151
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Luo J, Norris RH, Gordon SL, Nithianantharajah J. Neurodevelopmental synaptopathies: Insights from behaviour in rodent models of synapse gene mutations. Prog Neuropsychopharmacol Biol Psychiatry 2018; 84:424-439. [PMID: 29217145 DOI: 10.1016/j.pnpbp.2017.12.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 11/28/2017] [Accepted: 12/03/2017] [Indexed: 11/15/2022]
Abstract
The genomic revolution has begun to unveil the enormous complexity and heterogeneity of the genetic basis of neurodevelopmental disorders such as such epilepsy, intellectual disability, autism spectrum disorder and schizophrenia. Increasingly, human mutations in synapse genes are being identified across these disorders. These neurodevelopmental synaptopathies highlight synaptic homeostasis pathways as a convergence point underlying disease mechanisms. Here, we review some of the key pre- and postsynaptic genes in which penetrant human mutations have been identified in neurodevelopmental disorders for which genetic rodent models have been generated. Specifically, we focus on the main behavioural phenotypes that have been documented in these animal models, to consolidate our current understanding of how synapse genes regulate key behavioural and cognitive domains. These studies provide insights into better understanding the basis of the overlapping genetic and cognitive heterogeneity observed in neurodevelopmental disorders.
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Affiliation(s)
- J Luo
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria 3052, Australia
| | - R H Norris
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria 3052, Australia
| | - S L Gordon
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria 3052, Australia
| | - J Nithianantharajah
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria 3052, Australia.
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152
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Exocytosis-related genes and response to methylphenidate treatment in adults with ADHD. Mol Psychiatry 2018; 23:1446-1452. [PMID: 28461697 DOI: 10.1038/mp.2017.90] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 02/10/2017] [Accepted: 02/28/2017] [Indexed: 01/11/2023]
Abstract
Experimental studies have demonstrated that methylphenidate (MPH) modulates the synaptic vesicle trafficking and synaptotagmin-1 (SytI) mRNA levels. SytI is a regulatory protein of the SNARE complex, a neurotransmitter exocytosis mediator. Despite this evidence, most SNARE complex-related genes have never been evaluated in attention-deficit/hyperactivity disorder (ADHD) pharmacogenetics. This study evaluates, for we believe the first time, polymorphisms on the SNARE complex-related genes STX1A (rs2228607), VAMP2 (26bp Ins/Del) and SYT1 (rs1880867 and rs2251214) on the response to immediate-release methylphenidate (IR-MPH) in a naturalistic sample of adults with ADHD. The sample comprised 433 subjects, of which 272 (62.8%) have completed the short-term IR-MPH treatment (at least 30 days). The main outcome measure was the categorical variable of short-term response to IR-MPH based on the Swanson, Nolan and Pelham Rating Scale version 4 (SNAP-IV), and on the clinical global impression-improvement scale. Additional analyses evaluated the percentage of SNAP-IV symptom reduction for each dimension as well as short- and long- (7 years) term treatment persistence. SYT1-rs2251214 was associated with the categorical short-term response to IR-MPH (P=0.006, PFDR=0.028), and with the percentage of inattention and oppositional defiant disorder symptoms reduction (P=0.007, PFDR=0.028 and P=0.017, PFDR=0.048, respectively). SYT1-rs2251214 was also associated with short-term treatment persistence (P=0.018, PFDR=0.048), and with months of treatment (P=0.002, PFDR=0.016) in the long-term protocol. Our findings suggest that SYT1-rs2251214 presents a broad influence in IR-MPH response variability in adults with ADHD, being involved with both symptom response and treatment persistence. If such findings are replicated, SytI could represent a key element in MPH pharmacodynamics in adults with ADHD.
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153
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Ramachandran R. Neurogenic inflammation and its role in migraine. Semin Immunopathol 2018; 40:301-314. [PMID: 29568973 DOI: 10.1007/s00281-018-0676-y] [Citation(s) in RCA: 159] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 03/06/2018] [Indexed: 11/28/2022]
Abstract
The etiology of migraine pain involves sensitized meningeal afferents that densely innervate the dural vasculature. These afferents, with their cell bodies located in the trigeminal ganglion, project to the nucleus caudalis, which in turn transmits signals to higher brain centers. Factors such as chronic stress, diet, hormonal fluctuations, or events like cortical spreading depression can generate a state of "sterile inflammation" in the intracranial meninges resulting in the sensitization and activation of trigeminal meningeal nociceptors. This sterile inflammatory phenotype also referred to as neurogenic inflammation is characterized by the release of neuropeptides (such as substance P, calcitonin gene related peptide) from the trigeminal innervation. This release leads to vasodilation, plasma extravasation secondary to capillary leakage, edema, and mast cell degranulation. Although neurogenic inflammation has been observed and extensively studied in peripheral tissues, its role has been primarily investigated in the genesis and maintenance of migraine pain. While some aspects of neurogenic inflammation has been disregarded in the occurrence of migraine pain, targeted analysis of factors have opened up the possibilities of a dialogue between the neurons and immune cells in driving such a sterile neuroinflammatory state in migraine pathophysiology.
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Affiliation(s)
- Roshni Ramachandran
- Anesthesiology Research, Department of Anesthesiology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA.
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154
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Williams CL, Smith SM. Calcium dependence of spontaneous neurotransmitter release. J Neurosci Res 2018; 96:335-347. [PMID: 28699241 PMCID: PMC5766384 DOI: 10.1002/jnr.24116] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 06/16/2017] [Accepted: 06/19/2017] [Indexed: 01/14/2023]
Abstract
Spontaneous release of neurotransmitters is regulated by extracellular [Ca2+ ] and intracellular [Ca2+ ]. Curiously, some of the mechanisms of Ca2+ signaling at central synapses are different at excitatory and inhibitory synapses. While the stochastic activity of voltage-activated Ca2+ channels triggers a majority of spontaneous release at inhibitory synapses, this is not the case at excitatory nerve terminals. Ca2+ release from intracellular stores regulates spontaneous release at excitatory and inhibitory terminals, as do agonists of the Ca2+ -sensing receptor. Molecular machinery triggering spontaneous vesicle fusion may differ from that underlying evoked release and may be one of the sources of heterogeneity in release mechanisms.
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Affiliation(s)
- Courtney L Williams
- Department of Medicine, Division of Pulmonary & Critical Care Medicine, Oregon Health & Science University, Portland, Oregon
- Section of Pulmonary & Critical Care Medicine, VA Portland Health Care System, Portland, Oregon
| | - Stephen M Smith
- Department of Medicine, Division of Pulmonary & Critical Care Medicine, Oregon Health & Science University, Portland, Oregon
- Section of Pulmonary & Critical Care Medicine, VA Portland Health Care System, Portland, Oregon
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155
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Yu Y, Chen S, Mo X, Gong J, Li C, Yang X. Accessory and Central α-helices of Complexin Selectively Activate Ca 2+ Triggering of Synaptic Exocytosis. Front Mol Neurosci 2018. [PMID: 29535609 PMCID: PMC5834437 DOI: 10.3389/fnmol.2018.00061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Complexins, binding to assembling soluble NSF-attachment protein receptor (SNARE) complexes, activate Ca2+ triggered exocytosis and clamp spontaneous release in the presynaptic terminal. Functions of complexin are structural dependent and mechanistically distinct. To further understand the functional/structural dependence of complexin, here we show that the accessory and central α-helices of complexin are sufficient in activation of Ca2+ triggered vesicle fusion but not in clamping spontaneous release. Targeting the two α-helices to synaptic vesicle suppresses spontaneous release, thus further emphasizing the importance of curvature membrane localization in clamping function.
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Affiliation(s)
- Yi Yu
- Key Laboratory of Cognitive Science, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis & Treatment, Laboratory of Membrane Ion Channels and Medicine, College of Biomedical Engineering, South-Central University for Nationalities, Wuhan, China
| | - Su Chen
- Key Laboratory of Cognitive Science, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis & Treatment, Laboratory of Membrane Ion Channels and Medicine, College of Biomedical Engineering, South-Central University for Nationalities, Wuhan, China
| | - Xiaoqiang Mo
- Youjiang Medical University for Nationalities, Baise, China
| | - Jihong Gong
- Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Chenhong Li
- Key Laboratory of Cognitive Science, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis & Treatment, Laboratory of Membrane Ion Channels and Medicine, College of Biomedical Engineering, South-Central University for Nationalities, Wuhan, China
| | - Xiaofei Yang
- Key Laboratory of Cognitive Science, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis & Treatment, Laboratory of Membrane Ion Channels and Medicine, College of Biomedical Engineering, South-Central University for Nationalities, Wuhan, China
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156
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Hu ML, Zhu HM, Zhang QL, Liu JJ, Ding Y, Zhong JM, Vodyanoy V, Ding MX. Exploring the Mechanisms of Electroacupuncture-Induced Analgesia through RNA Sequencing of the Periaqueductal Gray. Int J Mol Sci 2017; 19:ijms19010002. [PMID: 29295561 PMCID: PMC5795954 DOI: 10.3390/ijms19010002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2017] [Revised: 12/15/2017] [Accepted: 12/17/2017] [Indexed: 12/19/2022] Open
Abstract
Electroacupuncture (EA) can relieve various pains. However, its mechanism in terms of the transcriptome is still not well-known. To explore the full profile of EA-induced molecular modification in the central nerve system, three twins of goats were selected for a match-paired experiment: EA stimulation (60 Hz, 30 min) and none-EA (control). Goats in the EA group showed an increased (p < 0.05) nociceptive threshold compared with the control goats. Experimental goats were sacrificed at 4 h of the experiment, and the periaqueductal grays were harvested for RNA sequencing. As a result, 2651 differentially expressed genes (1803 up-regulated and 848 down-regulated genes) were found and enriched in 30 Kyoto Encyclopedia of Genes and Genomes pathways and 149 gene ontology terms. EA-regulated five neuropeptide genes (proenkephalin, proopiomelanocortin, preprodynorphin, diazepam-binding inhibitor and proprotein convertase 1 inhibitor) were validated with quantitative PCR. Furthermore, up-regulated glutamate receptors, glutamate transporters, γ-aminobutyric acid (GABA) receptors, GABA transporters, synaptotagmins or mitogen-activated protein kinase (MAPK) genes might contribute to EA-induced analgesia through regulating the glutamatergic synapse, GABAergic synapse, MAPKs, ribosome or ubiquitin-proteasome pathways. Our findings reveal a full profile of molecular modification in response to EA and provide a solid experimental framework for exploring the mechanisms underlying EA-induced analgesia.
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Affiliation(s)
- Man-Li Hu
- College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
| | - Hong-Mei Zhu
- College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
| | - Qiu-Lin Zhang
- College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
| | - Jing-Jing Liu
- College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
| | - Yi Ding
- College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
| | - Ju-Ming Zhong
- College of Physiology and Pharmacology, Auburn University, Auburn, AL 36849, USA.
| | - Vitaly Vodyanoy
- College of Physiology and Pharmacology, Auburn University, Auburn, AL 36849, USA.
| | - Ming-Xing Ding
- College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
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157
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Synaptotagmin-1 drives synchronous Ca 2+-triggered fusion by C 2B-domain-mediated synaptic-vesicle-membrane attachment. Nat Neurosci 2017; 21:33-40. [PMID: 29230057 PMCID: PMC5742540 DOI: 10.1038/s41593-017-0037-5] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 10/14/2017] [Indexed: 12/19/2022]
Abstract
The synaptic vesicle (SV) protein Synaptotagmin-1 (Syt1) is the Ca2+ sensor for fast synchronous release. Biochemical and structural data suggest that Syt1 interacts with phospholipids and SNARE complex, but how these interactions translate into SV fusion remains poorly understood. Utilizing flash-and-freeze electron microscopy, which triggers action potentials (AP) with light and coordinately arrests synaptic structures with rapid freezing, we found synchronous release-impairing mutations in the Syt1 C2B domain (K325, 327; R398, 399) to also disrupt SV-active zone plasma membrane attachment. Single AP induction rescued membrane attachment in these mutants within <10ms through activation of the Syt1 Ca2+ binding site. The rapid SV membrane translocation temporarily correlates with resynchronization of release and paired pulse facilitation. Based on these findings, we redefine the role of Syt1 as part of Ca2+-dependent vesicle translocation machinery, and propose that Syt1 enables fast neurotransmitter release by means of its dynamic membrane attachment activities.
