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Koesters AG, Rich MM, Engisch KL. Homeostatic Synaptic Plasticity of Miniature Excitatory Postsynaptic Currents in Mouse Cortical Cultures Requires Neuronal Rab3A. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.06.14.544980. [PMID: 39071374 PMCID: PMC11275788 DOI: 10.1101/2023.06.14.544980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
Following prolonged activity blockade, amplitudes of miniature excitatory postsynaptic currents (mEPSCs) increase, a form of plasticity termed "homeostatic synaptic plasticity." We previously showed that a presynaptic protein, the small GTPase Rab3A, is required for full expression of the increase in miniature endplate current amplitudes following prolonged blockade of action potential activity at the mouse neuromuscular junction in vivo (Wang et al., 2011), but it is unknown whether this form of Rab3A-dependent homeostatic plasticity shares any characteristics with central synapses. We show here that homeostatic synaptic plasticity of mEPSCs is impaired in mouse cortical neuron cultures prepared from Rab3A-/- and mutant mice expressing a single point mutation of Rab3A, Rab3A Earlybird mice. To determine if Rab3A is involved in the well-established homeostatic increase in postsynaptic AMPA-type receptors (AMPARs), we performed a series of experiments in which electrophysiological recordings of mEPSCs and confocal imaging of synaptic AMPAR immunofluorescence were assessed within the same cultures. We found that Rab3A was required for the increase in synaptic AMPARs following prolonged activity blockade, but the increase in mEPSC amplitudes was not always accompanied by an increase in postsynaptic AMPAR levels, suggesting other factors may contribute. Finally, we demonstrate that Rab3A is acting in neurons because only selective loss of Rab3A in neurons, not glia, disrupted the homeostatic increase in mEPSC amplitudes. This is the first demonstration that neuronal Rab3A is required for homeostatic synaptic plasticity and that it does so partially through regulation of the surface expression of AMPA receptors.
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Affiliation(s)
- Andrew G. Koesters
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
| | - Mark M. Rich
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine, Wright State University, Dayton, OH 45345
| | - Kathrin L. Engisch
- Department of Neuroscience, Cell Biology and Physiology, Boonshoft School of Medicine and the College of Science and Mathematics, Wright State University, Dayton, OH 45435
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Kim MH, Strazza P, Puthussery T, Gross OP, Taylor WR, von Gersdorff H. Functional maturation of the rod bipolar to AII-amacrine cell ribbon synapse in the mouse retina. Cell Rep 2023; 42:113440. [PMID: 37976158 DOI: 10.1016/j.celrep.2023.113440] [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: 10/09/2022] [Revised: 09/05/2023] [Accepted: 10/30/2023] [Indexed: 11/19/2023] Open
Abstract
Retinal ribbon synapses undergo functional changes after eye opening that remain uncharacterized. Using light-flash stimulation and paired patch-clamp recordings, we examined the maturation of the ribbon synapse between rod bipolar cells (RBCs) and AII-amacrine cells (AII-ACs) after eye opening (postnatal day 14) in the mouse retina at near physiological temperatures. We find that light-evoked excitatory postsynaptic currents (EPSCs) in AII-ACs exhibit a slow sustained component that increases in magnitude with advancing age, whereas a fast transient component remains unchanged. Similarly, paired recordings reveal a dual-component EPSC with a slower sustained component that increases during development, even though the miniature EPSC (mEPSC) amplitude and kinetics do not change significantly. We thus propose that the readily releasable pool of vesicles from RBCs increases after eye opening, and we estimate that a short light flash can evoke the release of ∼4,000 vesicles onto a single mature AII-AC.
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Affiliation(s)
- Mean-Hwan Kim
- The Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA; Allen Institute for Brain Science, Seattle, WA 98109, USA.
| | - Paulo Strazza
- The Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Teresa Puthussery
- Casey Eye Institute, Oregon Health & Science University, Portland, OR 97239, USA; Herbert Wertheim School of Optometry & Vision Science, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Owen P Gross
- The Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA; Department of Physics, Reed College, Portland, OR 97202, USA
| | - W Rowland Taylor
- Casey Eye Institute, Oregon Health & Science University, Portland, OR 97239, USA; Herbert Wertheim School of Optometry & Vision Science, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Henrique von Gersdorff
- The Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA; Casey Eye Institute, Oregon Health & Science University, Portland, OR 97239, USA.
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Dittrich A, Ramesh G, Jung M, Schmitz F. Rabconnectin-3α/DMXL2 Is Locally Enriched at the Synaptic Ribbon of Rod Photoreceptor Synapses. Cells 2023; 12:1665. [PMID: 37371135 DOI: 10.3390/cells12121665] [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: 04/28/2023] [Revised: 06/08/2023] [Accepted: 06/17/2023] [Indexed: 06/29/2023] Open
Abstract
Ribbon synapses reliably transmit synaptic signals over a broad signalling range. Rod photoreceptor ribbon synapses are capable of transmitting signals generated by the absorption of single photons. The high precision of ribbon synapses emphasizes the need for particularly efficient signalling mechanisms. Synaptic ribbons are presynaptic specializations of ribbon synapses and are anchored to the active zone. Synaptic ribbons bind many synaptic vesicles that are delivered to the active zone for continuous and faithful signalling. In the present study we demonstrate with independent antibodies at the light- and electron microscopic level that rabconnectin-3α (RC3α)-alternative name Dmx-like 2 (DMXL2)-is localized to the synaptic ribbons of rod photoreceptor synapses in the mouse retina. In the brain, RC3α-containing complexes are known to interact with important components of synaptic vesicles, including Rab3-activating/inactivating enzymes, priming proteins and the vesicular H+-ATPase that acidifies the synaptic vesicle lumen to promote full neurotransmitter loading. The association of RC3α/DMXL2 with rod synaptic ribbons of the mouse retina could enable these structures to deliver only fully signalling-competent synaptic vesicles to the active zone thus contributing to reliable synaptic communication.
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Affiliation(s)
- Alina Dittrich
- Institute of Anatomy and Cell Biology, Saarland University, 66421 Homburg, Germany
| | - Girish Ramesh
- Institute of Anatomy and Cell Biology, Saarland University, 66421 Homburg, Germany
- Institute of Biophysics, Saarland University, 66421 Homburg, Germany
| | - Martin Jung
- Institute of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany
| | - Frank Schmitz
- Institute of Anatomy and Cell Biology, Saarland University, 66421 Homburg, Germany
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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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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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Analysis of RIM Expression and Function at Mouse Photoreceptor Ribbon Synapses. J Neurosci 2017; 37:7848-7863. [PMID: 28701482 DOI: 10.1523/jneurosci.2795-16.2017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 05/15/2017] [Accepted: 06/18/2017] [Indexed: 12/18/2022] Open
Abstract
RAB3A-interacting molecule (RIM) proteins are important regulators of transmitter release from active zones. At conventional chemical synapses, RIMs contribute substantially to vesicle priming and docking and their loss reduces the readily releasable pool of synaptic vesicles by up to 75%. The priming function of RIMs is mediated via the formation of a tripartite complex with Munc13 and RAB3A, which brings synaptic vesicles in close proximity to Ca2+ channels and the fusion site and activates Munc13. We reported previously that, at mouse photoreceptor ribbon synapses, vesicle priming is Munc13 independent. In this study, we examined RIM expression, distribution, and function at male and female mouse photoreceptor ribbon synapses. We provide evidence that RIM1α and RIM1β are highly likely absent from mouse photoreceptors and that RIM2α is the major large RIM isoform present at photoreceptor ribbon synapses. We show that mouse photoreceptors predominantly express RIM2 variants that lack the interaction domain for Munc13. Loss of full-length RIM2α in a RIM2α mutant mouse only marginally perturbs photoreceptor synaptic transmission. Our findings therefore strongly argue for a priming mechanism at the photoreceptor ribbon synapse that is independent of the formation of a RIM-Munc13-RAB3A complex and thus provide further evidence for a fundamental difference between photoreceptor ribbon synapses and conventional chemical synapses in synaptic vesicle exocytosis.SIGNIFICANCE STATEMENT RAB3A-interacting molecules 1 and 2 (RIM1/2) are essential regulators of exocytosis. At conventional chemical synapses, their function involves Ca2+ channel clustering and synaptic vesicle priming and docking through interactions with Munc13 and RAB3A, respectively. Examining wild-type and RIM2 mutant mice, we show here that the sensory photoreceptor ribbon synapses most likely lack RIM1 and predominantly express RIM2 variants that lack the interaction domain for Munc13. Our findings demonstrate that the photoreceptor-specific RIM variants are not essential for synaptic vesicle priming at photoreceptor ribbon synapses, which represents a fundamental difference between photoreceptor ribbon synapses and conventional chemical synapses with respect to synaptic vesicle priming mechanisms.
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RIBEYE(B)-domain binds to lipid components of synaptic vesicles in an NAD(H)-dependent, redox-sensitive manner. Biochem J 2017; 474:1205-1220. [PMID: 28202712 DOI: 10.1042/bcj20160886] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2016] [Revised: 02/14/2017] [Accepted: 02/14/2017] [Indexed: 12/26/2022]
Abstract
Synaptic ribbons are needed for fast and continuous exocytosis in ribbon synapses. RIBEYE is a main protein component of synaptic ribbons and is necessary to build the synaptic ribbon. RIBEYE consists of a unique A-domain and a carboxyterminal B-domain, which binds NAD(H). Within the presynaptic terminal, the synaptic ribbons are in physical contact with large numbers of synaptic vesicle (SV)s. How this physical contact between ribbons and synaptic vesicles is established at a molecular level is not well understood. In the present study, we demonstrate that the RIBEYE(B)-domain can directly interact with lipid components of SVs using two different sedimentation assays with liposomes of defined chemical composition. Similar binding results were obtained with a SV-containing membrane fraction. The binding of liposomes to RIBEYE(B) depends upon the presence of a small amount of lysophospholipids present in the liposomes. Interestingly, binding of liposomes to RIBEYE(B) depends on NAD(H) in a redox-sensitive manner. The binding is enhanced by NADH, the reduced form, and is inhibited by NAD+, the oxidized form. Lipid-mediated attachment of vesicles is probably part of a multi-step process that also involves additional, protein-dependent processes.
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Kim MH, von Gersdorff H. Postsynaptic Plasticity Triggered by Ca²⁺-Permeable AMPA Receptor Activation in Retinal Amacrine Cells. Neuron 2016; 89:507-20. [PMID: 26804991 DOI: 10.1016/j.neuron.2015.12.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 07/18/2015] [Accepted: 12/15/2015] [Indexed: 01/04/2023]
Abstract
Amacrine cells are thought to be a major locus for mechanisms of light adaptation and contrast enhancement in the retina. However, the potential for plasticity in their AMPA receptor currents remains largely unknown. Using paired patch-clamp recordings between bipolar cell terminals and amacrine cells, we have simultaneously measured presynaptic membrane capacitance changes and EPSCs. Repetitive bipolar cell depolarizations, designed to maintain the same amount of exocytosis, nevertheless significantly potentiated evoked EPSCs in a subpopulation of amacrine cells. Likewise, repetitive iontophoresis (or puffs) of glutamate (or AMPA) onto the dendrites of amacrine cells also significantly potentiated evoked currents and [Ca(2+)]i rises. However, strong postsynaptic Ca(2+) buffering with BAPTA abolished the potentiation and selective antagonists of Ca(2+)-permeable AMPA receptors also blocked the potentiation of AMPA-mediated currents. Together these results suggest that Ca(2+) influx via Ca(2+)-permeable AMPA receptors can elicit a rapid form of postsynaptic plasticity in a subgroup of amacrine cell dendrites.
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Affiliation(s)
- Mean-Hwan Kim
- The Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Henrique von Gersdorff
- The Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA; Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, OR 97239, USA; Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, OR 97239, USA.
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Mohankumar KM, Currle DS, White E, Boulos N, Dapper J, Eden C, Nimmervoll B, Thiruvenkatam R, Connelly M, Kranenburg TA, Neale G, Olsen S, Wang YD, Finkelstein D, Wright K, Gupta K, Ellison DW, Thomas AO, Gilbertson RJ. An in vivo screen identifies ependymoma oncogenes and tumor-suppressor genes. Nat Genet 2015; 47:878-87. [PMID: 26075792 PMCID: PMC4520751 DOI: 10.1038/ng.3323] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 05/06/2015] [Indexed: 12/14/2022]
Abstract
Cancers are characterized by non-random chromosome copy number alterations that presumably contain oncogenes and tumor-suppressor genes (TSGs). The affected loci are often large, making it difficult to pinpoint which genes are driving the cancer. Here we report a cross-species in vivo screen of 84 candidate oncogenes and 39 candidate TSGs, located within 28 recurrent chromosomal alterations in ependymoma. Through a series of mouse models, we validate eight new ependymoma oncogenes and ten new ependymoma TSGs that converge on a small number of cell functions, including vesicle trafficking, DNA modification and cholesterol biosynthesis, identifying these as potential new therapeutic targets.
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Affiliation(s)
- Kumarasamypet M Mohankumar
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - David S Currle
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Elsie White
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Nidal Boulos
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Jason Dapper
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Christopher Eden
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Birgit Nimmervoll
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Radhika Thiruvenkatam
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Michele Connelly
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Tanya A Kranenburg
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Geoffrey Neale
- Hartwell Center for Biotechnology and Bioinformatics, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Scott Olsen
- Hartwell Center for Biotechnology and Bioinformatics, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Yong-Dong Wang
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - David Finkelstein
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Karen Wright
- Department of Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Kirti Gupta
- Department of Pathology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - David W Ellison
- Department of Pathology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Arzu Onar Thomas
- Department of Biostatistics, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Richard J Gilbertson
- 1] Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA. [2] Department of Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
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Bustos MA, Roggero CM, De la Iglesia PX, Mayorga LS, Tomes CN. GTP-bound Rab3A exhibits consecutive positive and negative roles during human sperm dense-core granule exocytosis. J Mol Cell Biol 2015; 6:286-98. [PMID: 25053757 DOI: 10.1093/jmcb/mju021] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Exocytosis of mammalian sperm dense-core secretory granule relies on the same fusion molecules as all other secretory cells; one such molecule is the small GTPase Rab3A. Here, we report an in-depth biochemical characterization of the role of Rab3A in secretion by scrutinizing the exocytotic response of streptolysin O-permeabilized human sperm to the acute application of a number of Rab3A-containing constructs and correlating the findings with those gathered with the endogenous protein. Full length, geranylgeranylated, and active Rab3A elicited human sperm exocytosis per se. With Rab3A/Rab22A chimeric proteins, we demonstrated that the carboxy-terminal domain of the Rab3A molecule was necessary and sufficient to promote exocytosis, whereas its amino-terminus prevented calcium-triggered secretion. Interestingly, full length Rab3A halted secretion when added after the docking of the acrosome to the plasma membrane. This effect depended on the inability of Rab3A to hydrolyze GTP. We combined modified immunofluorescence and acrosomal staining protocols to detect membrane fusion and the activation status of endogenous Rab3 simultaneously in individual cells, and found that GTP hydrolysis on endogenous Rab3 was mandatory for fusion pores to open. Our findings contribute to establishing that Rab3 modulates regulated exocytosis differently depending on the nucleotide bound and the exocytosis stage under study.
