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Baraldi C, Lo Castro F, Ornello R, Sacco S, Pani L, Guerzoni S. OnabotulinumtoxinA: Still the Present for Chronic Migraine. Toxins (Basel) 2023; 15:59. [PMID: 36668879 PMCID: PMC9865956 DOI: 10.3390/toxins15010059] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 12/28/2022] [Accepted: 01/04/2023] [Indexed: 01/13/2023] Open
Abstract
OnabotulinumtoxinA (BT-A) is one of the few drugs approved for the preventive treatment of chronic migraine (CM). Despite this, some aspects of its mechanism of action are still a matter of debate, and the precise magnitude of BT-A effects needs to be completely elucidated. BT-A acts primarily upon trigeminal and cervical nerve endings, by inhibiting the release of inflammatory mediators such as calcitonin gene-related peptide, as well as reducing the insertion of ionotropic and metabotropic receptors into the neuronal membrane. These actions increase the depolarization threshold of trigeminal and cervical nerve fibers, thus reducing their activation. The central actions of BT-A are still a matter of debate: a retrograde axonal transport has been postulated, but not clearly assessed in humans. Clinically, the efficacy of BT-A in CM has been assessed by large, randomized placebo-controlled trials, such as the Phase 3 REsearch Evaluating Migraine Prophylaxis Therapy (PREEMPT) trials. Those results were also confirmed in a wide range of open-label studies, even for long-term periods. Recently, novel findings have led to a better understanding of its pharmacological actions and clinical usefulness in migraine prevention. This narrative review summarizes, updates and critically revises the available data on BT-A and its possible implementation in chronic migraine. Moreover, the current role of BT-A in CM treatment has been discussed.
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Affiliation(s)
- Carlo Baraldi
- Department of Biomedical, Metabolic and Neural Sciences, PhD School in Neurosciences, University of Modena and Reggio Emilia, 41124 Modena, Italy
| | - Flavia Lo Castro
- Department of Biomedical, Metabolic and Neural Sciences, Post Graduate School of Pharmacology and Clinical Toxicology, University of Modena and Reggio Emilia, 41124 Modena, Italy
| | - Raffaele Ornello
- Department of Applied Clinical Sciences and Biotechnology, University of L’Aquila, 67100 L’Aquila, Italy
| | - Simona Sacco
- Department of Applied Clinical Sciences and Biotechnology, University of L’Aquila, 67100 L’Aquila, Italy
| | - Luca Pani
- Department of Biomedical, Metabolic and Neural Sciences, Pharmacology Unit, University of Modena and Reggio Emilia, 41124 Modena, Italy
- Department of Psychiatry and Behavioral Sciences, University of Miami, Miami, FL 33136, USA
- VeraSci, Durham, NC 27707, USA
- Department of Specialist Medicines, Digital and Predictive Medicine, Pharmacology and Clinical Metabolic Toxicology-Headache Center and Drug Abuse, Laboratory of Clinical Pharmacology and Pharmacogenomics, AOU Policlinico Di Modena, 41124 Modena, Italy
| | - Simona Guerzoni
- Department of Specialist Medicines, Digital and Predictive Medicine, Pharmacology and Clinical Metabolic Toxicology-Headache Center and Drug Abuse, Laboratory of Clinical Pharmacology and Pharmacogenomics, AOU Policlinico Di Modena, 41124 Modena, Italy
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Heuser JE. The Structural Basis of Long-Term Potentiation in Hippocampal Synapses, Revealed by Electron Microscopy Imaging of Lanthanum-Induced Synaptic Vesicle Recycling. Front Cell Neurosci 2022; 16:920360. [PMID: 35978856 PMCID: PMC9376242 DOI: 10.3389/fncel.2022.920360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 05/05/2022] [Indexed: 11/29/2022] Open
Abstract
Hippocampal neurons in dissociated cell cultures were exposed to the trivalent cation lanthanum for short periods (15–30 min) and prepared for electron microscopy (EM), to evaluate the stimulatory effects of this cation on synaptic ultrastructure. Not only were characteristic ultrastructural changes of exaggerated synaptic vesicle turnover seen within the presynapses of these cultures—including synaptic vesicle depletion and proliferation of vesicle-recycling structures—but the overall architecture of a large proportion of the synapses in the cultures was dramatically altered, due to large postsynaptic “bulges” or herniations into the presynapses. Moreover, in most cases, these postsynaptic herniations or protrusions produced by lanthanum were seen by EM to distort or break or “perforate” the so-called postsynaptic densities (PSDs) that harbor receptors and recognition molecules essential for synaptic function. These dramatic EM observations lead us to postulate that such PSD breakages or “perforations” could very possibly create essential substrates or “tags” for synaptic growth, simply by creating fragmented free edges around the PSDs, into which new receptors and recognition molecules could be recruited more easily, and thus, they could represent the physical substrate for the important synaptic growth process known as “long-term potentiation” (LTP). All of this was created simply in hippocampal dissociated cell cultures, and simply by pushing synaptic vesicle recycling way beyond its normal limits with the trivalent cation lanthanum, but we argued in this report that such fundamental changes in synaptic architecture—given that they can occur at all—could also occur at the extremes of normal neuronal activity, which are presumed to lead to learning and memory.
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Quantum-dot-labeled synuclein seed assay identifies drugs modulating the experimental prion-like transmission. Commun Biol 2022; 5:636. [PMID: 35768587 PMCID: PMC9243017 DOI: 10.1038/s42003-022-03590-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 06/15/2022] [Indexed: 11/08/2022] Open
Abstract
Synucleinopathies are neurodegenerative disorders including Parkinson disease (PD), dementia with Lewy body (DLB), and multiple system atrophy (MSA) that involve deposits of the protein alpha-synuclein (α-syn) in the brain. The inoculation of α-syn aggregates derived from synucleinopathy or preformed fibrils (PFF) formed in vitro induces misfolding and deposition of endogenous α-syn. This is referred to as prion-like transmission, and the mechanism is still unknown. In this study, we label α-syn PFF with quantum dots and visualize their movement directly in acute slices of brain tissue inoculated with α-syn PFF seeds. Using this system, we find that the trafficking of α-syn seeds is dependent on fast axonal transport and the seed spreading is dependent on endocytosis and neuronal activity. We also observe pharmacological effects on α-syn seed spreading; clinically available drugs including riluzole are effective in reducing the spread of α-syn seeds and this effect is also observed in vivo. Our quantum-dot-labeled α-syn seed assay system combined with in vivo transmission experiment reveals an early phase of transmission, in which uptake and spreading of seeds occur depending on neuronal activity, and a later phase, in which seeds induce the propagation of endogenous misfolded α-syn.
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Fabris F, Šoštarić P, Matak I, Binz T, Toffan A, Simonato M, Montecucco C, Pirazzini M, Rossetto O. Detection of VAMP Proteolysis by Tetanus and Botulinum Neurotoxin Type B In Vivo with a Cleavage-Specific Antibody. Int J Mol Sci 2022; 23:ijms23084355. [PMID: 35457172 PMCID: PMC9024618 DOI: 10.3390/ijms23084355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 04/08/2022] [Accepted: 04/12/2022] [Indexed: 11/17/2022] Open
Abstract
Tetanus and Botulinum type B neurotoxins are bacterial metalloproteases that specifically cleave the vesicle-associated membrane protein VAMP at an identical peptide bond, resulting in inhibition of neuroexocytosis. The minute amounts of these neurotoxins commonly used in experimental animals are not detectable, nor is detection of their VAMP substrate sensitive enough. The immune detection of the cleaved substrate is much more sensitive, as we have previously shown for botulinum neurotoxin type A. Here, we describe the production in rabbit of a polyclonal antibody raised versus a peptide encompassing the 13 residues C-terminal with respect to the neurotoxin cleavage site. The antibody was affinity purified and found to recognize, with high specificity and selectivity, the novel N-terminus of VAMP that becomes exposed after cleavage by tetanus toxin and botulinum toxin type B. This antibody recognizes the neoepitope not only in native and denatured VAMP but also in cultured neurons and in neurons in vivo in neurotoxin-treated mice or rats, suggesting the great potential of this novel tool to elucidate tetanus and botulinum B toxin activity in vivo.
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Affiliation(s)
- Federico Fabris
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy; (F.F.); (C.M.)
| | - Petra Šoštarić
- Department of Pharmacology, School of Medicine, University of Zagreb, Šalata 11, 10000 Zagreb, Croatia; (P.Š.); (I.M.)
| | - Ivica Matak
- Department of Pharmacology, School of Medicine, University of Zagreb, Šalata 11, 10000 Zagreb, Croatia; (P.Š.); (I.M.)
| | - Thomas Binz
- Institute of Cellular Biochemistry, Hannover Medical School, Carl-Neuberg-Straße 1, 30625 Hannover, Germany;
| | - Anna Toffan
- Istituto Zooprofilattico Sperimentale delle Venezie, Viale dell’Università 10, 35020 Legnaro, Italy;
| | - Morena Simonato
- Institute of Neuroscience, Italian Research Council, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy;
| | - Cesare Montecucco
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy; (F.F.); (C.M.)
- Institute of Neuroscience, Italian Research Council, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy;
| | - Marco Pirazzini
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy; (F.F.); (C.M.)
- Interdepartmental Research Center of Myology CIR-Myo, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy
- Correspondence: (M.P.); (O.R.)
| | - Ornella Rossetto
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy; (F.F.); (C.M.)
- Institute of Neuroscience, Italian Research Council, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy;
- Interdepartmental Research Center of Myology CIR-Myo, University of Padova, Via Ugo Bassi 58/B, 35131 Padova, Italy
- Correspondence: (M.P.); (O.R.)
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A Deep Learning Approach with Data Augmentation to Predict Novel Spider Neurotoxic Peptides. Int J Mol Sci 2021; 22:ijms222212291. [PMID: 34830173 PMCID: PMC8619404 DOI: 10.3390/ijms222212291] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 11/09/2021] [Accepted: 11/11/2021] [Indexed: 11/17/2022] Open
Abstract
As major components of spider venoms, neurotoxic peptides exhibit structural diversity, target specificity, and have great pharmaceutical potential. Deep learning may be an alternative to the laborious and time-consuming methods for identifying these peptides. However, the major hurdle in developing a deep learning model is the limited data on neurotoxic peptides. Here, we present a peptide data augmentation method that improves the recognition of neurotoxic peptides via a convolutional neural network model. The neurotoxic peptides were augmented with the known neurotoxic peptides from UniProt database, and the models were trained using a training set with or without the generated sequences to verify the augmented data. The model trained with the augmented dataset outperformed the one with the unaugmented dataset, achieving accuracy of 0.9953, precision of 0.9922, recall of 0.9984, and F1 score of 0.9953 in simulation dataset. From the set of all RNA transcripts of Callobius koreanus spider, we discovered neurotoxic peptides via the model, resulting in 275 putative peptides of which 252 novel sequences and only 23 sequences showing homology with the known peptides by Basic Local Alignment Search Tool. Among these 275 peptides, four were selected and shown to have neuromodulatory effects on the human neuroblastoma cell line SH-SY5Y. The augmentation method presented here may be applied to the identification of other functional peptides from biological resources with insufficient data.
