and 4 OFF bipolar cell dendrites sprouted into the outer nuclear layer and even expressed glutamate receptors at the base of newly formed cone terminals. These results indicate that cones may be able to form new synapses with OFF bipolar cells in adult mice. In contrast, cone terminals lost their invaginating contacts with ON bipolar cells, highlighting the importance of horizontal cells for synapse maintenance. Taken together, our data demonstrate that early postnatal horizontal cell ablation leads to differential remodeling in the cone pathway: whereas synapses between cones and ON bipolar cells were lost, new putative synapses were established between cones and OFF bipolar cells. These results suggest that synapse formation and maintenance are regulated very differently between flat and invaginating contacts at cone terminals.
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Affiliation(s)
- Lena Nemitz
- Visual Neuroscience, Department of Neuroscience, University of Oldenburg, Oldenburg, Germany
| | - Karin Dedek
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany.,Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
| | - Ulrike Janssen-Bienhold
- Visual Neuroscience, Department of Neuroscience, University of Oldenburg, Oldenburg, Germany.,Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
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12
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Burger CA, Jiang D, Mackin RD, Samuel MA. Development and maintenance of vision's first synapse. Dev Biol 2021; 476:218-239. [PMID: 33848537 DOI: 10.1016/j.ydbio.2021.04.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 04/02/2021] [Accepted: 04/03/2021] [Indexed: 12/21/2022]
Abstract
Synapses in the outer retina are the first information relay points in vision. Here, photoreceptors form synapses onto two types of interneurons, bipolar cells and horizontal cells. Because outer retina synapses are particularly large and highly ordered, they have been a useful system for the discovery of mechanisms underlying synapse specificity and maintenance. Understanding these processes is critical to efforts aimed at restoring visual function through repairing or replacing neurons and promoting their connectivity. We review outer retina neuron synapse architecture, neural migration modes, and the cellular and molecular pathways that play key roles in the development and maintenance of these connections. We further discuss how these mechanisms may impact connectivity in the retina.
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Affiliation(s)
- Courtney A Burger
- Huffington Center on Aging, Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Danye Jiang
- Huffington Center on Aging, Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Robert D Mackin
- Huffington Center on Aging, Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Melanie A Samuel
- Huffington Center on Aging, Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA.
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13
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Thoreson WB. Transmission at rod and cone ribbon synapses in the retina. Pflugers Arch 2021; 473:1469-1491. [PMID: 33779813 DOI: 10.1007/s00424-021-02548-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 02/23/2021] [Accepted: 02/25/2021] [Indexed: 12/29/2022]
Abstract
Light-evoked voltage responses of rod and cone photoreceptor cells in the vertebrate retina must be converted to a train of synaptic vesicle release events for transmission to downstream neurons. This review discusses the processes, proteins, and structures that shape this critical early step in vision, focusing on studies from salamander retina with comparisons to other experimental animals. Many mechanisms are conserved across species. In cones, glutamate release is confined to ribbon release sites although rods are also capable of release at non-ribbon sites. The role of non-ribbon release in rods remains unclear. Release from synaptic ribbons in rods and cones involves at least three vesicle pools: a readily releasable pool (RRP) matching the number of membrane-associated vesicles along the ribbon base, a ribbon reserve pool matching the number of additional vesicles on the ribbon, and an enormous cytoplasmic reserve. Vesicle release increases in parallel with Ca2+ channel activity. While the opening of only a few Ca2+ channels beneath each ribbon can trigger fusion of a single vesicle, sustained release rates in darkness are governed by the rate at which the RRP can be replenished. The number of vacant release sites, their functional status, and the rate of vesicle delivery in turn govern replenishment. Along with an overview of the mechanisms of exocytosis and endocytosis, we consider specific properties of ribbon-associated proteins and pose a number of remaining questions about this first synapse in the visual system.
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Affiliation(s)
- Wallace B Thoreson
- Truhlsen Eye Institute, Departments of Ophthalmology & Visual Sciences and Pharmacology & Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
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14
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Mochida S. Neurotransmitter Release Site Replenishment and Presynaptic Plasticity. Int J Mol Sci 2020; 22:ijms22010327. [PMID: 33396919 PMCID: PMC7794938 DOI: 10.3390/ijms22010327] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 12/23/2020] [Accepted: 12/27/2020] [Indexed: 12/19/2022] Open
Abstract
An action potential (AP) triggers neurotransmitter release from synaptic vesicles (SVs) docking to a specialized release site of presynaptic plasma membrane, the active zone (AZ). The AP simultaneously controls the release site replenishment with SV for sustainable synaptic transmission in response to incoming neuronal signals. Although many studies have suggested that the replenishment time is relatively slow, recent studies exploring high speed resolution have revealed SV dynamics with milliseconds timescale after an AP. Accurate regulation is conferred by proteins sensing Ca2+ entering through voltage-gated Ca2+ channels opened by an AP. This review summarizes how millisecond Ca2+ dynamics activate multiple protein cascades for control of the release site replenishment with release-ready SVs that underlie presynaptic short-term plasticity.
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Affiliation(s)
- Sumiko Mochida
- Department of Physiology, Tokyo Medical University, Tokyo 160-8402, Japan
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15
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Mukherjee A, Katiyar R, Dembla E, Dembla M, Kumar P, Belkacemi A, Jung M, Beck A, Flockerzi V, Schwarz K, Schmitz F. Disturbed Presynaptic Ca 2+ Signaling in Photoreceptors in the EAE Mouse Model of Multiple Sclerosis. iScience 2020; 23:101830. [PMID: 33305185 PMCID: PMC7711289 DOI: 10.1016/j.isci.2020.101830] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 10/10/2020] [Accepted: 11/16/2020] [Indexed: 02/06/2023] Open
Abstract
Multiple sclerosis (MS) is a demyelinating disease caused by an auto-reactive immune system. Recent studies also demonstrated synapse dysfunctions in MS patients and MS mouse models. We previously observed decreased synaptic vesicle exocytosis in photoreceptor synapses in the EAE mouse model of MS at an early, preclinical stage. In the present study, we analyzed whether synaptic defects are associated with altered presynaptic Ca2+ signaling. Using high-resolution immunolabeling, we found a reduced signal intensity of Cav-channels and RIM2 at active zones in early, preclinical EAE. In line with these morphological alterations, depolarization-evoked increases of presynaptic Ca2+ were significantly smaller. In contrast, basal presynaptic Ca2+ was elevated. We observed a decreased expression of Na+/K+-ATPase and plasma membrane Ca2+ ATPase 2 (PMCA2), but not PMCA1, in photoreceptor terminals of EAE mice that could contribute to elevated basal Ca2+. Thus, complex Ca2+ signaling alterations contribute to synaptic dysfunctions in photoreceptors in early EAE. Less Cav-channels and RIM2 at the active zones of EAE photoreceptor synapses Decreased depolarization-evoked Ca2+-responses in EAE photoreceptor synapses Elevated basal, resting Ca2+ levels in preclinical EAE photoreceptor terminals Decreased expression of PMCA2 and Na+/K+-ATPase in EAE photoreceptor synapses
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Affiliation(s)
- Amrita Mukherjee
- Institute of Anatomy and Cell Biology, Department of Neuroanatomy, Saarland University, Medical School, 66421 Homburg, Germany
| | - Rashmi Katiyar
- Institute of Anatomy and Cell Biology, Department of Neuroanatomy, Saarland University, Medical School, 66421 Homburg, Germany
| | - Ekta Dembla
- Institute of Anatomy and Cell Biology, Department of Neuroanatomy, Saarland University, Medical School, 66421 Homburg, Germany
| | - Mayur Dembla
- Institute of Anatomy and Cell Biology, Department of Neuroanatomy, Saarland University, Medical School, 66421 Homburg, Germany
| | - Praveen Kumar
- Institute of Anatomy and Cell Biology, Department of Neuroanatomy, Saarland University, Medical School, 66421 Homburg, Germany
| | - Anouar Belkacemi
- Institute of Experimental and Clinical Pharmacology and Toxicology, Saarland University, Medical School, 66421 Homburg, Germany
| | - Martin Jung
- Institute of Medical Biochemistry and Molecular Biology, Saarland University, Medical School, 66421 Homburg, Germany
| | - Andreas Beck
- Institute of Experimental and Clinical Pharmacology and Toxicology, Saarland University, Medical School, 66421 Homburg, Germany
| | - Veit Flockerzi
- Institute of Experimental and Clinical Pharmacology and Toxicology, Saarland University, Medical School, 66421 Homburg, Germany
| | - Karin Schwarz
- Institute of Anatomy and Cell Biology, Department of Neuroanatomy, Saarland University, Medical School, 66421 Homburg, Germany
| | - Frank Schmitz
- Institute of Anatomy and Cell Biology, Department of Neuroanatomy, Saarland University, Medical School, 66421 Homburg, Germany
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16
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Radulovic T, Dong W, Goral RO, Thomas CI, Veeraraghavan P, Montesinos MS, Guerrero-Given D, Goff K, Lübbert M, Kamasawa N, Ohtsuka T, Young SM. Presynaptic development is controlled by the core active zone proteins CAST/ELKS. J Physiol 2020; 598:2431-2452. [PMID: 32304329 DOI: 10.1113/jp279736] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 04/14/2020] [Indexed: 12/24/2022] Open
Abstract
KEY POINTS CAST/ELKS are positive regulators of presynaptic growth and are suppressors of active zone expansion at the developing mouse calyx of Held. CAST/ELKS regulate all three CaV 2 subtype channel levels in the presynaptic terminal and not just CaV 2.1. The half-life of ELKS is on the timescale of days and not weeks. Synaptic transmission was not impacted by the loss of CAST/ELKS. CAST/ELKS are involved in pathways regulating morphological properties of presynaptic terminals during an early stage of circuit maturation. ABSTRACT Many presynaptic active zone (AZ) proteins have multiple regulatory roles that vary during distinct stages of neuronal circuit development. The CAST/ELKS protein family are evolutionarily conserved presynaptic AZ molecules that regulate presynaptic calcium channels, synaptic transmission and plasticity in the mammalian CNS. However, how these proteins regulate synapse development and presynaptic function in a developing neuronal circuit in its native environment is unclear. To unravel the roles of CAST/ELKS in glutamatergic synapse development and in presynaptic function, we used CAST knockout (KO) and ELKS conditional KO (CKO) mice to examine how their loss during the early stages of circuit maturation impacted the calyx of Held presynaptic terminal development and function. Morphological analysis from confocal z-stacks revealed that combined deletion of CAST/ELKS resulted in a reduction in the surface area and volume of the calyx. Analysis of AZ ultrastructure showed that AZ size was increased in the absence of CAST/ELKS. Patch clamp recordings demonstrated a reduction of all presynaptic CaV 2 channel subtype currents that correlated with a loss in presynaptic CaV 2 channel numbers. However, these changes did not impair synaptic transmission and plasticity and synaptic vesicle release kinetics. We conclude that CAST/ELKS proteins are positive regulators of presynaptic growth and are suppressors of AZ expansion and CaV 2 subtype currents and levels during calyx of Held development. We propose that CAST/ELKS are involved in pathways regulating presynaptic morphological properties and CaV 2 channel subtypes and suggest there is developmental compensation to preserve synaptic transmission during early stages of neuronal circuit maturation.
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Affiliation(s)
- Tamara Radulovic
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Wei Dong
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Medical Electrophysiological Key Lab of Sichuan Province, Institute of Cardiovascular Research of Southwest Medical University, Luzhou, 646000, China
| | - R Oliver Goral
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Connon I Thomas
- Electron Microscopy Facility, Max Planck Florida Institute for Neuroscience, Jupiter, FL, 33458, USA
| | | | - Monica Suarez Montesinos
- Research Group Molecular Mechanisms of Synaptic Function, Max Planck Florida Institute for Neuroscience, Jupiter, FL, 33458, USA
| | - Debbie Guerrero-Given
- Electron Microscopy Facility, Max Planck Florida Institute for Neuroscience, Jupiter, FL, 33458, USA
| | - Kevin Goff
- Research Group Molecular Mechanisms of Synaptic Function, Max Planck Florida Institute for Neuroscience, Jupiter, FL, 33458, USA
| | - Matthias Lübbert
- Research Group Molecular Mechanisms of Synaptic Function, Max Planck Florida Institute for Neuroscience, Jupiter, FL, 33458, USA
| | - Naomi Kamasawa
- Electron Microscopy Facility, Max Planck Florida Institute for Neuroscience, Jupiter, FL, 33458, USA
| | - Toshihisa Ohtsuka
- Department of Biochemistry , Graduate School of Medicine/Faculty of Medicine, University of Yamanashi, 1110 Shimokato Chuo, Yamanashi, 409-3898, Japan
| | - Samuel M Young
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA.,Department of Otolaryngology, Iowa Neuroscience Institute, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
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17
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Furukawa T, Ueno A, Omori Y. Molecular mechanisms underlying selective synapse formation of vertebrate retinal photoreceptor cells. Cell Mol Life Sci 2020; 77:1251-1266. [PMID: 31586239 PMCID: PMC11105113 DOI: 10.1007/s00018-019-03324-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 09/21/2019] [Accepted: 09/25/2019] [Indexed: 11/29/2022]
Abstract
In vertebrate central nervous systems (CNSs), highly diverse neurons are selectively connected via synapses, which are essential for building an intricate neural network. The vertebrate retina is part of the CNS and is comprised of a distinct laminar organization, which serves as a good model system to study developmental synapse formation mechanisms. In the retina outer plexiform layer, rods and cones, two types of photoreceptor cells, elaborate selective synaptic contacts with ON- and/or OFF-bipolar cell terminals as well as with horizontal cell terminals. In the mouse retina, three photoreceptor subtypes and at least 15 bipolar subtypes exist. Previous and recent studies have significantly progressed our understanding of how selective synapse formation, between specific subtypes of photoreceptor and bipolar cells, is designed at the molecular level. In the ON pathway, photoreceptor-derived secreted and transmembrane proteins directly interact in trans with the GRM6 (mGluR6) complex, which is localized to ON-bipolar cell dendritic terminals, leading to selective synapse formation. Here, we review our current understanding of the key factors and mechanisms underlying selective synapse formation of photoreceptor cells with bipolar and horizontal cells in the retina. In addition, we describe how defects/mutations of the molecules involved in photoreceptor synapse formation are associated with human retinal diseases and visual disorders.
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Affiliation(s)
- Takahisa Furukawa
- Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
| | - Akiko Ueno
- Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Yoshihiro Omori
- Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
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18
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Hagiwara A, Sugiyama N, Ohtsuka T. Impaired experience-dependent maternal care in presynaptic active zone protein CAST-deficient dams. Sci Rep 2020; 10:5238. [PMID: 32251313 PMCID: PMC7090055 DOI: 10.1038/s41598-020-62072-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 03/09/2020] [Indexed: 11/24/2022] Open
Abstract
Although sociological studies affirm the importance of parental care in the survival of offspring, maltreatment—including child neglect—remains prevalent in many countries. While child neglect is well known to affect child development, the causes of maternal neglect are poorly understood. Here, we found that female mice with a deletion mutation of CAST (a presynaptic release-machinery protein) showed significantly reduced weaning rate when primiparous and a recovered rate when multiparous. Indeed, when nurturing, primiparous and nulliparous CAST knock out (KO) mice exhibited less crouching time than control mice and moved greater distances. Contrary to expectations, plasma oxytocin (OXT) was not significantly reduced in CAST KO mice even though terminals of magnocellular neurons in the posterior pituitary expressed CAST. We further found that compared with control mice, CAST KO mice drank significantly less water when nurturing and had a greater preference for sucrose during pregnancy. We suggest that deficiency in presynaptic release-machinery protein impairs the facilitation of some maternal behaviours, which can be compensated for by experience and learning.
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Affiliation(s)
- Akari Hagiwara
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Naoko Sugiyama
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Toshihisa Ohtsuka
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan.
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19
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ELKS/Voltage-Dependent Ca 2+ Channel-β Subunit Module Regulates Polarized Ca 2+ Influx in Pancreatic β Cells. Cell Rep 2020; 26:1213-1226.e7. [PMID: 30699350 DOI: 10.1016/j.celrep.2018.12.106] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Revised: 10/29/2018] [Accepted: 12/27/2018] [Indexed: 12/14/2022] Open
Abstract
Pancreatic β cells secrete insulin by Ca2+-triggered exocytosis. However, there is no apparent secretory site similar to the neuronal active zones, and the cellular and molecular localization mechanism underlying polarized exocytosis remains elusive. Here, we report that ELKS, a vertebrate active zone protein, is used in β cells to regulate Ca2+ influx for insulin secretion. β cell-specific ELKS-knockout (KO) mice showed impaired glucose-stimulated first-phase insulin secretion and reduced L-type voltage-dependent Ca2+ channel (VDCC) current density. In situ Ca2+ imaging of β cells within islets expressing a membrane-bound G-CaMP8b Ca2+ sensor demonstrated initial local Ca2+ signals at the ELKS-localized vascular side of the β cell plasma membrane, which were markedly decreased in ELKS-KO β cells. Mechanistically, ELKS directly interacted with the VDCC-β subunit via the GK domain. These findings suggest that ELKS and VDCCs form a potent insulin secretion complex at the vascular side of the β cell plasma membrane for polarized Ca2+ influx and first-phase insulin secretion from pancreatic islets.
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20
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Hagiwara A, Hamada S, Hida Y, Ohtsuka T. Double deletion of the active zone proteins CAST/ELKS in the mouse forebrain causes high mortality of newborn pups. Mol Brain 2020; 13:13. [PMID: 31996256 PMCID: PMC6988216 DOI: 10.1186/s13041-020-0557-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 01/21/2020] [Indexed: 11/10/2022] Open
Abstract
Presynaptic active zone cytomatrix proteins are essential elements of neurotransmitter release machinery that govern neural transmission. Among active zone proteins, cytomatrix at the active zone-associated structural protein (CAST) is known to regulate active zone size in retinal photoreceptors and neurotransmitter release by recruiting Ca2+ channels at various synapses. However, the role of ELKS-a protein from the same family as CAST-and the synergistic roles of CAST/ELKS have not been thoroughly investigated, particularly with regard to mouse behavior. Here, we generated ELKS conditional KO in mouse forebrain synapses by crossing ELKS flox mice with a CaMKII promoter-induced Cre line. Results showed that CAST is dominant at these synapses and that ELKS can support CAST function, but is less effective in the ELKS single KO. Pups of CAST/ELKS double KO in the forebrain were born in Mendelian rations but resulted in eventual death right after the birth. Anatomically, the forebrain neuronal compositions of CAST KO and CAST/ELKS double KO mice were indistinguishable, and the sensory neural network from whiskers on the face was identified as barrelette-like patches in the spinal trigeminal nucleus. Therefore, depletion of CAST and ELKS disrupts neurotransmission from sensory to motor networks, which can lead to deficits in exploration and failure to suckle.
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Affiliation(s)
- Akari Hagiwara
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan
| | - Shun Hamada
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan
| | - Yamato Hida
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan
| | - Toshihisa Ohtsuka
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi, 409-3898, Japan.
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21
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Moser T, Grabner CP, Schmitz F. Sensory Processing at Ribbon Synapses in the Retina and the Cochlea. Physiol Rev 2020; 100:103-144. [DOI: 10.1152/physrev.00026.2018] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In recent years, sensory neuroscientists have made major efforts to dissect the structure and function of ribbon synapses which process sensory information in the eye and ear. This review aims to summarize our current understanding of two key aspects of ribbon synapses: 1) their mechanisms of exocytosis and endocytosis and 2) their molecular anatomy and physiology. Our comparison of ribbon synapses in the cochlea and the retina reveals convergent signaling mechanisms, as well as divergent strategies in different sensory systems.
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Affiliation(s)
- Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
| | - Chad P. Grabner
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
| | - Frank Schmitz
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
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22
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Dong W, Radulovic T, Goral RO, Thomas C, Suarez Montesinos M, Guerrero-Given D, Hagiwara A, Putzke T, Hida Y, Abe M, Sakimura K, Kamasawa N, Ohtsuka T, Young SM. CAST/ELKS Proteins Control Voltage-Gated Ca 2+ Channel Density and Synaptic Release Probability at a Mammalian Central Synapse. Cell Rep 2019; 24:284-293.e6. [PMID: 29996090 PMCID: PMC6372087 DOI: 10.1016/j.celrep.2018.06.024] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 04/25/2018] [Accepted: 06/05/2018] [Indexed: 12/29/2022] Open
Abstract
In the presynaptic terminal, the magnitude and location of Ca2+ entry through voltage-gated Ca2+ channels (VGCCs) regulate the efficacy of neurotransmitter release. However, how presynaptic active zone proteins control mammalian VGCC levels and organization is unclear. To address this, we deleted the CAST/ELKS protein family at the calyx of Held, a CaV2.1 channel-exclusive presynaptic terminal. We found that loss of CAST/ELKS reduces the CaV2.1 current density with concomitant reductions in CaV2.1 channel numbers and clusters. Surprisingly, deletion of CAST/ELKS increases release probability while decreasing the readily releasable pool, with no change in active zone ultrastructure. In addition, Ca2+ channel coupling is unchanged, but spontaneous release rates are elevated. Thus, our data identify distinct roles for CAST/ELKS as positive regulators of CaV2.1 channel density and suggest that they regulate release probability through a post-priming step that controls synaptic vesicle fusogenicity. Dong et al. show that CAST/ELKS have multiple roles in presynaptic function. These proteins positively regulate CaV2.1 channel abundance and negatively regulate release probability. The authors propose that CAST/ELKS regulate release probability at a step in synaptic vesicle release that regulates the energy barrier for synaptic vesicle fusion.
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Affiliation(s)
- Wei Dong
- Research Group Molecular Mechanisms of Synaptic Function, Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA; Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease, Institute of Cardiovascular Research, Southwest Medical University, Luzhou 646000, China
| | - Tamara Radulovic
- Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA 52242, USA
| | - R Oliver Goral
- Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA 52242, USA
| | - Connon Thomas
- Max Planck Florida Institute for Neuroscience Electron Microscopy Facility, Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA
| | - Monica Suarez Montesinos
- Research Group Molecular Mechanisms of Synaptic Function, Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA
| | - Debbie Guerrero-Given
- Max Planck Florida Institute for Neuroscience Electron Microscopy Facility, Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA
| | - Akari Hagiwara
- Department of Biochemistry, University of Yamanashi, Yamanashi 409-3898, Japan
| | - Travis Putzke
- Research Group Molecular Mechanisms of Synaptic Function, Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA
| | - Yamato Hida
- Department of Biochemistry, University of Yamanashi, Yamanashi 409-3898, Japan
| | - Manabu Abe
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Kenji Sakimura
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Naomi Kamasawa
- Max Planck Florida Institute for Neuroscience Electron Microscopy Facility, Max Planck Florida Institute for Neuroscience, Jupiter, FL 33458, USA
| | - Toshihisa Ohtsuka
- Department of Biochemistry, University of Yamanashi, Yamanashi 409-3898, Japan.
| | - Samuel M Young
- Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA 52242, USA; Department of Otolaryngology, University of Iowa, Iowa City, IA 52242, USA; Iowa Neuroscience Institute, University of Iowa, Iowa City, IA 52242, USA; Aging Mind Brain Initiative, University of Iowa, Iowa City, IA 52242, USA.
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23
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Nemitz L, Dedek K, Janssen-Bienhold U. Rod Bipolar Cells Require Horizontal Cells for Invagination Into the Terminals of Rod Photoreceptors. Front Cell Neurosci 2019; 13:423. [PMID: 31619966 PMCID: PMC6760018 DOI: 10.3389/fncel.2019.00423] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 09/03/2019] [Indexed: 01/22/2023] Open
Abstract
In the central nervous system, neuronal processing relies on the precisely orchestrated formation of synapses during development. The first synapse of the visual system is a triad synapse, comprising photoreceptors, horizontal cells and bipolar cells. During the second postnatal week, the axon terminal processes of horizontal cells invaginate rod spherules, followed by rod bipolar cell dendrites. Both elements finally oppose the synaptic ribbon (the release site of glutamate). However, it has not been fully elucidated whether horizontal cells are essential for rod bipolar cell dendrites to find their way into the rod terminal. In the present study, we investigated this question by specifically ablating horizontal cells from the early postnatal mouse retina. We monitored the formation of the rod-to-rod bipolar cell synapse during retinal maturation until postnatal day 21. Based on quantitative electron microscopy, we found that without horizontal cells, the dendrites of rod bipolar cells never entered rod terminals. Furthermore, rods displayed significantly fewer and shorter presynaptic ribbons, suggesting that glutamate release is decreased, which coincided with significantly reduced expression of postsynaptic proteins (mGluR6, GPR179) in rod bipolar cells. Collectively, our findings uncover that horizontal cells are indeed necessary guideposts for rod bipolar cells. Whether horizontal cells release diffusible guidance cues or provide structural guidance by expressing specific cell adhesion molecules remains to be seen.
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Affiliation(s)
- Lena Nemitz
- Visual Neuroscience, Department of Neuroscience, University of Oldenburg, Oldenburg, Germany
| | - Karin Dedek
- Animal Navigation/Neurosensorics, Institute for Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany.,Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
| | - Ulrike Janssen-Bienhold
- Visual Neuroscience, Department of Neuroscience, University of Oldenburg, Oldenburg, Germany.,Research Center Neurosensory Science, University of Oldenburg, Oldenburg, Germany
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24
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Grassmeyer JJ, Cahill AL, Hays CL, Barta C, Quadros RM, Gurumurthy CB, Thoreson WB. Ca 2+ sensor synaptotagmin-1 mediates exocytosis in mammalian photoreceptors. eLife 2019; 8:e45946. [PMID: 31172949 PMCID: PMC6588344 DOI: 10.7554/elife.45946] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2019] [Accepted: 06/06/2019] [Indexed: 11/24/2022] Open
Abstract
To encode light-dependent changes in membrane potential, rod and cone photoreceptors utilize synaptic ribbons to sustain continuous exocytosis while making rapid, fine adjustments to release rate. Release kinetics are shaped by vesicle delivery down ribbons and by properties of exocytotic Ca2+ sensors. We tested the role for synaptotagmin-1 (Syt1) in photoreceptor exocytosis by using novel mouse lines in which Syt1 was conditionally removed from rods or cones. Photoreceptors lacking Syt1 exhibited marked reductions in exocytosis as measured by electroretinography and single-cell recordings. Syt1 mediated all evoked release in cones, whereas rods appeared capable of some slow Syt1-independent release. Spontaneous release frequency was unchanged in cones but increased in rods lacking Syt1. Loss of Syt1 did not alter synaptic anatomy or reduce Ca2+ currents. These results suggest that Syt1 mediates both phasic and tonic release at photoreceptor synapses, revealing unexpected flexibility in the ability of Syt1 to regulate Ca2+-dependent synaptic transmission.
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Affiliation(s)
- Justin J Grassmeyer
- Truhlsen Eye Institute, Department of Ophthalmology and Visual SciencesUniversity of Nebraska Medical CenterOmahaUnited States
- Department of Pharmacology and Experimental NeuroscienceUniversity of Nebraska Medical CenterOmahaUnited States
| | - Asia L Cahill
- Truhlsen Eye Institute, Department of Ophthalmology and Visual SciencesUniversity of Nebraska Medical CenterOmahaUnited States
| | - Cassandra L Hays
- Truhlsen Eye Institute, Department of Ophthalmology and Visual SciencesUniversity of Nebraska Medical CenterOmahaUnited States
- Department of Cellular and Integrative PhysiologyUniversity of Nebraska Medical CenterOmahaUnited States
| | - Cody Barta
- Truhlsen Eye Institute, Department of Ophthalmology and Visual SciencesUniversity of Nebraska Medical CenterOmahaUnited States
| | - Rolen M Quadros
- Mouse Genome Engineering Core Facility, Vice Chancellor for Research OfficeUniversity of Nebraska Medical CenterOmahaUnited States
| | - Channabasavaiah B Gurumurthy
- Mouse Genome Engineering Core Facility, Vice Chancellor for Research OfficeUniversity of Nebraska Medical CenterOmahaUnited States
- Developmental Neuroscience, Munroe Meyer Institute for Genetics and RehabilitationUniversity of Nebraska Medical CenterOmahaUnited States
| | - Wallace B Thoreson
- Truhlsen Eye Institute, Department of Ophthalmology and Visual SciencesUniversity of Nebraska Medical CenterOmahaUnited States
- Department of Pharmacology and Experimental NeuroscienceUniversity of Nebraska Medical CenterOmahaUnited States
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25
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Assawachananont J, Kim SY, Kaya KD, Fariss R, Roger JE, Swaroop A. Cone-rod homeobox CRX controls presynaptic active zone formation in photoreceptors of mammalian retina. Hum Mol Genet 2019; 27:3555-3567. [PMID: 30084954 DOI: 10.1093/hmg/ddy272] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 07/19/2018] [Indexed: 12/14/2022] Open
Abstract
In the mammalian retina, rod and cone photoreceptors transmit the visual information to bipolar neurons through highly specialized ribbon synapses. We have limited understanding of regulatory pathways that guide morphogenesis and organization of photoreceptor presynaptic architecture in the developing retina. While neural retina leucine zipper (NRL) transcription factor determines rod cell fate and function, cone-rod homeobox (CRX) controls the expression of both rod- and cone-specific genes and is critical for terminal differentiation of photoreceptors. A comprehensive immunohistochemical evaluation of Crx-/- (null), CrxRip/+ and CrxRip/Rip (models of dominant congenital blindness) mouse retinas revealed abnormal photoreceptor synapses, with atypical ribbon shape, number and length. Integrated analysis of retinal transcriptomes of Crx-mutants with CRX- and NRL-ChIP-Seq data identified a subset of differentially expressed CRX target genes that encode presynaptic proteins associated with the cytomatrix active zone (CAZ) and synaptic vesicles. Immunohistochemistry of Crx-mutant retina validated aberrant expression of REEP6, PSD95, MPP4, UNC119, UNC13, RGS7 and RGS11, with some reduction in Ribeye and no significant change in immunostaining of RIMS1, RIMS2, Bassoon and Pikachurin. Our studies demonstrate that CRX controls the establishment of CAZ and anchoring of ribbons, but not the formation of ribbon itself, in photoreceptor presynaptic terminals.