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Affiliation(s)
- Matías A Bustos
- Instituto de Histología y Embriología, IHEM-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - Carlos M Roggero
- Instituto de Histología y Embriología, IHEM-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina Present address: Department of Biophysics, UT Southwestern Medical Center, Dallas, TX, USA
| | - Paola X De la Iglesia
- Instituto de Histología y Embriología, IHEM-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina Present address: Servicio de Patología, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina
| | - Luis S Mayorga
- Instituto de Histología y Embriología, IHEM-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - Claudia N Tomes
- Instituto de Histología y Embriología, IHEM-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Mendoza, Argentina
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Van Hook MJ, Parmelee CM, Chen M, Cork KM, Curto C, Thoreson WB. Calmodulin enhances ribbon replenishment and shapes filtering of synaptic transmission by cone photoreceptors. ACTA ACUST UNITED AC 2014; 144:357-78. [PMID: 25311636 PMCID: PMC4210432 DOI: 10.1085/jgp.201411229] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
At the first synapse in the vertebrate visual pathway, light-evoked changes in photoreceptor membrane potential alter the rate of glutamate release onto second-order retinal neurons. This process depends on the synaptic ribbon, a specialized structure found at various sensory synapses, to provide a supply of primed vesicles for release. Calcium (Ca(2+)) accelerates the replenishment of vesicles at cone ribbon synapses, but the mechanisms underlying this acceleration and its functional implications for vision are unknown. We studied vesicle replenishment using paired whole-cell recordings of cones and postsynaptic neurons in tiger salamander retinas and found that it involves two kinetic mechanisms, the faster of which was diminished by calmodulin (CaM) inhibitors. We developed an analytical model that can be applied to both conventional and ribbon synapses and showed that vesicle resupply is limited by a simple time constant, τ = 1/(Dρδs), where D is the vesicle diffusion coefficient, δ is the vesicle diameter, ρ is the vesicle density, and s is the probability of vesicle attachment. The combination of electrophysiological measurements, modeling, and total internal reflection fluorescence microscopy of single synaptic vesicles suggested that CaM speeds replenishment by enhancing vesicle attachment to the ribbon. Using electroretinogram and whole-cell recordings of light responses, we found that enhanced replenishment improves the ability of cone synapses to signal darkness after brief flashes of light and enhances the amplitude of responses to higher-frequency stimuli. By accelerating the resupply of vesicles to the ribbon, CaM extends the temporal range of synaptic transmission, allowing cones to transmit higher-frequency visual information to downstream neurons. Thus, the ability of the visual system to encode time-varying stimuli is shaped by the dynamics of vesicle replenishment at photoreceptor synaptic ribbons.
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Affiliation(s)
- Matthew J Van Hook
- Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198
| | - Caitlyn M Parmelee
- Department of Mathematics, University of Nebraska-Lincoln, Lincoln, NE 68588
| | - Minghui Chen
- Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198 Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198
| | - Karlene M Cork
- Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198 Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198
| | - Carina Curto
- Department of Mathematics, University of Nebraska-Lincoln, Lincoln, NE 68588 Department of Mathematics, The Pennsylvania State University, University Park, State College, PA 16802
| | - Wallace B Thoreson
- Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198 Department of Ophthalmology and Visual Sciences and Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198
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ArfGAP3 is a component of the photoreceptor synaptic ribbon complex and forms an NAD(H)-regulated, redox-sensitive complex with RIBEYE that is important for endocytosis. J Neurosci 2014; 34:5245-60. [PMID: 24719103 DOI: 10.1523/jneurosci.3837-13.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Ribbon synapses are tonically active synapses in the retina and inner ear with intense vesicle traffic. How this traffic is organized and regulated is still unknown. Synaptic ribbons, large presynaptic structures associated with numerous synaptic vesicles, appear to be essential for this process. The base of the synaptic ribbon is anchored at the active zone and is a hotspot of exocytosis. The synaptic ribbon complex is also important for vesicle replenishment. RIBEYE is a unique and major component of synaptic ribbons. It consists of a unique A-domain and an NAD(H)-binding, C-terminal B-domain. In the present study, we show that the Arf-GTPase activating protein-3 (ArfGAP3), a well characterized regulator of vesicle formation at the Golgi apparatus, is also a component of the synaptic ribbon complex in photoreceptor synapses of the mouse retina and interacts with RIBEYE as shown by multiple, independent approaches. ArfGAP3 binds to RIBEYE(B)-domain in an NAD(H)-dependent manner. The interaction is redox sensitive because NADH is more efficient than the oxidized NAD(+) in promoting ArfGAP3-RIBEYE interaction. RIBEYE competes with the GTP-binding protein Arf1 for binding to ArfGAP3. Thus, binding of RIBEYE(B) to ArfGAP3 could prevent inactivation of Arf1 by ArfGAP3 and provides the synaptic ribbon with the possibility to control Arf1 function. The interaction is relevant for endocytic vesicle trafficking because overexpression of ArfGAP3 in photoreceptors strongly inhibited endocytotic uptake of FM1-43.
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13
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3D structure generation, virtual screening and docking of human Ras-associated binding (Rab3A) protein involved in tumourigenesis. Mol Biol Rep 2014; 41:3951-9. [DOI: 10.1007/s11033-014-3263-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 02/11/2014] [Indexed: 10/25/2022]
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Jiang Z, Yang J, Purpura LA, Liu Y, Ripps H, Shen W. Glycinergic feedback enhances synaptic gain in the distal retina. J Physiol 2014; 592:1479-92. [PMID: 24421349 DOI: 10.1113/jphysiol.2013.265785] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Glycine input originates with interplexiform cells, a group of neurons situated within the inner retina that transmit signals centrifugally to the distal retina. The effect on visual function of this novel mechanism is largely unknown. Using gramicidin-perforated patch whole cell recordings, intracellular recordings and specific antibody labelling techniques, we examined the effects of the synaptic connections between glycinergic interplexiform cells, photoreceptors and bipolar cells. To confirm that interplexiform cells make centrifugal feedback on bipolar cell dendrites, we recorded the postsynaptic glycine currents from axon-detached bipolar cells while stimulating presynaptic interplexiform cells. The results show that glycinergic interplexiform cells activate bipolar cell dendrites that express the α3 subunit of the glycine receptor, as well as a subclass of unidentified receptors on photoreceptors. By virtue of their synaptic contacts, glycine centrifugal feedback increases glutamate release from photoreceptors and suppresses the uptake of glutamate by the type 2A excitatory amino acid transporter on photoreceptors. The net effect is a significant increase in synaptic gain between photoreceptors and their second-order neurons.
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Affiliation(s)
- Zheng Jiang
- Department of Biomedical Science, Charles E Schmidt College of Medicine, Florida Atlantic University, Boca Raton, FL 33431, USA.
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Synapsin II and Rab3a cooperate in the regulation of epileptic and synaptic activity in the CA1 region of the hippocampus. J Neurosci 2014; 33:18319-30. [PMID: 24227741 DOI: 10.1523/jneurosci.5293-12.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Some forms of idiopathic epilepsy in animals and humans are associated with deficiency of synapsin, a phosphoprotein that reversibly associates with synaptic vesicles. We have previously shown that the epileptic phenotype seen in synapsin II knock-out mice (SynII(-)) can be rescued by the genetic deletion of the Rab3a protein. Here we have examined the cellular basis for this rescue using whole-cell recordings from CA1 hippocampal pyramidal cells in brain slices. We find that SynII(-) neurons have increased spontaneous activity and a reduced threshold for the induction of epileptiform activity by 4-aminopyridine (4-AP). Using selective recordings of glutamatergic and GABAergic activity we show that in wild-type neurons low concentrations of 4-AP facilitate glutamatergic and GABAergic transmission in a balanced way, whereas in SynII(-) neurons this balance is shifted toward excitation. This imbalance reflects a deficit in inhibitory synaptic transmission that appears to be secondary to reduced Ca(2+) sensitivity in SynII(-) neurons. This suggestion is supported by our finding that synaptic and epileptiform activity at SynII(-) and wild-type synapses is similar when GABAergic transmission is blocked. Deletion of Rab3a results in glutamatergic synapses that have a compromised responsiveness to either low 4-AP concentrations or elevated extracellular Ca(2+). These changes mitigate the overexcitable phenotype observed in SynII(-) neurons. Thus, Rab3a deletion appears to restore the excitatory/inhibitory imbalance observed in SynII(-) hippocampal slices indirectly, not by correcting the deficit in GABAergic synaptic transmission but rather by impairing excitatory glutamatergic synaptic transmission.
