1
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Gaidin SG, Kosenkov AM. mRNA editing of kainate receptor subunits: what do we know so far? Rev Neurosci 2022; 33:641-655. [DOI: 10.1515/revneuro-2021-0144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 01/18/2022] [Indexed: 11/15/2022]
Abstract
Abstract
Kainate receptors (KARs) are considered one of the key modulators of synaptic activity in the mammalian central nervous system. These receptors were discovered more than 30 years ago, but their role in brain functioning remains unclear due to some peculiarities. One such feature of these receptors is the editing of pre-mRNAs encoding GluK1 and GluK2 subunits. Despite the long history of studying this phenomenon, numerous questions remain unanswered. This review summarizes the current data about the mechanism and role of pre-mRNA editing of KAR subunits in the mammalian brain and proposes a perspective of future investigations.
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Affiliation(s)
- Sergei G. Gaidin
- Institute of Cell Biophysics of the Russian Academy of Sciences , 142290 , Pushchino , Russia
| | - Artem M. Kosenkov
- Institute of Cell Biophysics of the Russian Academy of Sciences , 142290 , Pushchino , Russia
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2
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Li WR, Wang YL, Li C, Gao P, Zhang FF, Hu M, Li JC, Zhang S, Li R, Zhang CX. Synaptotagmin-11 inhibits spontaneous neurotransmission through vti1a. J Neurochem 2021; 159:729-741. [PMID: 34599505 DOI: 10.1111/jnc.15523] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 11/25/2020] [Accepted: 09/26/2021] [Indexed: 12/25/2022]
Abstract
Recent work has revealed that spontaneous release plays critical roles in the central nervous system, but how it is regulated remains elusive. Here, we report that synaptotagmin-11 (Syt11), a Ca2+ -independent Syt isoform associated with schizophrenia and Parkinson's disease, suppressed spontaneous release. Syt11-knockout hippocampal neurons showed an increased frequency of miniature excitatory post-synaptic currents while over-expression of Syt11 inversely decreased the frequency. Neither knockout nor over-expression of Syt11 affected the average amplitude, suggesting the pre-synaptic regulation of spontaneous neurotransmission by Syt11. Glutathione S-transferase pull-down, co-immunoprecipitation, and affinity-purification experiments demonstrated a direct interaction of Syt11 with vps10p-tail-interactor-1a (vti1a), a non-canonical SNARE protein that maintains spontaneous release. Importantly, knockdown of vti1a reversed the phenotype of Syt11 knockout, identifying vti1a as the main target of Syt11 inhibition. Domain analysis revealed that the C2A domain of Syt11 bound vti1a with high affinity. Consistently, expression of the C2A domain alone rescued the phenotype of elevated spontaneous release in Syt11-knockout neurons similar to the full-length protein. Altogether, our results suggest that Syt11 inhibits vti1a-containing vesicles during spontaneous release.
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Affiliation(s)
- Wan-Ru Li
- Beijing Institute of Brain Disorders, Laboratory of Brain Disorders, Ministry of Science and Technology, Collaborative Innovation Center for Brain Disorders, Capital Medical University, Beijing, China
| | - Ya-Long Wang
- Beijing Institute of Brain Disorders, Laboratory of Brain Disorders, Ministry of Science and Technology, Collaborative Innovation Center for Brain Disorders, Capital Medical University, Beijing, China
| | - Chao Li
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Pei Gao
- Beijing Institute of Brain Disorders, Laboratory of Brain Disorders, Ministry of Science and Technology, Collaborative Innovation Center for Brain Disorders, Capital Medical University, Beijing, China
| | - Fei-Fan Zhang
- Beijing Institute of Brain Disorders, Laboratory of Brain Disorders, Ministry of Science and Technology, Collaborative Innovation Center for Brain Disorders, Capital Medical University, Beijing, China
| | - Meiqin Hu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Jing-Chen Li
- Beijing Institute of Brain Disorders, Laboratory of Brain Disorders, Ministry of Science and Technology, Collaborative Innovation Center for Brain Disorders, Capital Medical University, Beijing, China
| | - Shuli Zhang
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Rena Li
- Beijing Key Laboratory of Mental Disorders, Beijing Anding Hospital and Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
| | - Claire Xi Zhang
- Beijing Institute of Brain Disorders, Laboratory of Brain Disorders, Ministry of Science and Technology, Collaborative Innovation Center for Brain Disorders, Capital Medical University, Beijing, China.,Academy of Pharmacy, Xi'an Jiaotong-Liverpool University, Suzhou, China
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3
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Metabotropic actions of kainate receptors modulating glutamate release. Neuropharmacology 2021; 197:108696. [PMID: 34274351 DOI: 10.1016/j.neuropharm.2021.108696] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 06/03/2021] [Accepted: 06/07/2021] [Indexed: 12/06/2022]
Abstract
Presynaptic kainate (KA) receptors (KARs) modulate GABA and glutamate release in the central nervous system of mammals. While some of the actions of KARs are ionotropic, metabotropic actions for these receptors have also been seen to modulate both GABA and glutamate release. In general, presynaptic KARs modulate glutamate release through their metabotropic actions in a biphasic manner, with low KA concentrations producing an increase in glutamate release and higher concentrations of KA driving weaker release of this neurotransmitter. Different molecular mechanisms are involved in this modulation of glutamate release, with a G-protein independent, Ca2+-calmodulin adenylate cyclase (AC) and protein kinase A (PKA) dependent mechanism facilitating glutamate release, and a G-protein, AC and PKA dependent mechanism mediating the decrease in neurotransmitter release. Here, we describe the events underlying the KAR modulation of glutamatergic transmission in different brain regions, addressing the possible functions of this modulation and proposing future research lines in this field.
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4
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Pons-Bennaceur A, Tsintsadze V, Bui TT, Tsintsadze T, Minlebaev M, Milh M, Scavarda D, Giniatullin R, Giniatullina R, Shityakov S, Wright M, Miller AD, Lozovaya N, Burnashev N. Diadenosine-Polyphosphate Analogue AppCH2ppA Suppresses Seizures by Enhancing Adenosine Signaling in the Cortex. Cereb Cortex 2020; 29:3778-3795. [PMID: 30295710 DOI: 10.1093/cercor/bhy257] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 08/15/2018] [Accepted: 09/14/2018] [Indexed: 01/16/2023] Open
Abstract
Epilepsy is a multifactorial disorder associated with neuronal hyperexcitability that affects more than 1% of the human population. It has long been known that adenosine can reduce seizure generation in animal models of epilepsies. However, in addition to various side effects, the instability of adenosine has precluded its use as an anticonvulsant treatment. Here we report that a stable analogue of diadenosine-tetraphosphate: AppCH2ppA effectively suppresses spontaneous epileptiform activity in vitro and in vivo in a Tuberous Sclerosis Complex (TSC) mouse model (Tsc1+/-), and in postsurgery cortical samples from TSC human patients. These effects are mediated by enhanced adenosine signaling in the cortex post local neuronal adenosine release. The released adenosine induces A1 receptor-dependent activation of potassium channels thereby reducing neuronal excitability, temporal summation, and hypersynchronicity. AppCH2ppA does not cause any disturbances of the main vital autonomous functions of Tsc1+/- mice in vivo. Therefore, we propose this compound to be a potent new candidate for adenosine-related treatment strategies to suppress intractable epilepsies.
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Affiliation(s)
- Alexandre Pons-Bennaceur
- INSERM UMR1249, Mediterranean Institute of Neurobiology (INMED), Aix-Marseille University, Parc Scientifique de Luminy, Marseille, France
| | - Vera Tsintsadze
- INSERM UMR1249, Mediterranean Institute of Neurobiology (INMED), Aix-Marseille University, Parc Scientifique de Luminy, Marseille, France.,Knight Cardiovascular Institute, Oregon Health and Science University, OR, USA
| | - Thi-Thien Bui
- B&A Therapeutics, Ben-Ari Institute of Neuroarcheology, Batiment Beret-Delaage, Zone Luminy Biotech Entreprises, Marseille, Cedex 09, France
| | - Timur Tsintsadze
- INSERM UMR1249, Mediterranean Institute of Neurobiology (INMED), Aix-Marseille University, Parc Scientifique de Luminy, Marseille, France
| | - Marat Minlebaev
- INSERM UMR1249, Mediterranean Institute of Neurobiology (INMED), Aix-Marseille University, Parc Scientifique de Luminy, Marseille, France.,Laboratory of Neurobiology, Kazan Federal University, Kazan, Russia
| | - Mathieu Milh
- APHM, Department of Pediatric Neurosurgery and Neurology, CHU Timone, Marseille Cedex 5, France
| | - Didier Scavarda
- APHM, Department of Pediatric Neurosurgery and Neurology, CHU Timone, Marseille Cedex 5, France
| | - Rashid Giniatullin
- Laboratory of Neurobiology, Kazan Federal University, Kazan, Russia.,A.I. Virtanen Institute for Molecular Sciences, Department of Neurobiology, University of Eastern Finland, Kuopio, Finland
| | - Raisa Giniatullina
- A.I. Virtanen Institute for Molecular Sciences, Department of Neurobiology, University of Eastern Finland, Kuopio, Finland
| | - Sergey Shityakov
- Department of Anaesthesia and Critical Care, University of Würzburg, Josef-Schneider-Street 2, Würzburg, Germany
| | - Michael Wright
- School of Cancer and Pharmaceutical Sciences, King's College London, Franklin-Wilkins Building, Waterloo Campus, 150 Stamford Street, London, UK
| | - Andrew D Miller
- School of Cancer and Pharmaceutical Sciences, King's College London, Franklin-Wilkins Building, Waterloo Campus, 150 Stamford Street, London, UK.,Veterinary Research Institute, Hudcova 296/70, Brno, Czech Republic.,KP Therapeutics Ltd, 86 Deansgate, Manchester, UK
| | - Natalia Lozovaya
- B&A Therapeutics, Ben-Ari Institute of Neuroarcheology, Batiment Beret-Delaage, Zone Luminy Biotech Entreprises, Marseille, Cedex 09, France
| | - Nail Burnashev
- INSERM UMR1249, Mediterranean Institute of Neurobiology (INMED), Aix-Marseille University, Parc Scientifique de Luminy, Marseille, France
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5
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Ge D, Noakes PG, Lavidis NA. What are Neurotransmitter Release Sites and Do They Interact? Neuroscience 2020; 425:157-168. [DOI: 10.1016/j.neuroscience.2019.11.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2019] [Revised: 11/10/2019] [Accepted: 11/11/2019] [Indexed: 12/22/2022]
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6
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Blakemore LJ, Corthell JT, Trombley PQ. Kainate Receptors Play a Role in Modulating Synaptic Transmission in the Olfactory Bulb. Neuroscience 2018; 391:25-49. [PMID: 30213766 DOI: 10.1016/j.neuroscience.2018.09.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 08/31/2018] [Accepted: 09/03/2018] [Indexed: 02/06/2023]
Abstract
Glutamate is the neurotransmitter used at most excitatory synapses in the mammalian brain, including those in the olfactory bulb (OB). There, ionotropic glutamate receptors including N-methyl-d-aspartate receptors (NMDARs) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) play a role in processes such as reciprocal inhibition and glomerular synchronization. Kainate receptors (KARs) represent another type of ionotropic glutamate receptor, which are composed of five (GluK1-GluK5) subunits. Whereas KARs appear to be heterogeneously expressed in the OB, evidence as to whether these KARs are functional, found at synapses, or modify synaptic transmission is limited. In the present study, coapplication of KAR agonists (kainate, SYM 2081) and AMPAR antagonists (GYKI 52466, SYM 2206) demonstrated that functional KARs are expressed by OB neurons, with a subset of receptors located at synapses. Application of kainate and the GluK1-selective agonist ATPA had modulatory effects on excitatory postsynaptic currents (EPSCs) evoked by stimulation of the olfactory nerve layer. Application of kainate and ATPA also had modulatory effects on reciprocal inhibitory postsynaptic currents (IPSCs) evoked using a protocol that evokes dendrodendritic inhibition. The latter finding suggests that KARs, with relatively slow kinetics, may play a role in circuits in which the relatively brief duration of AMPAR-mediated currents limits the role of AMPARs in synaptic transmission (e.g., reciprocal inhibition at dendrodendritic synapses). Collectively, our findings suggest that KARs, including those containing the GluK1 subunit, modulate excitatory and inhibitory transmission in the OB. These data further suggest that KARs participate in the regulation of synaptic circuits that encode odor information.
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Affiliation(s)
- Laura J Blakemore
- Program in Neuroscience, Florida State University, Tallahassee, FL, United States; Department of Biological Science, Florida State University, Tallahassee, FL, United States
| | - John T Corthell
- Program in Neuroscience, Florida State University, Tallahassee, FL, United States; