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Rohou A, Morris EP, Makarova J, Tonevitsky AG, Ushkaryov YA. α-Latrotoxin Tetramers Spontaneously Form Two-Dimensional Crystals in Solution and Coordinated Multi-Pore Assemblies in Biological Membranes. Toxins (Basel) 2024; 16:248. [PMID: 38922143 PMCID: PMC11209280 DOI: 10.3390/toxins16060248] [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: 04/10/2024] [Accepted: 05/15/2024] [Indexed: 06/27/2024] Open
Abstract
α-Latrotoxin (α-LTX) was found to form two-dimensional (2D) monolayer arrays in solution at relatively low concentrations (0.1 mg/mL), with the toxin tetramer constituting a unit cell. The crystals were imaged using cryogenic electron microscopy (cryoEM), and image analysis yielded a ~12 Å projection map. At this resolution, no major conformational changes between the crystalline and solution states of α-LTX tetramers were observed. Electrophysiological studies showed that, under the conditions of crystallization, α-LTX simultaneously formed multiple channels in biological membranes that displayed coordinated gating. Two types of channels with conductance levels of 120 and 208 pS were identified. Furthermore, we observed two distinct tetramer conformations of tetramers both when observed as monodisperse single particles and within the 2D crystals, with pore diameters of 11 and 13.5 Å, suggestive of a flickering pore in the middle of the tetramer, which may correspond to the two states of toxin channels with different conductance levels. We discuss the structural changes that occur in α-LTX tetramers in solution and propose a mechanism of α-LTX insertion into the membrane. The propensity of α-LTX tetramers to form 2D crystals may explain many features of α-LTX toxicology and suggest that other pore-forming toxins may also form arrays of channels to exert maximal toxic effect.
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Affiliation(s)
- Alexis Rohou
- Division of Cell and Molecular Biology, Imperial College London, Exhibition Road, London SW7 2AZ, UK;
| | - Edward P. Morris
- Division of Structural Biology, The Institute of Cancer Research (ICR), London SW7 3RP, UK;
| | - Julia Makarova
- Faculty of Biology and Biotechnology, HSE University, 117997 Moscow, Russia;
| | | | - Yuri A. Ushkaryov
- Division of Cell and Molecular Biology, Imperial College London, Exhibition Road, London SW7 2AZ, UK;
- Medway School of Pharmacy, University of Kent, Chatham ME4 4TB, UK
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2
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Ruan Y, Yuan R, He J, Jiang Y, Chu S, Chen N. New perspective on sustained antidepressant effect: focus on neurexins regulating synaptic plasticity. Cell Death Discov 2024; 10:205. [PMID: 38693106 PMCID: PMC11063156 DOI: 10.1038/s41420-024-01974-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2024] [Revised: 04/17/2024] [Accepted: 04/17/2024] [Indexed: 05/03/2024] Open
Abstract
Depression is highly prevalent globally, however, currently available medications face challenges such as low response rates and short duration of efficacy. Additionally, depression mostly accompany other psychiatric disorders, further progressing to major depressive disorder without long-term effective management. Thus, sustained antidepressant strategies are urgently needed. Recently, ketamine and psilocybin gained attention as potential sustained antidepressants. Review of recent studies highlights that synaptic plasticity changes as key events of downstream long-lasting changes in sustained antidepressant effect. This underscores the significance of synaptic plasticity in sustained antidepressant effect. Moreover, neurexins, key molecules involved in the regulation of synaptic plasticity, act as critical links between synaptic plasticity and sustained antidepressant effects, involving mechanisms including protein level, selective splicing, epigenetics, astrocytes, positional redistribution and protein structure. Based on the regulation of synaptic plasticity by neurexins, several drugs with potential for sustained antidepressant effect are also discussed. Focusing on neurexins in regulating synaptic plasticity promises much for further understanding underlying mechanisms of sustained antidepressant and the next step in new drug development. This research represents a highly promising future research direction.
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Affiliation(s)
- Yuan Ruan
- Tianjin University of Traditional Chinese Medicine, Tianjin, PR China
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, PR China
| | - Ruolan Yuan
- Tianjin University of Traditional Chinese Medicine, Tianjin, PR China
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, PR China
| | - Jiaqi He
- Tianjin University of Traditional Chinese Medicine, Tianjin, PR China
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, PR China
| | - Yutong Jiang
- Tianjin University of Traditional Chinese Medicine, Tianjin, PR China
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, PR China
| | - Shifeng Chu
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, PR China.
| | - Naihong Chen
- Tianjin University of Traditional Chinese Medicine, Tianjin, PR China.
- State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, PR China.
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3
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Silva CA, Yalnizyan-Carson A, Fernández Busch MV, van Zwieten M, Verhage M, Lohmann C. Activity-dependent regulation of mitochondrial motility in developing cortical dendrites. eLife 2021; 10:62091. [PMID: 34491202 PMCID: PMC8423438 DOI: 10.7554/elife.62091] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 08/24/2021] [Indexed: 11/13/2022] Open
Abstract
Developing neurons form synapses at a high rate. Synaptic transmission is very energy-demanding and likely requires ATP production by mitochondria nearby. Mitochondria might be targeted to active synapses in young dendrites, but whether such motility regulation mechanisms exist is unclear. We investigated the relationship between mitochondrial motility and neuronal activity in the primary visual cortex of young mice in vivo and in slice cultures. During the first 2 postnatal weeks, mitochondrial motility decreases while the frequency of neuronal activity increases. Global calcium transients do not affect mitochondrial motility. However, individual synaptic transmission events precede local mitochondrial arrest. Pharmacological stimulation of synaptic vesicle release, but not focal glutamate application alone, stops mitochondria, suggesting that an unidentified factor co-released with glutamate is required for mitochondrial arrest. A computational model of synaptic transmission-mediated mitochondrial arrest shows that the developmental increase in synapse number and transmission frequency can contribute substantially to the age-dependent decrease of mitochondrial motility.
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Affiliation(s)
- Catia Ap Silva
- Department of Synapse and Network Development, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
| | | | - M Victoria Fernández Busch
- Department of Synapse and Network Development, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
| | - Mike van Zwieten
- Department of Synapse and Network Development, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
| | - Matthijs Verhage
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, University Amsterdam, Amsterdam, Netherlands
| | - Christian Lohmann
- Department of Synapse and Network Development, Netherlands Institute for Neuroscience, Amsterdam, Netherlands.,Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, University Amsterdam, Amsterdam, Netherlands
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4
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Melland H, Carr EM, Gordon SL. Disorders of synaptic vesicle fusion machinery. J Neurochem 2020; 157:130-164. [PMID: 32916768 DOI: 10.1111/jnc.15181] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/20/2020] [Accepted: 08/26/2020] [Indexed: 12/11/2022]
Abstract
The revolution in genetic technology has ushered in a new age for our understanding of the underlying causes of neurodevelopmental, neuromuscular and neurodegenerative disorders, revealing that the presynaptic machinery governing synaptic vesicle fusion is compromised in many of these neurological disorders. This builds upon decades of research showing that disturbance to neurotransmitter release via toxins can cause acute neurological dysfunction. In this review, we focus on disorders of synaptic vesicle fusion caused either by toxic insult to the presynapse or alterations to genes encoding the key proteins that control and regulate fusion: the SNARE proteins (synaptobrevin, syntaxin-1 and SNAP-25), Munc18, Munc13, synaptotagmin, complexin, CSPα, α-synuclein, PRRT2 and tomosyn. We discuss the roles of these proteins and the cellular and molecular mechanisms underpinning neurological deficits in these disorders.
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Affiliation(s)
- Holly Melland
- The Florey Institute of Neuroscience and Mental Health, Melbourne Dementia Research Centre, The University of Melbourne, Melbourne, Vic., Australia
| | - Elysa M Carr
- The Florey Institute of Neuroscience and Mental Health, Melbourne Dementia Research Centre, The University of Melbourne, Melbourne, Vic., Australia
| | - Sarah L Gordon
- The Florey Institute of Neuroscience and Mental Health, Melbourne Dementia Research Centre, The University of Melbourne, Melbourne, Vic., Australia
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5
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Li J, Xie Y, Cornelius S, Jiang X, Sando R, Kordon SP, Pan M, Leon K, Südhof TC, Zhao M, Araç D. Alternative splicing controls teneurin-latrophilin interaction and synapse specificity by a shape-shifting mechanism. Nat Commun 2020; 11:2140. [PMID: 32358586 PMCID: PMC7195488 DOI: 10.1038/s41467-020-16029-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 04/06/2020] [Indexed: 02/07/2023] Open
Abstract
The trans-synaptic interaction of the cell-adhesion molecules teneurins (TENs) with latrophilins (LPHNs/ADGRLs) promotes excitatory synapse formation when LPHNs simultaneously interact with FLRTs. Insertion of a short alternatively-spliced region within TENs abolishes the TEN-LPHN interaction and switches TEN function to specify inhibitory synapses. How alternative-splicing regulates TEN-LPHN interaction remains unclear. Here, we report the 2.9 Å resolution cryo-EM structure of the TEN2-LPHN3 complex, and describe the trimeric TEN2-LPHN3-FLRT3 complex. The structure reveals that the N-terminal lectin domain of LPHN3 binds to the TEN2 barrel at a site far away from the alternatively spliced region. Alternative-splicing regulates the TEN2-LPHN3 interaction by hindering access to the LPHN-binding surface rather than altering it. Strikingly, mutagenesis of the LPHN-binding surface of TEN2 abolishes the LPHN3 interaction and impairs excitatory but not inhibitory synapse formation. These results suggest that a multi-level coincident binding mechanism mediated by a cryptic adhesion complex between TENs and LPHNs regulates synapse specificity. The trans-synaptic interaction of the cell-adhesion molecules teneurins (TENs) with latrophilins (LPHNs) promotes excitatory synapse formation. Here authors report the high resolution cryo-EM structure of the TEN2-LPHN3 complex, describe the trimeric TEN2-LPHN3-FLRT3 complex and show how alternative-splicing regulates the TEN2-LPHN3 interaction.