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158
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Bian X, Saheki Y, De Camilli P. Ca 2+ releases E-Syt1 autoinhibition to couple ER-plasma membrane tethering with lipid transport. EMBO J 2017; 37:219-234. [PMID: 29222176 DOI: 10.15252/embj.201797359] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 11/08/2017] [Accepted: 11/10/2017] [Indexed: 11/09/2022] Open
Abstract
The extended synaptotagmins (E-Syts) are endoplasmic reticulum (ER) proteins that bind the plasma membrane (PM) via C2 domains and transport lipids between them via SMP domains. E-Syt1 tethers and transports lipids in a Ca2+-dependent manner, but the role of Ca2+ in this regulation is unclear. Of the five C2 domains of E-Syt1, only C2A and C2C contain Ca2+-binding sites. Using liposome-based assays, we show that Ca2+ binding to C2C promotes E-Syt1-mediated membrane tethering by releasing an inhibition that prevents C2E from interacting with PI(4,5)P2-rich membranes, as previously suggested by studies in semi-permeabilized cells. Importantly, Ca2+ binding to C2A enables lipid transport by releasing a charge-based autoinhibitory interaction between this domain and the SMP domain. Supporting these results, E-Syt1 constructs defective in Ca2+ binding in either C2A or C2C failed to rescue two defects in PM lipid homeostasis observed in E-Syts KO cells, delayed diacylglycerol clearance from the PM and impaired Ca2+-triggered phosphatidylserine scrambling. Thus, a main effect of Ca2+ on E-Syt1 is to reverse an autoinhibited state and to couple membrane tethering with lipid transport.
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Affiliation(s)
- Xin Bian
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA.,Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA.,Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, USA
| | - Yasunori Saheki
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA .,Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA.,Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, USA.,Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Pietro De Camilli
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA .,Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA.,Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, USA.,Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT, USA
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159
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Gorkhali R, Huang K, Kirberger M, Yang JJ. Defining potential roles of Pb(2+) in neurotoxicity from a calciomics approach. Metallomics 2017; 8:563-78. [PMID: 27108875 DOI: 10.1039/c6mt00038j] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Metal ions play crucial roles in numerous biological processes, facilitating biochemical reactions by binding to various proteins. An increasing body of evidence suggests that neurotoxicity associated with exposure to nonessential metals (e.g., Pb(2+)) involves disruption of synaptic activity, and these observed effects are associated with the ability of Pb(2+) to interfere with Zn(2+) and Ca(2+)-dependent functions. However, the molecular mechanism behind Pb(2+) toxicity remains a topic of debate. In this review, we first discuss potential neuronal Ca(2+) binding protein (CaBP) targets for Pb(2+) such as calmodulin (CaM), synaptotagmin, neuronal calcium sensor-1 (NCS-1), N-methyl-d-aspartate receptor (NMDAR) and family C of G-protein coupled receptors (cGPCRs), and their involvement in Ca(2+)-signalling pathways. We then compare metal binding properties between Ca(2+) and Pb(2+) to understand the structural implications of Pb(2+) binding to CaBPs. Statistical and biophysical studies (e.g., NMR and fluorescence spectroscopy) of Pb(2+) binding are discussed to investigate the molecular mechanism behind Pb(2+) toxicity. These studies identify an opportunistic, allosteric binding of Pb(2+) to CaM, which is distinct from ionic displacement. Together, these data suggest three potential modes of Pb(2+) activity related to molecular and/or neural toxicity: (i) Pb(2+) can occupy Ca(2+)-binding sites, inhibiting the activity of the protein by structural modulation, (ii) Pb(2+) can mimic Ca(2+) in the binding sites, falsely activating the protein and perturbing downstream activities, or (iii) Pb(2+) can bind outside of the Ca(2+)-binding sites, resulting in the allosteric modulation of the protein activity. Moreover, the data further suggest that even low concentrations of Pb(2+) can interfere at multiple points within the neuronal Ca(2+) signalling pathways to cause neurotoxicity.
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Affiliation(s)
- Rakshya Gorkhali
- Department of Chemistry, Center for Diagnostics and Therapeutics, and Drug Design and Biotechnology, Georgia State University, Atlanta, GA 3030, USA.
| | - Kenneth Huang
- Department of Chemistry, Center for Diagnostics and Therapeutics, and Drug Design and Biotechnology, Georgia State University, Atlanta, GA 3030, USA.
| | - Michael Kirberger
- Department of Chemistry and Physics, Clayton State University, Morrow, GA 30260, USA.
| | - Jenny J Yang
- Department of Chemistry, Center for Diagnostics and Therapeutics, and Drug Design and Biotechnology, Georgia State University, Atlanta, GA 3030, USA.
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160
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Kim J, Shin YK. Productive and Non-productive Pathways for Synaptotagmin 1 to Support Ca 2+-Triggered Fast Exocytosis. Front Mol Neurosci 2017; 10:380. [PMID: 29187811 PMCID: PMC5695160 DOI: 10.3389/fnmol.2017.00380] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 11/01/2017] [Indexed: 12/17/2022] Open
Abstract
Ca2+-triggered SNARE-mediated membrane fusion is essential for neuronal communication. The speed of this process is of particular importance because it sets a time limit to cognitive and physical activities. In this work, we expand the proteoliposome-to-supported bilayer (SBL) fusion assay by successfully incorporating synaptotagmin 1 (Syt1), a major Ca2+ sensor. We report that Syt1 and Ca2+ together can elicit more than a 50-fold increase in the number of membrane fusion events when compared with membrane fusion mediated by SNAREs only. What is remarkable is that ~55% of all vesicle fusion events occurs within 20 ms upon vesicle docking. Furthermore, pre-binding of Syt1 to SNAREs prior to Ca2+ inhibits spontaneous fusion, but intriguingly, this leads to a complete loss of the Ca2+ responsiveness. Thus, our results suggest that there is a productive and a non-productive pathway for Syt1, depending on whether there is a premature interaction between Syt1 and SNAREs. Our results show that Ca2+ binding to Syt1 prior to Syt1's binding to SNAREs may be a prerequisite for the productive pathway. The successful reconstitution of Syt1 activities in the physiological time scale provides new opportunities to test the current mechanistic models for Ca2+-triggered exocytosis.
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Affiliation(s)
- Jaewook Kim
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, United States
| | - Yeon-Kyun Shin
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, United States
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161
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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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162
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Michalski N, Goutman JD, Auclair SM, Boutet de Monvel J, Tertrais M, Emptoz A, Parrin A, Nouaille S, Guillon M, Sachse M, Ciric D, Bahloul A, Hardelin JP, Sutton RB, Avan P, Krishnakumar SS, Rothman JE, Dulon D, Safieddine S, Petit C. Otoferlin acts as a Ca 2+ sensor for vesicle fusion and vesicle pool replenishment at auditory hair cell ribbon synapses. eLife 2017; 6:e31013. [PMID: 29111973 PMCID: PMC5700815 DOI: 10.7554/elife.31013] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 11/06/2017] [Indexed: 01/01/2023] Open
Abstract
Hearing relies on rapid, temporally precise, and sustained neurotransmitter release at the ribbon synapses of sensory cells, the inner hair cells (IHCs). This process requires otoferlin, a six C2-domain, Ca2+-binding transmembrane protein of synaptic vesicles. To decipher the role of otoferlin in the synaptic vesicle cycle, we produced knock-in mice (OtofAla515,Ala517/Ala515,Ala517) with lower Ca2+-binding affinity of the C2C domain. The IHC ribbon synapse structure, synaptic Ca2+ currents, and otoferlin distribution were unaffected in these mutant mice, but auditory brainstem response wave-I amplitude was reduced. Lower Ca2+ sensitivity and delay of the fast and sustained components of synaptic exocytosis were revealed by membrane capacitance measurement upon modulations of intracellular Ca2+ concentration, by varying Ca2+ influx through voltage-gated Ca2+-channels or Ca2+ uncaging. Otoferlin thus functions as a Ca2+ sensor, setting the rates of primed vesicle fusion with the presynaptic plasma membrane and synaptic vesicle pool replenishment in the IHC active zone.
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Affiliation(s)
- Nicolas Michalski
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Juan D Goutman
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y TécnicasBuenos AiresArgentina
| | - Sarah Marie Auclair
- Department of Cell BiologyYale University School of MedicineNew HavenUnited States
| | - Jacques Boutet de Monvel
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Margot Tertrais
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Laboratoire de Neurophysiologie de la Synapse Auditive, Bordeaux NeurocampusUniversité de BordeauxBordeauxFrance
| | - Alice Emptoz
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Alexandre Parrin
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Sylvie Nouaille
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Marc Guillon
- Wave Front Engineering Microscopy Group, Neurophotonics Laboratory, Centre National de la Recherche Scientifique, UMR 8250University Paris Descartes, Sorbonne Paris CitéParisFrance
| | - Martin Sachse
- Center for Innovation & Technological ResearchUltrapole, Institut PasteurParisFrance
| | - Danica Ciric
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Amel Bahloul
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
- Centre National de la Recherche ScientifiqueFrance
| | - Jean-Pierre Hardelin
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
| | - Roger Bryan Sutton
- Department of Cell Physiology and Molecular BiophysicsTexas Tech University Health Sciences CenterLubbockUnited States
- Center for Membrane Protein ResearchTexas Tech University Health Sciences CenterLubbockUnited States
| | - Paul Avan
- Laboratoire de Biophysique SensorielleUniversité Clermont AuvergneClermont-FerrandFrance
- UMR 1107, Institut National de la Santé et de la Recherche MédicaleClermont-FerrandFrance
- Centre Jean PerrinClermont-FerrandFrance
| | - Shyam S Krishnakumar
- Department of Cell BiologyYale University School of MedicineNew HavenUnited States
- Department of Clinical and Experimental EpilepsyInstitute of Neurology, University College LondonLondonUnited Kingdom
| | - James E Rothman
- Department of Cell BiologyYale University School of MedicineNew HavenUnited States
- Department of Clinical and Experimental EpilepsyInstitute of Neurology, University College LondonLondonUnited Kingdom
| | - Didier Dulon
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Laboratoire de Neurophysiologie de la Synapse Auditive, Bordeaux NeurocampusUniversité de BordeauxBordeauxFrance
| | - Saaid Safieddine
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
- Centre National de la Recherche ScientifiqueFrance
| | - Christine Petit
- Unité de Génétique et Physiologie de l’AuditionInstitut PasteurParisFrance
- UMRS 1120, Institut National de la Santé et de la Recherche MédicaleParisFrance
- Sorbonne Universités, UPMC Université Paris 06, Complexité du VivantParisFrance
- Syndrome de Usher et Autres Atteintes Rétino-CochléairesInstitut de la VisionParisFrance
- Collège de FranceParisFrance
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163
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Kaempf N, Maritzen T. Safeguards of Neurotransmission: Endocytic Adaptors as Regulators of Synaptic Vesicle Composition and Function. Front Cell Neurosci 2017; 11:320. [PMID: 29085282 PMCID: PMC5649181 DOI: 10.3389/fncel.2017.00320] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 09/26/2017] [Indexed: 11/13/2022] Open
Abstract
Communication between neurons relies on neurotransmitters which are released from synaptic vesicles (SVs) upon Ca2+ stimuli. To efficiently load neurotransmitters, sense the rise in intracellular Ca2+ and fuse with the presynaptic membrane, SVs need to be equipped with a stringently controlled set of transmembrane proteins. In fact, changes in SV protein composition quickly compromise neurotransmission and most prominently give rise to epileptic seizures. During exocytosis SVs fully collapse into the presynaptic membrane and consequently have to be replenished to sustain neurotransmission. Therefore, surface-stranded SV proteins have to be efficiently retrieved post-fusion to be used for the generation of a new set of fully functional SVs, a process in which dedicated endocytic sorting adaptors play a crucial role. The question of how the precise reformation of SVs is achieved is intimately linked to how SV membranes are retrieved. For a long time both processes were believed to be two sides of the same coin since Clathrin-mediated endocytosis (CME), the proposed predominant SV recycling mode, will jointly retrieve SV membranes and proteins. However, with the recent proposal of Clathrin-independent SV recycling pathways SV membrane retrieval and SV reformation turn into separable events. This review highlights the progress made in unraveling the molecular mechanisms mediating the high-fidelity retrieval of SV proteins and discusses how the gathered knowledge about SV protein recycling fits in with the new notions of SV membrane endocytosis.
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Affiliation(s)
- Natalie Kaempf
- Molecular Physiology and Cell Biology Section, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Tanja Maritzen
- Molecular Physiology and Cell Biology Section, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
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164
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Wickner W, Rizo J. A cascade of multiple proteins and lipids catalyzes membrane fusion. Mol Biol Cell 2017; 28:707-711. [PMID: 28292915 PMCID: PMC5349777 DOI: 10.1091/mbc.e16-07-0517] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 01/05/2017] [Accepted: 01/10/2017] [Indexed: 11/11/2022] Open
Abstract
Recent studies suggest revisions to the SNARE paradigm of membrane fusion. Membrane tethers and/or SNAREs recruit proteins of the Sec 1/Munc18 family to catalyze SNARE assembly into trans-complexes. SNARE-domain zippering draws the bilayers into immediate apposition and provides a platform to position fusion triggers such as Sec 17/α-SNAP and/or synaptotagmin, which insert their apolar "wedge" domains into the bilayers, initiating the lipid rearrangements of fusion.
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Affiliation(s)
- William Wickner
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755 )
| | - Josep Rizo
- Departments of Biophysics, Biochemistry, and Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390 )
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165
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Exceptionally tight membrane-binding may explain the key role of the synaptotagmin-7 C 2A domain in asynchronous neurotransmitter release. Proc Natl Acad Sci U S A 2017; 114:E8518-E8527. [PMID: 28923929 DOI: 10.1073/pnas.1710708114] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Synaptotagmins (Syts) act as Ca2+ sensors in neurotransmitter release by virtue of Ca2+-binding to their two C2 domains, but their mechanisms of action remain unclear. Puzzlingly, Ca2+-binding to the C2B domain appears to dominate Syt1 function in synchronous release, whereas Ca2+-binding to the C2A domain mediates Syt7 function in asynchronous release. Here we show that crystal structures of the Syt7 C2A domain and C2AB region, and analyses of intrinsic Ca2+-binding to the Syt7 C2 domains using isothermal titration calorimetry, did not reveal major differences that could explain functional differentiation between Syt7 and Syt1. However, using liposome titrations under Ca2+ saturating conditions, we show that the Syt7 C2A domain has a very high membrane affinity and dominates phospholipid binding to Syt7 in the presence or absence of l-α-phosphatidylinositol 4,5-diphosphate (PIP2). For Syt1, the two Ca2+-saturated C2 domains have similar affinities for membranes lacking PIP2, but the C2B domain dominates binding to PIP2-containing membranes. Mutagenesis revealed that the dramatic differences in membrane affinity between the Syt1 and Syt7 C2A domains arise in part from apparently conservative residue substitutions, showing how striking biochemical and functional differences can result from the cumulative effects of subtle residue substitutions. Viewed together, our results suggest that membrane affinity may be a key determinant of the functions of Syt C2 domains in neurotransmitter release.
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166
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Lai Y, Choi UB, Leitz J, Rhee HJ, Lee C, Altas B, Zhao M, Pfuetzner RA, Wang AL, Brose N, Rhee J, Brunger AT. Molecular Mechanisms of Synaptic Vesicle Priming by Munc13 and Munc18. Neuron 2017; 95:591-607.e10. [PMID: 28772123 DOI: 10.1016/j.neuron.2017.07.004] [Citation(s) in RCA: 160] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 05/08/2017] [Accepted: 07/06/2017] [Indexed: 11/18/2022]
Abstract
Munc13 catalyzes the transit of syntaxin from a closed complex with Munc18 into the ternary SNARE complex. Here we report a new function of Munc13, independent of Munc18: it promotes the proper syntaxin/synaptobrevin subconfiguration during assembly of the ternary SNARE complex. In cooperation with Munc18, Munc13 additionally ensures the proper syntaxin/SNAP-25 subconfiguration. In a reconstituted fusion assay with SNAREs, complexin, and synaptotagmin, inclusion of both Munc13 and Munc18 quadruples the Ca2+-triggered amplitude and achieves Ca2+ sensitivity at near-physiological concentrations. In Munc13-1/2 double-knockout neurons, expression of a constitutively open mutant of syntaxin could only minimally restore neurotransmitter release relative to Munc13-1 rescue. Together, the physiological functions of Munc13 may be related to regulation of proper SNARE complex assembly.
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Affiliation(s)
- Ying Lai
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University, Stanford, CA 94305, USA; Department of Photon Science, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
| | - Ucheor B Choi
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University, Stanford, CA 94305, USA; Department of Photon Science, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
| | - Jeremy Leitz
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University, Stanford, CA 94305, USA; Department of Photon Science, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
| | - Hong Jun Rhee
- Department of Molecular Neurobiology, Max Planck Institute for Experimental Medicine, 37075 Göttingen, Germany
| | - Choongku Lee
- Department of Molecular Neurobiology, Max Planck Institute for Experimental Medicine, 37075 Göttingen, Germany
| | - Bekir Altas
- Department of Molecular Neurobiology, Max Planck Institute for Experimental Medicine, 37075 Göttingen, Germany
| | - Minglei Zhao
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University, Stanford, CA 94305, USA; Department of Photon Science, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
| | - Richard A Pfuetzner
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University, Stanford, CA 94305, USA; Department of Photon Science, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
| | - Austin L Wang
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University, Stanford, CA 94305, USA; Department of Photon Science, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute for Experimental Medicine, 37075 Göttingen, Germany
| | - JeongSeop Rhee
- Department of Molecular Neurobiology, Max Planck Institute for Experimental Medicine, 37075 Göttingen, Germany
| | - Axel T Brunger
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University, Stanford, CA 94305, USA; Department of Photon Science, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA.
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167
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Guan Z, Bykhovskaia M, Jorquera RA, Sutton RB, Akbergenova Y, Littleton JT. A synaptotagmin suppressor screen indicates SNARE binding controls the timing and Ca 2+ cooperativity of vesicle fusion. eLife 2017; 6:28409. [PMID: 28895532 PMCID: PMC5617632 DOI: 10.7554/elife.28409] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 09/11/2017] [Indexed: 01/05/2023] Open
Abstract
The synaptic vesicle Ca2+ sensor Synaptotagmin binds Ca2+ through its two C2 domains to trigger membrane interactions. Beyond membrane insertion by the C2 domains, other requirements for Synaptotagmin activity are still being elucidated. To identify key residues within Synaptotagmin required for vesicle cycling, we took advantage of observations that mutations in the C2B domain Ca2+-binding pocket dominantly disrupt release from invertebrates to humans. We performed an intragenic screen for suppressors of lethality induced by expression of Synaptotagmin C2B Ca2+-binding mutants in Drosophila. This screen uncovered essential residues within Synaptotagmin that suggest a structural basis for several activities required for fusion, including a C2B surface implicated in SNARE complex interaction that is required for rapid synchronization and Ca2+ cooperativity of vesicle release. Using electrophysiological, morphological and computational characterization of these mutants, we propose a sequence of molecular interactions mediated by Synaptotagmin that promote Ca2+ activation of the synaptic vesicle fusion machinery.
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Affiliation(s)
- Zhuo Guan
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Maria Bykhovskaia
- Department of Neurology, School of Medicine, Wayne State University, Detroit, United States
| | - Ramon A Jorquera
- Neuroscience Department, Universidad Central del Caribe, Bayamon, Puerto Rico
| | - Roger Bryan Sutton
- Department of Cell Physiology and Molecular Biophysics, Texas Tech University Health Sciences Center, Lubbock, United States
| | - Yulia Akbergenova
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - J Troy Littleton
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
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168
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Liu X, Seven AB, Xu J, Esser V, Su L, Ma C, Rizo J. Simultaneous lipid and content mixing assays for in vitro reconstitution studies of synaptic vesicle fusion. Nat Protoc 2017; 12:2014-2028. [PMID: 28858288 PMCID: PMC6163043 DOI: 10.1038/nprot.2017.068] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
This protocol describes reconstitution assays to study how the neurotransmitter release machinery triggers Ca2+-dependent synaptic vesicle fusion. The assays monitor fusion between proteoliposomes containing the synaptic vesicle SNARE synaptobrevin (with or without the Ca2+ sensor synaptotagmin-1) and proteoliposomes initially containing the plasma membrane SNAREs syntaxin-1 and soluble NSF attachment protein (SNAP)-25. Lipid mixing (from fluorescence de-quenching of Marina-Blue-labeled lipids) and content mixing (from development of fluorescence resonance energy transfer (FRET) between phycoerythrin-biotin (PhycoE-Biotin) and Cy5-streptavidin trapped in the two proteoliposome populations) are measured simultaneously to ensure that true, nonleaky membrane fusion is monitored. This protocol is based on a method developed to study yeast vacuolar fusion. In contrast to other protocols used to study the release machinery, this assay incorporates N-ethylmaleimide sensitive factor (NSF) and α-SNAP, which disassemble syntaxin-1 and SNAP-25 heterodimers. As a result, fusion requires Munc18-1, which binds to the released syntaxin-1, and Munc13-1, which, together with Munc18-1, orchestrates SNARE complex assembly. The protocol can be readily adapted to investigation of other types of intracellular membrane fusion by using appropriate alternative proteins. Total time required for one round of the assay is 4 d.
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Affiliation(s)
- Xiaoxia Liu
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Alpay Burak Seven
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Junjie Xu
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Victoria Esser
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Lijing Su
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Cong Ma
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Josep Rizo
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
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169
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Wang J, Li F, Bello OD, Sindelar CV, Pincet F, Krishnakumar SS, Rothman JE. Circular oligomerization is an intrinsic property of synaptotagmin. eLife 2017; 6. [PMID: 28850328 PMCID: PMC5576491 DOI: 10.7554/elife.27441] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 08/11/2017] [Indexed: 11/13/2022] Open
Abstract
Previously, we showed that synaptotagmin1 (Syt1) forms Ca2+-sensitive ring-like oligomers on membranes containing acidic lipids and proposed a potential role in regulating neurotransmitter release (Zanetti et al., 2016). Here, we report that Syt1 assembles into similar ring-like oligomers in solution when triggered by naturally occurring polyphosphates (PIP2 and ATP) and magnesium ions (Mg2+). These soluble Syt1 rings were observed by electron microscopy and independently demonstrated and quantified using fluorescence correlation spectroscopy. Oligomerization is triggered when polyphosphates bind to the polylysine patch in C2B domain and is stabilized by Mg2+, which neutralizes the Ca2+-binding aspartic acids that likely contribute to the C2B interface in the oligomer. Overall, our data show that ring-like polymerization is an intrinsic property of Syt1 with reasonable affinity that can be triggered by the vesicle docking C2B-PIP2 interaction and raise the possibility that Syt1 rings could pre-form on the synaptic vesicle to facilitate docking.
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Affiliation(s)
- Jing Wang
- Departments of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Feng Li
- Departments of Cell Biology, Yale University School of Medicine, New Haven, United States
| | - Oscar D Bello
- Departments of Cell Biology, Yale University School of Medicine, New Haven, United States.,Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United Kingdom
| | - Charles Vaughn Sindelar
- Departments of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, United States
| | - Frédéric Pincet
- Departments of Cell Biology, Yale University School of Medicine, New Haven, United States.,Laboratoire de Physique Statistique, UMR CNRS 8550 Associée aux Universités Paris 6 et Paris 7, Paris, France
| | - Shyam S Krishnakumar
- Departments of Cell Biology, Yale University School of Medicine, New Haven, United States.,Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United Kingdom
| | - James E Rothman
- Departments of Cell Biology, Yale University School of Medicine, New Haven, United States.,Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, London, United Kingdom
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170
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Gipson P, Fukuda Y, Danev R, Lai Y, Chen DH, Baumeister W, Brunger AT. Morphologies of synaptic protein membrane fusion interfaces. Proc Natl Acad Sci U S A 2017; 114:9110-9115. [PMID: 28739947 PMCID: PMC5576828 DOI: 10.1073/pnas.1708492114] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Neurotransmitter release is orchestrated by synaptic proteins, such as SNAREs, synaptotagmin, and complexin, but the molecular mechanisms remain unclear. We visualized functionally active synaptic proteins reconstituted into proteoliposomes and their interactions in a native membrane environment by electron cryotomography with a Volta phase plate for improved resolvability. The images revealed individual synaptic proteins and synaptic protein complex densities at prefusion contact sites between membranes. We observed distinct morphologies of individual synaptic proteins and their complexes. The minimal system, consisting of neuronal SNAREs and synaptotagmin-1, produced point and long-contact prefusion states. Morphologies and populations of these states changed as the regulatory factors complexin and Munc13 were added. Complexin increased the membrane separation, along with a higher propensity of point contacts. Further inclusion of the priming factor Munc13 exclusively restricted prefusion states to point contacts, all of which efficiently fused upon Ca2+ triggering. We conclude that synaptic proteins have evolved to limit possible contact site assemblies and morphologies to those that promote fast Ca2+-triggered release.
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Affiliation(s)
- Preeti Gipson
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305
- Department of Structural Biology, Stanford University, Stanford, CA 94305
- Department of Photon Science, Stanford University, Stanford, CA 94305
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305
| | - Yoshiyuki Fukuda
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Radostin Danev
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Ying Lai
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305
- Department of Structural Biology, Stanford University, Stanford, CA 94305
- Department of Photon Science, Stanford University, Stanford, CA 94305
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305
| | - Dong-Hua Chen
- Department of Structural Biology, Stanford University, Stanford, CA 94305
| | - Wolfgang Baumeister
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Axel T Brunger
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305;
- Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305
- Department of Structural Biology, Stanford University, Stanford, CA 94305
- Department of Photon Science, Stanford University, Stanford, CA 94305
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305
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171
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Interactions Between SNAP-25 and Synaptotagmin-1 Are Involved in Vesicle Priming, Clamping Spontaneous and Stimulating Evoked Neurotransmission. J Neurosci 2017; 36:11865-11880. [PMID: 27881774 DOI: 10.1523/jneurosci.1011-16.2016] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Revised: 09/29/2016] [Accepted: 09/29/2016] [Indexed: 01/20/2023] Open
Abstract
Whether interactions between synaptotagmin-1 (syt-1) and the soluble NSF attachment protein receptors (SNAREs) are required during neurotransmission is debated. We examined five SNAP-25 mutations designed to interfere with syt-1 interactions. One mutation, D51/E52/E55A, targeted negative charges within region II of the primary interface (Zhou et al., 2015); two mutations targeted region I (D166A and D166/E170A) and one mutation targeted both (D51/E52/E55/D166A). The final mutation (D186/D193A) targeted C-terminal residues not expected to interact with syt-1. An in vitro assay showed that the region I, region II, and region I+II (D51/E52/E55/D166A) mutants markedly reduced the attachment between syt-1 and t-SNARE-carrying vesicles in the absence of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]. In the presence of PI(4,5)P2, vesicle attachment was unaffected by mutation. When expressed in Snap-25-null mouse autaptic neurons, region I mutations reduced the size of the readily releasable pool of vesicles, whereas the region II mutation reduced vesicular release probability. Combining both in the D51/E52/E55/D166A mutation abrogated evoked release. These data point to a division of labor between region I (vesicle priming) and region II (evoked release). Spontaneous release was disinhibited by region I mutations and found to correlate with defective complexin (Cpx) clamping in an in vitro fusion assay, pointing to an interdependent role of synaptotagmin and Cpx in release clamping. Mutation in region II (D51/E52/E55A) also unclamped release, but this effect could be overcome by synaptotagmin overexpression, arguing against an obligatory role in clamping. We conclude that three synaptic release functions of syt-1, vesicle priming, spontaneous release clamping, and evoked release triggering, depend on direct SNARE complex interaction. SIGNIFICANCE STATEMENT The function of synaptotagmin-1 (syt-1):soluble NSF attachment protein receptor (SNARE) interactions during neurotransmission remains unclear. We mutated SNAP-25 within the recently identified region I and region II of the primary synaptotagmin:SNARE interface. Using in vitro assays and rescue experiments in autaptic neurons, we show that interactions within region II of the primary interface are necessary for synchronized calcium-triggered release, whereas region I is involved in vesicle priming. Spontaneous release was disinhibited by region I mutation and found to correlate with defective complexin (Cpx) clamping in vitro, pointing to an interdependent role of synaptotagmin and Cpx in release clamping. Therefore, vesicle priming, clamping spontaneous release, and eliciting evoked release are three different functions of syt-1 that involve different interaction modes with the SNARE complex.
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172
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van der Stijl R, Withoff S, Verbeek DS. Spinocerebellar ataxia: miRNAs expose biological pathways underlying pervasive Purkinje cell degeneration. Neurobiol Dis 2017; 108:148-158. [PMID: 28823930 DOI: 10.1016/j.nbd.2017.08.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 07/21/2017] [Accepted: 08/16/2017] [Indexed: 01/09/2023] Open
Abstract
Recent work has demonstrated the importance of miRNAs in the pathogenesis of various brain disorders including the neurodegenerative disorder spinocerebellar ataxia (SCA). This review focuses on the role of miRNAs in the shared pathogenesis of the different SCA types. We examine the novel findings of a recent cell-type-specific RNA-sequencing study in mouse brain and discuss how the identification of Purkinje-cell-enriched miRNAs highlights biological pathways that expose the mechanisms behind pervasive Purkinje cell degeneration in SCA. These key pathways are likely to contain targets for therapeutic development and represent potential candidate genes for genetically unsolved SCAs.
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Affiliation(s)
- Rogier van der Stijl
- Department of Genetics, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands
| | - Sebo Withoff
- Department of Genetics, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands
| | - Dineke S Verbeek
- Department of Genetics, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands.
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173
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The primed SNARE-complexin-synaptotagmin complex for neuronal exocytosis. Nature 2017; 548:420-425. [PMID: 28813412 DOI: 10.1038/nature23484] [Citation(s) in RCA: 181] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 07/14/2017] [Indexed: 12/17/2022]
Abstract
Synaptotagmin, complexin, and neuronal SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptor) proteins mediate evoked synchronous neurotransmitter release, but the molecular mechanisms mediating the cooperation between these molecules remain unclear. Here we determine crystal structures of the primed pre-fusion SNARE-complexin-synaptotagmin-1 complex. These structures reveal an unexpected tripartite interface between synaptotagmin-1 and both the SNARE complex and complexin. Simultaneously, a second synaptotagmin-1 molecule interacts with the other side of the SNARE complex via the previously identified primary interface. Mutations that disrupt either interface in solution also severely impair evoked synchronous release in neurons, suggesting that both interfaces are essential for the primed pre-fusion state. Ca2+ binding to the synaptotagmin-1 molecules unlocks the complex, allows full zippering of the SNARE complex, and triggers membrane fusion. The tripartite SNARE-complexin-synaptotagmin-1 complex at a synaptic vesicle docking site has to be unlocked for triggered fusion to start, explaining the cooperation between complexin and synaptotagmin-1 in synchronizing evoked release on the sub-millisecond timescale.
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174
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Geerts CJ, Mancini R, Chen N, Koopmans FTW, Li KW, Smit AB, van Weering JRT, Verhage M, Groffen AJA. Tomosyn associates with secretory vesicles in neurons through its N- and C-terminal domains. PLoS One 2017; 12:e0180912. [PMID: 28746398 PMCID: PMC5529015 DOI: 10.1371/journal.pone.0180912] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 06/22/2017] [Indexed: 02/03/2023] Open
Abstract
The secretory pathway in neurons requires efficient targeting of cargos and regulatory proteins to their release sites. Tomosyn contributes to synapse function by regulating synaptic vesicle (SV) and dense-core vesicle (DCV) secretion. While there is large support for the presynaptic accumulation of tomosyn in fixed preparations, alternative subcellular locations have been suggested. Here we studied the dynamic distribution of tomosyn-1 (Stxbp5) and tomosyn-2 (Stxbp5l) in mouse hippocampal neurons and observed a mixed diffuse and punctate localization pattern of both isoforms. Tomosyn-1 accumulations were present in axons and dendrites. As expected, tomosyn-1 was expressed in about 75% of the presynaptic terminals. Interestingly, also bidirectional moving tomosyn-1 and -2 puncta were observed. Despite the lack of a membrane anchor these puncta co-migrated with synapsin and neuropeptide Y, markers for respectively SVs and DCVs. Genetic blockade of two known tomosyn interactions with synaptotagmin-1 and its cognate SNAREs did not abolish its vesicular co-migration, suggesting an interplay of protein interactions mediated by the WD40 and SNARE domains. We hypothesize that the vesicle-binding properties of tomosyns may control the delivery, pan-synaptic sharing and secretion of neuronal signaling molecules, exceeding its canonical role at the plasma membrane.
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Affiliation(s)
- Cornelia J. Geerts
- Department of Functional Genomics, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - Roberta Mancini
- Department of Functional Genomics, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - Ning Chen
- Molecular and Cellular Neurobiology, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - Frank T. W. Koopmans
- Department of Functional Genomics, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - Ka Wan Li
- Molecular and Cellular Neurobiology, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - August B. Smit
- Molecular and Cellular Neurobiology, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | | | - Matthijs Verhage
- Department of Functional Genomics, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
- Department of Clinical Genetics, VU Medical Center, Amsterdam, The Netherlands
| | - Alexander J. A. Groffen
- Department of Functional Genomics, Centre for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
- Department of Clinical Genetics, VU Medical Center, Amsterdam, The Netherlands
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175
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Song H, Orr A, Duan M, Merz AJ, Wickner W. Sec17/Sec18 act twice, enhancing membrane fusion and then disassembling cis-SNARE complexes. eLife 2017; 6. [PMID: 28718762 PMCID: PMC5540461 DOI: 10.7554/elife.26646] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 07/17/2017] [Indexed: 12/17/2022] Open
Abstract
At physiological protein levels, the slow HOPS- and SNARE-dependent fusion which occurs upon complete SNARE zippering is stimulated by Sec17 and Sec18:ATP without requiring ATP hydrolysis. To stimulate, Sec17 needs its central residues which bind the 0-layer of the SNARE complex and its N-terminal apolar loop. Adding a transmembrane anchor to the N-terminus of Sec17 bypasses this requirement for apolarity of the Sec17 loop, suggesting that the loop functions for membrane binding rather than to trigger bilayer rearrangement. In contrast, when complete C-terminal SNARE zippering is prevented, fusion strictly requires Sec18 and Sec17, and the Sec17 apolar loop has functions beyond membrane anchoring. Thus Sec17 and Sec18 act twice in the fusion cycle, binding to trans-SNARE complexes to accelerate fusion, then hydrolyzing ATP to disassemble cis-SNARE complexes.
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Affiliation(s)
- Hongki Song
- Department of Biochemistry and Cell Biology, Geisel School of Medicine, Hanover, United States
| | - Amy Orr
- Department of Biochemistry and Cell Biology, Geisel School of Medicine, Hanover, United States
| | - Mengtong Duan
- Departments of Biochemistry, University of Washington, Seattle, United States
| | - Alexey J Merz
- Departments of Biochemistry, University of Washington, Seattle, United States.,Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - William Wickner
- Department of Biochemistry and Cell Biology, Geisel School of Medicine, Hanover, United States
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176
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Neurotransmitter Release Can Be Stabilized by a Mechanism That Prevents Voltage Changes Near the End of Action Potentials from Affecting Calcium Currents. J Neurosci 2017; 36:11559-11572. [PMID: 27911759 DOI: 10.1523/jneurosci.0066-16.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 08/29/2016] [Accepted: 09/14/2016] [Indexed: 11/21/2022] Open
Abstract
At chemical synapses, presynaptic action potentials (APs) activate voltage-gated calcium channels, allowing calcium to enter and trigger neurotransmitter release. The duration, peak amplitude, and shape of the AP falling phase alter calcium entry, which can affect neurotransmitter release significantly. In many neurons, APs do not immediately return to the resting potential, but instead exhibit a period of depolarization or hyperpolarization referred to as an afterpotential. We hypothesized that presynaptic afterpotentials should alter neurotransmitter release by affecting the electrical driving force for calcium entry and calcium channel gating. In support of this, presynaptic calcium entry is affected by afterpotentials after standard instant voltage jumps. Here, we used the mouse calyx of Held synapse, which allows simultaneous presynaptic and postsynaptic patch-clamp recording, to show that the postsynaptic response is affected significantly by presynaptic afterpotentials after voltage jumps. We therefore tested the effects of presynaptic afterpotentials using simultaneous presynaptic and postsynaptic recordings and AP waveforms or real APs. Surprisingly, presynaptic afterpotentials after AP stimuli did not alter calcium channel responses or neurotransmitter release appreciably. We show that the AP repolarization time course causes afterpotential-induced changes in calcium driving force and changes in calcium channel gating to effectively cancel each other out. This mechanism, in which electrical driving force is balanced by channel gating, prevents changes in calcium influx from occurring at the end of the AP and therefore acts to stabilize synaptic transmission. In addition, this mechanism can act to stabilize neurotransmitter release when the presynaptic resting potential changes. SIGNIFICANCE STATEMENT The shape of presynaptic action potentials (APs), particularly the falling phase, affects calcium entry and small changes in calcium influx can produce large changes in postsynaptic responses. We hypothesized that afterpotentials, which often follow APs, affect calcium entry and neurotransmitter release. We tested this in calyx of Held nerve terminals, which allow simultaneous recording of presynaptic calcium currents and postsynaptic responses. Surprisingly, presynaptic afterpotentials did not alter calcium current or neurotransmitter release. We show that the AP falling phase causes afterpotential-induced changes in electrical driving force and calcium channel gating to cancel each other out. This mechanism regulates calcium entry at the end of APs and therefore stabilizes synaptic transmission. This also stabilizes responses when the presynaptic resting potential changes.
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177
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Hypertension-induced synapse loss and impairment in synaptic plasticity in the mouse hippocampus mimics the aging phenotype: implications for the pathogenesis of vascular cognitive impairment. GeroScience 2017; 39:385-406. [PMID: 28664509 DOI: 10.1007/s11357-017-9981-y] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 05/30/2017] [Indexed: 12/22/2022] Open
Abstract
Strong epidemiological and experimental evidence indicates that hypertension has detrimental effects on the cerebral microcirculation and thereby promotes accelerated brain aging. Hypertension is an independent risk factor for both vascular cognitive impairment (VCI) and Alzheimer's disease (AD). However, the pathophysiological link between hypertension-induced cerebromicrovascular injury (e.g., blood-brain barrier disruption, increased microvascular oxidative stress, and inflammation) and cognitive decline remains elusive. The present study was designed to characterize neuronal functional and morphological alterations induced by chronic hypertension and compare them to those induced by aging. To achieve that goal, we induced hypertension in young C57BL/6 mice by chronic (4 weeks) infusion of angiotensin II. We found that long-term potentiation (LTP) of performant path synapses following high-frequency stimulation of afferent fibers was decreased in hippocampal slices obtained from hypertensive mice, mimicking the aging phenotype. Hypertension and advanced age were associated with comparable decline in synaptic density in the stratum radiatum of the mouse hippocampus. Hypertension, similar to aging, was associated with changes in mRNA expression of several genes involved in regulation of neuronal function, including down-regulation of Bdnf, Homer1, and Dlg4, which may have a role in impaired synaptic plasticity. Collectively, hypertension impairs synaptic plasticity, reduces synaptic density, and promotes dysregulation of genes involved in synaptic function in the mouse hippocampus mimicking the aging phenotype. These hypertension-induced neuronal alterations may impair establishment of memories in the hippocampus and contribute to the pathogenesis and clinical manifestation of both vascular cognitive impairment (VCI) and Alzheimer's disease (AD).
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178
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Song H, Wickner W. A short region upstream of the yeast vacuolar Qa-SNARE heptad-repeats promotes membrane fusion through enhanced SNARE complex assembly. Mol Biol Cell 2017. [PMID: 28637767 PMCID: PMC5555656 DOI: 10.1091/mbc.e17-04-0218] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Membrane fusion requires that four SNARE domains form a complex. A short conserved region just upstream of the Qa-SNARE heptad-repeat domain promotes SNARE-complex assembly and hence fusion. Whereas SNARE (soluble N-ethylmaleimide–sensitive factor attachment protein receptor) heptad-repeats are well studied, SNAREs also have upstream N-domains of indeterminate function. The assembly of yeast vacuolar SNAREs into complexes for fusion can be studied in chemically defined reactions. Complementary proteoliposomes bearing a Rab:GTP and either the vacuolar R-SNARE or one of the three integrally anchored Q-SNAREs were incubated with the tethering/SM protein complex HOPS and the two other soluble SNAREs (lacking a transmembrane anchor) or their SNARE heptad-repeat domains. Fusion required a transmembrane-anchored R-SNARE on one membrane and an anchored Q-SNARE on the other. The N-domain of the Qb-SNARE was completely dispensable for fusion. Whereas fusion can be promoted by very high concentrations of the Qa-SNARE heptad-repeat domain alone, at physiological concentrations the Qa-SNARE heptad-repeat domain alone has almost no fusion activity. The 181–198 region of Qa, immediately upstream of the SNARE heptad-repeat domain, is required for normal fusion activity with HOPS. This region is needed for normal SNARE complex assembly.
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Affiliation(s)
- Hongki Song
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755-3844
| | - William Wickner
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755-3844
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179
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Katti S, Nyenhuis SB, Her B, Srivastava AK, Taylor AB, Hart PJ, Cafiso DS, Igumenova TI. Non-Native Metal Ion Reveals the Role of Electrostatics in Synaptotagmin 1-Membrane Interactions. Biochemistry 2017; 56:3283-3295. [PMID: 28574251 DOI: 10.1021/acs.biochem.7b00188] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
C2 domains are independently folded modules that often target their host proteins to anionic membranes in a Ca2+-dependent manner. In these cases, membrane association is triggered by Ca2+ binding to the negatively charged loop region of the C2 domain. Here, we used a non-native metal ion, Cd2+, in lieu of Ca2+ to gain insight into the contributions made by long-range Coulombic interactions and direct metal ion-lipid bridging to membrane binding. Using X-ray crystallography, NMR, Förster resonance energy transfer, and vesicle cosedimentation assays, we demonstrate that, although Cd2+ binds to the loop region of C2A/B domains of synaptotagmin 1 with high affinity, long-range Coulombic interactions are too weak to support membrane binding of individual domains. We attribute this behavior to two factors: the stoichiometry of Cd2+ binding to the loop regions of the C2A and C2B domains and the impaired ability of Cd2+ to directly coordinate the lipids. In contrast, electron paramagnetic resonance experiments revealed that Cd2+ does support membrane binding of the C2 domains in full-length synaptotagmin 1, where the high local lipid concentrations that result from membrane tethering can partially compensate for lack of a full complement of divalent metal ions and specific lipid coordination in Cd2+-complexed C2A/B domains. Our data suggest that long-range Coulombic interactions alone can drive the initial association of C2A/B with anionic membranes and that Ca2+ further augments membrane binding by the formation of metal ion-lipid coordination bonds and additional Ca2+ ion binding to the C2 domain loop regions.
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Affiliation(s)
- Sachin Katti
- Department of Biochemistry and Biophysics, Texas A&M University , 300 Olsen Boulevard, College Station, Texas 77843, United States
| | - Sarah B Nyenhuis
- Department of Chemistry and Biophysics Program, University of Virginia , Charlottesville, Virginia 22904, United States
| | - Bin Her
- Department of Biochemistry and Biophysics, Texas A&M University , 300 Olsen Boulevard, College Station, Texas 77843, United States
| | - Atul K Srivastava
- Department of Biochemistry and Biophysics, Texas A&M University , 300 Olsen Boulevard, College Station, Texas 77843, United States
| | - Alexander B Taylor
- Department of Biochemistry and Structural Biology and the X-ray Crystallography Core Laboratory, University of Texas Health Science Center at San Antonio , San Antonio, Texas 78229, United States
| | - P John Hart
- Department of Biochemistry and Structural Biology and the X-ray Crystallography Core Laboratory, University of Texas Health Science Center at San Antonio , San Antonio, Texas 78229, United States
| | - David S Cafiso
- Department of Chemistry and Biophysics Program, University of Virginia , Charlottesville, Virginia 22904, United States
| | - Tatyana I Igumenova
- Department of Biochemistry and Biophysics, Texas A&M University , 300 Olsen Boulevard, College Station, Texas 77843, United States
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180
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Graber ZT, Shi Z, Baumgart T. Cations induce shape remodeling of negatively charged phospholipid membranes. Phys Chem Chem Phys 2017; 19:15285-15295. [PMID: 28569910 PMCID: PMC5562360 DOI: 10.1039/c7cp00718c] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The divalent cation Ca2+ is a key component in many cell signaling and membrane trafficking pathways. Ca2+ signal transduction commonly occurs through interaction with protein partners. However, in this study we show a novel mechanism by which Ca2+ may impact membrane structure. We find an asymmetric concentration of Ca2+ across the membrane triggers deformation of membranes containing negatively charged lipids such as phosphatidylserine (PS) and phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2). Membrane invaginations in vesicles were observed forming away from the leaflet with higher Ca2+ concentration, showing that Ca2+ induces negative curvature. We hypothesize that the negative curvature is produced by Ca2+-induced clustering of PS and PI(4,5)P2. In support of this notion, we find that Ca2+-induced membrane deformation is stronger for membranes containing PI(4,5)P2, which is known to more readily cluster in the presence of Ca2+. The observed Ca2+-induced membrane deformation is strongly influenced by Na+ ions. A high symmetric [Na+] across the membrane reduces Ca2+ binding by electrostatic shielding, inhibiting Ca2+-induced membrane deformation. An asymmetric [Na+] across the membrane, however, can either oppose or support Ca2+-induced deformation, depending on the direction of the gradient in [Na+]. At a sufficiently high asymmetric Na+ concentration it can impact membrane structure in the absence of Ca2+. We propose that Ca2+ works in concert with curvature generating proteins to modulate membrane curvature and shape transitions. This novel structural impact of Ca2+ could be important for Ca2+-dependent cellular processes that involve the creation of membrane curvature, including exocytosis, invadopodia, and cell motility.
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Affiliation(s)
- Z T Graber
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA.
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181
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Li YC, Kavalali ET. Synaptic Vesicle-Recycling Machinery Components as Potential Therapeutic Targets. Pharmacol Rev 2017; 69:141-160. [PMID: 28265000 DOI: 10.1124/pr.116.013342] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Presynaptic nerve terminals are highly specialized vesicle-trafficking machines. Neurotransmitter release from these terminals is sustained by constant local recycling of synaptic vesicles independent from the neuronal cell body. This independence places significant constraints on maintenance of synaptic protein complexes and scaffolds. Key events during the synaptic vesicle cycle-such as exocytosis and endocytosis-require formation and disassembly of protein complexes. This extremely dynamic environment poses unique challenges for proteostasis at synaptic terminals. Therefore, it is not surprising that subtle alterations in synaptic vesicle cycle-associated proteins directly or indirectly contribute to pathophysiology seen in several neurologic and psychiatric diseases. In contrast to the increasing number of examples in which presynaptic dysfunction causes neurologic symptoms or cognitive deficits associated with multiple brain disorders, synaptic vesicle-recycling machinery remains an underexplored drug target. In addition, irrespective of the involvement of presynaptic function in the disease process, presynaptic machinery may also prove to be a viable therapeutic target because subtle alterations in the neurotransmitter release may counter disease mechanisms, correct, or compensate for synaptic communication deficits without the need to interfere with postsynaptic receptor signaling. In this article, we will overview critical properties of presynaptic release machinery to help elucidate novel presynaptic avenues for the development of therapeutic strategies against neurologic and neuropsychiatric disorders.
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Affiliation(s)
- Ying C Li
- Departments of Neuroscience (Y.C.L., E.T.K.) and Physiology (E.T.K.), University of Texas Southwestern Medical Center, Dallas, Texas
| | - Ege T Kavalali
- Departments of Neuroscience (Y.C.L., E.T.K.) and Physiology (E.T.K.), University of Texas Southwestern Medical Center, Dallas, Texas
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182
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Shi Y, Zhang Y, Lou J. The influence of cell membrane and SNAP25 linker loop on the dynamics and unzipping of SNARE complex. PLoS One 2017; 12:e0176235. [PMID: 28426820 PMCID: PMC5398687 DOI: 10.1371/journal.pone.0176235] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 04/08/2017] [Indexed: 11/29/2022] Open
Abstract
The soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex is composed of three neuronal proteins VAMP2, Syntaxin and SNAP25, which plays a core role during the process of membrane fusion. The zipping assembly of the SNARE complex releases energies and drives the vesicle and cell membrane into close proximity. In this study, we use all-atom molecular dynamics simulations to probe the dynamics of SNARE and its unzipping process in the context of membrane at the atomistic details. Our results indicated that the NTD of SNARE core domain is relatively more stable than CTD, which is in agreement with previous experiments. More importantly, possible interactions between the linker loop (LL) region of SNAP25 and VAMP2 are observed, suggests that the LL region may facilitate VAMP2 binding and SNARE initiation. The forced unzipping of SNARE in the presence of membrane and LL of SNAP25 reveals the possible pathway for energy generation of SNARE zipping, provides information to understand how force may regulate the cooperativity between the membrane and the SNARE complex.
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Affiliation(s)
- Yi Shi
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Yong Zhang
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Jizhong Lou
- Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- * E-mail:
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183
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Li YC, Chanaday NL, Xu W, Kavalali ET. Synaptotagmin-1- and Synaptotagmin-7-Dependent Fusion Mechanisms Target Synaptic Vesicles to Kinetically Distinct Endocytic Pathways. Neuron 2017; 93:616-631.e3. [PMID: 28111077 DOI: 10.1016/j.neuron.2016.12.010] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 08/30/2016] [Accepted: 12/02/2016] [Indexed: 12/26/2022]
Abstract
Synaptic vesicle recycling is essential for maintaining normal synaptic function. The coupling of exocytosis and endocytosis is assumed to be Ca2+ dependent, but the exact role of Ca2+ and its key effector synaptotagmin-1 (syt1) in regulation of endocytosis is poorly understood. Here, we probed the role of syt1 in single- as well as multi-vesicle endocytic events using high-resolution optical recordings. Our experiments showed that the slowed endocytosis phenotype previously reported after syt1 loss of function can also be triggered by other manipulations that promote asynchronous release such as Sr2+ substitution and complexin loss of function. The link between asynchronous release and slowed endocytosis was due to selective targeting of fused synaptic vesicles toward slow retrieval by the asynchronous release Ca2+ sensor synaptotagmin-7. In contrast, after single synaptic vesicle fusion, syt1 acted as an essential determinant of synaptic vesicle endocytosis time course by delaying the kinetics of vesicle retrieval in response to increasing Ca2+ levels.
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Affiliation(s)
- Ying C Li
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Natali L Chanaday
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Wei Xu
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Ege T Kavalali
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA.
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184
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Li X, Wang C, Wang W, Yue C, Tang Y. Neonatal exposure to BDE 209 impaired learning and memory, decreased expression of hippocampal core SNAREs and synaptophysin in adult rats. Neurotoxicology 2017; 59:40-48. [PMID: 28104350 DOI: 10.1016/j.neuro.2017.01.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 01/10/2017] [Accepted: 01/10/2017] [Indexed: 12/17/2022]
Abstract
Polybrominated diphenyl ethers (PBDEs) are a class of flame retardants. While the mechanism remains unknown, the potential neurotoxic effects of PBDEs remain a relevant issue. In the present study, neonatal Sprague-Dawley rats of both sexes were administered BDE 209 (1, 10, or 20mg/kg body weight) or peanut oil once daily from postnatal day (PND) 5 to PND 10. We examined the spatial learning and memory by Morris water maze and the working and reference memory by eight-arm radial maze in the stage of adulthood. Compared with controls, significantly longer escape latencies and fewer platform-crossings in the Morris water maze were observed in rats exposed to 1, 10, and 20mg/kg BDE 209, and these effects were dose-dependent. Significantly higher working and reference memory error rates in the eight-arm radial maze were also observed in rats exposed to 10 and 20mg/kg BDE 209. Furthermore, we detected the mRNA and protein expressions of hippocampal synaptobrevin 2, syntaxin 1A, Synaptosome Associated Protein 25 (SNAP-25), and synaptophysin using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot methods. Compared with controls, the mRNA expressions of synaptobrevin 2, syntaxin 1A, SNAP-25, and synaptophysin were significantly decreased in the hippocampi of rats exposed to 1, 10, and 20 mg/kg BDE 209, and the protein expressions of synaptobrevin 2 and SNAP-25 were significantly decreased in the hippocampi of rats exposed to 10 and 20 mg/kg BDE 209, while syntaxin 1A and synaptophysin were significantly decreased in rats exposed to 1, 10, and 20 mg/kg BDE 209. Alterations that may be involved in the learning and memory deficits induced by BDE 209 reveal the possibility of synapse loss.
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Affiliation(s)
- Xiong Li
- Department of Occupational Medicine, School of Public Health, Southwest Medical University, Luzhou City 646000, PR China
| | - Chunmei Wang
- Experimental Teaching Center, School of Public Health, Southwest Medical University, Luzhou City 646000, PR China
| | - Wen Wang
- Department of Public Health, School of Public Health, Southwest Medical University, Luzhou City 646000, PR China
| | - Chengwei Yue
- Department of Prevention Medicine, School of Public Health, Southwest Medical University, Luzhou City 646000, PR China
| | - Yan Tang
- Experimental Teaching Center, School of Public Health, Southwest Medical University, Luzhou City 646000, PR China.
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185
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Oleinick A, Svir I, Amatore C. 'Full fusion' is not ineluctable during vesicular exocytosis of neurotransmitters by endocrine cells. Proc Math Phys Eng Sci 2017; 473:20160684. [PMID: 28265193 PMCID: PMC5312129 DOI: 10.1098/rspa.2016.0684] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 11/17/2016] [Indexed: 11/12/2022] Open
Abstract
Vesicular exocytosis is an essential and ubiquitous process in neurons and endocrine cells by which neurotransmitters are released in synaptic clefts or extracellular fluids. It involves the fusion of a vesicle loaded with chemical messengers with the cell membrane through a nanometric fusion pore. In endocrine cells, unless it closes after some flickering ('Kiss-and-Run' events), this initial pore is supposed to expand exponentially, leading to a full integration of the vesicle membrane into the cell membrane-a stage called 'full fusion'. We report here a compact analytical formulation that allows precise measurements of the fusion pore expansion extent and rate to be extracted from individual amperometric spike time courses. These data definitively establish that, during release of catecholamines, fusion pores enlarge at most to approximately one-fifth of the radius of their parent vesicle, hence ruling out the ineluctability of 'full fusion'.
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Affiliation(s)
| | | | - Christian Amatore
- Ecole Normale Supérieure-PSL Research University, Département de Chimie, Sorbonne Universités-UPMC Paris 06, CNRS UMR 8640 PASTEUR, 24 rue Lhomond, 75005 Paris, France
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186
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Afuwape OAT, Wasser CR, Schikorski T, Kavalali ET. Synaptic vesicle pool-specific modification of neurotransmitter release by intravesicular free radical generation. J Physiol 2016; 595:1223-1238. [PMID: 27723113 DOI: 10.1113/jp273115] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 10/04/2016] [Indexed: 01/22/2023] Open
Abstract
KEY POINTS Synaptic transmission is mediated by the release of neurotransmitters from synaptic vesicles in response to stimulation or through the spontaneous fusion of a synaptic vesicle with the presynaptic plasma membrane. There is growing evidence that synaptic vesicles undergoing spontaneous fusion versus those fusing in response to stimuli are functionally distinct. In this study, we acutely probe the effects of intravesicular free radical generation on synaptic vesicles that fuse spontaneously or in response to stimuli. By targeting vesicles that preferentially release spontaneously, we can dissociate the effects of intravesicular free radical generation on spontaneous neurotransmission from evoked neurotransmission and vice versa. Taken together, these results further advance our knowledge of the synapse and the nature of the different synaptic vesicle pools mediating neurotransmission. ABSTRACT Earlier studies suggest that spontaneous and evoked neurotransmitter release processes are maintained by synaptic vesicles which are segregated into functionally distinct pools. However, direct interrogation of the link between this putative synaptic vesicle pool heterogeneity and neurotransmission has been difficult. To examine this link, we tagged vesicles with horseradish peroxidase (HRP) - a haem-containing plant enzyme - or antibodies against synaptotagmin-1 (syt1). Filling recycling vesicles in hippocampal neurons with HRP and subsequent treatment with hydrogen peroxide (H2 O2 ) modified the properties of neurotransmitter release depending on the route of HRP uptake. While strong depolarization-induced uptake of HRP suppressed evoked release and augmented spontaneous release, HRP uptake during mild activity selectively impaired evoked release, whereas HRP uptake at rest solely potentiated spontaneous release. Expression of a luminal HRP-tagged syt1 construct and subsequent H2 O2 application resulted in a similar increase in spontaneous release and suppression as well as desynchronization of evoked release, recapitulating the canonical syt1 loss-of-function phenotype. An antibody targeting the luminal domain of syt1, on the other hand, showed that augmentation of spontaneous release and suppression of evoked release phenotypes are dissociable depending on whether the antibody uptake occurred at rest or during depolarization. Taken together, these findings indicate that vesicles that maintain spontaneous and evoked neurotransmitter release preserve their identity during recycling and syt1 function in suppression of spontaneous neurotransmission can be acutely dissociated from syt1 function to synchronize synaptic vesicle exocytosis upon stimulation.
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Affiliation(s)
- Olusoji A T Afuwape
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX, 75390-9111, USA
| | - Catherine R Wasser
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX, 75390-9111, USA
| | - Thomas Schikorski
- Department of Anatomy, Universidad Central Del Caribe, Bayamon, PR, 00960, Puerto Rico
| | - Ege T Kavalali
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX, 75390-9111, USA.,Department of Physiology, UT Southwestern Medical Center, Dallas, TX, 75390-9111, USA
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187
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Pan YZ, Quade B, Brewer KD, Szabo M, Swarbrick JD, Graham B, Rizo J. Sequence-specific assignment of methyl groups from the neuronal SNARE complex using lanthanide-induced pseudocontact shifts. JOURNAL OF BIOMOLECULAR NMR 2016; 66:281-293. [PMID: 27988858 PMCID: PMC5216067 DOI: 10.1007/s10858-016-0078-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 11/24/2016] [Indexed: 05/03/2023]
Abstract
Neurotransmitter release depends critically on the neuronal SNARE complex formed by syntaxin-1, SNAP-25 and synaptobrevin, as well as on other proteins such as Munc18-1, Munc13-1 and synaptotagmin-1. Although three-dimensional structures are available for these components, it is still unclear how they are assembled between the synaptic vesicle and plasma membranes to trigger fast, Ca2+-dependent membrane fusion. Methyl TROSY NMR experiments provide a powerful tool to study complexes between these proteins, but assignment of the methyl groups of the SNARE complex is hindered by its limited solubility. Here we report the assignment of the isoleucine, leucine, methionine and valine methyl groups of the four SNARE motifs of syntaxin-1, SNAP-25 and synaptobrevin within the SNARE complex based solely on measurements of lanthanide-induced pseudocontact shifts. Our results illustrate the power of this approach to assign protein resonances without the need of triple resonance experiments and provide an invaluable tool for future structural studies of how the SNARE complex binds to other components of the release machinery.
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Affiliation(s)
- Yun-Zu Pan
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Bradley Quade
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Kyle D Brewer
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Monika Szabo
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - James D Swarbrick
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Bim Graham
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia
| | - Josep Rizo
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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188
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Pinheiro PS, Houy S, Sørensen JB. C2-domain containing calcium sensors in neuroendocrine secretion. J Neurochem 2016; 139:943-958. [DOI: 10.1111/jnc.13865] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 09/17/2016] [Accepted: 10/05/2016] [Indexed: 12/11/2022]
Affiliation(s)
- Paulo S. Pinheiro
- Center for Neuroscience and Cell Biology; University of Coimbra; Coimbra Portugal
| | - Sébastien Houy
- Department of Neuroscience and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - Jakob B. Sørensen
- Department of Neuroscience and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
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189
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Qiu X, Ge J, Gao Y, Teng M, Niu L. Structural analysis of Ca 2+-binding pocket of synaptotagmin 5 C2A domain. Int J Biol Macromol 2016; 95:946-953. [PMID: 27793683 DOI: 10.1016/j.ijbiomac.2016.10.083] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 10/09/2016] [Accepted: 10/24/2016] [Indexed: 10/20/2022]
Abstract
Synaptotagmins constitute a family of multifunctional integral membrane proteins found predominantly on vesicles in neural and endocrine tissues. 17 isoforms of synaptotagmin family in mammals have been identified, 7 isoforms among them are known to be able to bind Ca2+ via their C2 domains. This study presents the crystal structure of the first C2 domain (C2A domain) of synaptotagmin 5 complexed with Ca2+ at 1.90Å resolution. Comparison of the Ca2+-binding pocket of synaptotagmin 5 C2A domain with other synaptotagmin C2 domains demonstrated that a serine residue locating at Ca2+-binding loop probably responsible to the conformational variation of Ca2+-binding pocket, and thus impacts the Ca2+-binding mechanism of C2 domain, which is verified by structural analysis of the serine mutant and Ca2+-binding assays via isothermal titration calorimetry. Alteration of Ca2+-binding mechanism might be correlated with different Ca2+ response rates of synaptotagmins, which is the basis of the functions of synaptotagmins in regulating various types of Ca2+-triggered vesicle-membrane fusion processes.
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Affiliation(s)
- Xiaoting Qiu
- Key Laboratory of Applied Marine Biotechnology of Ministry of Education, Ningbo University, Ningbo, Zhejiang 315211, PR China; School of Marine Sciences, Ningbo University, Ningbo, Zhejiang 315211, PR China; Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, PR China; Key Laboratory of Structural Biology, Chinese Academy of Sciences, Hefei, Anhui 230026, PR China
| | - Junyi Ge
- Key Laboratory of Applied Marine Biotechnology of Ministry of Education, Ningbo University, Ningbo, Zhejiang 315211, PR China; School of Marine Sciences, Ningbo University, Ningbo, Zhejiang 315211, PR China
| | - Yongxiang Gao
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, PR China; Key Laboratory of Structural Biology, Chinese Academy of Sciences, Hefei, Anhui 230026, PR China
| | - Maikun Teng
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, PR China; Key Laboratory of Structural Biology, Chinese Academy of Sciences, Hefei, Anhui 230026, PR China.
| | - Liwen Niu
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, PR China; Key Laboratory of Structural Biology, Chinese Academy of Sciences, Hefei, Anhui 230026, PR China.
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190
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Xiu MH, Tian L, Chen S, Tan YL, Chen DC, Chen J, Chen N, De Yang F, Licinio J, Kosten TR, Soares JC, Zhang XY. Contribution of IL-10 and its -592 A/C polymorphism to cognitive functions in first-episode drug-naive schizophrenia. Brain Behav Immun 2016; 57:116-124. [PMID: 26971470 DOI: 10.1016/j.bbi.2016.03.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 02/29/2016] [Accepted: 03/09/2016] [Indexed: 11/30/2022] Open
Abstract
Numerous studies have shown that proinflammatory cytokines produced by immune cells in the brain have deleterious effects on cognitive functions. In contrast, IL-10, an anti-inflammatory cytokine, can be neuroprotective and prevent neuronal dysfunction. However, few studies have linked the role of IL-10 to cognitive deficits in schizophrenia. In this study, serum IL-10 levels and genotypes for the IL10 -592 A/C promoter polymorphism were measured in a cohort of first-episode drug-naïve schizophrenic patients (FEDN-S) (n=256) and healthy control subjects (HC) (n=540). All participants were assessed by the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), and psychopathology was assessed by the Positive and Negative Syndrome Scale (PANSS). In a separate transcriptomic data set containing 577 healthy human brain samples, we analyzed IL-10 and IL-10 RA/B-associated genetic networks in order to ascertain potential functions for IL-10 in the brain. We found a significant difference in allelic frequency between FEDN-S and HC subjects. The A allelic variant was associated with reduced serum IL-10 levels and worse attentional performance in FEDN-S but not in HC subjects. Moreover, serum IL-10 levels were correlated with the extent of cognitive impairment, especially attentional performance in the schizophrenic A-allele carriers. In human brain transcriptomic coexpression analysis, we found that genes most significantly co-expressed with IL10 were associated with synaptic vesicle transportation, and both IL10RA and IL10RB were most significantly co-expressed not only with genes that regulate inflammation but also with those that participate in synaptic formation. The IL10-592 A/C genetic variant was more common in schizophrenic patients than HC and was associated with lower IL-10 serum levels and worse attentional performance in these patients. Furthermore, the IL10 gene and its receptors in the healthy human brain appear to regulate inflammation and synaptic functions that are important for cognition, and hence its deficiency in schizophrenia may contribute to cognitive impairment.
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Affiliation(s)
- Mei Hong Xiu
- Beijing HuiLongGuan Hospital, Peking University, Beijing, China
| | - Li Tian
- Beijing HuiLongGuan Hospital, Peking University, Beijing, China; Neuroscience Center, University of Helsinki, Helsinki, Finland.
| | - Song Chen
- Beijing HuiLongGuan Hospital, Peking University, Beijing, China
| | - Yun Long Tan
- Beijing HuiLongGuan Hospital, Peking University, Beijing, China
| | - Da Chun Chen
- Beijing HuiLongGuan Hospital, Peking University, Beijing, China
| | - Jing Chen
- School of Medical and Health Management, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, China
| | - Nan Chen
- Beijing HuiLongGuan Hospital, Peking University, Beijing, China
| | - Fu De Yang
- Beijing HuiLongGuan Hospital, Peking University, Beijing, China
| | - Julio Licinio
- South Australian Health and Medical Research Institute, and the Department of Psychiatry, Flinders University School of Medicine, Adelaide, Australia
| | - Thomas R Kosten
- Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, TX, USA
| | - Jair C Soares
- Department of Psychiatry and Behavioral Sciences, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Xiang Yang Zhang
- Beijing HuiLongGuan Hospital, Peking University, Beijing, China; Department of Psychiatry and Behavioral Sciences, The University of Texas Health Science Center at Houston, Houston, TX, USA.
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191
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Gupta VK, Pech U, Bhukel A, Fulterer A, Ender A, Mauermann SF, Andlauer TFM, Antwi-Adjei E, Beuschel C, Thriene K, Maglione M, Quentin C, Bushow R, Schwärzel M, Mielke T, Madeo F, Dengjel J, Fiala A, Sigrist SJ. Spermidine Suppresses Age-Associated Memory Impairment by Preventing Adverse Increase of Presynaptic Active Zone Size and Release. PLoS Biol 2016; 14:e1002563. [PMID: 27684064 PMCID: PMC5042543 DOI: 10.1371/journal.pbio.1002563] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Accepted: 08/26/2016] [Indexed: 01/24/2023] Open
Abstract
Memories are assumed to be formed by sets of synapses changing their structural or functional performance. The efficacy of forming new memories declines with advancing age, but the synaptic changes underlying age-induced memory impairment remain poorly understood. Recently, we found spermidine feeding to specifically suppress age-dependent impairments in forming olfactory memories, providing a mean to search for synaptic changes involved in age-dependent memory impairment. Here, we show that a specific synaptic compartment, the presynaptic active zone (AZ), increases the size of its ultrastructural elaboration and releases significantly more synaptic vesicles with advancing age. These age-induced AZ changes, however, were fully suppressed by spermidine feeding. A genetically enforced enlargement of AZ scaffolds (four gene-copies of BRP) impaired memory formation in young animals. Thus, in the Drosophila nervous system, aging AZs seem to steer towards the upper limit of their operational range, limiting synaptic plasticity and contributing to impairment of memory formation. Spermidine feeding suppresses age-dependent memory impairment by counteracting these age-dependent changes directly at the synapse.