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16
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Epiretinal membrane: a treatable cause of visual disability in myotonic dystrophy type 1. J Neurol 2013; 261:37-44. [DOI: 10.1007/s00415-013-7141-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 09/30/2013] [Accepted: 09/30/2013] [Indexed: 10/26/2022]
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A local, periactive zone endocytic machinery at photoreceptor synapses in close vicinity to synaptic ribbons. J Neurosci 2013; 33:10278-300. [PMID: 23785143 DOI: 10.1523/jneurosci.5048-12.2013] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Photoreceptor ribbon synapses are continuously active synapses with large active zones that contain synaptic ribbons. Synaptic ribbons are anchored to the active zones and are associated with large numbers of synaptic vesicles. The base of the ribbon that is located close to L-type voltage-gated Ca(2+) channels is a hotspot of exocytosis. The continuous exocytosis at the ribbon synapse needs to be balanced by compensatory endocytosis. Recent analyses indicated that vesicle recycling at the synaptic ribbon is also an important determinant of synaptic signaling at the photoreceptor synapse. To get insights into mechanisms of vesicle recycling at the photoreceptor ribbon synapse, we performed super-resolution structured illumination microscopy and immunogold electron microscopy to localize major components of the endocytotic membrane retrieval machinery in the photoreceptor synapse of the mouse retina. We found dynamin, syndapin, amphiphysin, and calcineurin, a regulator of activity-dependent endocytosis, to be highly enriched around the active zone and the synaptic ribbon. We present evidence for two clathrin heavy chain variants in the photoreceptor terminal; one is enriched around the synaptic ribbon, whereas the other is localized in the entry region of the terminal. The focal enrichment of endocytic proteins around the synaptic ribbon is consistent with a focal uptake of endocytic markers at that site. This endocytic activity functionally depends on dynamin. These data propose that the presynaptic periactive zone surrounding the synaptic ribbon complex is a hotspot of endocytosis in photoreceptor ribbon synapses.
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Pearring JN, Salinas RY, Baker SA, Arshavsky VY. Protein sorting, targeting and trafficking in photoreceptor cells. Prog Retin Eye Res 2013; 36:24-51. [PMID: 23562855 DOI: 10.1016/j.preteyeres.2013.03.002] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 03/22/2013] [Accepted: 03/26/2013] [Indexed: 01/24/2023]
Abstract
Vision is the most fundamental of our senses initiated when photons are absorbed by the rod and cone photoreceptor neurons of the retina. At the distal end of each photoreceptor resides a light-sensing organelle, called the outer segment, which is a modified primary cilium highly enriched with proteins involved in visual signal transduction. At the proximal end, each photoreceptor has a synaptic terminal, which connects this cell to the downstream neurons for further processing of the visual information. Understanding the mechanisms involved in creating and maintaining functional compartmentalization of photoreceptor cells remains among the most fascinating topics in ocular cell biology. This review will discuss how photoreceptor compartmentalization is supported by protein sorting, targeting and trafficking, with an emphasis on the best-studied cases of outer segment-resident proteins.
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Affiliation(s)
- Jillian N Pearring
- Department of Ophthalmology, Duke University Medical Center, Durham, NC 27710, USA
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