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Affiliation(s)
- Jingxian Li
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA.,Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, 60637, USA
| | - Yuan Xie
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA
| | - Shaleeka Cornelius
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, 94305, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Xian Jiang
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, 94305, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Richard Sando
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, 94305, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Szymon P Kordon
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA.,Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, 60637, USA
| | - Man Pan
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA
| | - Katherine Leon
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA.,Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, 60637, USA
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, 94305, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Minglei Zhao
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA.
| | - Demet Araç
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, 60637, USA. .,Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL, 60637, USA.
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6
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Morlighem JÉRL, Radis-Baptista G. The Place for Enzymes and Biologically Active Peptides from Marine Organisms for Application in Industrial and Pharmaceutical Biotechnology. Curr Protein Pept Sci 2019; 20:334-355. [PMID: 30255754 DOI: 10.2174/1389203719666180926121722] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 09/10/2018] [Accepted: 09/15/2018] [Indexed: 01/07/2023]
Abstract
Since the beginning of written history, diverse texts have reported the use of enzymatic preparations in food processing and have described the medicinal properties of crude and fractionated venoms to treat various diseases and injuries. With the biochemical characterization of enzymes from distinct sources and bioactive polypeptides from animal venoms, the last sixty years have testified the advent of industrial enzymology and protein therapeutics, which are currently applicable in a wide variety of industrial processes, household products, and pharmaceuticals. Bioprospecting of novel biocatalysts and bioactive peptides is propelled by their unsurpassed properties that are applicable for current and future green industrial processes, biotechnology, and biomedicine. The demand for both novel enzymes with desired characteristics and novel peptides that lead to drug development, has experienced a steady increase in response to the expanding global market for industrial enzymes and peptidebased drugs. Moreover, although largely unexplored, oceans and marine realms, with their unique ecosystems inhabited by a large variety of species, including a considerable number of venomous animals, are recognized as untapped reservoirs of molecules and macromolecules (enzymes and bioactive venom-derived peptides) that can potentially be converted into highly valuable biopharmaceutical products. In this review, we have focused on enzymes and animal venom (poly)peptides that are presently in biotechnological use, and considering the state of prospection of marine resources, on the discovery of useful industrial biocatalysts and drug leads with novel structures exhibiting selectivity and improved performance.
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Affiliation(s)
- Jean-Étienne R L Morlighem
- Institute for Marine Sciences, Federal University of Ceara, Av da Abolicao 3207. Fortaleza/CE. 60165081, Brazil
| | - Gandhi Radis-Baptista
- Institute for Marine Sciences, Federal University of Ceara, Av da Abolicao 3207. Fortaleza/CE. 60165081, Brazil
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7
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Ablation of All Synaptobrevin vSNAREs Blocks Evoked But Not Spontaneous Neurotransmitter Release at Neuromuscular Synapses. J Neurosci 2019; 39:6049-6066. [PMID: 31160536 DOI: 10.1523/jneurosci.0403-19.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 04/26/2019] [Accepted: 05/13/2019] [Indexed: 01/16/2023] Open
Abstract
Synaptic transmission occurs when an action potential triggers neurotransmitter release via the fusion of synaptic vesicles with the presynaptic membrane, driven by the formation of SNARE complexes composed of the vesicular (v)-SNARE synaptobrevin and the target (t)-SNAREs Snap-25 and syntaxin-1. Neurotransmitters are also released spontaneously, independent of an action potential, through the fusion of synaptic vesicles with the presynaptic membrane. The major neuronal vSNAREs, synaptobrevin-1 and synaptobrevin-2, are expressed at the developing neuromuscular junction (NMJ) in mice, but their specific roles in NMJ formation and function remain unclear. Here, we examine the NMJs in mutant mouse embryos lacking either synaptobrevin 1 (Syb1lew/lew ) or synaptobrevin 2 (Syb2 -/-), and those lacking both (Syb1lew/lewSyb2 -/-). We found that, compared with controls: (1) the number and size of NMJs was markedly increased in Syb2 -/- and Syb1lew/lewSyb2 -/- mice, but not in Syb1lew/lew mice; (2) synaptic vesicle density was markedly reduced in Syb1lew/lewSyb2 -/- NMJs; and (3) evoked neurotransmission was markedly reduced in Syb2 -/- NMJs and completely abolished in Syb1lew/lewSyb2 -/- NMJs. Surprisingly, however, spontaneous neurotransmission persists in the absence of both Syb1 and Syb2. Furthermore, spontaneous neurotransmission remains constant in Syb1lew/lewSyb2 -/- NMJs despite changing Ca2+ levels. These findings reveal an overlapping role for Syb1 and Syb2 (with Syb2 being dominant) in developing NMJs in mice. Moreover, because spontaneous release becomes Ca2+-insensitive in Syb1lew/lewSyb2 -/- NMJs, our findings suggest that synaptobrevin-based SNARE complexes play a critical role in conferring Ca2+ sensitivity during spontaneous release.SIGNIFICANCE STATEMENT Neurotransmitters can be released at synapses with (evoked) or without (spontaneous) the influence of action potentials. Whereas evoked neurotransmission requires Ca2+ influx, those underlying the spontaneous neurotransmission may occur with or without Ca2+ Our findings show that, in the absence neuronal vSNARE synaptobrevin-1 and synaptobrevin-2, evoked neurotransmission is completely abolished; however, spontaneous synaptic transmission not only persists but even increased. Furthermore, spontaneous synaptic transmission that is normally highly Ca2+-sensitive became Ca2+-independent upon deletion of vSNARE synaptobrevin-1 and synaptobrevin-2. These findings reveal distinct mechanisms for evoked and spontaneous neurotransmitter release. Moreover, these findings suggest that synaptobrevin-based SNARE complexes play critical roles in conferring Ca2+ sensitivity during spontaneous neurotransmission at developing neuromuscular synapses in mice.
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8
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Haney RA, Matte T, Forsyth FS, Garb JE. Alternative Transcription at Venom Genes and Its Role as a Complementary Mechanism for the Generation of Venom Complexity in the Common House Spider. Front Ecol Evol 2019; 7. [PMID: 31431897 PMCID: PMC6700725 DOI: 10.3389/fevo.2019.00085] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The complex composition of venom, a proteinaceous secretion used by
diverse animal groups for predation or defense, is typically viewed as being
driven by gene duplication in conjunction with positive selection, leading to
large families of diversified toxins with selective venom gland expression. Yet,
the production of alternative transcripts at venom genes is often overlooked as
another potentially important process that could contribute proteins to venom,
and requires comprehensive datasets integrating genome and transcriptome
sequences together with proteomic characterization of venom to be fully
documented. In the common house spider, Parasteatoda
tepidariorum, we used RNA sequencing of four tissue types in
conjunction with the sequenced genome to provide a comprehensive transcriptome
annotation. We also used mass spectrometry to identify a minimum of 99 distinct
proteins in P tepidariorum venom, including at least 33
latrotoxins, pore-forming neurotoxins shared with the confamilial black widow.
We found that venom proteins are much more likely to come from multiple
transcript genes, whose transcripts produced distinct protein sequences. The
presence of multiple distinct proteins in venom from transcripts at individual
genes was confirmed for eight loci by mass spectrometry, and is possible at 21
others. Alternative transcripts from the same gene, whether encoding or not
encoding a protein found in venom, showed a range of expression patterns, but
were not necessarily restricted to the venom gland. However, approximately half
of venom protein encoding transcripts were found among the 1,318 transcripts
with strongly venom gland biased expression. Our findings revealed an important
role for alternative transcription in generating venom protein complexity and
expanded the traditional model of venom evolution.
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Affiliation(s)
- Robert A Haney
- Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, United States
| | - Taylor Matte
- Center for Regenerative Medicine, Boston University, Medical, Boston, MA, United States
| | - FitzAnthony S Forsyth
- Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, United States
| | - Jessica E Garb
- Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, United States
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9
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Araç D, Li J. Teneurins and latrophilins: two giants meet at the synapse. Curr Opin Struct Biol 2019; 54:141-151. [PMID: 30952063 DOI: 10.1016/j.sbi.2019.01.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 01/10/2019] [Accepted: 01/22/2019] [Indexed: 12/19/2022]
Abstract
Teneurins and latrophilins are both conserved families of cell adhesion proteins that mediate cellular communication and play critical roles in embryonic and neural development. However, their mechanisms of action remain poorly understood. In the past several years, three-dimensional structures of teneurins and latrophilins have been reported at atomic resolutions and revealed distinct protein folds and unique structural features. In this review, we discuss these structures which, together with structure-guided biochemical and functional analyses, provide hints for the mechanisms of trans-cellular communication at the synapse and other cell-cell contact sites.
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Affiliation(s)
- Demet Araç
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, IL 60637, USA.
| | - Jingxian Li
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, IL 60637, USA
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10
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Ushkaryov YA, Lelianova V, Vysokov NV. Catching Latrophilin With Lasso: A Universal Mechanism for Axonal Attraction and Synapse Formation. Front Neurosci 2019; 13:257. [PMID: 30967757 PMCID: PMC6438917 DOI: 10.3389/fnins.2019.00257] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Accepted: 03/05/2019] [Indexed: 11/24/2022] Open
Abstract
Latrophilin-1 (LPHN1) was isolated as the main high-affinity receptor for α-latrotoxin from black widow spider venom, a powerful presynaptic secretagogue. As an adhesion G-protein-coupled receptor, LPHN1 is cleaved into two fragments, which can behave independently on the cell surface, but re-associate upon binding the toxin. This triggers intracellular signaling that involves the Gαq/phospholipase C/inositol 1,4,5-trisphosphate cascade and an increase in cytosolic Ca2+, leading to vesicular exocytosis. Using affinity chromatography on LPHN1, we isolated its endogenous ligand, teneurin-2/Lasso. Both LPHN1 and Ten2/Lasso are expressed early in development and are enriched in neurons. LPHN1 primarily resides in axons, growth cones and presynaptic terminals, while Lasso largely localizes on dendrites. LPHN1 and Ten2/Lasso form a trans-synaptic receptor pair that has both structural and signaling functions. However, Lasso is proteolytically cleaved at multiple sites and its extracellular domain is partially released into the intercellular space, especially during neuronal development, suggesting that soluble Lasso has additional functions. We discovered that the soluble fragment of Lasso can diffuse away and bind to LPHN1 on axonal growth cones, triggering its redistribution on the cell surface and intracellular signaling which leads to local exocytosis. This causes axons to turn in the direction of spatio-temporal Lasso gradients, while LPHN1 knockout blocks this effect. These results suggest that the LPHN1-Ten2/Lasso pair can participate in long- and short-distance axonal guidance and synapse formation.
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Affiliation(s)
- Yuri A Ushkaryov
- Medway School of Pharmacy, University of Kent, Chatham, United Kingdom
| | - Vera Lelianova
- Medway School of Pharmacy, University of Kent, Chatham, United Kingdom
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11
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Neurobiology and therapeutic applications of neurotoxins targeting transmitter release. Pharmacol Ther 2019; 193:135-155. [DOI: 10.1016/j.pharmthera.2018.08.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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12
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Vysokov NV, Silva JP, Lelianova VG, Suckling J, Cassidy J, Blackburn JK, Yankova N, Djamgoz MB, Kozlov SV, Tonevitsky AG, Ushkaryov YA. Proteolytically released Lasso/teneurin-2 induces axonal attraction by interacting with latrophilin-1 on axonal growth cones. eLife 2018; 7:37935. [PMID: 30457553 PMCID: PMC6245728 DOI: 10.7554/elife.37935] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 10/19/2018] [Indexed: 11/15/2022] Open
Abstract
A presynaptic adhesion G-protein-coupled receptor, latrophilin-1, and a postsynaptic transmembrane protein, Lasso/teneurin-2, are implicated in trans-synaptic interaction that contributes to synapse formation. Surprisingly, during neuronal development, a substantial proportion of Lasso is released into the intercellular space by regulated proteolysis, potentially precluding its function in synaptogenesis. We found that released Lasso binds to cell-surface latrophilin-1 on axonal growth cones. Using microfluidic devices to create stable gradients of soluble Lasso, we show that it induces axonal attraction, without increasing neurite outgrowth. Using latrophilin-1 knockout in mice, we demonstrate that latrophilin-1 is required for this effect. After binding latrophilin-1, Lasso causes downstream signaling, which leads to an increase in cytosolic calcium and enhanced exocytosis, processes that are known to mediate growth cone steering. These findings reveal a novel mechanism of axonal pathfinding, whereby latrophilin-1 and Lasso mediate both short-range interaction that supports synaptogenesis, and long-range signaling that induces axonal attraction. The brain is a complex mesh of interconnected neurons, with each cell making tens, hundreds, or even thousands of connections. These links can stretch over long distances, and establishing them correctly during development is essential. Developing neurons send out long and thin structures, called axons, to reach distant cells. To guide these growing axons, neurons release molecules that work as traffic signals: some attract axons whilst others repel them, helping the burgeoning structures to twist and turn along their travel paths. When an axon reaches its target cell, the two cells join to each other by forming a structure called a synapse. To make the connection, surface proteins on the axon latch onto matching proteins on the target cell, zipping up the synapse. There are many different types of synapses in the brain, but we only know a few of the surface molecules involved in their creation – not enough to explain synaptic variety. Two of these surface proteins are latrophilin-1, which is produced by the growing axon, and Lasso, which sits on the membrane of the target cell. The two proteins interact strongly, anchoring the axon to the target cell and allowing the synapse to form. However, a previous recent discovery by Vysokov et al. has revealed that an enzyme can also cut Lasso from the membrane of the target cell. The ‘free’ protein can still interact with latrophilin-1, but as it is shed by the target cell, it can no longer serve as an anchor for the synapse. Could it be that free Lasso acts as a traffic signal instead? Here, Vysokov et al. tried to answer this by growing neurons from a part of the brain called the hippocampus in a special labyrinth dish. When free Lasso was gradually introduced in the culture through microscopic channels, it interacted with latrophilin-1 on the surface of the axons. This triggered internal changes that led the axons to add more membrane where they had sensed Lasso, making them grow towards the source of the signal. The results demonstrate that a target cell can both carry and release Lasso, using this duplicitous protein to help attract growing axons as well as anchor them. The work by Vysokov et al. contributes to our knowledge of how neurons normally connect, which could shed light on how this process can go wrong. This may be relevant to understand conditions such as schizophrenia and ADHD, where patients’ brains often show incorrect wiring.
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Affiliation(s)
- Nickolai V Vysokov
- School of Pharmacy, University of Kent, Chatham, United Kingdom.,Department of Life Sciences, Imperial College London, London, United Kingdom.,Wolfson Centre for Age Related Diseases, King's College London, London, United Kingdom.,BrainPatch Ltd, London, United Kingdom
| | - John-Paul Silva
- Department of Life Sciences, Imperial College London, London, United Kingdom.,Department of Bioanalytical Sciences, Non-clinical development, UCB-Pharma, Berkshire, United Kingdom
| | - Vera G Lelianova
- School of Pharmacy, University of Kent, Chatham, United Kingdom.,Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Jason Suckling
- Department of Life Sciences, Imperial College London, London, United Kingdom.,Thomsons Online Benefits, London, United Kingdom
| | - John Cassidy
- Department of Life Sciences, Imperial College London, London, United Kingdom.,Arix Bioscience, London, United Kingdom
| | - Jennifer K Blackburn
- School of Pharmacy, University of Kent, Chatham, United Kingdom.,Division of Molecular Psychiatry, Yale University School of Medicine, New Haven, United States
| | - Natalia Yankova
- Department of Life Sciences, Imperial College London, London, United Kingdom.,Institute of Psychiatry, Psychology & Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Department of Basic and Clinical Neuroscience, King's College London, London, United Kingdom
| | - Mustafa Ba Djamgoz
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Serguei V Kozlov
- Center for Advanced Preclinical Research, National Cancer Institute, Frederick, United States
| | - Alexander G Tonevitsky
- Higher School of Economics, Moscow, Russia.,Scientific Research Centre Bioclinicum, Moscow, Russia
| | - Yuri A Ushkaryov
- School of Pharmacy, University of Kent, Chatham, United Kingdom.,Department of Life Sciences, Imperial College London, London, United Kingdom
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13
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Nazarko O, Kibrom A, Winkler J, Leon K, Stoveken H, Salzman G, Merdas K, Lu Y, Narkhede P, Tall G, Prömel S, Araç D. A Comprehensive Mutagenesis Screen of the Adhesion GPCR Latrophilin-1/ADGRL1. iScience 2018; 3:264-278. [PMID: 30428326 PMCID: PMC6137404 DOI: 10.1016/j.isci.2018.04.019] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 04/16/2018] [Accepted: 04/24/2018] [Indexed: 11/15/2022] Open
Abstract
Adhesion G-protein-coupled receptors (aGPCRs) play critical roles in diverse cellular processes in neurobiology, development, immunity, and numerous diseases. The lack of molecular understanding of their activation mechanisms, especially with regard to the transmembrane domains, hampers further studies to facilitate aGPCR-targeted drug development. Latrophilin-1/ADGRL1 is a model aGPCR that regulates synapse formation and embryogenesis, and its mutations are associated with cancer and attention-deficit/hyperactivity disorder. Here, we established functional assays to monitor latrophilin-1 function and showed the activation of latrophilin-1 by its endogenous agonist peptide. Via a comprehensive mutagenesis screen, we identified transmembrane domain residues essential for latrophilin-1 basal activity and for agonist peptide response. Strikingly, a cancer-associated mutation exhibited increased basal activity and failed to rescue the embryonic developmental phenotype in transgenic worms. These results provide a mechanistic foundation for future aGPCR-targeted drug design.
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Affiliation(s)
- Olha Nazarko
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Amanuel Kibrom
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Jana Winkler
- Rudolf Schönheimer Institute of Biochemistry, Molecular Biochemistry, Medical Faculty, University of Leipzig, 04103 Leipzig, Germany
| | - Katherine Leon
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Hannah Stoveken
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
| | - Gabriel Salzman
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Katarzyna Merdas
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Yue Lu
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Pradnya Narkhede
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Gregory Tall
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
| | - Simone Prömel
- Rudolf Schönheimer Institute of Biochemistry, Molecular Biochemistry, Medical Faculty, University of Leipzig, 04103 Leipzig, Germany
| | - Demet Araç
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA.
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14
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Homozygous Expression of Mutant ELOVL4 Leads to Seizures and Death in a Novel Animal Model of Very Long-Chain Fatty Acid Deficiency. Mol Neurobiol 2017; 55:1795-1813. [PMID: 29168048 PMCID: PMC5820379 DOI: 10.1007/s12035-017-0824-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 11/07/2017] [Indexed: 10/24/2022]
Abstract
Lipids are essential components of the nervous system. However, the functions of very long-chain fatty acids (VLC-FA; ≥ 28 carbons) in the brain are unknown. The enzyme ELOngation of Very Long-chain fatty acids-4 (ELOVL4) catalyzes the rate-limiting step in the biosynthesis of VLC-FA (Agbaga et al., Proc Natl Acad Sci USA 105(35): 12843-12848, 2008; Logan et al., J Lipid Res 55(4): 698-708, 2014), which we identified in the brain as saturated fatty acids (VLC-SFA). Homozygous mutations in ELOVL4 cause severe neuropathology in humans (Ozaki et al., JAMA Neurol 72(7): 797-805, 2015; Mir et al., BMC Med Genet 15: 25, 2014; Cadieux-Dion et al., JAMA Neurol 71(4): 470-475, 2014; Bourassa et al., JAMA Neurol 72(8): 942-943, 2015; Aldahmesh et al., Am J Hum Genet 89(6): 745-750, 2011) and are post-natal lethal in mice (Cameron et al., Int J Biol Sci 3(2): 111-119, 2007; Li et al., Int J Biol Sci 3(2): 120-128, 2007; McMahon et al., Molecular Vision 13: 258-272, 2007; Vasireddy et al., Hum Mol Genet 16(5): 471-482, 2007) from dehydration due to loss of VLC-SFA that comprise the skin permeability barrier. Double transgenic mice with homozygous knock-in of the Stargardt-like macular dystrophy (STDG3; 797-801_AACTT) mutation of Elovl4 with skin-specific rescue of wild-type Elovl4 expression (S + Elovl4 mut/mut mice) develop seizures by P19 and die by P21. Electrophysiological analyses of hippocampal slices showed aberrant epileptogenic activity in S + Elovl4 mut/mut mice. FM1-43 dye release studies showed that synapses made by cultured hippocampal neurons from S + Elovl4 mut/mut mice exhibited accelerated synaptic release kinetics. Supplementation of VLC-SFA to cultured hippocampal neurons from mutant mice rescued defective synaptic release to wild-type rates. Together, these studies establish a critical, novel role for ELOVL4 and its VLC-SFA products in regulating synaptic release kinetics and epileptogenesis. Future studies aimed at understanding the molecular mechanisms by which VLC-SFA regulate synaptic function may provide new targets for improved seizure therapies.