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Affiliation(s)
- Juthaporn Assawachananont
- Neurobiology-Neurodegeneration & Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Soo-Young Kim
- Neurobiology-Neurodegeneration & Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Koray D Kaya
- Neurobiology-Neurodegeneration & Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Robert Fariss
- Imaging Core, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jerome E Roger
- Neurobiology-Neurodegeneration & Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.,Centre d'Etude et de Recherches Thérapeutiques en Ophthalmologie, Retina France, Orsay, France.,Paris-Saclay Institute of Neuroscience, CNRS, Univ Paris Sud, Université Paris-Saclay, Orsay, France
| | - Anand Swaroop
- Neurobiology-Neurodegeneration & Repair Laboratory, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
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26
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Held RG, Kaeser PS. ELKS active zone proteins as multitasking scaffolds for secretion. Open Biol 2019; 8:rsob.170258. [PMID: 29491150 PMCID: PMC5830537 DOI: 10.1098/rsob.170258] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2017] [Accepted: 02/06/2018] [Indexed: 12/18/2022] Open
Abstract
Synaptic vesicle exocytosis relies on the tethering of release ready vesicles close to voltage-gated Ca2+ channels and specific lipids at the future site of fusion. This enables rapid and efficient neurotransmitter secretion during presynaptic depolarization by an action potential. Extensive research has revealed that this tethering is mediated by an active zone, a protein dense structure that is attached to the presynaptic plasma membrane and opposed to postsynaptic receptors. Although roles of individual active zone proteins in exocytosis are in part understood, the molecular mechanisms that hold the protein scaffold at the active zone together and link it to the presynaptic plasma membrane have remained unknown. This is largely due to redundancy within and across scaffolding protein families at the active zone. Recent studies, however, have uncovered that ELKS proteins, also called ERC, Rab6IP2 or CAST, act as active zone scaffolds redundant with RIMs. This redundancy has led to diverse synaptic phenotypes in studies of ELKS knockout mice, perhaps because different synapses rely to a variable extent on scaffolding redundancy. In this review, we first evaluate the need for presynaptic scaffolding, and we then discuss how the diverse synaptic and non-synaptic functional roles of ELKS support the hypothesis that ELKS provides molecular scaffolding for organizing vesicle traffic at the presynaptic active zone and in other cellular compartments.
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Affiliation(s)
- Richard G Held
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
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27
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Lahtinen A, Puttonen S, Vanttola P, Viitasalo K, Sulkava S, Pervjakova N, Joensuu A, Salo P, Toivola A, Härmä M, Milani L, Perola M, Paunio T. A distinctive DNA methylation pattern in insufficient sleep. Sci Rep 2019; 9:1193. [PMID: 30718923 PMCID: PMC6362278 DOI: 10.1038/s41598-018-38009-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 12/17/2018] [Indexed: 12/11/2022] Open
Abstract
Short sleep duration or insomnia may lead to an increased risk of various psychiatric and cardio-metabolic conditions. Since DNA methylation plays a critical role in the regulation of gene expression, studies of differentially methylated positions (DMPs) might be valuable for understanding the mechanisms underlying insomnia. We performed a cross-sectional genome-wide analysis of DNA methylation in relation to self-reported insufficient sleep in individuals from a community-based sample (79 men, aged 39.3 ± 7.3), and in relation to shift work disorder in an occupational cohort (26 men, aged 44.9 ± 9.0). The analysis of DNA methylation data revealed that genes corresponding to selected DMPs form a distinctive pathway: "Nervous System Development" (FDR P value < 0.05). We found that 78% of the DMPs were hypomethylated in cases in both cohorts, suggesting that insufficient sleep may be associated with loss of DNA methylation. A karyoplot revealed clusters of DMPs at various chromosomal regions, including 12 DMPs on chromosome 17, previously associated with Smith-Magenis syndrome, a rare condition comprising disturbed sleep and inverse circadian rhythm. Our findings give novel insights into the DNA methylation patterns associated with sleep loss, possibly modifying processes related to neuroplasticity and neurodegeneration. Future prospective studies are needed to confirm the observed associations.
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Affiliation(s)
- Alexandra Lahtinen
- Department of Public Health Solutions, Genomics and Biomarkers Unit, National Institute for Health and Welfare, PO Box 30, FI-00271, Helsinki, Finland.
- Department of Psychiatry, University of Helsinki and Helsinki University Central Hospital, PO Box 590, FIN-00029, HUS, Helsinki, Finland.
| | - Sampsa Puttonen
- Work Ability and Working Career, Finnish Institute of Occupational Health, PO Box 40, FI-00032, Työterveyslaitos, Helsinki, Finland
| | - Päivi Vanttola
- Work Ability and Working Career, Finnish Institute of Occupational Health, PO Box 40, FI-00032, Työterveyslaitos, Helsinki, Finland
| | | | - Sonja Sulkava
- Department of Public Health Solutions, Genomics and Biomarkers Unit, National Institute for Health and Welfare, PO Box 30, FI-00271, Helsinki, Finland
- Department of Psychiatry, University of Helsinki and Helsinki University Central Hospital, PO Box 590, FIN-00029, HUS, Helsinki, Finland
| | - Natalia Pervjakova
- Estonian Genome Center, Institute of Genomics, University of Tartu, Tartu, 51010, Estonia
| | - Anni Joensuu
- Department of Public Health Solutions, Genomics and Biomarkers Unit, National Institute for Health and Welfare, PO Box 30, FI-00271, Helsinki, Finland
- Diabetes and Obesity Research Program, University of Helsinki, PO Box 63, FI-00014, Helsinki, Finland
| | - Perttu Salo
- Department of Public Health Solutions, Genomics and Biomarkers Unit, National Institute for Health and Welfare, PO Box 30, FI-00271, Helsinki, Finland
| | - Auli Toivola
- Department of Public Health Solutions, Genomics and Biomarkers Unit, National Institute for Health and Welfare, PO Box 30, FI-00271, Helsinki, Finland
| | - Mikko Härmä
- Work Ability and Working Career, Finnish Institute of Occupational Health, PO Box 40, FI-00032, Työterveyslaitos, Helsinki, Finland
| | - Lili Milani
- Estonian Genome Center, Institute of Genomics, University of Tartu, Tartu, 51010, Estonia
| | - Markus Perola
- Department of Public Health Solutions, Genomics and Biomarkers Unit, National Institute for Health and Welfare, PO Box 30, FI-00271, Helsinki, Finland
- Diabetes and Obesity Research Program, University of Helsinki, PO Box 63, FI-00014, Helsinki, Finland
| | - Tiina Paunio
- Department of Public Health Solutions, Genomics and Biomarkers Unit, National Institute for Health and Welfare, PO Box 30, FI-00271, Helsinki, Finland.
- Department of Psychiatry, University of Helsinki and Helsinki University Central Hospital, PO Box 590, FIN-00029, HUS, Helsinki, Finland.
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28
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A Multiple Piccolino-RIBEYE Interaction Supports Plate-Shaped Synaptic Ribbons in Retinal Neurons. J Neurosci 2019; 39:2606-2619. [PMID: 30696732 DOI: 10.1523/jneurosci.2038-18.2019] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 01/08/2019] [Accepted: 01/08/2019] [Indexed: 01/28/2023] Open
Abstract
Active zones at chemical synapses are highly specialized sites for the regulated release of neurotransmitters. Despite a high degree of active zone protein conservation in vertebrates, every type of chemical synapse expresses a given set of protein isoforms and splice variants adapted to the demands on neurotransmitter release. So far, we know little about how specific active zone proteins contribute to the structural and functional diversity of active zones. In this study, we explored the nanodomain organization of ribbon-type active zones by addressing the significance of Piccolino, the ribbon synapse-specific splice variant of Piccolo, for shaping the ribbon structure. We followed up on previous results, which indicated that rod photoreceptor synaptic ribbons lose their structural integrity in a knockdown of Piccolino. Here, we demonstrate an interaction between Piccolino and the major ribbon component RIBEYE that supports plate-shaped synaptic ribbons in retinal neurons. In a detailed ultrastructural analysis of three different types of retinal ribbon synapses in Piccolo/Piccolino-deficient male and female rats, we show that the absence of Piccolino destabilizes the superstructure of plate-shaped synaptic ribbons, although with variable manifestation in the cell types examined. Our analysis illustrates how the expression of a specific active zone protein splice variant (e.g., Piccolino) contributes to structural diversity of vertebrate active zones.SIGNIFICANCE STATEMENT Retinal ribbon synapses are a specialized type of chemical synapse adapted for the regulated fast and tonic release of neurotransmitter. The hallmark of retinal ribbon synapses is the plate-shaped synaptic ribbon, which extends from the release site into the terminals' cytoplasm and tethers hundreds of synaptic vesicles. Here, we show that Piccolino, the synaptic ribbon specific splice variant of Piccolo, interacts with RIBEYE, the main component of synaptic ribbons. This interaction occurs via several PxDLS-like motifs located at the C terminus of Piccolino, which can connect multiple RIBEYE molecules. Loss of Piccolino disrupts the characteristic plate-shaped structure of synaptic ribbons, indicating a role of Piccolino in synaptic ribbon assembly.
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29
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Pangrsic T, Singer JH, Koschak A. Voltage-Gated Calcium Channels: Key Players in Sensory Coding in the Retina and the Inner Ear. Physiol Rev 2019; 98:2063-2096. [PMID: 30067155 DOI: 10.1152/physrev.00030.2017] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Calcium influx through voltage-gated Ca (CaV) channels is the first step in synaptic transmission. This review concerns CaV channels at ribbon synapses in primary sense organs and their specialization for efficient coding of stimuli in the physical environment. Specifically, we describe molecular, biochemical, and biophysical properties of the CaV channels in sensory receptor cells of the retina, cochlea, and vestibular apparatus, and we consider how such properties might change over the course of development and contribute to synaptic plasticity. We pay particular attention to factors affecting the spatial arrangement of CaV channels at presynaptic, ribbon-type active zones, because the spatial relationship between CaV channels and release sites has been shown to affect synapse function critically in a number of systems. Finally, we review identified synaptopathies affecting sensory systems and arising from dysfunction of L-type, CaV1.3, and CaV1.4 channels or their protein modulatory elements.
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Affiliation(s)
- Tina Pangrsic
- Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen and Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine , Göttingen, Germany ; Department of Biology, University of Maryland , College Park, Maryland ; and Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck , Innsbruck , Austria
| | - Joshua H Singer
- Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen and Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine , Göttingen, Germany ; Department of Biology, University of Maryland , College Park, Maryland ; and Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck , Innsbruck , Austria
| | - Alexandra Koschak
- Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen and Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine , Göttingen, Germany ; Department of Biology, University of Maryland , College Park, Maryland ; and Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck , Innsbruck , Austria
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30
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Hagiwara A, Kitahara Y, Grabner CP, Vogl C, Abe M, Kitta R, Ohta K, Nakamura K, Sakimura K, Moser T, Nishi A, Ohtsuka T. Cytomatrix proteins CAST and ELKS regulate retinal photoreceptor development and maintenance. J Cell Biol 2018; 217:3993-4006. [PMID: 30190286 PMCID: PMC6219712 DOI: 10.1083/jcb.201704076] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 06/18/2018] [Accepted: 08/03/2018] [Indexed: 01/06/2023] Open
Abstract
The retinal ribbon synapse is important for the processing of visual information. Hagiwara et al. show that the active zone proteins CAST and ELKS perform both redundant and unique functions in photoreceptors to promote the maturation, maintenance, and activity of ribbon synapses. At the presynaptic active zone (AZ), the related cytomatrix proteins CAST and ELKS organize the presynaptic release machinery. While CAST is known to regulate AZ size and neurotransmitter release, the role of ELKS and the integral system of CAST/ELKS together is poorly understood. Here, we show that CAST and ELKS have both redundant and unique roles in coordinating synaptic development, function, and maintenance of retinal photoreceptor ribbon synapses. A CAST/ELKS double knockout (dKO) mouse showed high levels of ectopic synapses and reduced responses to visual stimulation. Ectopic formation was not observed in ELKS conditional KO but progressively increased with age in CAST KO mice with higher rates in the dKO. Presynaptic calcium influx was strongly reduced in rod photoreceptors of CAST KO and dKO mice. Three-dimensional scanning EM reconstructions showed structural abnormalities in rod triads of CAST KO and dKO. Remarkably, AAV-mediated acute ELKS deletion after synapse maturation induced neurodegeneration and loss of ribbon synapses. These results suggest that CAST and ELKS work in concert to promote retinal synapse formation, transmission, and maintenance.
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Affiliation(s)
- Akari Hagiwara
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Yosuke Kitahara
- Department of Pharmacology, Kurume University School of Medicine, Fukuoka, Japan
| | - Chad Paul Grabner
- Institute for Auditory Neuroscience and Inner Ear Lab, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Christian Vogl
- Institute for Auditory Neuroscience and Inner Ear Lab, University Medical Center Göttingen, Göttingen, Germany
| | - Manabu Abe
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Ryo Kitta
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan
| | - Keisuke Ohta
- Department of Anatomy, Kurume University School of Medicine, Fukuoka, Japan
| | - Keiichiro Nakamura
- Department of Anatomy, Kurume University School of Medicine, Fukuoka, Japan
| | - Kenji Sakimura
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Tobias Moser
- Institute for Auditory Neuroscience and Inner Ear Lab, University Medical Center Göttingen, Göttingen, Germany .,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
| | - Akinori Nishi
- Department of Pharmacology, Kurume University School of Medicine, Fukuoka, Japan
| | - Toshihisa Ohtsuka
- Department of Biochemistry, Faculty of Medicine, University of Yamanashi, Yamanashi, Japan
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31
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Hamada S, Ohtsuka T. CAST: Its molecular structure and phosphorylation-dependent regulation of presynaptic plasticity. Neurosci Res 2018; 127:25-32. [DOI: 10.1016/j.neures.2017.12.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 12/05/2017] [Accepted: 12/06/2017] [Indexed: 11/16/2022]
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32
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Walter AM, Böhme MA, Sigrist SJ. Vesicle release site organization at synaptic active zones. Neurosci Res 2017; 127:3-13. [PMID: 29275162 DOI: 10.1016/j.neures.2017.12.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 12/04/2017] [Accepted: 12/06/2017] [Indexed: 11/30/2022]
Abstract
Information transfer between nerve cells (neurons) forms the basis of behavior, emotion, and survival. Signal transduction from one neuron to another occurs at synapses, and relies on both electrical and chemical signal propagation. At chemical synapses, incoming electrical action potentials trigger the release of chemical neurotransmitters that are sensed by the connected cell and here reconverted to an electrical signal. The presynaptic conversion of an electrical to a chemical signal is an energy demanding, highly regulated process that relies on a complex, evolutionarily conserved molecular machinery. Here, we review the biophysical characteristics of this process, the current knowledge of the molecules operating in this reaction and genetic specializations that may have evolved to shape inter-neuronal signaling.
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Affiliation(s)
- Alexander M Walter
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, Berlin 13125, Germany.
| | - Mathias A Böhme
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, Berlin 13125, Germany
| | - Stephan J Sigrist
- Freie Universität Berlin, Institute for Biology/Genetics, Takustraße 6, 14195 Berlin, Germany; NeuroCure, Cluster of Excellence, Charité Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany.
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33
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SAD-B Phosphorylation of CAST Controls Active Zone Vesicle Recycling for Synaptic Depression. Cell Rep 2017; 16:2901-2913. [PMID: 27626661 DOI: 10.1016/j.celrep.2016.08.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 06/28/2016] [Accepted: 08/05/2016] [Indexed: 12/25/2022] Open
Abstract
Short-term synaptic depression (STD) is a common form of activity-dependent plasticity observed widely in the nervous system. Few molecular pathways that control STD have been described, but the active zone (AZ) release apparatus provides a possible link between neuronal activity and plasticity. Here, we show that an AZ cytomatrix protein CAST and an AZ-associated protein kinase SAD-B coordinately regulate STD by controlling reloading of the AZ with release-ready synaptic vesicles. SAD-B phosphorylates the N-terminal serine (S45) of CAST, and S45 phosphorylation increases with higher firing rate. A phosphomimetic CAST (S45D) mimics CAST deletion, which enhances STD by delaying reloading of the readily releasable pool (RRP), resulting in a pool size decrease. A phosphonegative CAST (S45A) inhibits STD and accelerates RRP reloading. Our results suggest that the CAST/SAD-B reaction serves as a brake on synaptic transmission by temporal calibration of activity and synaptic depression via RRP size regulation.
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34
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Torres VI, Inestrosa NC. Vertebrate Presynaptic Active Zone Assembly: a Role Accomplished by Diverse Molecular and Cellular Mechanisms. Mol Neurobiol 2017; 55:4513-4528. [PMID: 28685386 DOI: 10.1007/s12035-017-0661-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 06/14/2017] [Indexed: 01/22/2023]
Abstract
Among all the biological systems in vertebrates, the central nervous system (CNS) is the most complex, and its function depends on specialized contacts among neurons called synapses. The assembly and organization of synapses must be exquisitely regulated for a normal brain function and network activity. There has been a tremendous effort in recent decades to understand the molecular and cellular mechanisms participating in the formation of new synapses and their organization, maintenance, and regulation. At the vertebrate presynapses, proteins such as Piccolo, Bassoon, RIM, RIM-BPs, CAST/ELKS, liprin-α, and Munc13 are constant residents and participate in multiple and dynamic interactions with other regulatory proteins, which define network activity and normal brain function. Here, we review the function of these active zone (AZ) proteins and diverse factors involved in AZ assembly and maintenance, with an emphasis on axonal trafficking of precursor vesicles, protein homo- and hetero-oligomeric interactions as a mechanism of AZ trapping and stabilization, and the role of F-actin in presynaptic assembly and its modulation by Wnt signaling.
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Affiliation(s)
- Viviana I Torres
- Centro de Envejecimiento y Regeneración (CARE), Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Nibaldo C Inestrosa
- Centro de Envejecimiento y Regeneración (CARE), Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile. .,Center for Healthy Brain Ageing, School of Psychiatry, Faculty of Medicine, University of New South Wales, Sydney, Australia. .,Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile.