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Gustafsson JK, Davis JE, Rappai T, McDonald KG, Kulkarni DH, Knoop KA, Hogan SP, Fitzpatrick JAJ, Lencer WI, Newberry RD. Intestinal goblet cells sample and deliver lumenal antigens by regulated endocytic uptake and transcytosis. eLife 2021; 10:e67292. [PMID: 34677124 PMCID: PMC8594945 DOI: 10.7554/elife.67292] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 10/20/2021] [Indexed: 12/12/2022] Open
Abstract
Intestinal goblet cells maintain the protective epithelial barrier through mucus secretion and yet sample lumenal substances for immune processing through formation of goblet cell associated antigen passages (GAPs). The cellular biology of GAPs and how these divergent processes are balanced and regulated by goblet cells remains unknown. Using high-resolution light and electron microscopy, we found that in mice, GAPs were formed by an acetylcholine (ACh)-dependent endocytic event remarkable for delivery of fluid-phase cargo retrograde into the trans-golgi network and across the cell by transcytosis - in addition to the expected transport of fluid-phase cargo by endosomes to multi-vesicular bodies and lysosomes. While ACh also induced goblet cells to secrete mucins, ACh-induced GAP formation and mucin secretion were functionally independent and mediated by different receptors and signaling pathways, enabling goblet cells to differentially regulate these processes to accommodate the dynamically changing demands of the mucosal environment for barrier maintenance and sampling of lumenal substances.
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Affiliation(s)
- Jenny K Gustafsson
- Department of Neuroscience and Physiology, University of GothenburgGothenburgSweden
- Department of Internal Medicine, Washington University School of MedicineSt LouisUnited States
| | - Jazmyne E Davis
- Department of Internal Medicine, Washington University School of MedicineSt LouisUnited States
| | - Tracy Rappai
- Center for Cellular Imaging, Washington University School of MedicineSt LouisUnited States
| | - Keely G McDonald
- Department of Internal Medicine, Washington University School of MedicineSt LouisUnited States
| | - Devesha H Kulkarni
- Department of Internal Medicine, Washington University School of MedicineSt LouisUnited States
| | - Kathryn A Knoop
- Department of Internal Medicine, Washington University School of MedicineSt LouisUnited States
| | - Simon P Hogan
- Mary H. Weiser Food Allergy Center, University of Michigan School of Medicine,Ann ArborUnited States
| | - James AJ Fitzpatrick
- Center for Cellular Imaging, Washington University School of MedicineSt LouisUnited States
- Department of Cell Biology &Physiology, Washington University School of MedicineSt LouisUnited States
- Department of Neuroscience, Washington University School of MedicineSt LouisUnited States
- Department of Biomedical Engineering, Washington University in St. LouisSt. LouisUnited States
| | - Wayne I Lencer
- Department of Pediatrics, Harvard Medical SchoolBostonUnited States
- Division of Gastroenterology, Nutrition and Hepatology, Boston Children’s HospitalBostonUnited States
- Harvard Digestive Disease Center, Harvard Medical SchoolBostonUnited States
| | - Rodney D Newberry
- Department of Internal Medicine, Washington University School of MedicineSt LouisUnited States
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7
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Solabre Valois L, Shi V(H, Bishop P, Zhu B, Nakamura Y, Wilkinson KA, Henley JM. Neurotrophic effects of Botulinum neurotoxin type A in hippocampal neurons involve activation of Rac1 by the non-catalytic heavy chain (HC C/A). IBRO Neurosci Rep 2021; 10:196-207. [PMID: 34041508 PMCID: PMC8143998 DOI: 10.1016/j.ibneur.2021.04.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 04/22/2021] [Indexed: 12/19/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are extremely potent naturally occurring poisons that act by silencing neurotransmission. Intriguingly, in addition to preventing presynaptic vesicle fusion, BoNT serotype A (BoNT/A) can also promote axonal regeneration in preclinical models. Here we report that the non-toxic C-terminal region of the receptor-binding domain of heavy chain BoNT/A (HCC/A) activates the small GTPase Rac1 and ERK pathway to potentiate axonal outgrowth, dendritic protrusion formation and synaptic vesicle release in hippocampal neurons. These data are consistent with HCC/A exerting neurotrophic properties, at least in part, independent of any BoNT catalytic activity or toxic effect.
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Affiliation(s)
- Luis Solabre Valois
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Vanilla (Hua) Shi
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Paul Bishop
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Bangfu Zhu
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Yasuko Nakamura
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Kevin A. Wilkinson
- School of Biochemistry, Centre for Synaptic Plasticity, Biomedical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
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8
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Winner BM, Bodt SML, McNutt PM. Special Delivery: Potential Mechanisms of Botulinum Neurotoxin Uptake and Trafficking within Motor Nerve Terminals. Int J Mol Sci 2020; 21:ijms21228715. [PMID: 33218099 PMCID: PMC7698961 DOI: 10.3390/ijms21228715] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Revised: 11/11/2020] [Accepted: 11/16/2020] [Indexed: 02/06/2023] Open
Abstract
Botulinum neurotoxins (BoNTs) are highly potent, neuroparalytic protein toxins that block the release of acetylcholine from motor neurons and autonomic synapses. The unparalleled toxicity of BoNTs results from the highly specific and localized cleavage of presynaptic proteins required for nerve transmission. Currently, the only pharmacotherapy for botulism is prophylaxis with antitoxin, which becomes progressively less effective as symptoms develop. Treatment for symptomatic botulism is limited to supportive care and artificial ventilation until respiratory function spontaneously recovers, which can take weeks or longer. Mechanistic insights into intracellular toxin behavior have progressed significantly since it was shown that toxins exploit synaptic endocytosis for entry into the nerve terminal, but fundamental questions about host-toxin interactions remain unanswered. Chief among these are mechanisms by which BoNT is internalized into neurons and trafficked to sites of molecular toxicity. Elucidating how receptor-bound toxin is internalized and conditions under which the toxin light chain engages with target SNARE proteins is critical for understanding the dynamics of intoxication and identifying novel therapeutics. Here, we discuss the implications of newly discovered modes of synaptic vesicle recycling on BoNT uptake and intraneuronal trafficking.
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Affiliation(s)
- Brittany M. Winner
- United States Army Medical Research Institute of Chemical Defense, Gunpowder, MD 21047, USA;
| | - Skylar M. L. Bodt
- Department of Cellular and Molecular Physiology, Penn State College of Medicine, Hershey, PA 17033, USA;
| | - Patrick M. McNutt
- Wake Forest Institute for Regenerative Medicine, Wake Forest University, Winston-Salem, NC 27101, USA
- Correspondence:
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Poulain B, Lemichez E, Popoff MR. Neuronal selectivity of botulinum neurotoxins. Toxicon 2020; 178:20-32. [PMID: 32094099 DOI: 10.1016/j.toxicon.2020.02.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 02/03/2020] [Accepted: 02/10/2020] [Indexed: 12/12/2022]
Abstract
Botulinum neurotoxins (BoNTs) are highly potent toxins responsible for a severe disease, called botulism. They are also efficient therapeutic tools with an increasing number of indications ranging from neuromuscular dysfunction to hypersecretion syndrome, pain release, depression as well as cosmetic application. BoNTs are known to mainly target the motor-neurons terminals and to induce flaccid paralysis. BoNTs recognize a specific double receptor on neuronal cells consisting of gangliosides and synaptic vesicle protein, SV2 or synaptotagmin. Using cultured neuronal cells, BoNTs have been established blocking the release of a wide variety of neurotransmitters. However, BoNTs are more potent in motor-neurons than in the other neuronal cell types. In in vivo models, BoNT/A impairs the cholinergic neuronal transmission at the motor-neurons but also at neurons controlling secretions and smooth muscle neurons, and blocks several neuronal pathways including excitatory, inhibitory, and sensitive neurons. However, only a few reports investigated the neuronal selectivity of BoNTs in vivo. In the intestinal wall, BoNT/A and BoNT/B target mainly the cholinergic neurons and to a lower extent the other non-cholinergic neurons including serotonergic, glutamatergic, GABAergic, and VIP-neurons. The in vivo effects induced by BoNTs on the non-cholinergic neurons remain to be precisely investigated. We report here a literature review of the neuronal selectivity of BoNTs.
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Affiliation(s)
- Bernard Poulain
- Université de Strasbourg, CNRS, Institut des Neurosciences Cellulaires et Intégratives, Strasbourg, France
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Carbone E, Borges R, Eiden LE, García AG, Hernández‐Cruz A. Chromaffin Cells of the Adrenal Medulla: Physiology, Pharmacology, and Disease. Compr Physiol 2019; 9:1443-1502. [DOI: 10.1002/cphy.c190003] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Okuzumi A, Kurosawa M, Hatano T, Takanashi M, Nojiri S, Fukuhara T, Yamanaka T, Miyazaki H, Yoshinaga S, Furukawa Y, Shimogori T, Hattori N, Nukina N. Rapid dissemination of alpha-synuclein seeds through neural circuits in an in-vivo prion-like seeding experiment. Acta Neuropathol Commun 2018; 6:96. [PMID: 30231908 PMCID: PMC6145187 DOI: 10.1186/s40478-018-0587-0] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 08/21/2018] [Indexed: 02/26/2023] Open
Abstract
Accumulating evidence suggests that the lesions of Parkinson's disease (PD) expand due to transneuronal spreading of fibrils composed of misfolded alpha-synuclein (a-syn), over the course of 5-10 years. However, the precise mechanisms and the processes underlying the spread of these fibril seeds have not been clarified in vivo. Here, we investigated the speed of a-syn transmission, which has not been a focus of previous a-syn transmission experiments, and whether a-syn pathologies spread in a neural circuit-dependent manner in the mouse brain. We injected a-syn preformed fibrils (PFFs), which are seeds for the propagation of a-syn deposits, either before or after callosotomy, to disconnect bilateral hemispheric connections. In mice that underwent callosotomy before the injection, the propagation of a-syn pathology to the contralateral hemisphere was clearly reduced. In contrast, mice that underwent callosotomy 24 h after a-syn PFFs injection showed a-syn pathology similar to that seen in mice without callosotomy. These results suggest that a-syn seeds are rapidly disseminated through neuronal circuits immediately after seed injection, in a prion-like seeding experiment in vivo, although it is believed that clinical a-syn pathologies take years to spread throughout the brain. In addition, we found that botulinum toxin B blocked the transsynaptic transmission of a-syn seeds by specifically inactivating the synaptic vesicle fusion machinery. This study offers a novel concept regarding a-syn propagation, based on the Braak hypothesis, and also cautions that experimental transmission systems may be examining a unique type of transmission, which differs from the clinical disease state.
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Affiliation(s)
- Ayami Okuzumi
- Department of Neurology, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan
| | - Masaru Kurosawa
- Institute for Environmental and Gender-specific Medicine, Juntendo University Graduate School of Medicine, 2-1-1 Tomioka, Urayasu-shi, Chiba, 279-0021, Japan
| | - Taku Hatano
- Department of Neurology, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan
| | - Masashi Takanashi
- Department of Neurology Juntendo University Koshigaya Hospital, 560 Fukuroyama, Koshigaya city, Saitama, 343-0032, Japan
| | - Shuuko Nojiri
- Medical Technology Innovation Center, Clinical Research and Trial Center, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Takeshi Fukuhara
- Department of Neurology, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan
| | - Tomoyuki Yamanaka
- Laboratory of Structural Neuropathology, Doshisha University Graduate School of Brain Science, 1-3 Tatara Miyakodani, Kyotanabe-shi, Kyoto, 610-0394, Japan
| | - Haruko Miyazaki
- Laboratory of Structural Neuropathology, Doshisha University Graduate School of Brain Science, 1-3 Tatara Miyakodani, Kyotanabe-shi, Kyoto, 610-0394, Japan
| | - Saki Yoshinaga
- Laboratory of Structural Neuropathology, Doshisha University Graduate School of Brain Science, 1-3 Tatara Miyakodani, Kyotanabe-shi, Kyoto, 610-0394, Japan
| | - Yoshiaki Furukawa
- Laboratory for Mechanistic Chemistry of Biomolecules, Department of Chemistry, Keio University, 3-14-1 Hiyoshi, Kohoku, Yokohama, 223-8522, Japan
| | - Tomomi Shimogori
- Laboratory for Molecular Mechanisms of Brain Development, RIKEN Center for Brain Science, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Nobutaka Hattori
- Department of Neurology, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan.
| | - Nobuyuki Nukina
- Department of Neurology, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan.
- Laboratory of Structural Neuropathology, Doshisha University Graduate School of Brain Science, 1-3 Tatara Miyakodani, Kyotanabe-shi, Kyoto, 610-0394, Japan.
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Zuverink M, Barbieri JT. Protein Toxins That Utilize Gangliosides as Host Receptors. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2018; 156:325-354. [PMID: 29747819 DOI: 10.1016/bs.pmbts.2017.11.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Subsets of protein toxins utilize gangliosides as host receptors. Gangliosides are preferred receptors due to their extracellular localization on the eukaryotic cell and due to their essential nature in host physiology. Glycosphingolipids, including gangliosides, are mediators of signal transduction within and between eukaryotic cells. Protein toxins possess AB structure-function organization, where the A domain encodes a catalytic function for the posttranslational modification of a host macromolecule, including proteins and nucleic acids, and a B domain, which encodes host receptor recognition, including proteins and glycosphingolipids, alone or in combination. Protein toxins use similar strategies to bind glycans by pockets and loops, generally employing hydrogen bonding and aromatic stacking to stabilize interactions with sugars. In some cases, glycan binding facilitates uptake, while in other cases, cross-linking or a second receptor is necessary to stimulate entry. The affinity that protein toxins have for host glycans is necessary for tissue targeting, but not always sufficient to cause disease. In addition to affinity for binding the glycan, the lipid moiety also plays an important role in productive uptake and tissue tropism. Upon endocytosis, the protein toxin must escape to another intracellular compartment or into cytosol to modify a host substrate, modulating host signaling, often resulting in cytotoxic or apoptotic events in the cell, and a unique morbidity for the organism. The study of protein toxins that utilize gangliosides as host receptors has illuminated numerous eukaryotic cellular processes, identified the basis for developing interventions to prevent disease through vaccines and control bacterial diseases through therapies. In addition, subsets of these protein toxins have been utilized as therapeutic agents to treat numerous human inflictions.
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Khounlo R, Kim J, Yin L, Shin YK. Botulinum Toxins A and E Inflict Dynamic Destabilization on t-SNARE to Impair SNARE Assembly and Membrane Fusion. Structure 2017; 25:1679-1686.e5. [PMID: 29033286 PMCID: PMC5685167 DOI: 10.1016/j.str.2017.09.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 08/24/2017] [Accepted: 09/12/2017] [Indexed: 01/08/2023]
Abstract
Botulinum toxins (BoNTs) A and E block neurotransmitter release by specifically cleaving the C- terminal ends of SNAP-25, a plasma membrane SNARE protein. Here, we find that SNAP-25A and E, the cleavage products of BoNT A and E, respectively, terminate membrane fusion via completely different mechanisms. Combined studies of single-molecule FRET and single-vesicle fusion assays reveal that SNAP-25E is incapable of supporting SNARE pairing and thus, vesicle docking. In contrast, SNAP-25A facilitates robust SNARE pairing and vesicle docking with somewhat reduced SNARE zippering, which leads to severe impairment of fusion pore opening. The electron paramagnetic resonance results show that the discrepancy between SNAP-25A and E might stem from the extent of the dynamic destabilization of the t-SNARE core at the N-terminal half, which plays a pivotal role in nucleating SNARE complex formation. Thus, the results provide insights into the structure/dynamics-based mechanism by which BoNT A and E impair membrane fusion.
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Affiliation(s)
- Ryan Khounlo
- Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - Jaewook Kim
- Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - Linxiang Yin
- Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - Yeon-Kyun Shin
- Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology, Iowa State University, Ames, IA 50011, USA.
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14
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Pirazzini M, Rossetto O, Eleopra R, Montecucco C. Botulinum Neurotoxins: Biology, Pharmacology, and Toxicology. Pharmacol Rev 2017; 69:200-235. [PMID: 28356439 PMCID: PMC5394922 DOI: 10.1124/pr.116.012658] [Citation(s) in RCA: 410] [Impact Index Per Article: 58.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The study of botulinum neurotoxins (BoNT) is rapidly progressing in many aspects.
Novel BoNTs are being discovered owing to next generation sequencing, but their
biologic and pharmacological properties remain largely unknown. The molecular
structure of the large protein complexes that the toxin forms with accessory
proteins, which are included in some BoNT type A1 and B1 pharmacological
preparations, have been determined. By far the largest effort has been dedicated to
the testing and validation of BoNTs as therapeutic agents in an ever increasing
number of applications, including pain therapy. BoNT type A1 has been also exploited
in a variety of cosmetic treatments, alone or in combination with other agents, and
this specific market has reached the size of the one dedicated to the treatment of
medical syndromes. The pharmacological properties and mode of action of BoNTs have
shed light on general principles of neuronal transport and protein-protein
interactions and are stimulating basic science studies. Moreover, the wide array of
BoNTs discovered and to be discovered and the production of recombinant BoNTs endowed
with specific properties suggest novel uses in therapeutics with increasing
disease/symptom specifity. These recent developments are reviewed here to provide an
updated picture of the biologic mechanism of action of BoNTs, of their increasing use
in pharmacology and in cosmetics, and of their toxicology.
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Affiliation(s)
- Marco Pirazzini
- Department of Biomedical Sciences, University of Padova, Italy (M.P., O.R., C.M.); Neurologic Department, University-Hospital S. Maria della Misericordia, Udine, Italy (R.E.); and Consiglio Nazionale delle Ricerche, Institute of Neuroscience, University of Padova, Italy (C.M.)
| | - Ornella Rossetto
- Department of Biomedical Sciences, University of Padova, Italy (M.P., O.R., C.M.); Neurologic Department, University-Hospital S. Maria della Misericordia, Udine, Italy (R.E.); and Consiglio Nazionale delle Ricerche, Institute of Neuroscience, University of Padova, Italy (C.M.)
| | - Roberto Eleopra
- Department of Biomedical Sciences, University of Padova, Italy (M.P., O.R., C.M.); Neurologic Department, University-Hospital S. Maria della Misericordia, Udine, Italy (R.E.); and Consiglio Nazionale delle Ricerche, Institute of Neuroscience, University of Padova, Italy (C.M.)
| | - Cesare Montecucco
- Department of Biomedical Sciences, University of Padova, Italy (M.P., O.R., C.M.); Neurologic Department, University-Hospital S. Maria della Misericordia, Udine, Italy (R.E.); and Consiglio Nazionale delle Ricerche, Institute of Neuroscience, University of Padova, Italy (C.M.)
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15
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Connan C, Popoff MR. Uptake of Clostridial Neurotoxins into Cells and Dissemination. Curr Top Microbiol Immunol 2017; 406:39-78. [PMID: 28879524 DOI: 10.1007/82_2017_50] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Clostridial neurotoxins, botulinum neurotoxins (BoNT) and tetanus neurotoxin (TeNT), are potent toxins, which are responsible for severe neurological diseases in man and animals. BoNTs induce a flaccid paralysis (botulism) by inhibiting acetylcholine release at the neuromuscular junctions, whereas TeNT causes a spastic paralysis (tetanus) by blocking the neurotransmitter release (glycine, GABA) in inhibitory interneurons within the central nervous system. Clostridial neurotoxins recognize specific receptor(s) on the target neuronal cells and enter via a receptor-mediated endocytosis. They transit through an acidic compartment which allows the translocation of the catalytic chain into the cytosol, a prerequisite step for the intracellular activity of the neurotoxins. TeNT migrates to the central nervous system by using a motor neuron as transport cell. TeNT enters a neutral pH compartment and undergoes a retrograde axonal transport to the spinal cord or brain, where the whole undissociated toxin is delivered and interacts with target neurons. Botulism most often results from ingestion of food contaminated with BoNT. Thus, BoNT passes through the intestinal epithelial barrier mainly via a transcytotic mechanism and then diffuses or is transported to the neuromuscular junctions by the lymph or blood circulation. Indeed, clostridial neurotoxins are specific neurotoxins which transit through a transport cell to gain access to the target neuron, and use distinct trafficking pathways in both cell types.
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Affiliation(s)
- Chloé Connan
- Unité Des Bactéries Anaérobies et Toxines, Institut Pasteur, 25 Rue Du Dr Roux, 75724, Paris Cedex 15, France
| | - Michel R Popoff
- Unité Des Bactéries Anaérobies et Toxines, Institut Pasteur, 25 Rue Du Dr Roux, 75724, Paris Cedex 15, France.
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16
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da Silva LB, Poulsen JN, Arendt-Nielsen L, Gazerani P. Botulinum neurotoxin type A modulates vesicular release of glutamate from satellite glial cells. J Cell Mol Med 2015; 19:1900-9. [PMID: 25754332 PMCID: PMC4549040 DOI: 10.1111/jcmm.12562] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Accepted: 01/20/2015] [Indexed: 01/06/2023] Open
Abstract
This study investigated the presence of cell membrane docking proteins synaptosomal-associated protein, 25 and 23 kD (SNAP-25 and SNAP-23) in satellite glial cells (SGCs) of rat trigeminal ganglion; whether cultured SGCs would release glutamate in a time- and calcium-dependent manner following calcium-ionophore ionomycin stimulation; and if botulinum neurotoxin type A (BoNTA), in a dose-dependent manner, could block or decrease vesicular release of glutamate. SGCs were isolated from the trigeminal ganglia (TG) of adult Wistar rats and cultured for 7 days. The presence of SNAPs in TG sections and isolated SGCs were investigated using immunohistochemistry and immunocytochemistry, respectively. SGCs were stimulated with ionomycin (5 μM for 4, 8, 12 and 30 min.) to release glutamate. SGCs were then pre-incubated with BoNTA (24 hrs with 0.1, 1, 10 and 100 pM) to investigate if BoNTA could potentially block ionomycin-stimulated glutamate release. Glutamate concentrations were measured by ELISA. SNAP-25 and SNAP-23 were present in SGCs in TG sections and in cultured SGCs. Ionomycin significantly increased glutamate release from cultured SGCs 30 min. following the treatment (P < 0.001). BoNTA (100 pM) significantly decreased glutamate release (P < 0.01). Results from this study demonstrated that SGCs, when stimulated with ionomycin, released glutamate that was inhibited by BoNTA, possibly through cleavage of SNAP-25 and/or SNAP-23. These novel findings demonstrate the existence of vesicular glutamate release from SGCs, which could potentially play a role in the trigeminal sensory transmission. In addition, interaction of BoNTA with non-neuronal cells at the level of TG suggests a potential analgesic mechanism of action of BoNTA.
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Affiliation(s)
- Larissa Bittencourt da Silva
- Center for Sensory - Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg UniversityAalborg East, Denmark
| | - Jeppe Nørgaard Poulsen
- Center for Sensory - Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg UniversityAalborg East, Denmark
| | - Lars Arendt-Nielsen
- Center for Sensory - Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg UniversityAalborg East, Denmark
| | - Parisa Gazerani
- Center for Sensory - Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg UniversityAalborg East, Denmark
- Laboratory for Cancer Biology, Biomedicine, Department of Health Science and Technology, Faculty of Medicine, Aalborg UniversityAalborg East, Denmark
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17
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Pellett S, Tepp WH, Scherf JM, Johnson EA. Botulinum Neurotoxins Can Enter Cultured Neurons Independent of Synaptic Vesicle Recycling. PLoS One 2015; 10:e0133737. [PMID: 26207366 PMCID: PMC4514655 DOI: 10.1371/journal.pone.0133737] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 06/15/2015] [Indexed: 11/25/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are the causative agent of the severe and long-lasting disease botulism. At least seven different serotypes of BoNTs (denoted A-G) have been described. All BoNTs enter human or animal neuronal cells via receptor mediated endocytosis and cleave cytosolic SNARE proteins, resulting in a block of synaptic vesicle exocytosis, leading to the flaccid paralysis characteristic of botulism. Previous data have indicated that once a neuronal cell has been intoxicated by a BoNT, further entry of the same or other BoNTs is prevented due to disruption of synaptic vesicle recycling. However, it has also been shown that cultured neurons exposed to BoNT/A are still capable of taking up BoNT/E. In this report we show that in general BoNTs can enter cultured human or mouse neuronal cells that have previously been intoxicated with another BoNT serotype. Quantitative analysis of cell entry by assessing SNARE cleavage revealed none or only a minor difference in the efficiency of uptake of BoNTs into previously intoxicated neurons. Examination of the endocytic entry pathway by specific endocytosis inhibitors indicated that BoNTs are taken up by clathrin coated pits in both non pre-exposed and pre-exposed neurons. LDH release assays indicated that hiPSC derived neurons exposed consecutively to two different BoNT serotypes remained viable and healthy except in the case of BoNT/E or combinations of BoNT/E with BoNT/B, /D, or /F. Overall, our data indicate that previous intoxication of neuronal cells with BoNT does not inhibit further uptake of BoNTs.
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Affiliation(s)
- Sabine Pellett
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, 53706, United States of America
| | - William H. Tepp
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, 53706, United States of America
| | - Jacob M. Scherf
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, 53706, United States of America
| | - Eric A. Johnson
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, 53706, United States of America
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18
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Transneuronal propagation of mutant huntingtin contributes to non-cell autonomous pathology in neurons. Nat Neurosci 2014; 17:1064-72. [PMID: 25017010 DOI: 10.1038/nn.3761] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 06/17/2014] [Indexed: 12/11/2022]
Abstract
In Huntington's disease (HD), whether transneuronal spreading of mutant huntingtin (mHTT) occurs and its contribution to non-cell autonomous damage in brain networks is largely unknown. We found mHTT spreading in three different neural network models: human neurons integrated in the neural network of organotypic brain slices of HD mouse model, an ex vivo corticostriatal slice model and the corticostriatal pathway in vivo. Transneuronal propagation of mHTT was blocked by two different botulinum neurotoxins, each known for specifically inactivating a single critical component of the synaptic vesicle fusion machinery. Moreover, healthy human neurons in HD mouse model brain slices displayed non-cell autonomous changes in morphological integrity that were more pronounced when these neurons bore mHTT aggregates. Altogether, our findings suggest that transneuronal propagation of mHTT might be an important and underestimated contributor to the pathophysiology of HD.
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19
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Abstract
Synaptic vesicle recycling is one of the best-studied cellular pathways. Many of the proteins involved are known, and their interactions are becoming increasingly clear. However, as for many other pathways, it is still difficult to understand synaptic vesicle recycling as a whole. While it is generally possible to point out how synaptic reactions take place, it is not always easy to understand what triggers or controls them. Also, it is often difficult to understand how the availability of the reaction partners is controlled: how the reaction partners manage to find each other in the right place, at the right time. I present here an overview of synaptic vesicle recycling, discussing the mechanisms that trigger different reactions, and those that ensure the availability of reaction partners. A central argument is that synaptic vesicles bind soluble cofactor proteins, with low affinity, and thus control their availability in the synapse, forming a buffer for cofactor proteins. The availability of cofactor proteins, in turn, regulates the different synaptic reactions. Similar mechanisms, in which one of the reaction partners buffers another, may apply to many other processes, from the biogenesis to the degradation of the synaptic vesicle.
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Affiliation(s)
- Silvio O Rizzoli
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen European Neuroscience Institute, Göttingen, Germany
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20
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Mechanisms of staphylococcal enterotoxin-induced emesis. Eur J Pharmacol 2014; 722:95-107. [DOI: 10.1016/j.ejphar.2013.08.050] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Revised: 06/11/2013] [Accepted: 08/03/2013] [Indexed: 01/16/2023]
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21
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Watanabe S, Rost BR, Camacho-Pérez M, Davis MW, Söhl-Kielczynski B, Rosenmund C, Jorgensen EM. Ultrafast endocytosis at mouse hippocampal synapses. Nature 2013; 504:242-247. [PMID: 24305055 PMCID: PMC3957339 DOI: 10.1038/nature12809] [Citation(s) in RCA: 378] [Impact Index Per Article: 34.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 11/01/2013] [Indexed: 01/21/2023]
Abstract
To sustain neurotransmission, synaptic vesicles and their associated proteins must be recycled locally at synapses. Synaptic vesicles are thought to be regenerated approximately 20 s after fusion by the assembly of clathrin scaffolds or in approximately 1 s by the reversal of fusion pores via 'kiss-and-run' endocytosis. Here we use optogenetics to stimulate cultured hippocampal neurons with a single stimulus, rapidly freeze them after fixed intervals and examine the ultrastructure using electron microscopy--'flash-and-freeze' electron microscopy. Docked vesicles fuse and collapse into the membrane within 30 ms of the stimulus. Compensatory endocytosis occurs within 50 to 100 ms at sites flanking the active zone. Invagination is blocked by inhibition of actin polymerization, and scission is blocked by inhibiting dynamin. Because intact synaptic vesicles are not recovered, this form of recycling is not compatible with kiss-and-run endocytosis; moreover, it is 200-fold faster than clathrin-mediated endocytosis. It is likely that 'ultrafast endocytosis' is specialized to restore the surface area of the membrane rapidly.
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Affiliation(s)
- Shigeki Watanabe
- Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah, U.S.A
| | - Benjamin R Rost
- Neuroscience Research Centre, Charité Universitätsmedizin, Berlin, Germany
| | | | - M Wayne Davis
- Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah, U.S.A
| | | | | | - Erik M Jorgensen
- Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, Utah, U.S.A
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22
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Shetty A, Sytnyk V, Leshchyns'ka I, Puchkov D, Haucke V, Schachner M. The neural cell adhesion molecule promotes maturation of the presynaptic endocytotic machinery by switching synaptic vesicle recycling from adaptor protein 3 (AP-3)- to AP-2-dependent mechanisms. J Neurosci 2013; 33:16828-45. [PMID: 24133283 PMCID: PMC6618524 DOI: 10.1523/jneurosci.2192-13.2013] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Revised: 08/27/2013] [Accepted: 09/13/2013] [Indexed: 02/05/2023] Open
Abstract
Newly formed synapses undergo maturation during ontogenetic development via mechanisms that remain poorly understood. We show that maturation of the presynaptic endocytotic machinery in CNS neurons requires substitution of the adaptor protein 3 (AP-3) with AP-2 at the presynaptic plasma membrane. In mature synapses, AP-2 associates with the intracellular domain of the neural cell adhesion molecule (NCAM). NCAM promotes binding of AP-2 over binding of AP-3 to presynaptic membranes, thus favoring the substitution of AP-3 for AP-2 during formation of mature synapses. The presynaptic endocytotic machinery remains immature in adult NCAM-deficient (NCAM-/-) mice accumulating AP-3 instead of AP-2 and its partner protein AP180 in synaptic membranes and vesicles. NCAM deficiency or disruption of the NCAM/AP-2 complex in wild-type (NCAM+/+) neurons by overexpression of AP-2 binding-defective mutant NCAM interferes with efficient retrieval of the synaptic vesicle v-SNARE synaptobrevin 2. Abnormalities in synaptic vesicle endocytosis and recycling may thus contribute to neurological disorders associated with mutations in NCAM.
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Affiliation(s)
- Aparna Shetty
- Zentrum für Molekulare Neurobiologie, Universität Hamburg, 20246 Hamburg, Germany
| | - Vladimir Sytnyk
- Zentrum für Molekulare Neurobiologie, Universität Hamburg, 20246 Hamburg, Germany
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Iryna Leshchyns'ka
- Zentrum für Molekulare Neurobiologie, Universität Hamburg, 20246 Hamburg, Germany
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Dmytro Puchkov
- Zentrum für Molekulare Neurobiologie, Universität Hamburg, 20246 Hamburg, Germany
| | - Volker Haucke
- Leibniz Institut für Molekulare Pharmakologie and Freie Universität Berlin, 13125 Berlin, Germany
| | - Melitta Schachner
- Zentrum für Molekulare Neurobiologie, Universität Hamburg, 20246 Hamburg, Germany
- Keck Center for Collaborative Neuroscience, Rutgers University, Piscataway, New Jersey 08854-8082, and
- Center for Neuroscience, Shantou University Medical College, Shantou 515041, People's Republic of China
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23
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Watanabe S, Liu Q, Davis MW, Hollopeter G, Thomas N, Jorgensen NB, Jorgensen EM. Ultrafast endocytosis at Caenorhabditis elegans neuromuscular junctions. eLife 2013; 2:e00723. [PMID: 24015355 PMCID: PMC3762212 DOI: 10.7554/elife.00723] [Citation(s) in RCA: 152] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 07/12/2013] [Indexed: 11/13/2022] Open
Abstract
Synaptic vesicles can be released at extremely high rates, which places an extraordinary demand on the recycling machinery. Previous ultrastructural studies of vesicle recycling were conducted in dissected preparations using an intense stimulation to maximize the probability of release. Here, a single light stimulus was applied to motor neurons in intact Caenorhabditis elegans nematodes expressing channelrhodopsin, and the animals rapidly frozen. We found that docked vesicles fuse along a broad active zone in response to a single stimulus, and are replenished with a time constant of about 2 s. Endocytosis occurs within 50 ms adjacent to the dense projection and after 1 s adjacent to adherens junctions. These studies suggest that synaptic vesicle endocytosis may occur on a millisecond time scale following a single physiological stimulus in the intact nervous system and is unlikely to conform to current models of endocytosis. DOI:http://dx.doi.org/10.7554/eLife.00723.001.
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Affiliation(s)
- Shigeki Watanabe
- Department of Biology , Howard Hughes Medical Institute, University of Utah , Salt Lake City , United States
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24
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Megighian A, Zordan M, Pantano S, Scorzeto M, Rigoni M, Zanini D, Rossetto O, Montecucco C. Evidence for a radial SNARE super-complex mediating neurotransmitter release at the Drosophila neuromuscular junction. J Cell Sci 2013; 126:3134-40. [PMID: 23687382 DOI: 10.1242/jcs.123802] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The SNARE proteins VAMP/synaptobrevin, SNAP-25 and syntaxin are core components of the apparatus that mediates neurotransmitter release. They form a heterotrimeric complex, and an undetermined number of SNARE complexes assemble to form a super-complex. Here, we present a radial model of this nanomachine. Experiments performed with botulinum neurotoxins led to the identification of one arginine residue in SNAP-25 and one aspartate residue in syntaxin (R206 and D253 in Drosophila melanogaster). These residues are highly conserved and predicted to play a major role in the protein-protein interactions between SNARE complexes by forming an ionic couple. Accordingly, we generated transgenic Drosophila lines expressing SNAREs mutated in these residues and performed an electrophysiological analysis of their neuromuscular junctions. Our results indicate that SNAP-25-R206 and syntaxin-D253 play a major role in neuroexocytosis and support a radial assembly of several SNARE complexes interacting via the ionic couple formed by these two residues.
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Affiliation(s)
- Aram Megighian
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 56 B, 35121 Padova, Italy
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25
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Karalewitz APA, Fu Z, Baldwin MR, Kim JJP, Barbieri JT. Botulinum neurotoxin serotype C associates with dual ganglioside receptors to facilitate cell entry. J Biol Chem 2012; 287:40806-16. [PMID: 23027864 PMCID: PMC3504792 DOI: 10.1074/jbc.m112.404244] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND How botulinum neurotoxin serotype C (BoNT/C) enters neurons is unclear. RESULTS BoNT/C utilizes dual gangliosides as host cell receptors. CONCLUSION BoNT/C accesses gangliosides on the plasma membrane. SIGNIFICANCE Plasma membrane accessibility of the dual ganglioside receptors suggests synaptic vesicle exocytosis may not be necessary to expose BoNT/C receptors. Botulinum neurotoxins (BoNTs) cleave SNARE proteins in motor neurons that inhibits synaptic vesicle (SV) exocytosis, resulting in flaccid paralysis. There are seven BoNT serotypes (A-G). In current models, BoNTs initially bind gangliosides on resting neurons and upon SV exocytosis associate with the luminal domains of SV-associated proteins as a second receptor. The entry of BoNT/C is less clear. Characterizing the heavy chain receptor binding domain (HCR), BoNT/C was shown to utilize gangliosides as dual host receptors. Crystallographic and biochemical studies showed that the two ganglioside binding sites, termed GBP2 and Sia-1, were independent and utilized unique mechanisms to bind complex gangliosides. The GBP2 binding site recognized gangliosides that contained a sia5 sialic acid, whereas the Sia-1 binding site recognized gangliosides that contained a sia7 sialic acid and sugars within the backbone of the ganglioside. Utilizing gangliosides that uniquely recognized the GBP2 and Sia-1 binding sites, HCR/C entry into Neuro-2A cells required both functional ganglioside binding sites. HCR/C entered cells differently than the HCR of tetanus toxin, which also utilizes dual gangliosides as host receptors. A point-mutated HCR/C that lacked GBP2 binding potential retained the ability to bind and enter Neuro-2A cells. This showed that ganglioside binding at the Sia-1 site was accessible on the plasma membrane, suggesting that SV exocytosis may not be required to expose BoNT/C receptors. These studies highlight the utility of BoNT HCRs as probes to study the role of gangliosides in neurotransmission.
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Affiliation(s)
| | - Zhuji Fu
- Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 and
| | - Michael R. Baldwin
- the Department of Microbiology and Molecular Genetics, University of Missouri, Columbia, Missouri 65212
| | - Jung-Ja P. Kim
- Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 and
| | - Joseph T. Barbieri
- From the Departments of Microbiology and Molecular Genetics and , To whom correspondence should be addressed: Dept. of Microbiology and Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226. Tel.: 414-955-8412; Fax: 414-955-6535; E-mail:
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26
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Whitemarsh RCM, Pier CL, Tepp WH, Pellett S, Johnson EA. Model for studying Clostridium botulinum neurotoxin using differentiated motor neuron-like NG108-15 cells. Biochem Biophys Res Commun 2012; 427:426-30. [PMID: 23000406 DOI: 10.1016/j.bbrc.2012.09.082] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2012] [Accepted: 09/13/2012] [Indexed: 11/16/2022]
Abstract
Cancerous cell lines have traditionally shown low sensitivity to laboratory or pharmaceutical preparations of botulinum neurotoxin. The work presented here demonstrates that the mouse neuroblastoma/rat glioma hybrid cell line NG108-15 is capable of more sensitively detecting BoNT/A1 than any cell line previously described. This cell line has previously been described to have motor neuron like characteristics, therefore making it a good model to study BoNTs. Differentiation of NG108-15 cells in serum-free medium containing retinoic acid and purmorphamine dramatically increased sensitivity of the neurons to BoNT/A (EC(50) = ~16 LD(50) U). Additional pre-treatment with triasialoganglioside GT1B prior to toxin exposure reduced the EC(50) further to ~11 LD(50) U. Co-culture of the neurons with C2C12 myotubes also significantly increased BoNT/A sensitivity of NG108-15 cells (EC(50) = 26 U) in the absence of differentiation factors.
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Affiliation(s)
- Regina C M Whitemarsh
- Department of Bacteriology, University of Wisconsin, Madison, Madison, WI 53706, USA
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27
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Singh AK, Stanker LH, Sharma SK. Botulinum neurotoxin: where are we with detection technologies? Crit Rev Microbiol 2012; 39:43-56. [PMID: 22676403 DOI: 10.3109/1040841x.2012.691457] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Because of its high toxicity, botulinum neurotoxin (BoNT) poses a significant risk to humans and it represents a possible biological warfare agent. Nevertheless, BoNT serotypes A and B are considered an effective treatment for a variety of neurological disorders. The growing applicability of BoNT as a drug, and its potential use as a biological threat agent, highlight the urgent need to develop sensitive detection assays and therapeutic counter measures. In the last decade, significant progress has been made in BoNT detection technologies but none have fully replaced the mouse lethality assay, the current "gold standard". Recently, new advances in robotics and the availability of new reagents have allowed development of methods for rapid toxin analysis. These technologies while promising need further refinement.
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Affiliation(s)
- Ajay K Singh
- Food and Drug Administration, Center for Food Safety and Applied Nutrition, College Park, MD 20740, USA
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Bleckert A, Photowala H, Alford S. Dual pools of actin at presynaptic terminals. J Neurophysiol 2012; 107:3479-92. [PMID: 22457456 DOI: 10.1152/jn.00789.2011] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated actin's function in vesicle recycling and exocytosis at lamprey synapses and show that FM1-43 puncta and phalloidin-labeled filamentous actin (F-actin) structures are colocalized, yet recycling vesicles are not contained within F-actin clusters. Additionally, phalloidin also labels a plasma membrane-associated cortical actin. Injection of fluorescent G-actin revealed activity-independent dynamic actin incorporation into presynaptic synaptic vesicle clusters but not into cortical actin. Latrunculin-A, which sequesters G-actin, dispersed vesicle-associated actin structures and prevented subsequent labeled G-actin and phalloidin accumulation at presynaptic puncta, yet cortical phalloidin labeling persisted. Dispersal of presynaptic F-actin structures by latrunculin-A did not disrupt vesicle clustering or recycling or alter the amplitude or kinetics of excitatory postsynaptic currents (EPSCs). However, it slightly enhanced release during repetitive stimulation. While dispersal of presynaptic actin puncta with latrunculin-A failed to disperse synaptic vesicles or inhibit synaptic transmission, presynaptic phalloidin injection blocked exocytosis and reduced endocytosis measured by action potential-evoked FM1-43 staining. Furthermore, phalloidin stabilization of only cortical actin following pretreatment with latrunculin-A was sufficient to inhibit synaptic transmission. Conversely, treatment of axons with jasplakinolide, which induces F-actin accumulation but disrupts F-actin structures in vivo, resulted in increased synaptic transmission accompanied by a loss of phalloidin labeling of cortical actin but no loss of actin labeling within vesicle clusters. Marked synaptic deficits seen with phalloidin stabilization of cortical F-actin, in contrast to the minimal effects of disruption of a synaptic vesicle-associated F-actin, led us to conclude that two structurally and functionally distinct pools of actin exist at presynaptic sites.
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Affiliation(s)
- Adam Bleckert
- Dept. of Biological Sciences, Univ. of Illinois at Chicago, Chicago, IL 60607, USA
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Neurotransmitter vesicle release from human model neurons (NT2) is sensitive to botulinum toxin A. Cell Mol Neurobiol 2012; 32:1021-9. [PMID: 22373696 DOI: 10.1007/s10571-012-9818-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 02/14/2012] [Indexed: 01/06/2023]
Abstract
Botulinum neurotoxins (BoNTs) internalize into nerve terminals and block the release of neurotransmitters into the synapse. BoNTs are widely used as a therapeutic agent for treatment of movement disorders and recently gained more attention as a biological weapon. Consequently, there is strong interest to develop a cell-based assay platform to screen the toxicity and bioactivity of the BoNTs. In this study, we present an in vitro screening assay for BoNT/A based on differentiated human embryonal carcinoma stem (NT2) cells. The human NT2 cells fully differentiated into mature neurons that display immunoreactivity to cytoskeletal markers (βIII-tubulin and MAP2) and presynaptic proteins (synapsin and synaptotagmin I). We showed that the human NT2 cells undergo a process of exo-endocytotic synaptic vesicle recycling upon depolarization with high K(+) buffer. By employing an antibody directed against light chain of BoNT/A, we detected internalized toxin as a punctate staining along the neurites of the NT2 neurons. Using well-established methods of synaptic vesicle exocytosis assay (luminal synaptotagmin I and FM1-43 imaging) we show that pre-incubation with BoNT/A resulted in a blockade of vesicle release from human NT2 neurons in a dose-dependent manner. Moreover, this blocking effect of BoNT/A was abolished by pre-adsorbing the toxin with neutralizing antibody. In a proof of principle, we demonstrate that our cell culture assay for vesicle release is sensitive to BoNT/A and the activity of BoNT/A can be blocked by specific neutralizing antibodies. Overall our data suggest that human NT2 neurons are suitable for large scale screening of botulinum bioactivity.
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Whitemarsh RCM, Strathman MJ, Chase LG, Stankewicz C, Tepp WH, Johnson EA, Pellett S. Novel application of human neurons derived from induced pluripotent stem cells for highly sensitive botulinum neurotoxin detection. Toxicol Sci 2012; 126:426-35. [PMID: 22223483 DOI: 10.1093/toxsci/kfr354] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Human induced pluripotent stem cells (hiPSC) hold great promise for providing various differentiated cell models for in vitro toxigenicity testing. For Clostridium botulinum neurotoxin (BoNT) detection and mechanistic studies, several cell models currently exist, but none examine toxin function with species-specific relevance while exhibiting high sensitivity. The most sensitive cell models to date are mouse or rat primary cells and neurons derived from mouse embryonic stem cells, both of which require significant technical expertise for culture preparation. This study describes for the first time the use of hiPSC-derived neurons for BoNT detection. The neurons used in this study were differentiated and cryopreserved by Cellular Dynamics International (Madison, WI) and consist of an almost pure pan-neuronal population of predominantly gamma aminoisobutyric acidergic and glutamatergic neurons. Western blot and quantitative PCR data show that these neurons express all the necessary receptors and substrates for BoNT intoxication. BoNT/A intoxication studies demonstrate that the hiPSC-derived neurons reproducibly and quantitatively detect biologically active BoNT/A with high sensitivity (EC(50) ∼0.3 U). Additionally, the quantitative detection of BoNT serotypes B, C, E, and BoNT/A complex was demonstrated, and BoNT/A specificity was confirmed through antibody protection studies. A direct comparison of BoNT detection using primary rat spinal cord cells and hiPSC-derived neurons showed equal or increased sensitivity, a steeper dose-response curve and a more complete SNARE protein target cleavage for hiPSC-derived neurons. In summary, these data suggest that neurons derived from hiPSCs provide an ideal and highly sensitive platform for BoNT potency determination, neutralizing antibody detection and for mechanistic studies.
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Affiliation(s)
- Regina C M Whitemarsh
- Department of Bacteriology, University of Wisconsin, Madison, Madison, Wisconsin 53706, USA
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Uncoupling the roles of synaptotagmin I during endo- and exocytosis of synaptic vesicles. Nat Neurosci 2011; 15:243-9. [PMID: 22197832 PMCID: PMC3435110 DOI: 10.1038/nn.3013] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 11/14/2011] [Indexed: 11/29/2022]
Abstract
Synaptotagmin I (syt1) is required for normal rates of synaptic vesicle endo- and exocytosis. However, whether the kinetic defects observed during endocytosis in syt1 knock-out neurons are secondary to defective exocytosis, or whether syt1 directly regulates the rate of vesicle retrieval, remains unresolved. In order to address this question, it is necessary to dissociate these two activities. Here, we have uncoupled the function of syt1 in exo- and endocytosis by re-targeting of the protein, or via mutagenesis of its tandem C2-domains; the impact of these manipulations on exo- and endocytosis were analyzed via electrophysiology, in conjunction with optical imaging of the vesicle cycle. These experiments uncovered a direct role for syt1 in endocytosis. Surprisingly, either C2-domain of syt1 - C2A or C2B - was able to function as Ca2+-sensor for endocytosis. Hence, syt1 functions as a dual Ca2+ sensor for both endo- and exocytosis, potentially coupling these two limbs of the vesicle cycle.
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Kiris E, Nuss JE, Burnett JC, Kota KP, Koh DC, Wanner LM, Torres-Melendez E, Gussio R, Tessarollo L, Bavari S. Embryonic stem cell-derived motoneurons provide a highly sensitive cell culture model for botulinum neurotoxin studies, with implications for high-throughput drug discovery. Stem Cell Res 2011; 6:195-205. [PMID: 21353660 PMCID: PMC3081902 DOI: 10.1016/j.scr.2011.01.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Revised: 01/05/2011] [Accepted: 01/10/2011] [Indexed: 11/21/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) inhibit cholinergic synaptic transmission by specifically cleaving proteins that are crucial for neurotransmitter exocytosis. Due to the lethality of these toxins, there are elevated concerns regarding their possible use as bioterrorism agents. Moreover, their widespread use for cosmetic purposes, and as medical treatments, has increased the potential risk of accidental overdosing and environmental exposure. Hence, there is an urgent need to develop novel modalities to counter BoNT intoxication. Mammalian motoneurons are the main target of BoNTs; however, due to the difficulty and poor efficiency of the procedures required to isolate the cells, they are not suitable for high-throughput drug screening assays. Here, we explored the suitability of embryonic stem (ES) cell-derived motoneurons as a renewable, reproducible, and physiologically relevant system for BoNT studies. We found that the sensitivity of ES-derived motoneurons to BoNT/A intoxication is comparable to that of primary mouse spinal motoneurons. Additionally, we demonstrated that several BoNT/A inhibitors protected SNAP-25, the BoNT/A substrate, in the ES-derived motoneuron system. Furthermore, this system is compatible with immunofluorescence-based high-throughput studies. These data suggest that ES-derived motoneurons provide a highly sensitive system that is amenable to large-scale screenings to rapidly identify and evaluate the biological efficacies of novel therapeutics.
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Affiliation(s)
- Erkan Kiris
- Department of Target Discovery and Experimental Microbiology, US Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA
- Neural Development Group, Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Jonathan E. Nuss
- Department of Target Discovery and Experimental Microbiology, US Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA
| | - James C. Burnett
- SAIC Frederick, Inc., Target Structure-Based Drug Discovery Group (TSBDDG), National Cancer Institute at Frederick, MD 21702, USA
- TSBDDG, Information Technology Branch, Developmental Therapeutics Program, National Cancer Institute at Frederick, MD 2170, USA
| | - Krishna P. Kota
- Department of Target Discovery and Experimental Microbiology, US Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA
| | - Dawn C. Koh
- Neural Development Group, Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Laura M. Wanner
- Department of Target Discovery and Experimental Microbiology, US Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA
| | - Edna Torres-Melendez
- Department of Target Discovery and Experimental Microbiology, US Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA
| | - Rick Gussio
- TSBDDG, Information Technology Branch, Developmental Therapeutics Program, National Cancer Institute at Frederick, MD 2170, USA
| | - Lino Tessarollo
- Neural Development Group, Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA
| | - Sina Bavari
- Department of Target Discovery and Experimental Microbiology, US Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA
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Megighian A, Scorzeto M, Zanini D, Pantano S, Rigoni M, Benna C, Rossetto O, Montecucco C, Zordan M. Arg206 of SNAP-25 is essential for neuroexocytosis at the Drosophila melanogaster neuromuscular junction. J Cell Sci 2010; 123:3276-83. [DOI: 10.1242/jcs.071316] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An analysis of SNAP-25 isoform sequences indicates that there is a highly conserved arginine residue (198 in vertebrates, 206 in the genus Drosophila) within the C-terminal region, which is cleaved by botulinum neurotoxin A, with consequent blockade of neuroexocytosis. The possibility that it may play an important role in the function of the neuroexocytosis machinery was tested at neuromuscular junctions of Drosophila melanogaster larvae expressing SNAP-25 in which Arg206 had been replaced by alanine. Electrophysiological recordings of spontaneous and evoked neurotransmitter release under different conditions as well as testing for the assembly of the SNARE complex indicate that this residue, which is at the P1′ position of the botulinum neurotoxin A cleavage site, plays an essential role in neuroexocytosis. Computer graphic modelling suggests that this arginine residue mediates protein–protein contacts within a rosette of SNARE complexes that assembles to mediate the fusion of synaptic vesicles with the presynaptic plasma membrane.
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Affiliation(s)
- Aram Megighian
- Department of Human Anatomy and Physiology, Section of Physiology, University of Padova, 35131, Italy
| | - Michele Scorzeto
- Department of Human Anatomy and Physiology, Section of Physiology, University of Padova, 35131, Italy
| | - Damiano Zanini
- Department of Human Anatomy and Physiology, Section of Physiology, University of Padova, 35131, Italy
- Department of Biology, University of Padova, 35121, Italy
| | - Sergio Pantano
- Biomolecular Simulations Group, Institut Pasteur de Montevideo, Mataojo 2020, CP 11400, Montevideo, Uruguay
| | - Michela Rigoni
- Department of Biomedical Sciences, University of Padova, 35121, Italy
| | - Clara Benna
- Department of Biology, University of Padova, 35121, Italy
| | - Ornella Rossetto
- Department of Biomedical Sciences, University of Padova, 35121, Italy
| | - Cesare Montecucco
- Department of Biomedical Sciences, University of Padova, 35121, Italy
| | - Mauro Zordan
- Department of Biology, University of Padova, 35121, Italy
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A pathologic cascade leading to synaptic dysfunction in alpha-synuclein-induced neurodegeneration. J Neurosci 2010; 30:8083-95. [PMID: 20554859 DOI: 10.1523/jneurosci.1091-10.2010] [Citation(s) in RCA: 250] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Several neurodegenerative diseases are typified by intraneuronal alpha-synuclein deposits, synaptic dysfunction, and dementia. While even modest alpha-synuclein elevations can be pathologic, the precise cascade of events induced by excessive alpha-synuclein and eventually culminating in synaptotoxicity is unclear. To elucidate this, we developed a quantitative model system to evaluate evolving alpha-synuclein-induced pathologic events with high spatial and temporal resolution, using cultured neurons from brains of transgenic mice overexpressing fluorescent-human-alpha-synuclein. Transgenic alpha-synuclein was pathologically altered over time and overexpressing neurons showed striking neurotransmitter release deficits and enlarged synaptic vesicles; a phenotype reminiscent of previous animal models lacking critical presynaptic proteins. Indeed, several endogenous presynaptic proteins involved in exocytosis and endocytosis were undetectable in a subset of transgenic boutons ("vacant synapses") with diminished levels in the remainder, suggesting that such diminutions were triggering the overall synaptic pathology. Similar synaptic protein alterations were also retrospectively seen in human pathologic brains, highlighting potential relevance to human disease. Collectively the data suggest a previously unknown cascade of events where pathologic alpha-synuclein leads to a loss of a number of critical presynaptic proteins, thereby inducing functional synaptic deficits.
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Popoff MR, Poulain B. Bacterial toxins and the nervous system: neurotoxins and multipotential toxins interacting with neuronal cells. Toxins (Basel) 2010; 2:683-737. [PMID: 22069606 PMCID: PMC3153206 DOI: 10.3390/toxins2040683] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2010] [Revised: 03/18/2010] [Accepted: 04/07/2010] [Indexed: 12/13/2022] Open
Abstract
Toxins are potent molecules used by various bacteria to interact with a host organism. Some of them specifically act on neuronal cells (clostridial neurotoxins) leading to characteristics neurological affections. But many other toxins are multifunctional and recognize a wider range of cell types including neuronal cells. Various enterotoxins interact with the enteric nervous system, for example by stimulating afferent neurons or inducing neurotransmitter release from enterochromaffin cells which result either in vomiting, in amplification of the diarrhea, or in intestinal inflammation process. Other toxins can pass the blood brain barrier and directly act on specific neurons.
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Affiliation(s)
- Michel R. Popoff
- Neurotransmission et Sécrétion Neuroendocrine, CNRS UPR 2356 IFR 37 - Neurosciences, Centre de Neurochimie, 5, rue Blaise Pascal, F-67084 STRASBOURG cedex, France;
- Author to whom correspondence should be addressed;
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Pellett S, Tepp WH, Toth SI, Johnson EA. Comparison of the primary rat spinal cord cell (RSC) assay and the mouse bioassay for botulinum neurotoxin type A potency determination. J Pharmacol Toxicol Methods 2010; 61:304-10. [PMID: 20100585 DOI: 10.1016/j.vascn.2010.01.003] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 01/15/2010] [Accepted: 01/15/2010] [Indexed: 11/19/2022]
Abstract
INTRODUCTION Botulinum neurotoxin (BoNT) type A is increasingly used in humans for pharmaceutical and cosmetic purposes. Currently, the standard assay used to determine potency of clinical samples, and the only assay approved by the FDA, is the in vivo mouse bioassay (MBA). However, due to several drawbacks of this assay (relatively large error, high cost, no standardization, requirement of high technical expertise, and use of large numbers of mice), there is an increasing need to replace this assay. A cell-based assay using primary rat spinal cord cells (RSC assay) has been previously reported to sensitively detect purified botulinum neurotoxin type A, and requires all biological properties of the toxin for detection. METHODS This study presents data on quantitative detection of potency of purified BoNT/A by a cell-based assay, using primary rat spinal cord cells (RSC assay). The sensitivity and error rate of the RSC assay was directly compared to the currently used mouse bioassay by repeated testing of the same purified BoNT/A sample by both assays. In addition, the potency of several samples of purified BoNT/A of unknown activity was determined in parallel by RSC assay and MBA. RESULTS The results indicate sensitivity of the RSC assay similar to the mouse bioassay, high reproducibility, and a lower error rate than the mouse bioassay. Direct comparison of potency determination of several purified BoNT/A samples by RSC assay and MBA resulted in very similar values, indicating very good correlation. DISCUSSION These data support the use of a cell-based assay for potency determination of purified BoNT/A as an alternative to the mouse bioassay.
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Affiliation(s)
- Sabine Pellett
- Department of Bacteriology, University of Wisconsin, Madison, Madison, WI 53706, USA
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Zhang P, Ray R, Singh BR, Li D, Adler M, Ray P. An efficient drug delivery vehicle for botulism countermeasure. BMC Pharmacol 2009; 9:12. [PMID: 19860869 PMCID: PMC2774289 DOI: 10.1186/1471-2210-9-12] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Accepted: 10/27/2009] [Indexed: 12/05/2022] Open
Abstract
Background Botulinum neurotoxin (BoNT) is the most potent poison known to mankind. Currently no antidote is available to rescue poisoned synapses. An effective medical countermeasure strategy would require developing a drug that could rescue poisoned neuromuscular synapses and include its efficient delivery specifically to poisoned presynaptic nerve terminals. Here we report a drug delivery strategy that could directly deliver toxin inhibitors into the intoxicated nerve terminal cytosol. Results A targeted delivery vehicle was developed for intracellular transport of emerging botulinum neurotoxin antagonists. The drug delivery vehicle consisted of the non-toxic recombinant heavy chain of botulinum neurotoxin-A coupled to a 10-kDa amino dextran via the heterobifunctional linker 3-(2-pyridylthio)-propionyl hydrazide. The heavy chain served to target botulinum neurotoxin-sensitive cells and promote internalization of the complex, while the dextran served as a platform to deliver model therapeutic molecules to the targeted neurons. Our results indicated that the drug delivery vehicle entry into neurons was via BoNT-A receptor mediated endocytosis. Once internalized into neurons, the drug carrier component separated from the drug delivery vehicle in a fashion similar to the separation of the BoNT-A light chain from the holotoxin. This drug delivery vehicle could be used to deliver BoNT-A antidotes into BoNT-A intoxicated cultured mouse spinal cord cells. Conclusion An effective BoNT-based drug delivery vehicle can be used to directly deliver toxin inhibitors into intoxicated nerve terminal cytosol. This approach can potentially be utilized for targeted drug delivery to treat other neuronal and neuromuscular disorders. This report also provides new knowledge of endocytosis and exocytosis as well as of BoNT trafficking.
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Affiliation(s)
- Peng Zhang
- Division of Experimental Therapeutic, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA.
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Schroeder AS, Ertl-Wagner B, Britsch S, Schröder JM, Nikolin S, Weis J, Müller-Felber W, Koerte I, Stehr M, Berweck S, Borggraefe I, Heinen F. Muscle biopsy substantiates long-term MRI alterations one year after a single dose of botulinum toxin injected into the lateral gastrocnemius muscle of healthy volunteers. Mov Disord 2009; 24:1494-503. [PMID: 19489066 DOI: 10.1002/mds.22661] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Despite numerous clinical and experimental studies on botulinum toxin type A (BoNT/A), long-term alterations of muscle texture and fine structure following BoNT/A treatment have thus far not been studied in normal human skeletal muscle. After obtaining institutional review board approval, we performed a prospective, placebo-controlled, double-blinded follow-up study on two healthy adults using magnetic resonance imaging (MRI) and muscle biopsy to visualize long-term alterations after a single BoNT/A injection into the lateral head of the gastrocnemius muscle. MRI disclosed a high-signal-intensity pattern in short tau inversion recovery sequences, and a reduction of the cross-sectional area in the BoNT/A-injected, but not in the saline-injected contralateral control muscle (at 6 to 9 months in volunteer A: 73%, in B: 62%; at 12 months in A: 88%, and in B: 78%). Enzyme histochemistry, 12 months after injection, confirmed neurogenic atrophy of muscle fibers only in the BoNT/A-injected muscle. Electron microscopy revealed additional degenerative changes at the neuromuscular junction. The data confirm that MRI is a suitable tool to monitor the long-term effect of BoNT/A on skeletal muscle. Neurogenic muscle atrophy following a single BoNT/A injection should be taken into consideration when repeated BoNT/A injections into the same muscles are proposed.
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Affiliation(s)
- A Sebastian Schroeder
- Department of Pediatric Neurology and Developmental Medicine, Dr. von Hauner's Children's Hospital, University of Munich, Munich, Germany.
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Yao CK, Lin YQ, Ly CV, Ohyama T, Haueter CM, Moiseenkova-Bell VY, Wensel TG, Bellen HJ. A synaptic vesicle-associated Ca2+ channel promotes endocytosis and couples exocytosis to endocytosis. Cell 2009; 138:947-60. [PMID: 19737521 PMCID: PMC2749961 DOI: 10.1016/j.cell.2009.06.033] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2008] [Revised: 04/27/2009] [Accepted: 06/12/2009] [Indexed: 02/06/2023]
Abstract
Synaptic vesicle (SV) exo- and endocytosis are tightly coupled to sustain neurotransmission in presynaptic terminals, and both are regulated by Ca(2+). Ca(2+) influx triggered by voltage-gated Ca(2+) channels is necessary for SV fusion. However, extracellular Ca(2+) has also been shown to be required for endocytosis. The intracellular Ca(2+) levels (<1 microM) that trigger endocytosis are typically much lower than those (>10 microM) needed to induce exocytosis, and endocytosis is inhibited when the Ca(2+) level exceeds 1 microM. Here, we identify and characterize a transmembrane protein associated with SVs that, upon SV fusion, localizes at periactive zones. Loss of Flower results in impaired intracellular resting Ca(2+) levels and impaired endocytosis. Flower multimerizes and is able to form a channel to control Ca(2+) influx. We propose that Flower functions as a Ca(2+) channel to regulate synaptic endocytosis and hence couples exo- with endocytosis.
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Affiliation(s)
- Chi-Kuang Yao
- Howard Hughes Medical Institute, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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Bethani I, Werner A, Kadian C, Geumann U, Jahn R, Rizzoli SO. Endosomal fusion upon SNARE knockdown is maintained by residual SNARE activity and enhanced docking. Traffic 2009; 10:1543-59. [PMID: 19624487 DOI: 10.1111/j.1600-0854.2009.00959.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
SNARE proteins mediate membrane fusion in the secretory pathway of eukaryotic cells. Genetic deletion and siRNA-based knockdown have been instrumental in assigning given SNAREs to defined intracellular transport steps. However, SNARE depletion occasionally results in barely detectable phenotypes. To understand how cells cope with SNARE loss, we have knocked down several SNAREs functioning in early endosome fusion. Surprisingly, knockdown of syntaxin 13, syntaxin 6 and vti1a, alone or in combinations, did not result in measurable changes of endosomal trafficking or fusion. We found that the residual SNARE levels (typically approximately 10%) were sufficient for a substantial amount of SNARE-SNARE interactions. Conversely, in wild-type cells, most SNARE molecules were concentrated in clusters, constituting a spare pool not readily available for interactions. Additionally, the knockdown organelles exhibited enhanced docking. We conclude that SNAREs are expressed at much higher levels than needed for maintenance of organelle fusion, and that loss of SNAREs is compensated for by the co-regulation of the docking machinery.
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Affiliation(s)
- Ioanna Bethani
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, 37077 Göttingen, Germany
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Bozzi Y, Costantin L, Antonucci F, Caleo M. Action of botulinum neurotoxins in the central nervous system: Antiepileptic effects. Neurotox Res 2009; 9:197-203. [PMID: 16785118 DOI: 10.1007/bf03033939] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Botulinum neurotoxins (BoNTs) are metalloproteases which act on nerve terminals and cause a long-lasting inhibition of neurotransmitter release. BoNTs act by cleaving core proteins of the neurotransmitter release machinery, namely the SNARE (soluble NSF-attachment receptors) proteins. The action of BoNTs in the peripheral nervous system (PNS) has been extensively documented, and knowledge gained in this field laid the foundations for the use of BoNTs in human disorders characterized by hyperfunction of peripheral nerve terminals. Much less is known about the action of BoNTs on the central nervous system (CNS). In vitro studies have demonstrated that BoNTs can affect the release of several neurotransmitters from central neurons. Recent studies have provided the first characterization of the effects of BoNT/E on CNS neurons in vivo. It has been shown that BoNT/E injected into the rat hippocampus inhibits glutamate release and blocks spike activity of pyramidal neurons. Intrahippocampal injection of BoNT/E resulted in significant inhibition of seizure activity in experimental models of epilepsy, suggesting a potential therapeutic use of BoNTs in the CNS.