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15
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Crawford DC, Kavalali ET. Molecular underpinnings of synaptic vesicle pool heterogeneity. Traffic 2015; 16:338-64. [PMID: 25620674 DOI: 10.1111/tra.12262] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 01/06/2015] [Indexed: 12/31/2022]
Abstract
Neuronal communication relies on chemical synaptic transmission for information transfer and processing. Chemical neurotransmission is initiated by synaptic vesicle fusion with the presynaptic active zone resulting in release of neurotransmitters. Classical models have assumed that all synaptic vesicles within a synapse have the same potential to fuse under different functional contexts. In this model, functional differences among synaptic vesicle populations are ascribed to their spatial distribution in the synapse with respect to the active zone. Emerging evidence suggests, however, that synaptic vesicles are not a homogenous population of organelles, and they possess intrinsic molecular differences and differential interaction partners. Recent studies have reported a diverse array of synaptic molecules that selectively regulate synaptic vesicles' ability to fuse synchronously and asynchronously in response to action potentials or spontaneously irrespective of action potentials. Here we discuss these molecular mediators of vesicle pool heterogeneity that are found on the synaptic vesicle membrane, on the presynaptic plasma membrane, or within the cytosol and consider some of the functional consequences of this diversity. This emerging molecular framework presents novel avenues to probe synaptic function and uncover how synaptic vesicle pools impact neuronal signaling.
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Affiliation(s)
- Devon C Crawford
- Department of Neuroscience, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9111, USA
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16
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Yan S, Wang X. Recent Advances in Research on Widow Spider Venoms and Toxins. Toxins (Basel) 2015; 7:5055-67. [PMID: 26633495 PMCID: PMC4690112 DOI: 10.3390/toxins7124862] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Revised: 11/02/2015] [Accepted: 11/16/2015] [Indexed: 01/29/2023] Open
Abstract
Widow spiders have received much attention due to the frequently reported human and animal injures caused by them. Elucidation of the molecular composition and action mechanism of the venoms and toxins has vast implications in the treatment of latrodectism and in the neurobiology and pharmaceutical research. In recent years, the studies of the widow spider venoms and the venom toxins, particularly the α-latrotoxin, have achieved many new advances; however, the mechanism of action of the venom toxins has not been completely clear. The widow spider is different from many other venomous animals in that it has toxic components not only in the venom glands but also in other parts of the adult spider body, newborn spiderlings, and even the eggs. More recently, the molecular basis for the toxicity outside the venom glands has been systematically investigated, with four proteinaceous toxic components being purified and preliminarily characterized, which has expanded our understanding of the widow spider toxins. This review presents a glance at the recent advances in the study on the venoms and toxins from the Latrodectus species.
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Affiliation(s)
- Shuai Yan
- Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha 410081, China.
| | - Xianchun Wang
- Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha 410081, China.
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17
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Synaptotagmin-7 Is Essential for Ca2+-Triggered Delayed Asynchronous Release But Not for Ca2+-Dependent Vesicle Priming in Retinal Ribbon Synapses. J Neurosci 2015; 35:11024-33. [PMID: 26245964 DOI: 10.1523/jneurosci.0759-15.2015] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
UNLABELLED Most synapses release neurotransmitters in two phases: (1) a fast synchronous phase lasting a few milliseconds; and (2) a delayed "asynchronous" phase lasting hundreds of milliseconds. Ca(2+) triggers fast synchronous neurotransmitter release by binding to synaptotagmin-1, synaptotagmin-2, or synaptotagmin-9, but how Ca(2+) triggers delayed asynchronous release has long remained enigmatic. Recent results suggested that consistent with the Ca(2+)-sensor function of synaptotagmin-7 in neuroendocrine exocytosis, synaptotagmin-7 also functions as a Ca(2+) sensor for synaptic vesicle exocytosis but operates during delayed asynchronous release. Puzzlingly, a subsequent study postulated that synaptotagmin-7 is not a Ca(2+) sensor for release but mediates Ca(2+)-dependent vesicle repriming after intense stimulation. To address these issues, we here analyzed synaptic transmission at rod bipolar neuron-AII amacrine cell synapses in acute mouse retina slices as a model system. Using paired recordings, we show that knock-out of synaptotagmin-7 selectively impairs delayed asynchronous release but not fast synchronous release. Delayed asynchronous release was blocked in wild-type synapses by intracellular addition of high concentrations of the slow Ca(2+)-chelator EGTA, but EGTA had no effect in synaptotagmin-7 knock-out neurons because delayed asynchronous release was already impaired. Moreover, direct measurements of vesicle repriming failed to uncover an effect of the synaptotagmin-7 knock-out on vesicle repriming. Our data demonstrate that synaptotagmin-7 is selectively essential for Ca(2+)-dependent delayed asynchronous release in retinal rod bipolar cell synapses, that its function can be blocked by simply introducing a slow Ca(2+) buffer into the cells, and that synaptotagmin-7 is not required for normal vesicle repriming. SIGNIFICANCE STATEMENT How Ca(2+) triggers delayed asynchronous release has long remained enigmatic. Synaptotagmin-7 has been implicated recently as Ca(2+) sensor in mediating delayed asynchronous release, or vesicle repriming, in cultured neurons. To test the precise function of synaptotagmin-7 in a physiologically important synapse in situ, we have used pair recordings to study the synaptic transmission between retinal rod bipolar cells and AII amacrine cells. Our data demonstrate that the knock-out of synaptotagmin-7 selectively impaired delayed asynchronous release but not synchronous release. In contrast, the readily releasable vesicles after depletion recover normally in knock-out mice. Therefore, our findings extend our knowledge of synaptotagmins as Ca(2+) sensors in vesicle fusion and support the idea that synapses are governed universally by different synaptotagmin Ca(2+) sensors mediating distinct release.
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18
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Hammel I, Meilijson I. Function Suggests Nano-Structure: Quantitative Structural Support for SNARE-Mediated Pore Formation. Neurotox Res 2015; 29:1-9. [PMID: 26407673 DOI: 10.1007/s12640-015-9559-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 08/22/2015] [Accepted: 08/24/2015] [Indexed: 10/23/2022]
Abstract
Granule secretory content is released in either basal or calcium-activated complete exocytosis mode. A vital element in these processes is the establishment of a fusion pore between the granule membrane and the plasma membrane, initiated by the formation of a circular rosette docking arrangement of SNARE protein complexes. The controversially disputed number of SNARE complexes needed for granule priming leading to the formation of the fusion pore, is granule-size dependent and varies between secretion modes. Resorting to a statistical mechanics approach that views SNARE complexes and Ca(2+) ions as interacting particles, we have developed a relationship that links secretion rate to SNARE rosette size, Ca(2+) concentration and Ca(2+) ion cooperativity. Data are presented and discussed which suggest this SNARE-dependent generalization of existing narrow-range biophysical models that correlate secretion rate with Ca(2+) concentration and maximal Ca(2+) ion cooperativity. Evidence from dozens of examples in the literature advocate for this relation, which holds through the entire biological range. The coalescence of so many areas of diverse research methodologies has greatly augmented our understanding of so many different sequences of granule life cycle. Accordingly, these new tools may become valuable in a variety of electrophysiological experiments.
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Affiliation(s)
- Ilan Hammel
- Department of Pathology, Sackler Faculty of Medicine, Tel Aviv University, 6997801, Tel Aviv, Israel.
| | - Isaac Meilijson
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Mathematical Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
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19
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Zhou C, Sun H, Klein PM, Jensen FE. Neonatal seizures alter NMDA glutamate receptor GluN2A and 3A subunit expression and function in hippocampal CA1 neurons. Front Cell Neurosci 2015; 9:362. [PMID: 26441533 PMCID: PMC4585040 DOI: 10.3389/fncel.2015.00362] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 08/31/2015] [Indexed: 12/02/2022] Open
Abstract
Neonatal seizures are commonly caused by hypoxic and/or ischemic injury during birth and can lead to long-term epilepsy and cognitive deficits. In a rodent hypoxic seizure (HS) model, we have previously demonstrated a critical role for seizure-induced enhancement of the AMPA subtype of glutamate receptor (GluA) in epileptogenesis and cognitive consequences, in part due to GluA maturational upregulation of expression. Similarly, as the expression and function of the N-Methyl-D-aspartate (NMDA) subtype of glutamate receptor (GluN) is also developmentally controlled, we examined how early life seizures during the critical period of synaptogenesis could modify GluN development and function. In a postnatal day (P)10 rat model of neonatal seizures, we found that seizures could alter GluN2/3 subunit composition of GluNs and physiological function of synaptic GluNs. In hippocampal slices removed from rats within 48–96 h following seizures, the amplitudes of synaptic GluN-mediated evoked excitatory postsynaptic currents (eEPSCs) were elevated in CA1 pyramidal neurons. Moreover, GluN eEPSCs showed a decreased sensitivity to GluN2B selective antagonists and decreased Mg2+ sensitivity at negative holding potentials, indicating a higher proportion of GluN2A and GluN3A subunit function, respectively. These physiological findings were accompanied by a concurrent increase in GluN2A phosphorylation and GluN3A protein. These results suggest that altered GluN function and expression could potentially contribute to future epileptogenesis following neonatal seizures, and may represent potential therapeutic targets for the blockade of future epileptogenesis in the developing brain.
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Affiliation(s)
- Chengwen Zhou
- Department of Neurology, Division of Neuroscience, Boston Children's Hospital Boston, MA, USA ; Program in Neurobiology, Harvard Medical School Boston, MA, USA
| | - Hongyu Sun
- Department of Neurology, Division of Neuroscience, Boston Children's Hospital Boston, MA, USA ; Program in Neurobiology, Harvard Medical School Boston, MA, USA ; Department of Neurology, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA, USA
| | - Peter M Klein
- Department of Neurology, Division of Neuroscience, Boston Children's Hospital Boston, MA, USA
| | - Frances E Jensen
- Department of Neurology, Division of Neuroscience, Boston Children's Hospital Boston, MA, USA ; Program in Neurobiology, Harvard Medical School Boston, MA, USA ; Department of Neurology, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA, USA
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20
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Lu YC, Nazarko OV, Sando R, Salzman GS, Li NS, Südhof TC, Araç D. Structural Basis of Latrophilin-FLRT-UNC5 Interaction in Cell Adhesion. Structure 2015; 23:1678-1691. [PMID: 26235030 DOI: 10.1016/j.str.2015.06.024] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 06/18/2015] [Accepted: 06/21/2015] [Indexed: 11/24/2022]
Abstract
Fibronectin leucine-rich repeat transmembrane proteins (FLRTs) are cell-adhesion molecules with emerging functions in cortical development and synapse formation. Their extracellular regions interact with latrophilins (LPHNs) to mediate synapse development, and with Uncoordinated-5 (UNC5)/netrin receptors to control the migration of neurons in the developing cortex. Here, we present the crystal structures of FLRT3 in isolation and in complex with LPHN3. The LPHN3/FLRT3 structure reveals that LPHN3 binds to FLRT3 at a site distinct from UNC5. Structure-based mutations specifically disrupt LPHN3/FLRT3 binding, but do not disturb their interactions with other proteins or their cell-membrane localization. Thus, they can be used as molecular tools to dissect the functions of FLRTs and LPHNs in vivo. Our results suggest that UNC5 and LPHN3 can simultaneously bind to FLRT3, forming a trimeric complex, and that FLRT3 may form transsynaptic complexes with both LPHN3 and UNC5. These findings provide molecular insights for understanding the role of cell-adhesion proteins in synapse function.
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Affiliation(s)
- Yue C Lu
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, GCIS W219, Chicago, IL 60637, USA
| | - Olha V Nazarko
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, GCIS W219, Chicago, IL 60637, USA
| | - Richard Sando
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
| | - Gabriel S Salzman
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, GCIS W219, Chicago, IL 60637, USA
| | - Nan-Sheng Li
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, GCIS W219, Chicago, IL 60637, USA
| | - Thomas C Südhof
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
| | - Demet Araç
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, GCIS W219, Chicago, IL 60637, USA.
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21
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Weber JP, Toft-Bertelsen TL, Mohrmann R, Delgado-Martinez I, Sørensen JB. Synaptotagmin-7 is an asynchronous calcium sensor for synaptic transmission in neurons expressing SNAP-23. PLoS One 2014; 9:e114033. [PMID: 25422940 PMCID: PMC4244210 DOI: 10.1371/journal.pone.0114033] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 11/03/2014] [Indexed: 12/25/2022] Open
Abstract
Synchronization of neurotransmitter release with the presynaptic action potential is essential for maintaining fidelity of information transfer in the central nervous system. However, synchronous release is frequently accompanied by an asynchronous release component that builds up during repetitive stimulation, and can even play a dominant role in some synapses. Here, we show that substitution of SNAP-23 for SNAP-25 in mouse autaptic glutamatergic hippocampal neurons results in asynchronous release and a higher frequency of spontaneous release events (mEPSCs). Use of neurons from double-knock-out (SNAP-25, synaptotagmin-7) mice in combination with viral transduction showed that SNAP-23-driven release is triggered by endogenous synaptotagmin-7. In the absence of synaptotagmin-7 release became even more asynchronous, and the spontaneous release rate increased even more, indicating that synaptotagmin-7 acts to synchronize release and suppress spontaneous release. However, compared to synaptotagmin-1, synaptotagmin-7 is a both leaky and asynchronous calcium sensor. In the presence of SNAP-25, consequences of the elimination of synaptotagmin-7 were small or absent, indicating that the protein pairs SNAP-25/synaptotagmin-1 and SNAP-23/synaptotagmin-7 might act as mutually exclusive calcium sensors. Expression of fusion proteins between pHluorin (pH-sensitive GFP) and synaptotagmin-1 or -7 showed that vesicles that fuse using the SNAP-23/synaptotagmin-7 combination contained synaptotagmin-1, while synaptotagmin-7 barely displayed activity-dependent trafficking between vesicle and plasma membrane, implying that it acts as a plasma membrane calcium sensor. Overall, these findings support the idea of alternative syt∶SNARE combinations driving release with different kinetics and fidelity.
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Affiliation(s)
- Jens P. Weber
- Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, The Netherlands
| | - Trine L. Toft-Bertelsen
- Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ralf Mohrmann
- Department of Physiology, University of Saarland, Homburg, Germany
| | | | - Jakob B. Sørensen
- Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
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22
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Ramirez DMO, Kavalali ET. The role of non-canonical SNAREs in synaptic vesicle recycling. CELLULAR LOGISTICS 2014; 2:20-27. [PMID: 22645707 PMCID: PMC3355972 DOI: 10.4161/cl.20114] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
An increasing number of studies suggest that distinct pools of synaptic vesicles drive specific forms of neurotransmission. Interspersed with these functional studies are analyses of the synaptic vesicle proteome which have consistently detected the presence of so-called “non-canonical” SNAREs that typically function in fusion and trafficking of other subcellular structures within the neuron. The recent identification of certain non-canonical vesicular SNAREs driving spontaneous (e.g., VAMP7 and vti1a) or evoked asynchronous (e.g., VAMP4) release integrates and corroborates existing data from functional and proteomic studies and implies that at least some complement of non-canonical SNAREs resident on synaptic vesicles function in neurotransmission. Here, we discuss the specific roles in neurotransmission of proteins homologous to each member of the classical neuronal SNARE complex consisting of synaptobrevin2, syntaxin-1 and SNAP-25.
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23
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Meriney SD, Umbach JA, Gundersen CB. Fast, Ca2+-dependent exocytosis at nerve terminals: shortcomings of SNARE-based models. Prog Neurobiol 2014; 121:55-90. [PMID: 25042638 DOI: 10.1016/j.pneurobio.2014.07.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 04/14/2014] [Accepted: 07/03/2014] [Indexed: 11/30/2022]
Abstract
Investigations over the last two decades have made major inroads in clarifying the cellular and molecular events that underlie the fast, synchronous release of neurotransmitter at nerve endings. Thus, appreciable progress has been made in establishing the structural features and biophysical properties of the calcium (Ca2+) channels that mediate the entry into nerve endings of the Ca2+ ions that trigger neurotransmitter release. It is now clear that presynaptic Ca2+ channels are regulated at many levels and the interplay of these regulatory mechanisms is just beginning to be understood. At the same time, many lines of research have converged on the conclusion that members of the synaptotagmin family serve as the primary Ca2+ sensors for the action potential-dependent release of neurotransmitter. This identification of synaptotagmins as the proteins which bind Ca2+ and initiate the exocytotic fusion of synaptic vesicles with the plasma membrane has spurred widespread efforts to reveal molecular details of synaptotagmin's action. Currently, most models propose that synaptotagmin interfaces directly or indirectly with SNARE (soluble, N-ethylmaleimide sensitive factor attachment receptors) proteins to trigger membrane fusion. However, in spite of intensive efforts, the field has not achieved consensus on the mechanism by which synaptotagmins act. Concurrently, the precise sequence of steps underlying SNARE-dependent membrane fusion remains controversial. This review considers the pros and cons of the different models of SNARE-mediated membrane fusion and concludes by discussing a novel proposal in which synaptotagmins might directly elicit membrane fusion without the intervention of SNARE proteins in this final fusion step.
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Affiliation(s)
- Stephen D Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Joy A Umbach
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095, USA
| | - Cameron B Gundersen
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095, USA.
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24
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Bal M, Leitz J, Reese AL, Ramirez DMO, Durakoglugil M, Herz J, Monteggia LM, Kavalali ET. Reelin mobilizes a VAMP7-dependent synaptic vesicle pool and selectively augments spontaneous neurotransmission. Neuron 2013; 80:934-46. [PMID: 24210904 DOI: 10.1016/j.neuron.2013.08.024] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2013] [Indexed: 02/07/2023]
Abstract
Reelin is a glycoprotein that is critical for proper layering of neocortex during development as well as dynamic regulation of glutamatergic postsynaptic signaling in mature synapses. Here, we show that Reelin also acts presynaptically, resulting in robust rapid enhancement of spontaneous neurotransmitter release without affecting properties of evoked neurotransmission. This effect of Reelin requires a modest but significant increase in presynaptic Ca(2+) initiated via ApoER2 signaling. The specificity of Reelin action on spontaneous neurotransmitter release is encoded at the level of vesicular SNARE machinery as it requires VAMP7 and SNAP-25 but not synaptobrevin2, VAMP4, or vti1a. These results uncover a presynaptic regulatory pathway that utilizes the heterogeneity of synaptic vesicle-associated SNAREs and selectively augments action potential-independent neurotransmission.
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Affiliation(s)
- Manjot Bal
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX 75390, USA
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25
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Song I, Volynski K, Brenner T, Ushkaryov Y, Walker M, Semyanov A. Different transporter systems regulate extracellular GABA from vesicular and non-vesicular sources. Front Cell Neurosci 2013; 7:23. [PMID: 23494150 PMCID: PMC3595500 DOI: 10.3389/fncel.2013.00023] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 02/25/2013] [Indexed: 11/25/2022] Open
Abstract
Tonic GABA type A (GABAA) conductance is a key factor regulating neuronal excitability and computation in neuronal networks. The magnitude of the tonic GABAA conductance depends on the concentration of ambient GABA originating from vesicular and non-vesicular sources and is tightly regulated by GABA uptake. Here we show that the transport system regulating ambient GABA responsible for tonic GABAA conductances in hippocampal CA1 interneurons depends on its source. In mice, GABA from vesicular sources is regulated by mouse GABA transporter 1 (mGAT1), while that from non-vesicular sources by mouse GABA transporters 3/4 (mGAT3/4). This finding suggests that the two transporter systems do not just provide backup for each other, but regulate distinct signaling pathways. This allows individual tuning of the two signaling systems and indicates that drugs designed to act at specific transporters will have distinct therapeutic actions.
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Affiliation(s)
- Inseon Song
- RIKEN Brain Science Institute Wako-shi, Saitama, Japan
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Hubbard KS, Gut IM, Lyman ME, Tuznik KM, Mesngon MT, McNutt PM. High yield derivation of enriched glutamatergic neurons from suspension-cultured mouse ESCs for neurotoxicology research. BMC Neurosci 2012; 13:127. [PMID: 23095170 PMCID: PMC3573964 DOI: 10.1186/1471-2202-13-127] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 10/10/2012] [Indexed: 12/23/2022] Open
Abstract
Background Recently, there has been a strong emphasis on identifying an in vitro model for neurotoxicity research that combines the biological relevance of primary neurons with the scalability, reproducibility and genetic tractability of continuous cell lines. Derived neurons should be homotypic, exhibit neuron-specific gene expression and morphology, form functioning synapses and consistently respond to neurotoxins in a fashion indistinguishable from primary neurons. However, efficient methods to produce neuronal populations that are suitable alternatives to primary neurons have not been available. Methods With the objective of developing a more facile, robust and efficient method to generate enriched glutamatergic neuronal cultures, we evaluated the neurogenic capacity of three mouse embryonic stem cell (ESC) lines (R1, C57BL/6 and D3) adapted to feeder-independent suspension culture. Neurogenesis and neuronal maturation were characterized as a function of time in culture using immunological, genomic, morphological and functional metrics. The functional responses of ESNs to neurotropic toxins with distinctly different targets and mechanisms of toxicity, such as glutamate, α-latrotoxin (LTX), and botulinum neurotoxin (BoNT), were also evaluated. Results Suspension-adapted ESCs expressed markers of pluripotency through at least 30 passages, and differentiation produced 97×106 neural progenitor cells (NPCs) per 10-cm dish. Greater than 99% of embryonic stem cell-derived neurons (ESNs) expressed neuron-specific markers by 96 h after plating and rapidly developed complex axodendritic arbors and appropriate compartmentalization of neurotypic proteins. Expression profiling demonstrated the presence of transcripts necessary for neuronal function and confirmed that ESN populations were predominantly glutamatergic. Furthermore, ESNs were functionally receptive to all toxins with sensitivities and responses consistent with primary neurons. Conclusions These findings demonstrate a cost-effective, scalable and flexible method to produce a highly enriched glutamatergic neuron population. The functional characterization of pathophysiological responses to neurotropic toxins and the compatibility with multi-well plating formats were used to demonstrate the suitability of ESNs as a discovery platform for molecular mechanisms of action, moderate-throughput analytical approaches and diagnostic screening. Furthermore, for the first time we demonstrate a cell-based model that is sensitive to all seven BoNT serotypes with EC50 values comparable to those reported in primary neuron populations. These data providing compelling evidence that ESNs offer a neuromimetic platform suitable for the evaluation of molecular mechanisms of neurotoxicity.
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Affiliation(s)
- Kyle S Hubbard
- United States Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Rd, Aberdeen Proving Ground, MD 21010, USA.
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Davletov B, Ferrari E, Ushkaryov Y. Presynaptic neurotoxins: an expanding array of natural and modified molecules. Cell Calcium 2012; 52:234-40. [PMID: 22658826 DOI: 10.1016/j.ceca.2012.05.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 05/04/2012] [Accepted: 05/13/2012] [Indexed: 11/15/2022]
Abstract
The process of neurotransmitter release from nerve terminals is a target for a wide array of presynaptic toxins produced by various species, from humble bacteria to arthropods to vertebrate animals. Unlike other toxins, most presynaptic neurotoxins do not kill cells but simply inhibit or activate synaptic transmission. In this review, we describe two types of presynaptic neurotoxins: clostridial toxins and latrotoxins, which are, respectively, the most potent blockers and stimulators of neurotransmitter release. These toxins have been instrumental in defining presynaptic functions and are now widely used in research and medicine. Here, we would like to analyse the diversity of these toxins and demonstrate how the knowledge of their structures and mechanisms of action can help us to design better tools for research and medical applications. We will look at natural and synthetic variations of these exquisite molecular machines, highlighting recent advances in our understanding of presynaptic toxins and questions that remain to be answered. If we can decipher how a given biomolecule is modified by nature to target different species, we will be able to design new variants that carry only desired characteristics to achieve specific therapeutic, agricultural or research goals. Indeed, a number of research groups have already initiated a quest to harness the power of natural toxins with the aim of making them more specifically targeted and safer for future research and medical applications.
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Affiliation(s)
- Bazbek Davletov
- Medical Research Council Laboratory of Molecular Biology, Cambridge, UK.
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Hoyte CO, Cushing TA, Heard KJ. Anaphylaxis to black widow spider antivenom. Am J Emerg Med 2012; 30:836.e1-2. [DOI: 10.1016/j.ajem.2011.03.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 03/15/2011] [Indexed: 10/18/2022] Open
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Ramirez DMO, Khvotchev M, Trauterman B, Kavalali ET. Vti1a identifies a vesicle pool that preferentially recycles at rest and maintains spontaneous neurotransmission. Neuron 2012; 73:121-34. [PMID: 22243751 DOI: 10.1016/j.neuron.2011.10.034] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/18/2011] [Indexed: 01/18/2023]
Abstract
Recent studies suggest that synaptic vesicles (SVs) giving rise to spontaneous neurotransmission are distinct from those that carry out evoked release. However, the molecular basis of this dichotomy remains unclear. Here, we focused on two noncanonical SNARE molecules, Vps10p-tail-interactor-1a (vti1a) and VAMP7, previously shown to reside on SVs. Using simultaneous multicolor imaging at individual synapses, we could show that compared to the more abundant vesicular SNARE synaptobrevin2, both vti1a and VAMP7 were reluctantly mobilized during activity. Vti1a, but not VAMP7, showed robust trafficking under resting conditions that could be partly matched by synaptobrevin2. Furthermore, loss of vti1a function selectively reduced high-frequency spontaneous neurotransmitter release detected postsynaptically. Expression of a truncated version of vti1a augmented spontaneous release more than full-length vti1a, suggesting that an autoinhibitory process regulates vti1a function. Taken together, these results support the premise that in its native form vti1a selectively maintains spontaneous neurotransmitter release.
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Affiliation(s)
- Denise M O Ramirez
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX 75390-9111, USA
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Araç D, Boucard AA, Bolliger MF, Nguyen J, Soltis SM, Südhof TC, Brunger AT. A novel evolutionarily conserved domain of cell-adhesion GPCRs mediates autoproteolysis. EMBO J 2012; 31:1364-78. [PMID: 22333914 PMCID: PMC3321182 DOI: 10.1038/emboj.2012.26] [Citation(s) in RCA: 323] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Accepted: 01/16/2012] [Indexed: 12/02/2022] Open
Abstract
Crystallographic structures encompassing GPCR autoproteolytic sequences (GPS) delineate a novel conserved structural domain called GAIN, which is found in cell-adhesion GPCRs, polycystic kidney disease proteins conserved throughout evolution. The G protein-coupled receptor (GPCR) Proteolysis Site (GPS) of cell-adhesion GPCRs and polycystic kidney disease (PKD) proteins constitutes a highly conserved autoproteolysis sequence, but its catalytic mechanism remains unknown. Here, we show that unexpectedly the ∼40-residue GPS motif represents an integral part of a much larger ∼320-residue domain that we termed GPCR-Autoproteolysis INducing (GAIN) domain. Crystal structures of GAIN domains from two distantly related cell-adhesion GPCRs revealed a conserved novel fold in which the GPS motif forms five β-strands that are tightly integrated into the overall GAIN domain. The GAIN domain is evolutionarily conserved from tetrahymena to mammals, is the only extracellular domain shared by all human cell-adhesion GPCRs and PKD proteins, and is the locus of multiple human disease mutations. Functionally, the GAIN domain is both necessary and sufficient for autoproteolysis, suggesting an autoproteolytic mechanism whereby the overall GAIN domain fine-tunes the chemical environment in the GPS to catalyse peptide bond hydrolysis. Thus, the GAIN domain embodies a unique, evolutionarily ancient and widespread autoproteolytic fold whose function is likely relevant for GPCR signalling and for multiple human diseases.
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Affiliation(s)
- Demet Araç
- Howard Hughes Medical Institute, Stanford, CA, USA.
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31
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Orenbuch A, Ayelet O, Shulman Y, Yoav S, Lipstein N, Noa L, Bechar A, Amit B, Lavy Y, Yotam L, Brumer E, Eliaz B, Vasileva M, Mariya V, Kahn J, Joy K, Barki-Harrington L, Liza BH, Kuner T, Thomas K, Gitler D, Daniel G. Inhibition of exocytosis or endocytosis blocks activity-dependent redistribution of synapsin. J Neurochem 2011; 120:248-58. [PMID: 22066784 DOI: 10.1111/j.1471-4159.2011.07579.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The synaptic vesicle cycle encompasses the pre-synaptic events that drive neurotransmission. Influx of calcium leads to the fusion of synaptic vesicles with the plasma membrane and the release of neurotransmitter, closely followed by endocytosis. Vacated release sites are repopulated with vesicles which are then primed for release. When activity is intense, reserve vesicles may be mobilized to counteract an eventual decline in transmission. Recently, interplay between endocytosis and repopulation of the readily releasable pool of vesicles has been identified. In this study, we show that exo-endocytosis is necessary to enable detachment of synapsin from reserve pool vesicles during synaptic activity. We report that blockage of exocytosis in cultured mouse hippocampal neurons, either by tetanus toxin or by the deletion of munc13, inhibits the activity-dependent redistribution of synapsin from the pre-synaptic terminal into the axon. Likewise, perturbation of endocytosis with dynasore or by a dynamin dominant-negative mutant fully prevents synapsin redistribution. Such inhibition of synapsin redistribution occurred despite the efficient phosphorylation of synapsin at its protein kinase A/CaMKI site, indicating that disengagement of synapsin from the vesicles requires exocytosis and endocytosis in addition to phosphorylation. Our results therefore reveal hitherto unidentified feedback within the synaptic vesicle cycle involving the synapsin-managed reserve pool.