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35
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Wang Y, Fehlhaber KE, Sarria I, Cao Y, Ingram NT, Guerrero-Given D, Throesch B, Baldwin K, Kamasawa N, Ohtsuka T, Sampath AP, Martemyanov KA. The Auxiliary Calcium Channel Subunit α2δ4 Is Required for Axonal Elaboration, Synaptic Transmission, and Wiring of Rod Photoreceptors. Neuron 2017; 93:1359-1374.e6. [PMID: 28262416 PMCID: PMC5364038 DOI: 10.1016/j.neuron.2017.02.021] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Revised: 12/31/2016] [Accepted: 02/08/2017] [Indexed: 11/24/2022]
Abstract
Neural circuit wiring relies on selective synapse formation whereby a presynaptic release apparatus is matched with its cognate postsynaptic machinery. At metabotropic synapses, the molecular mechanisms underlying this process are poorly understood. In the mammalian retina, rod photoreceptors form selective contacts with rod ON-bipolar cells by aligning the presynaptic voltage-gated Ca2+ channel directing glutamate release (CaV1.4) with postsynaptic mGluR6 receptors. We show this coordination requires an extracellular protein, α2δ4, which complexes with CaV1.4 and the rod synaptogenic mediator, ELFN1, for trans-synaptic alignment with mGluR6. Eliminating α2δ4 in mice abolishes rod synaptogenesis and synaptic transmission to rod ON-bipolar cells, and disrupts postsynaptic mGluR6 clustering. We further find that in rods, α2δ4 is crucial for organizing synaptic ribbons and setting CaV1.4 voltage sensitivity. In cones, α2δ4 is essential for CaV1.4 function, but is not required for ribbon organization, synaptogenesis, or synaptic transmission. These findings offer insights into retinal pathologies associated with α2δ4 dysfunction.
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Affiliation(s)
- Yuchen Wang
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Katherine E Fehlhaber
- Jules Stein Eye Institute, Department of Ophthalmology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Ignacio Sarria
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Yan Cao
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA
| | - Norianne T Ingram
- Jules Stein Eye Institute, Department of Ophthalmology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Debbie Guerrero-Given
- Electron Microscopy Core Facility, Max Planck Florida Institute, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Ben Throesch
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92121, USA
| | - Kristin Baldwin
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92121, USA
| | - Naomi Kamasawa
- Electron Microscopy Core Facility, Max Planck Florida Institute, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Toshihisa Ohtsuka
- Department of Biochemistry, University of Yamanashi, Yamanashi 409-3898, Japan
| | - Alapakkam P Sampath
- Jules Stein Eye Institute, Department of Ophthalmology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Kirill A Martemyanov
- Department of Neuroscience, The Scripps Research Institute, Jupiter, FL 33458, USA.
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36
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Kawabe H, Mitkovski M, Kaeser PS, Hirrlinger J, Opazo F, Nestvogel D, Kalla S, Fejtova A, Verrier SE, Bungers SR, Cooper BH, Varoqueaux F, Wang Y, Nehring RB, Gundelfinger ED, Rosenmund C, Rizzoli SO, Südhof TC, Rhee JS, Brose N. ELKS1 localizes the synaptic vesicle priming protein bMunc13-2 to a specific subset of active zones. J Cell Biol 2017; 216:1143-1161. [PMID: 28264913 PMCID: PMC5379939 DOI: 10.1083/jcb.201606086] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 06/18/2016] [Accepted: 01/10/2017] [Indexed: 12/26/2022] Open
Abstract
Presynaptic active zones (AZs) are unique subcellular structures at neuronal synapses, which contain a network of specific proteins that control synaptic vesicle (SV) tethering, priming, and fusion. Munc13s are core AZ proteins with an essential function in SV priming. In hippocampal neurons, two different Munc13s-Munc13-1 and bMunc13-2-mediate opposite forms of presynaptic short-term plasticity and thus differentially affect neuronal network characteristics. We found that most presynapses of cortical and hippocampal neurons contain only Munc13-1, whereas ∼10% contain both Munc13-1 and bMunc13-2. Whereas the presynaptic recruitment and activation of Munc13-1 depends on Rab3-interacting proteins (RIMs), we demonstrate here that bMunc13-2 is recruited to synapses by the AZ protein ELKS1, but not ELKS2, and that this recruitment determines basal SV priming and short-term plasticity. Thus, synapse-specific interactions of different Munc13 isoforms with ELKS1 or RIMs are key determinants of the molecular and functional heterogeneity of presynaptic AZs.
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Affiliation(s)
- Hiroshi Kawabe
- Department of Molecular Neurobiology, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Miso Mitkovski
- Light Microscopy Facility, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Pascal S Kaeser
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305.,Department of Neurobiology, Harvard Medical School, Boston, MA 02115
| | - Johannes Hirrlinger
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany.,Carl Ludwig Institute for Physiology, University of Leipzig, 04109 Leipzig, Germany
| | - Felipe Opazo
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Center, 37073 Göttingen, Germany.,Center for Biostructural Imaging of Neurodegeneration, University of Göttingen Medical Center, 37073 Göttingen, Germany
| | - Dennis Nestvogel
- Department of Molecular Neurobiology, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Stefan Kalla
- Department of Molecular Neurobiology, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Anna Fejtova
- Department of Neurochemistry and Molecular Biology, Leibniz Institute of Neurobiology, 39118 Magdeburg, Germany.,Research Group Presynaptic Plasticity, Leibniz Institute of Neurobiology and Center for Behavioral Brain Sciences, Otto von Guericke University, 39106 Magdeburg, Germany.,Department of Psychiatry and Psychotherapy, University Hospital, Friedrich Alexander University Erlangen-Nuremberg, 91054 Erlangen, Germany
| | - Sophie E Verrier
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Simon R Bungers
- Department of Molecular Neurobiology, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Benjamin H Cooper
- Department of Molecular Neurobiology, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Frederique Varoqueaux
- Department of Molecular Neurobiology, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Yun Wang
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Ralf B Nehring
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030.,Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030
| | - Eckart D Gundelfinger
- Department of Neurochemistry and Molecular Biology, Leibniz Institute of Neurobiology, 39118 Magdeburg, Germany
| | - Christian Rosenmund
- Neuroscience Research Centre and NeuroCure, Charité, University Medicine Berlin, 10117 Berlin, Germany
| | - Silvio O Rizzoli
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Center, 37073 Göttingen, Germany
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305
| | - Jeong-Seop Rhee
- Department of Molecular Neurobiology, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
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37
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Ca 2+-binding protein 2 inhibits Ca 2+-channel inactivation in mouse inner hair cells. Proc Natl Acad Sci U S A 2017; 114:E1717-E1726. [PMID: 28183797 DOI: 10.1073/pnas.1617533114] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Ca2+-binding protein 2 (CaBP2) inhibits the inactivation of heterologously expressed voltage-gated Ca2+ channels of type 1.3 (CaV1.3) and is defective in human autosomal-recessive deafness 93 (DFNB93). Here, we report a newly identified mutation in CABP2 that causes a moderate hearing impairment likely via nonsense-mediated decay of CABP2-mRNA. To study the mechanism of hearing impairment resulting from CABP2 loss of function, we disrupted Cabp2 in mice (Cabp2LacZ/LacZ ). CaBP2 was expressed by cochlear hair cells, preferentially in inner hair cells (IHCs), and was lacking from the postsynaptic spiral ganglion neurons (SGNs). Cabp2LacZ/LacZ mice displayed intact cochlear amplification but impaired auditory brainstem responses. Patch-clamp recordings from Cabp2LacZ/LacZ IHCs revealed enhanced Ca2+-channel inactivation. The voltage dependence of activation and the number of Ca2+ channels appeared normal in Cabp2LacZ/LacZ mice, as were ribbon synapse counts. Recordings from single SGNs showed reduced spontaneous and sound-evoked firing rates. We propose that CaBP2 inhibits CaV1.3 Ca2+-channel inactivation, and thus sustains the availability of CaV1.3 Ca2+ channels for synaptic sound encoding. Therefore, we conclude that human deafness DFNB93 is an auditory synaptopathy.
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38
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MOCHIDA S. Millisecond Ca 2+ dynamics activate multiple protein cascades for synaptic vesicle control. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2017; 93:802-820. [PMID: 29225307 PMCID: PMC5790758 DOI: 10.2183/pjab.93.050] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 08/21/2017] [Indexed: 06/07/2023]
Abstract
For reliable transmission at chemical synapses, neurotransmitters must be released dynamically in response to neuronal activity in the form of action potentials. Stable synaptic transmission is dependent on the efficacy of transmitter release and the rate of resupplying synaptic vesicles to their release sites. Accurate regulation is conferred by proteins sensing Ca2+ entering through voltage-gated Ca2+ channels opened by an action potential. Presynaptic Ca2+ concentration changes are dynamic functions in space and time, with wide fluctuations associated with different rates of neuronal activity. Thus, regulation of transmitter release includes reactions involving multiple Ca2+-dependent proteins, each operating over a specific time window. Classically, studies of presynaptic proteins function favored large invertebrate presynaptic terminals. I have established a useful mammalian synapse model based on sympathetic neurons in culture. This review summarizes the use of this model synapse to study the roles of presynaptic proteins in neuronal activity for the control of transmitter release efficacy and synaptic vesicle recycling.
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Affiliation(s)
- Sumiko MOCHIDA
- Department of Physiology, Tokyo Medical University, Tokyo, Japan
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39
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Rogers RS, Nishimune H. The role of laminins in the organization and function of neuromuscular junctions. Matrix Biol 2016; 57-58:86-105. [PMID: 27614294 DOI: 10.1016/j.matbio.2016.08.008] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 08/10/2016] [Accepted: 08/17/2016] [Indexed: 01/11/2023]
Abstract
The synapse between motor neurons and skeletal muscle is known as the neuromuscular junction (NMJ). Proper alignment of presynaptic and post-synaptic structures of motor neurons and muscle fibers, respectively, is essential for efficient motor control of skeletal muscles. The synaptic cleft between these two cells is filled with basal lamina. Laminins are heterotrimer extracellular matrix molecules that are key members of the basal lamina. Laminin α4, α5, and β2 chains specifically localize to NMJs, and these laminin isoforms play a critical role in maintenance of NMJs and organization of synaptic vesicle release sites known as active zones. These individual laminin chains exert their role in organizing NMJs by binding to their receptors including integrins, dystroglycan, and voltage-gated calcium channels (VGCCs). Disruption of these laminins or the laminin-receptor interaction occurs in neuromuscular diseases including Pierson syndrome and Lambert-Eaton myasthenic syndrome (LEMS). Interventions to maintain proper level of laminins and their receptor interactions may be insightful in treating neuromuscular diseases and aging related degeneration of NMJs.