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Affiliation(s)
- Varun K. Gupta
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | - Ulrike Pech
- Georg-August-Universität Göttingen, Molecular Neurobiology of Behavior, Göttingen, Germany
| | - Anuradha Bhukel
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | - Andreas Fulterer
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | - Anatoli Ender
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Stephan F. Mauermann
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | | | | | - Christine Beuschel
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Kerstin Thriene
- Centre for Systems Biological Analysis, University of Freiburg, Freiburg, Germany
| | - Marta Maglione
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | - Christine Quentin
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | - René Bushow
- Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Martin Schwärzel
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Thorsten Mielke
- Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Frank Madeo
- Institute for Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
| | - Joern Dengjel
- Centre for Systems Biological Analysis, University of Freiburg, Freiburg, Germany
| | - André Fiala
- Georg-August-Universität Göttingen, Molecular Neurobiology of Behavior, Göttingen, Germany
| | - Stephan J. Sigrist
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
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192
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Böhme MA, Beis C, Reddy-Alla S, Reynolds E, Mampell MM, Grasskamp AT, Lützkendorf J, Bergeron DD, Driller JH, Babikir H, Göttfert F, Robinson IM, O'Kane CJ, Hell SW, Wahl MC, Stelzl U, Loll B, Walter AM, Sigrist SJ. Active zone scaffolds differentially accumulate Unc13 isoforms to tune Ca2+ channel–vesicle coupling. Nat Neurosci 2016; 19:1311-20. [DOI: 10.1038/nn.4364] [Citation(s) in RCA: 136] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 07/20/2016] [Indexed: 01/05/2023]
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193
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Jackson RE, Burrone J. Visualizing Presynaptic Calcium Dynamics and Vesicle Fusion with a Single Genetically Encoded Reporter at Individual Synapses. Front Synaptic Neurosci 2016; 8:21. [PMID: 27507942 PMCID: PMC4960916 DOI: 10.3389/fnsyn.2016.00021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Accepted: 07/13/2016] [Indexed: 01/08/2023] Open
Abstract
Synaptic transmission depends on the influx of calcium into the presynaptic compartment, which drives neurotransmitter release. Genetically encoded reporters are widely used tools to understand these processes, particularly pHluorin-based reporters that report vesicle exocytosis and endocytosis through pH dependent changes in fluorescence, and genetically encoded calcium indicators (GECIs) that exhibit changes in fluorescence upon binding to calcium. The recent expansion of the color palette of available indicators has made it possible to image multiple probes simultaneously within a cell. We have constructed a single molecule reporter capable of concurrent imaging of both presynaptic calcium influx and exocytosis, by fusion of sypHy, the vesicle associated protein synaptophysin containing a GFP-based pHluorin sensor, with the red-shifted GECI R-GECO1. Due to the fixed stoichiometry of the two probes, the ratio of the two responses can also be measured, providing an all optical correlate of the calcium dependence of release. Here, we have characterized stimulus-evoked sypHy-RGECO responses of hippocampal synapses in vitro, exploring the effects of different stimulus strengths and frequencies as well as variations in external calcium concentrations. By combining live sypHy-RGECO imaging with post hoc fixation and immunofluorescence, we have also investigated correlations between structural and functional properties of synapses.
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Affiliation(s)
| | - Juan Burrone
- Centre for Developmental Neurobiology, King’s College LondonLondon, UK
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194
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Bullen HE, Soldati-Favre D. A central role for phosphatidic acid as a lipid mediator of regulated exocytosis in apicomplexa. FEBS Lett 2016; 590:2469-81. [PMID: 27403735 DOI: 10.1002/1873-3468.12296] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 07/10/2016] [Accepted: 07/11/2016] [Indexed: 11/08/2022]
Abstract
Lipids are commonly known for the structural roles they play, however, the specific contribution of different lipid classes to wide-ranging signalling pathways is progressively being unravelled. Signalling lipids and their associated effector proteins are emerging as significant contributors to a vast array of effector functions within cells, including essential processes such as membrane fusion and vesicle exocytosis. Many phospholipids have signalling capacity, however, this review will focus on phosphatidic acid (PA) and the enzymes implicated in its production from diacylglycerol (DAG) and phosphatidylcholine (PC): DGK and PLD respectively. PA is a negatively charged, cone-shaped lipid identified as a key mediator in specific membrane fusion and vesicle exocytosis events in a variety of mammalian cells, and has recently been implicated in specialised secretory organelle exocytosis in apicomplexan parasites. This review summarises the recent work implicating a role for PA regulation in exocytosis in various cell types. We will discuss how these signalling events are linked to pathogenesis in the phylum Apicomplexa.
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195
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Todd PAC, McCue HV, Haynes LP, Barclay JW, Burgoyne RD. Interaction of ARF-1.1 and neuronal calcium sensor-1 in the control of the temperature-dependency of locomotion in Caenorhabditis elegans. Sci Rep 2016; 6:30023. [PMID: 27435667 PMCID: PMC4951722 DOI: 10.1038/srep30023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 06/27/2016] [Indexed: 12/15/2022] Open
Abstract
Neuronal calcium sensor-1 (NCS-1) mediates changes in cellular function by regulating various target proteins. Many potential targets have been identified but the physiological significance of only a few has been established. Upon temperature elevation, Caenorhabditis elegans exhibits reversible paralysis. In the absence of NCS-1, worms show delayed onset and a shorter duration of paralysis. This phenotype can be rescued by re-expression of ncs-1 in AIY neurons. Mutants with defects in four potential NCS-1 targets (arf-1.1, pifk-1, trp-1 and trp-2) showed qualitatively similar phenotypes to ncs-1 null worms, although the effect of pifk-1 mutation on time to paralysis was considerably delayed. Inhibition of pifk-1 also resulted in a locomotion phenotype. Analysis of double mutants showed no additive effects between mutations in ncs-1 and trp-1 or trp-2. In contrast, double mutants of arf-1.1 and ncs-1 had an intermediate phenotype, consistent with NCS-1 and ARF-1.1 acting in the same pathway. Over-expression of arf-1.1 in the AIY neurons was sufficient to rescue partially the phenotype of both the arf-1.1 and the ncs-1 null worms. These findings suggest that ARF-1.1 interacts with NCS-1 in AIY neurons and potentially pifk-1 in the Ca(2+) signaling pathway that leads to inhibited locomotion at an elevated temperature.
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Affiliation(s)
- Paul A. C. Todd
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, United Kingdom
| | - Hannah V. McCue
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, United Kingdom
| | - Lee P. Haynes
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, United Kingdom
| | - Jeff W. Barclay
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, United Kingdom
| | - Robert D. Burgoyne
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, United Kingdom
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196
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Zanetti MN, Bello OD, Wang J, Coleman J, Cai Y, Sindelar CV, Rothman JE, Krishnakumar SS. Ring-like oligomers of Synaptotagmins and related C2 domain proteins. eLife 2016; 5. [PMID: 27434670 PMCID: PMC4977156 DOI: 10.7554/elife.17262] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 07/18/2016] [Indexed: 01/25/2023] Open
Abstract
We recently reported that the C2AB portion of Synaptotagmin 1 (Syt1) could self-assemble into Ca(2+)-sensitive ring-like oligomers on membranes, which could potentially regulate neurotransmitter release. Here we report that analogous ring-like oligomers assemble from the C2AB domains of other Syt isoforms (Syt2, Syt7, Syt9) as well as related C2 domain containing protein, Doc2B and extended Synaptotagmins (E-Syts). Evidently, circular oligomerization is a general and conserved structural aspect of many C2 domain proteins, including Synaptotagmins. Further, using electron microscopy combined with targeted mutations, we show that under physiologically relevant conditions, both the Syt1 ring assembly and its rapid disruption by Ca(2+) involve the well-established functional surfaces on the C2B domain that are important for synaptic transmission. Our data suggests that ring formation may be triggered at an early step in synaptic vesicle docking and positions Syt1 to synchronize neurotransmitter release to Ca(2+) influx.
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Affiliation(s)
- Maria N Zanetti
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Oscar D Bello
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Jing Wang
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Jeff Coleman
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Yiying Cai
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
| | - Charles V Sindelar
- Department of Molecular Biophysics and Biochemistry, Yale School of Medicine, New Haven, United States
| | - James E Rothman
- Department of Cell Biology, Yale School of Medicine, New Haven, United States
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197
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Abstract
The synaptotagmin family of vesicle proteins is believed to mediate calcium-dependent regulation of membrane trafficking. Detailed biochemical and in vivo studies of the most characterized isoform, synaptotagmin 1 (syt 1), have provided compelling evidence that it functions as a calcium sensor for fast neurotransmitter release at synapses. However, the function of the remaining isoforms is unclear, and multiple roles have been hypothesized for several of these. Recent evidence in Drosophila has given insight into the function of some of the remaining synaptotagmin family members. Of the five evolutionarily conserved isoforms in Drosophila, only two, syt 1 and syt 4, localize to most, if not all, synapses. The former is localized to presynaptic terminals, whereas the latter is predominantly postsynaptic. This suggests an intriguing possibility that syt 4 may mediate a postsynaptic vesicle trafficking pathway, providing a molecular basis for an evolutionarily conserved bidirectional vesicular trafficking communication system at synapses.
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Affiliation(s)
- Motojiro Yoshihara
- The Picower Center for Learning and Memory, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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198
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Kim J, Zhu Y, Shin YK. Preincubation of t-SNAREs with Complexin I Increases Content-Mixing Efficiency. Biochemistry 2016; 55:3667-73. [PMID: 27286417 DOI: 10.1021/acs.biochem.6b00114] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Complexin (Cpx) is a major regulator for Ca(2+)-triggered fast neuroexocytosis which underlies neuronal communication. Many psychiatric and neurological disorders accompany changes in the Cpx expression level, suggesting that abnormal Cpx levels may elicit aberrant cognitive symptoms. To comprehend how the changes in the Cpx level might affect neuronal communication, we investigated Ca(2+)-triggered exocytosis at various Cpx concentrations. Ca(2+)-triggered content-mixing between a single proteoliposome of t-SNARE and another single proteoliposome of v-SNARE plus Ca(2+)-sensor synaptotagmin 1 was examined with total internal reflection microscopy. We find that Cpx enhances Ca(2+)-triggered vesicle fusion with the yield changing from approximately 10% to 70% upon increasing Cpx from 0 to 100 nM. Unexpectedly, however, the fusion efficiency becomes reduced when Cpx is increased further, dropping to 20% in the micromolar range, revealing a bell-shaped dose-response curve. Intriguingly, we find that the rate of vesicle fusion is nearly invariant through the entire range of Cpx concentrations studied, suggesting that a reevaluation of the current Cpx clamping mechanism is necessary. Thus, our results provide insights into how delicately Cpx fine-tunes neuronal communication.
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Affiliation(s)
- Jaewook Kim
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University , Ames, Iowa 50011, United States
| | - Yicheng Zhu
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University , Ames, Iowa 50011, United States
| | - Yeon-Kyun Shin
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University , Ames, Iowa 50011, United States
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199
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Abstract
Intracellular membrane fusion is mediated in most cases by membrane-bridging complexes of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). However, the assembly of such complexes in vitro is inefficient, and their uncatalysed disassembly is undetectably slow. Here, we focus on the cellular machinery that orchestrates assembly and disassembly of SNARE complexes, thereby regulating processes ranging from vesicle trafficking to organelle fusion to neurotransmitter release. Rapid progress is being made on many fronts, including the development of more realistic cell-free reconstitutions, the application of single-molecule biophysics, and the elucidation of X-ray and high-resolution electron microscopy structures of the SNARE assembly and disassembly machineries 'in action'.
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Affiliation(s)
- Richard W Baker
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA.,Present address: Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, California 92093, USA
| | - Frederick M Hughson
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
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200
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Kochubey O, Babai N, Schneggenburger R. A Synaptotagmin Isoform Switch during the Development of an Identified CNS Synapse. Neuron 2016; 90:984-99. [DOI: 10.1016/j.neuron.2016.04.038] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 02/26/2016] [Accepted: 04/20/2016] [Indexed: 01/08/2023]
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