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Affiliation(s)
- Ayelet Orenbuch
- Department of Physiology and Neurobiology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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Cohen D, Segal M. Network bursts in hippocampal microcultures are terminated by exhaustion of vesicle pools. J Neurophysiol 2011; 106:2314-21. [DOI: 10.1152/jn.00969.2010] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Synchronized network activity is an essential attribute of the brain. Yet the cellular mechanisms that determine the duration of network bursts are not fully understood. In the present study, synchronized network bursts were evoked by triggering an action potential in a single neuron in otherwise silent microcultures consisting of 4–30 hippocampal neurons. The evoked burst duration, ∼2 s, depended on the recovery time after a previous burst. While interburst intervals of 35 s enabled full-length bursts, they were shortened by half at 5-s intervals. This reduction in burst duration could not be attributed to postsynaptic parameters such as glutamate receptor desensitization, accumulating afterhyperpolarization, inhibitory tone, or sodium channel inactivation. Reducing extracellular Ca2+ concentration ([Ca2+]o) relieved the effect of short intervals on burst duration, while depletion of synaptic vesicles with α-latrotoxin gradually eliminated network bursts. Finally, a transient exposure to high [K+]o slowed down the recovery time following a burst discharge. We conclude that the limiting factor regulating burst duration is most likely the depletion of presynaptic resources.
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Affiliation(s)
- Dror Cohen
- Department of Neurobiology, The Weizmann Institute, Rehovot, Israel
| | - Menahem Segal
- Department of Neurobiology, The Weizmann Institute, Rehovot, Israel
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Malarkey EB, Parpura V. Temporal characteristics of vesicular fusion in astrocytes: examination of synaptobrevin 2-laden vesicles at single vesicle resolution. J Physiol 2011; 589:4271-300. [PMID: 21746780 DOI: 10.1113/jphysiol.2011.210435] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Astrocytes can release various gliotransmitters in response to stimuli that cause increases in intracellular Ca(2+) levels; this secretion occurs via a regulated exocytosis pathway. Indeed, astrocytes express protein components of the vesicular secretory apparatus. However, the detailed temporal characteristics of vesicular fusions in astrocytes are not well understood. In order to start addressing this issue, we used total internal reflection fluorescence microscopy (TIRFM) to visualize vesicular fusion events in astrocytes expressing the fluorescent synaptobrevin 2 derivative, synapto-pHluorin. Although our cultured astrocytes from visual cortex express synaptosome-associated protein of 23 kDa (SNAP23), but not of 25 kDa (SNAP25), these glial cells exhibited a slow burst of exocytosis under mechanical stimulation; the expression of SNAP25B did not affect bursting behaviour. The relative amount of two distinct types of events observed, transient and full fusions, depended on the applied stimulus. Expression of exogenous synaptotagmin 1 (Syt1) in astrocytes endogenously expressing Syt4, led to a greater proportion of transient fusions when astrocytes were stimulated with bradykinin, a stimulus otherwise resulting in more full fusions. Additionally, we studied the stability of the transient fusion pore by measuring its dwell time, relation to vesicular size, flickering and decay slope; all of these characteristics were secretagogue dependent. The expression of SNAP25B or Syt1 had complex effects on transient fusion pore stability in a stimulus-specific manner. SNAP25B obliterated the appearance of flickers and reduced the dwell time when astrocytes were mechanically stimulated, while astrocytes expressing SNAP25B and stimulated with bradykinin had a reduction in decay slope. Syt1 reduced the dwell time when astrocytes were stimulated either mechanically or with bradykinin. Our detailed study of temporal characteristics of astrocytic exocytosis will not only aid the general understanding of this process, but also the interpretation of the events at the tripartite synapse, both in health and disease.
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Affiliation(s)
- Erik B Malarkey
- Departments of Neurobiology and Cell Biology, Center for Glial Biology inMedicine, Atomic Force Microscopy & Nanotechnology Laboratories, Civitan International Research Center, Evelyn F. McKnight Brain Institute, University of Alabama, Birmingham, AL, USA
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Latrophilin 1 and its endogenous ligand Lasso/teneurin-2 form a high-affinity transsynaptic receptor pair with signaling capabilities. Proc Natl Acad Sci U S A 2011; 108:12113-8. [PMID: 21724987 DOI: 10.1073/pnas.1019434108] [Citation(s) in RCA: 183] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Latrophilin 1 (LPH1), a neuronal receptor of α-latrotoxin, is implicated in neurotransmitter release and control of presynaptic Ca(2+). As an "adhesion G-protein-coupled receptor," LPH1 can convert cell surface interactions into intracellular signaling. To examine the physiological functions of LPH1, we used LPH1's extracellular domain to purify its endogenous ligand. A single protein of ∼275 kDa was isolated from rat brain and termed Lasso. Peptide sequencing and molecular cloning have shown that Lasso is a splice variant of teneurin-2, a brain-specific orphan cell surface receptor with a function in neuronal pathfinding and synaptogenesis. We show that LPH1 and Lasso interact strongly and specifically. They are always copurified from rat brain extracts. Coculturing cells expressing LPH1 with cells expressing Lasso leads to their mutual attraction and formation of multiple junctions to which both proteins are recruited. Cells expressing LPH1 form chimerical synapses with hippocampal neurons in cocultures; LPH1 and postsynaptic neuronal protein PSD-95 accumulate on opposite sides of these structures. Immunoblotting and immunoelectron microscopy of purified synapses and immunostaining of cultured hippocampal neurons show that LPH1 and Lasso are enriched in synapses; in both systems, LPH1 is presynaptic, whereas Lasso is postsynaptic. A C-terminal fragment of Lasso interacts with LPH1 and induces Ca(2+) signals in presynaptic boutons of hippocampal neurons and in neuroblastoma cells expressing LPH1. Thus, LPH1 and Lasso can form transsynaptic complexes capable of inducing presynaptic Ca(2+) signals, which might affect synaptic functions.
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Mesngon M, McNutt P. Alpha-latrotoxin rescues SNAP-25 from BoNT/A-mediated proteolysis in embryonic stem cell-derived neurons. Toxins (Basel) 2011; 3:489-503. [PMID: 22069721 PMCID: PMC3202834 DOI: 10.3390/toxins3050489] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 04/22/2011] [Accepted: 04/29/2011] [Indexed: 11/17/2022] Open
Abstract
The botulinum neurotoxins (BoNTs) exhibit zinc-dependent proteolytic activity against members of the core synaptic membrane fusion complex, preventing neurotransmitter release and resulting in neuromuscular paralysis. No pharmacologic therapies have been identified that clinically relieve botulinum poisoning. The black widow spider venom α-latrotoxin (LTX) has the potential to attenuate the severity or duration of BoNT-induced paralysis in neurons via the induction of synaptic degeneration and remodeling. The potential for LTX to antagonize botulinum poisoning was evaluated in embryonic stem cell-derived neurons (ESNs), using a novel screening assay designed around the kinetics of BoNT/A activation. Exposure of ESNs to 400 pM LTX for 6.5 or 13 min resulted in the nearly complete restoration of uncleaved SNAP-25 within 48 h, whereas treatment with 60 mM K+ had no effect. Time-lapse imaging demonstrated that LTX treatment caused a profound increase in Ca2+ influx and evidence of excitotoxicity, though ESNs remained viable 48 h after LTX treatment. This is the first instance of a cell-based treatment that has shown the ability to eliminate BoNT activity. These data suggest that LTX treatment may provide the basis for a new class of therapeutic approach to BoNT intoxication and may contribute to an improved understanding of long-term mechanisms of BoNT intoxication and recovery. They further demonstrate that ESNs are a novel, responsive and biologically relevant model for LTX research and BoNT therapeutic drug discovery.
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Affiliation(s)
- Mariano Mesngon
- United States Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Gunpowder, MD 21010, USA.
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36
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Ramirez DM, Kavalali ET. Differential regulation of spontaneous and evoked neurotransmitter release at central synapses. Curr Opin Neurobiol 2011; 21:275-82. [PMID: 21334193 PMCID: PMC3092808 DOI: 10.1016/j.conb.2011.01.007] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Accepted: 01/25/2011] [Indexed: 12/20/2022]
Abstract
Recent studies have begun to scrutinize the presynaptic machinery and vesicle populations that give rise to action potential evoked and spontaneous forms of neurotransmitter release. In several cases this work produced unexpected results which lend support to the notion that regulation, mechanisms, postsynaptic targets and possibly presynaptic origins of evoked and spontaneous neurotransmitter release differ. Furthermore, the list of regulatory pathways that impact spontaneous and evoked release in a divergent manner is rapidly growing. These findings challenge our classical views on the relationship between evoked and spontaneous neurotransmission. In contrast to the well-characterized neuromodulatory pathways that equally suppress or augment all forms of neurotransmitter release, molecular substrates specifically controlling spontaneous release remain unclear. In this review, we outline possible mechanisms that may underlie the differential regulation of distinct forms of neurotransmission and help demultiplex complex neuronal signals and generate parallel signaling events at their postsynaptic targets.
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Affiliation(s)
- Denise M.O. Ramirez
- Department of Neuroscience UT Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Ege T. Kavalali
- Department of Neuroscience UT Southwestern Medical Center, Dallas, TX 75390-9111, USA
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390-9111, USA
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Martinez AF, Muenke M, Arcos-Burgos M. From the black widow spider to human behavior: Latrophilins, a relatively unknown class of G protein-coupled receptors, are implicated in psychiatric disorders. Am J Med Genet B Neuropsychiatr Genet 2011; 156B:1-10. [PMID: 21184579 PMCID: PMC4101183 DOI: 10.1002/ajmg.b.31137] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 09/28/2010] [Indexed: 12/24/2022]
Abstract
The findings of a recent study associate LPHN3, a member of the latrophilin family, with an increased risk of developing attention deficit/hyperactivity disorder (ADHD), the most common psychiatric disorder in childhood and adolescence. Latrophilins comprise a new family of G protein-coupled receptors of unknown native physiological function that mediate the neurotoxic effects of α-latrotoxin, a potent toxin found in black widow spider venom. This receptor-toxin interaction has helped to elucidate the mechanistic aspects of neurotransmitter and hormone release in vertebrates. Such unprecedented discovery points to a new direction in the assessment of ADHD and suggest that further study of this receptor family may provide novel insights into the etiology and treatment of ADHD and other related psychiatric conditions.
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Affiliation(s)
| | | | - Mauricio Arcos-Burgos
- Correspondence to: Dr. Mauricio Arcos-Burgos, M.D., Ph.D., National Human Genome Research Institute, National Institutes of Health, 35 Convent Drive, MSC 3717, Building 35, Room 1B209, Bethesda, MD 20892.
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Hiramatsu H, Tadokoro S, Nakanishi M, Hirashima N. Latrotoxin-induced exocytosis in mast cells transfected with latrophilin. Toxicon 2010; 56:1372-80. [DOI: 10.1016/j.toxicon.2010.08.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Revised: 08/03/2010] [Accepted: 08/03/2010] [Indexed: 11/27/2022]
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Nauen DW. Methods of measuring activity at individual synapses: a review of techniques and the findings they have made possible. J Neurosci Methods 2010; 194:195-205. [PMID: 20888362 DOI: 10.1016/j.jneumeth.2010.09.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Revised: 09/20/2010] [Accepted: 09/21/2010] [Indexed: 10/19/2022]
Abstract
Neurons in the brain are often linked by single synaptic contacts (Gulyás et al., 1993) and the probabilistic character of synaptic activity makes it desirable to increase the resolution of physiological experiments by observing the function of the smallest possible number of synaptic terminals, ideally, one. Because they are critically important and technically difficult to resolve, several of the core questions investigated in singe-site experiments have been under study for decades (Auger and Marty, 2000). Many approaches have been taken toward the goal of measuring activity at few synapses, and consideration of the capabilities and limitations of each of these methods permits a review of the contributions each has made possible to present understanding of synaptic function. A number of methodological advances in recent years have increased resolving power. New techniques often build on previous developments and many effective approaches combine components of existing specialized methods with new technology. One theme that emerges is that synaptic properties vary among regions, reducing the utility of general questions such as whether synaptic glutamate saturates receptors or how rapidly synaptic vesicle pools are depleted. For several core questions, multiple studies using different methods have reached similar conclusions, suggesting that consensus may be emerging for some anatomic synapses.
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Affiliation(s)
- David W Nauen
- Department of Neurobiology, University of Pittsburgh School of Medicine, W1401 BST, 200 Lothrop Street, Pittsburgh, PA 15261, United States.
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Malinina E, Druzin M, Johansson S. Differential control of spontaneous and evoked GABA release by presynaptic L-type Ca(2+) channels in the rat medial preoptic nucleus. J Neurophysiol 2010; 104:200-9. [PMID: 20463198 DOI: 10.1152/jn.00570.2009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To clarify the role of presynaptic L-type Ca(2+) channels in GABA-mediated transmission in the medial preoptic nucleus (MPN), spontaneous, miniature, and impulse-evoked inhibitory postsynaptic currents (sIPSCs, mIPSCs, and eIPSCs, respectively) were recorded from MPN neurons in a slice preparation from rat brain. The effects of different stimulus protocols and pharmacological tools to detect contributions of L-type Ca(2+) channels and of Ca(2+)-activated K(+) (K(Ca)) channels were analyzed. Block of L-type channels did not affect the sIPSC and mIPSC properties (frequency, amplitude, decay time course) in the absence of external stimulation but unexpectedly potentiated the eIPSCs evoked at low stimulus frequency (0.1-2.0 Hz). This effect was similar to and overlapping with the effect of K(Ca)-channel blockers. High-frequency stimulation (50 Hz for 10 s) induced a substantial posttetanic potentiation (PTP) of the eIPSC amplitude and of the sIPSC frequency. Block of L-type channels still potentiated the eIPSC during PTP, but in contrast, reduced the sIPSC frequency during PTP. It was concluded that L-type channels provide a means for differential control of spontaneous and impulse-evoked GABA release and that this differential control is prominent during short-term synaptic plasticity. Functional coupling of the presynaptic L-type channels to K(Ca) channels explains the observed effects on eIPSCs.
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Affiliation(s)
- Evgenya Malinina
- Department of Integrative Medical Biology, Section for Physiology, Umeå University, Umeå, Sweden
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Silva JP, Ushkaryov YA. The latrophilins, "split-personality" receptors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 706:59-75. [PMID: 21618826 DOI: 10.1007/978-1-4419-7913-1_5] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Latrophilin, a neuronal "adhesion-G protein-coupled receptor", is the major brain receptor for alpha-latrotoxin, a black widow spidertoxin which stimulates strong neuronal exocytosis in vertebrates. Latrophilin has an unusual structure consisting of two fragments that are produced by the proteolytic cleavage of the parental molecule and that behave independently in the plasma membrane. On binding an agonist, the fragments reassociate and send an intracellular signal. This signal, transduced by a heterotrimeric G protein, causes release of calcium from intracellular stores and massive release of neurotransmitters. Latrophilin represents a phylogenetically conserved family of receptors, with orthologues found in all animals and up to three homologues present in most chordate species. From mammalian homologues, latrophilins 1 and 3 are expressed in neurons, while latrophilin 2 is ubiquitous. Latrophilin 1 may control synapse maturation and exocytosis, whereas latrophilin 2 may be involved in breast cancer. Latrophilins may play different roles during development and in adult animals: thus, LAT-1 determines cell fate in early embryogenesis in Caenorhabditis elegans and controls neurotransmitter release in adult nematodes. This diversity suggests that the functions of latrophilins may be determined by their interactions with respective ligands. The finding of the ligand of latrophilin 1, the large postsynaptic protein lasso, is the first step in the quest for the physiological functions of latrophilins.
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Tada H, Okano HJ, Takagi H, Shibata S, Yao I, Matsumoto M, Saiga T, Nakayama KI, Kashima H, Takahashi T, Setou M, Okano H. Fbxo45, a novel ubiquitin ligase, regulates synaptic activity. J Biol Chem 2009; 285:3840-3849. [PMID: 19996097 DOI: 10.1074/jbc.m109.046284] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neurons communicate with each other through synapses. To establish the precise yet flexible connections that make up neural networks in the brain, continuous synaptic modulation is required. The ubiquitin-proteasome system of protein degradation is one of the critical mechanisms that underlie this process, playing crucial roles in the regulation of synaptic structure and function. We identified a novel ubiquitin ligase, Fbxo45, that functions at synapses. Fbxo45 is evolutionarily conserved and selectively expressed in the nervous system. We demonstrated that the knockdown of Fbxo45 in primary cultured hippocampal neurons resulted in a greater frequency of miniature excitatory postsynaptic currents. We also found that Fbxo45 induces the degradation of a synaptic vesicle-priming factor, Munc13-1. We propose that Fbxo45 plays an important role in the regulation of neurotransmission by modulating Munc13-1 at the synapse.
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Affiliation(s)
- Hirobumi Tada
- From the Department of Physiology, Keio University School of Medicine, Tokyo 160-8582; the Department of Physiology, Yokohama City University School of Medicine, Kanagawa 236-0004; the Bridgestone Laboratory of Developmental and Regenerative Neurobiology, Keio University School of Medicine, Tokyo 160-8582
| | - Hirotaka James Okano
- From the Department of Physiology, Keio University School of Medicine, Tokyo 160-8582; SORST (Solution Oriented Research for Science and Technology), the Japan Science and Technology Agency, Saitama 332-0012.
| | - Hiroshi Takagi
- the Laboratory for Molecular Gerontology, Mitsubishi Kagaku Institute of Life Sciences Setou Group, Tokyo 194-8511
| | - Shinsuke Shibata
- From the Department of Physiology, Keio University School of Medicine, Tokyo 160-8582
| | - Ikuko Yao
- the Laboratory for Molecular Gerontology, Mitsubishi Kagaku Institute of Life Sciences Setou Group, Tokyo 194-8511
| | - Masaki Matsumoto
- the Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, and; CREST (Core Research for Evolutional Science and Technology), the Japan Science and Technology Agency, Saitama 332-0012
| | - Toru Saiga
- the Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, and; CREST (Core Research for Evolutional Science and Technology), the Japan Science and Technology Agency, Saitama 332-0012
| | - Keiichi I Nakayama
- the Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, and; CREST (Core Research for Evolutional Science and Technology), the Japan Science and Technology Agency, Saitama 332-0012
| | - Haruo Kashima
- the Department of Neuropsychiatry, Keio University School of Medicine, Tokyo 160-8582
| | - Takuya Takahashi
- the Department of Physiology, Yokohama City University School of Medicine, Kanagawa 236-0004
| | - Mitsutoshi Setou
- the Laboratory for Molecular Gerontology, Mitsubishi Kagaku Institute of Life Sciences Setou Group, Tokyo 194-8511; the Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, and; the Department of Molecular Anatomy, Hamamatsu University School of Medicine, Shizuoka 431-3192, Japan.
| | - Hideyuki Okano
- From the Department of Physiology, Keio University School of Medicine, Tokyo 160-8582; the Bridgestone Laboratory of Developmental and Regenerative Neurobiology, Keio University School of Medicine, Tokyo 160-8582; SORST (Solution Oriented Research for Science and Technology), the Japan Science and Technology Agency, Saitama 332-0012.
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Abstract
For more than three decades, the venom of the black widow spider and its principal active components, latrotoxins, have been used to induce release of neurotransmitters and hormones and to study the mechanisms of exocytosis. Given the complex nature of alpha--latrotoxin (alpha-LTX) actions, this research has been continuously overshadowed by many enigmas, misconceptions and perpetual changes of the underlying hypotheses. Some of the toxin's mechanisms of action are still not completely understood. Despite all these difficulties, the extensive work of several generations of neurobiologists has brought about a great deal of fascinating insights into pre-synaptic processes and has led to the discovery of several novel proteins and synaptic systems. For example, alpha-LTX studies have contributed to the widespread acceptance of the vesicular theory of transmitter release. Pre-synaptic receptors for alpha-LTX--neurexins, latrophilins and protein tyrosine phosphatase sigma--and their endogenous ligands have now become centrepieces of their own areas of research, with a potential of uncovering new mechanisms of synapse formation and regulation that may have medical implications. However, any future success of alpha-LTX research will require a better understanding of this unusual natural tool and a more precise dissection of its multiple mechanisms.
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Affiliation(s)
- John-Paul Silva
- Division of Cell and Molecular Biology, Imperial College London, Exhibition Road, London, UK
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