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Affiliation(s)
- Robert S Rogers
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, Kansas, USA.
| | - Hiroshi Nishimune
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, Kansas, USA.
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40
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Kobayashi S, Hida Y, Ishizaki H, Inoue E, Tanaka-Okamoto M, Yamasaki M, Miyazaki T, Fukaya M, Kitajima I, Takai Y, Watanabe M, Ohtsuka T, Manabe T. The active zone protein CAST regulates synaptic vesicle recycling and quantal size in the mouse hippocampus. Eur J Neurosci 2016; 44:2272-84. [PMID: 27422015 DOI: 10.1111/ejn.13331] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 07/07/2016] [Accepted: 07/13/2016] [Indexed: 01/13/2023]
Abstract
Synaptic efficacy is determined by various factors, including the quantal size, which is dependent on the amount of neurotransmitters in synaptic vesicles at the presynaptic terminal. It is essential for stable synaptic transmission that the quantal size is kept within a constant range and that synaptic efficacy during and after repetitive synaptic activation is maintained by replenishing release sites with synaptic vesicles. However, the mechanisms for these fundamental properties have still been undetermined. We found that the active zone protein CAST (cytomatrix at the active zone structural protein) played pivotal roles in both presynaptic regulation of quantal size and recycling of endocytosed synaptic vesicles. In the CA1 region of hippocampal slices of the CAST knockout mice, miniature excitatory synaptic responses were increased in size, and synaptic depression after prolonged synaptic activation was larger, which was attributable to selective impairment of synaptic vesicle trafficking via the endosome in the presynaptic terminal likely mediated by Rab6. Therefore, CAST serves as a key molecule that regulates dynamics and neurotransmitter contents of synaptic vesicles in the excitatory presynaptic terminal in the central nervous system.
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Affiliation(s)
- Shizuka Kobayashi
- Division of Neuronal Network, Department of Basic Medical Sciences, Institute of Medical Science, University of Tokyo, Tokyo, 108-8639, Japan
| | - Yamato Hida
- Department of Biochemistry, University of Yamanashi, Chuo, 409-3898, Japan
| | | | | | - Miki Tanaka-Okamoto
- Department of Molecular Biology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan
| | - Miwako Yamasaki
- Department of Anatomy and Embryology, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Taisuke Miyazaki
- Department of Anatomy and Embryology, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Masahiro Fukaya
- Department of Anatomy and Embryology, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Isao Kitajima
- Department of Clinical Laboratory and Molecular Pathology, Graduate School of Medicine and Pharmaceutical Science for Research, University of Toyama, Toyama, Japan
| | - Yoshimi Takai
- Division of Molecular and Cellular Biology, Department of Biochemistry and Molecular Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Masahiko Watanabe
- Department of Anatomy and Embryology, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Toshihisa Ohtsuka
- Department of Biochemistry, University of Yamanashi, Chuo, 409-3898, Japan
| | - Toshiya Manabe
- Division of Neuronal Network, Department of Basic Medical Sciences, Institute of Medical Science, University of Tokyo, Tokyo, 108-8639, Japan
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41
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Held RG, Liu C, Kaeser PS. ELKS controls the pool of readily releasable vesicles at excitatory synapses through its N-terminal coiled-coil domains. eLife 2016; 5. [PMID: 27253063 PMCID: PMC4935463 DOI: 10.7554/elife.14862] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 06/01/2016] [Indexed: 12/27/2022] Open
Abstract
In a presynaptic nerve terminal, synaptic strength is determined by the pool of readily releasable vesicles (RRP) and the probability of release (P) of each RRP vesicle. These parameters are controlled at the active zone and vary across synapses, but how such synapse specific control is achieved is not understood. ELKS proteins are enriched at vertebrate active zones and enhance P at inhibitory hippocampal synapses, but ELKS functions at excitatory synapses are not known. Studying conditional knockout mice for ELKS, we find that ELKS enhances the RRP at excitatory synapses without affecting P. Surprisingly, ELKS C-terminal sequences, which interact with RIM, are dispensable for RRP enhancement. Instead, the N-terminal ELKS coiled-coil domains that bind to Liprin-α and Bassoon are necessary to control RRP. Thus, ELKS removal has differential, synapse-specific effects on RRP and P, and our findings establish important roles for ELKS N-terminal domains in synaptic vesicle priming.
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Affiliation(s)
- Richard G Held
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Changliang Liu
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, Boston, United States
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42
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Kittel RJ, Heckmann M. Synaptic Vesicle Proteins and Active Zone Plasticity. Front Synaptic Neurosci 2016; 8:8. [PMID: 27148040 PMCID: PMC4834300 DOI: 10.3389/fnsyn.2016.00008] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 03/31/2016] [Indexed: 11/13/2022] Open
Abstract
Neurotransmitter is released from synaptic vesicles at the highly specialized presynaptic active zone (AZ). The complex molecular architecture of AZs mediates the speed, precision and plasticity of synaptic transmission. Importantly, structural and functional properties of AZs vary significantly, even for a given connection. Thus, there appear to be distinct AZ states, which fundamentally influence neuronal communication by controlling the positioning and release of synaptic vesicles. Vice versa, recent evidence has revealed that synaptic vesicle components also modulate organizational states of the AZ. The protein-rich cytomatrix at the active zone (CAZ) provides a structural platform for molecular interactions guiding vesicle exocytosis. Studies in Drosophila have now demonstrated that the vesicle proteins Synaptotagmin-1 (Syt1) and Rab3 also regulate glutamate release by shaping differentiation of the CAZ ultrastructure. We review these unexpected findings and discuss mechanistic interpretations of the reciprocal relationship between synaptic vesicles and AZ states, which has heretofore received little attention.
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Affiliation(s)
- Robert J Kittel
- Department of Neurophysiology, Institute of Physiology, Julius-Maximilians-University Würzburg Würzburg, Germany
| | - Manfred Heckmann
- Department of Neurophysiology, Institute of Physiology, Julius-Maximilians-University Würzburg Würzburg, Germany
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43
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Dopamine synapse is a neuroligin-2-mediated contact between dopaminergic presynaptic and GABAergic postsynaptic structures. Proc Natl Acad Sci U S A 2016; 113:4206-11. [PMID: 27035941 DOI: 10.1073/pnas.1514074113] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Midbrain dopamine neurons project densely to the striatum and form so-called dopamine synapses on medium spiny neurons (MSNs), principal neurons in the striatum. Because dopamine receptors are widely expressed away from dopamine synapses, it remains unclear how dopamine synapses are involved in dopaminergic transmission. Here we demonstrate that dopamine synapses are contacts formed between dopaminergic presynaptic and GABAergic postsynaptic structures. The presynaptic structure expressed tyrosine hydroxylase, vesicular monoamine transporter-2, and plasmalemmal dopamine transporter, which are essential for dopamine synthesis, vesicular filling, and recycling, but was below the detection threshold for molecules involving GABA synthesis and vesicular filling or for GABA itself. In contrast, the postsynaptic structure of dopamine synapses expressed GABAergic molecules, including postsynaptic adhesion molecule neuroligin-2, postsynaptic scaffolding molecule gephyrin, and GABAA receptor α1, without any specific clustering of dopamine receptors. Of these, neuroligin-2 promoted presynaptic differentiation in axons of midbrain dopamine neurons and striatal GABAergic neurons in culture. After neuroligin-2 knockdown in the striatum, a significant decrease of dopamine synapses coupled with a reciprocal increase of GABAergic synapses was observed on MSN dendrites. This finding suggests that neuroligin-2 controls striatal synapse formation by giving competitive advantage to heterologous dopamine synapses over conventional GABAergic synapses. Considering that MSN dendrites are preferential targets of dopamine synapses and express high levels of dopamine receptors, dopamine synapse formation may serve to increase the specificity and potency of dopaminergic modulation of striatal outputs by anchoring dopamine release sites to dopamine-sensing targets.
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44
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Jansen F, Kalbe B, Scholz P, Mikosz M, Wunderlich KA, Kurtenbach S, Nagel-Wolfrum K, Wolfrum U, Hatt H, Osterloh S. Impact of the Usher syndrome on olfaction. Hum Mol Genet 2015; 25:524-33. [PMID: 26620972 DOI: 10.1093/hmg/ddv490] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 11/24/2015] [Indexed: 12/21/2022] Open
Abstract
Usher syndrome is a genetically and clinically heterogeneous disease in humans, characterized by sensorineural hearing loss, retinitis pigmentosa and vestibular dysfunction. This disease is caused by mutations in genes encoding proteins that form complex networks in different cellular compartments. Currently, it remains unclear whether the Usher proteins also form networks within the olfactory epithelium (OE). Here, we describe Usher gene expression at the mRNA and protein level in the OE of mice and showed interactions between these proteins and olfactory signaling proteins. Additionally, we analyzed the odor sensitivity of different Usher syndrome mouse models using electro-olfactogram recordings and monitored significant changes in the odor detection capabilities in mice expressing mutant Usher proteins. Furthermore, we observed changes in the expression of signaling proteins that might compensate for the Usher protein deficiency. In summary, this study provides novel insights into the presence and purpose of the Usher proteins in olfactory signal transduction.
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Affiliation(s)
- Fabian Jansen
- Cell Physiology, Faculty for Biology and Biotechnology, Ruhr-University Bochum, 44801 Bochum, Germany and
| | - Benjamin Kalbe
- Cell Physiology, Faculty for Biology and Biotechnology, Ruhr-University Bochum, 44801 Bochum, Germany and
| | - Paul Scholz
- Cell Physiology, Faculty for Biology and Biotechnology, Ruhr-University Bochum, 44801 Bochum, Germany and
| | - Marta Mikosz
- Cell and Matrix Biology, Institute of Zoology, Johannes Gutenberg-University, 55099 Mainz, Germany
| | - Kirsten A Wunderlich
- Cell and Matrix Biology, Institute of Zoology, Johannes Gutenberg-University, 55099 Mainz, Germany
| | - Stefan Kurtenbach
- Cell Physiology, Faculty for Biology and Biotechnology, Ruhr-University Bochum, 44801 Bochum, Germany and
| | - Kerstin Nagel-Wolfrum
- Cell and Matrix Biology, Institute of Zoology, Johannes Gutenberg-University, 55099 Mainz, Germany
| | - Uwe Wolfrum
- Cell and Matrix Biology, Institute of Zoology, Johannes Gutenberg-University, 55099 Mainz, Germany
| | - Hanns Hatt
- Cell Physiology, Faculty for Biology and Biotechnology, Ruhr-University Bochum, 44801 Bochum, Germany and
| | - Sabrina Osterloh
- Cell Physiology, Faculty for Biology and Biotechnology, Ruhr-University Bochum, 44801 Bochum, Germany and
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45
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Abstract
The first synapses transmitting visual information contain an unusual organelle, the ribbon, which is involved in the transport and priming of vesicles to be released at the active zone. The ribbon is one of many design features that allow efficient refilling of the active zone, which in turn enables graded changes in membrane potential to be transmitted using a continuous mode of neurotransmitter release. The ribbon also plays a key role in supplying vesicles for rapid and transient bursts of release that signal fast changes, such as the onset of light. We increasingly understand how the physiological properties of ribbon synapses determine basic transformations of the visual signal and, in particular, how the process of refilling the active zone regulates the gain and adaptive properties of the retinal circuit. The molecular basis of ribbon function is, however, far from clear.
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Affiliation(s)
- Leon Lagnado
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom;
| | - Frank Schmitz
- Department of Neuroanatomy, Institute for Anatomy and Cell Biology, Medical School Saarland University, Homburg/Saar, Germany;
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46
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Cao Y, Sarria I, Fehlhaber KE, Kamasawa N, Orlandi C, James KN, Hazen JL, Gardner MR, Farzan M, Lee A, Baker S, Baldwin K, Sampath AP, Martemyanov KA. Mechanism for Selective Synaptic Wiring of Rod Photoreceptors into the Retinal Circuitry and Its Role in Vision. Neuron 2015; 87:1248-1260. [PMID: 26402607 PMCID: PMC4583715 DOI: 10.1016/j.neuron.2015.09.002] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 08/11/2015] [Accepted: 08/31/2015] [Indexed: 01/06/2023]
Abstract
In the retina, rod and cone photoreceptors form distinct connections with different classes of downstream bipolar cells. However, the molecular mechanisms responsible for their selective connectivity are unknown. Here we identify a cell-adhesion protein, ELFN1, to be essential for the formation of synapses between rods and rod ON-bipolar cells in the primary rod pathway. ELFN1 is expressed selectively in rods where it is targeted to the axonal terminals by the synaptic release machinery. At the synapse, ELFN1 binds in trans to mGluR6, the postsynaptic receptor on rod ON-bipolar cells. Elimination of ELFN1 in mice prevents the formation of synaptic contacts involving rods, but not cones, allowing a dissection of the contributions of primary and secondary rod pathways to retinal circuit function and vision. We conclude that ELFN1 is necessary for the selective wiring of rods into the primary rod pathway and is required for high sensitivity of vision.
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Affiliation(s)
- Yan Cao
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Ignacio Sarria
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Katherine E Fehlhaber
- Jules Stein Eye Institute, Department of Ophthalmology, University of California, Los Angeles, 100 Stein Plaza, Los Angeles, CA 90095, USA
| | - Naomi Kamasawa
- Electron Microscopy Core Facility, Max Planck Florida Institute, 1 Max Planck Way, Jupiter, FL 33458, USA
| | - Cesare Orlandi
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Kiely N James
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92121, USA
| | - Jennifer L Hazen
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92121, USA
| | - Matthew R Gardner
- Department of Infectious Disease, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Michael Farzan
- Department of Infectious Disease, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Amy Lee
- Department of Molecular Physiology and Biophysics, University of Iowa, 51 Newton Road, Iowa City, IA 52242, USA
| | - Sheila Baker
- Department of Biochemistry, University of Iowa, 51 Newton Road, Iowa City, IA 52242, USA
| | - Kristin Baldwin
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92121, USA
| | - Alapakkam P Sampath
- Jules Stein Eye Institute, Department of Ophthalmology, University of California, Los Angeles, 100 Stein Plaza, Los Angeles, CA 90095, USA
| | - Kirill A Martemyanov
- Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA.
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47
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Wichmann C. Molecularly and structurally distinct synapses mediate reliable encoding and processing of auditory information. Hear Res 2015; 330:178-90. [PMID: 26188105 DOI: 10.1016/j.heares.2015.07.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 06/21/2015] [Accepted: 07/10/2015] [Indexed: 01/20/2023]
Abstract
Hearing impairment is the most common human sensory deficit. Considering the sophisticated anatomy and physiology of the auditory system, disease-related failures frequently occur. To meet the demands of the neuronal circuits responsible for processing auditory information, the synapses of the lower auditory pathway are anatomically and functionally specialized to process acoustic information indefatigably with utmost temporal precision. Despite sharing some functional properties, the afferent synapses of the cochlea and of auditory brainstem differ greatly in their morphology and employ distinct molecular mechanisms for regulating synaptic vesicle release. Calyceal synapses of the endbulb of Held and the calyx of Held profit from a large number of release sites that project onto one principal cell. Cochlear inner hair cell ribbon synapses exhibit a unique one-to-one relation of the presynaptic active zone to the postsynaptic cell and use hair-cell-specific proteins such as otoferlin for vesicle release. The understanding of the molecular physiology of the hair cell ribbon synapse has been advanced by human genetics studies of sensorineural hearing impairment, revealing human auditory synaptopathy as a new nosological entity.
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Affiliation(s)
- Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience & InnerEarLab, University Medical Center, Göttingen, Germany.
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48
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Ackermann F, Waites CL, Garner CC. Presynaptic active zones in invertebrates and vertebrates. EMBO Rep 2015; 16:923-38. [PMID: 26160654 DOI: 10.15252/embr.201540434] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 06/19/2015] [Indexed: 11/09/2022] Open
Abstract
The regulated release of neurotransmitter occurs via the fusion of synaptic vesicles (SVs) at specialized regions of the presynaptic membrane called active zones (AZs). These regions are defined by a cytoskeletal matrix assembled at AZs (CAZ), which functions to direct SVs toward docking and fusion sites and supports their maturation into the readily releasable pool. In addition, CAZ proteins localize voltage-gated Ca(2+) channels at SV release sites, bringing the fusion machinery in close proximity to the calcium source. Proteins of the CAZ therefore ensure that vesicle fusion is temporally and spatially organized, allowing for the precise and reliable release of neurotransmitter. Importantly, AZs are highly dynamic structures, supporting presynaptic remodeling, changes in neurotransmitter release efficacy, and thus presynaptic forms of plasticity. In this review, we discuss recent advances in the study of active zones, highlighting how the CAZ molecularly defines sites of neurotransmitter release, endocytic zones, and the integrity of synapses.
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Affiliation(s)
- Frauke Ackermann
- German Center for Neurodegenerative Disease, Charité Medical University, Berlin, Germany
| | - Clarissa L Waites
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Craig C Garner
- German Center for Neurodegenerative Disease, Charité Medical University, Berlin, Germany
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Rab3-interacting molecules 2α and 2β promote the abundance of voltage-gated CaV1.3 Ca2+ channels at hair cell active zones. Proc Natl Acad Sci U S A 2015; 112:E3141-9. [PMID: 26034270 DOI: 10.1073/pnas.1417207112] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ca(2+) influx triggers the fusion of synaptic vesicles at the presynaptic active zone (AZ). Here we demonstrate a role of Ras-related in brain 3 (Rab3)-interacting molecules 2α and β (RIM2α and RIM2β) in clustering voltage-gated CaV1.3 Ca(2+) channels at the AZs of sensory inner hair cells (IHCs). We show that IHCs of hearing mice express mainly RIM2α, but also RIM2β and RIM3γ, which all localize to the AZs, as shown by immunofluorescence microscopy. Immunohistochemistry, patch-clamp, fluctuation analysis, and confocal Ca(2+) imaging demonstrate that AZs of RIM2α-deficient IHCs cluster fewer synaptic CaV1.3 Ca(2+) channels, resulting in reduced synaptic Ca(2+) influx. Using superresolution microscopy, we found that Ca(2+) channels remained clustered in stripes underneath anchored ribbons. Electron tomography of high-pressure frozen synapses revealed a reduced fraction of membrane-tethered vesicles, whereas the total number of membrane-proximal vesicles was unaltered. Membrane capacitance measurements revealed a reduction of exocytosis largely in proportion with the Ca(2+) current, whereas the apparent Ca(2+) dependence of exocytosis was unchanged. Hair cell-specific deletion of all RIM2 isoforms caused a stronger reduction of Ca(2+) influx and exocytosis and significantly impaired the encoding of sound onset in the postsynaptic spiral ganglion neurons. Auditory brainstem responses indicated a mild hearing impairment on hair cell-specific deletion of all RIM2 isoforms or global inactivation of RIM2α. We conclude that RIM2α and RIM2β promote a large complement of synaptic Ca(2+) channels at IHC AZs and are required for normal hearing.
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Astro V, de Curtis I. Plasma membrane-associated platforms: Dynamic scaffolds that organize membrane-associated events. Sci Signal 2015; 8:re1. [DOI: 10.1126/scisignal.aaa3312] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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