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Affiliation(s)
- Y Bozzi
- Istituto di Neuroscienze del CNR, Pisa, Italy
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The synaptic vesicle cluster: A source of endocytic proteins during neurotransmitter release. Neuroscience 2009; 158:204-10. [DOI: 10.1016/j.neuroscience.2008.03.035] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 03/17/2008] [Accepted: 03/18/2008] [Indexed: 12/11/2022]
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Hou J, Tamura T, Kidokoro Y. Delayed synaptic transmission in Drosophila cacophonynull embryos. J Neurophysiol 2008; 100:2833-42. [PMID: 18815348 DOI: 10.1152/jn.90342.2008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ca(2+) influx through the Drosophila N-type Ca(2+) channel, encoded by cacophony (cac), triggers fast synaptic transmission. We now ask whether the cac Ca(2+) channel is the Ca(2+) channel solely dedicated for fast synaptic transmission. Because the cac(null) mutation is lethal, we used cac(null) embryos to address this question. At the neuromuscular junction in HL3 solution, no fast synchronous synaptic transmission was detected on nerve stimulation. When the wild-type cac gene was introduced in the cac(null) background, fast synaptic transmission recovered. However, even in cac(null) embryos, nerve stimulation infrequently induced delayed synaptic events in the minority of cells in 1.5 mM [Ca(2+)](e) and in the majority of cells in 5 mM [Ca(2+)](e). The number of delayed quantal events per stimulus was greater in 5 mM [Ca(2+)](e) than in 1.5 mM. Thus the delayed release is [Ca(2+)](e) dependent. Plectreurys toxin II (PLTXII) (10 nM; a spider toxin analog) depressed the frequency of delayed events, suggesting that voltage-gated Ca(2+) channels, other than cac Ca(2+) channels, are contributing to them. However, delayed events were not affected by 50 microM La(3+). The frequency of miniature synaptic currents in cac(null) embryos was approximately 1/2 of control, whereas in high K(+) solutions, it was approximately 1/135. The hypertonicity response was approximately 1/10 of control. These findings indicate that the number of release-ready vesicles is smaller in cac(null) embryos. Taken together, the cac Ca(2+) channel is indispensable for fast synaptic transmission in normal conditions, and another type of Ca(2+) channel, the non-cac, PLTXII-sensitive Ca(2+) channel, is contributing to delayed release in cac(null) embryos.
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Affiliation(s)
- Jiamei Hou
- Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
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Eapen BR. Molecular biology of botulinum neurotoxin serotype A: a cosmetic perspective. J Cosmet Dermatol 2008; 7:221-5. [PMID: 18789058 DOI: 10.1111/j.1473-2165.2008.00392.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cosmetic use of botulinum neurotoxin serotype A (BoNT/A) involves low doses of toxin administered for facial wrinkles and hyperhidrosis. The structural and functional properties of BoNT/A can affect the degree and duration of effect. Actively using the injected muscle is favorable as it exposes more receptors to BoNT/A. Divided doses of BoNT/A at an interval of more than 3 days may be longer lasting than single dose by blocking nascent neuronal sprouts. Antibodies are unlikely to be effective in BoNT/A neutralization because of the large area of receptor interaction. Several commonly used drugs including zinc and chloroquine can interact with BoNT/A, necessitating dosage adjustment for optimum effect. Serotype E (BoNT/E) can emerge as an antidote for BoNT/A for cosmetic use.
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Cousin MA. Use of FM1-43 and other derivatives to investigate neuronal function. ACTA ACUST UNITED AC 2008; Chapter 2:Unit 2.6. [PMID: 18428675 DOI: 10.1002/0471142301.ns0206s43] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The fluorescent dye FM1-43 and its derivatives can be used to monitor the physiology of synaptic vesicle turnover in central nerve terminals. They do so by their ability to reversibly partition into membranes, a process that results in a huge increase in fluorescence in comparison to their quantum yield in solution. This unit provides protocols for quantifying total synaptic vesicle turnover, the kinetics and extent of synaptic vesicle exocytosis, and the kinetics and mode of synaptic vesicle endocytosis. Descriptions of other ways these protocols have been used to derive information about the life cycle of the synaptic vesicle are also provided.
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Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) play a key role in membrane fusion in the secretory pathway. In vitro, SNAREs spontaneously assemble into helical SNARE complexes with the transmembrane domains at the C-terminal end. During fusion, SNAREs are thought to bridge the two membranes and assemble in a zipper-like fashion, pulling the membranes together and initiating fusion. However, it is not clear to what extent SNARE assembly contributes to membrane attachment and membrane fusion. Using the neuronal SNAREs synaptobrevin (VAMP), SNAP-25, and syntaxin as examples, we show here that liposomes containing synaptobrevin firmly attach to planar surfaces containing immobilized syntaxin. Attachment requires the formation of SNARE complexes because it is dependent on the presence of SNAP-25. Binding is competed for by soluble SNARE fragments, with noncognate SNAREs such as endobrevin (VAMP8), VAMP4, and VAMP7 (Ti-VAMP) being effective but less potent in some cases. Furthermore, although SNAP-23 is unable to substitute for SNAP-25 in the attachment assay, it forms complexes of comparable stability and is capable of substituting in liposome fusion assays. Vesicle attachment is initiated by SNARE assembly at the N-terminal end of the helix bundle. We conclude that SNAREs can indeed form stable trans-complexes that result in vesicle attachment if progression to fusion is prevented, further supporting the zipper model of SNARE function.
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Pellett S, Tepp WH, Clancy CM, Borodic GE, Johnson EA. A neuronal cell-based botulinum neurotoxin assay for highly sensitive and specific detection of neutralizing serum antibodies. FEBS Lett 2007; 581:4803-8. [PMID: 17889852 PMCID: PMC2748649 DOI: 10.1016/j.febslet.2007.08.078] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Revised: 08/29/2007] [Accepted: 08/31/2007] [Indexed: 11/24/2022]
Abstract
Clostridium botulinum neurotoxin (BoNT) serotypes A and B are widely used as pharmaceuticals to treat various neurological disorders and in cosmetic applications. The major adverse effect of these treatments has been resistance to treatment after multiple injections. Currently, patients receiving BoNT therapies and patients enrolled in clinical trials for new applications and/or new formulations of BoNTs are not routinely monitored for the formation of neutralizing antibodies, since no assay other than the mouse protection procedure is commercially available that reliably tests for the presence of such antibodies. This report presents a highly sensitive and specific neuronal cell-based assay that provides sensitive and specific detection of neutralizing antibodies to BoNT/A.
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Affiliation(s)
- Sabine Pellett
- Food Research Institute, Department of Bacteriology, University of Wisconsin, Madison, Madison, WI, 53706, 1-(608) 263-7944, 1-(608) 263-1114 (fax),
| | - William H. Tepp
- Food Research Institute, Department of Bacteriology, University of Wisconsin, Madison, Madison, WI, 53706, 1-(608) 263-7944, 1-(608) 263-1114 (fax),
| | - Colin M. Clancy
- Food Research Institute, Department of Bacteriology, University of Wisconsin, Madison, Madison, WI, 53706, 1-(608) 263-7944, 1-(608) 263-1114 (fax),
| | - Gary E. Borodic
- Department of Ophthalmology, Harvard Medical School, Ocular Plastic and Reconstructive Surgery Division, 5 Cambridge Center, 8th Floor, Cambridge, MA
| | - Eric A Johnson
- Food Research Institute, Department of Bacteriology, University of Wisconsin, Madison, Madison, WI, 53706, 1-(608) 263-7944, 1-(608) 263-1114 (fax),
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Abstract
Two models of synaptic vesicle recycling have been intensely debated for decades: kiss-and-run, in which the vesicle opens and closes transiently, presumably through a small fusion pore, and full fusion, in which the vesicle collapses into the plasma membrane and is retrieved by clathrin-coat-dependent processes. Conceptually, it seems that kiss-and-run would be faster and would retrieve vesicles with greater fidelity. Is this the case? This review discusses recent evidence for both models. We conclude that both mechanisms allow for high fidelity of vesicle recycling. Also, the presence in the plasma membrane of a depot of previously fused vesicles that are already interacting with the endocytotic machinery (the 'readily retrievable' vesicles) allows full fusion to trigger quite fast endocytosis, further blurring the efficiency differences between the two models.
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Affiliation(s)
- Silvio O Rizzoli
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, 37077 Göttingen, Germany
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Bronk P, Deák F, Wilson MC, Liu X, Südhof TC, Kavalali ET. Differential effects of SNAP-25 deletion on Ca2+ -dependent and Ca2+ -independent neurotransmission. J Neurophysiol 2007; 98:794-806. [PMID: 17553942 DOI: 10.1152/jn.00226.2007] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
At the synapse, SNAP-25, along with syntaxin/HPC-1 and synaptobrevin/VAMP, forms SNARE N-ethylmaleimide-sensitive factor [soluble (NSF) attachment protein receptor] complexes that are thought to catalyze membrane fusion. Results from neuronal cultures of synaptobrevin-2 knockout (KO) mice showed that loss of synaptobrevin has a more severe effect on calcium-evoked release than on spontaneous release or on release evoked by hypertonicity. In this study, we recorded neurotransmitter release from neuronal cultures of SNAP-25 KO mice to determine whether they share this property. In neurons lacking SNAP-25, as those deficient in synaptobrevin-2, we found that approximately 10-12% of calcium-independent excitatory and inhibitory neurotransmitter release persisted. However, in contrast to synaptobrevin-2 knockouts, this remaining readily releasable pool in SNAP-25-deficient synapses was virtually insensitive to calcium-dependent-evoked stimulation. Although field stimulation reliably evoked neurotransmitter release in synaptobrevin-2 KO neurons, responses were rare in neurons lacking SNAP-25, and unlike synaptobrevin-2-deficient synapses, SNAP-25-deficient synapses did not exhibit facilitation of release during high-frequency stimulation. This severe loss of evoked exocytosis was matched by a reduction, but not a complete loss, of endocytosis during evoked stimulation. Moreover, synaptic vesicle turnover probed by FM-dye uptake and release during hypertonic stimulation was relatively unaffected by the absence of SNAP-25. This last difference indicates that in contrast to synaptobrevin, SNAP-25 does not directly function in endocytosis. Together, these results suggest that SNAP-25 has a more significant role in calcium-secretion coupling than synaptobrevin-2.
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Affiliation(s)
- Peter Bronk
- Department of Neuroscience, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-9111, USA
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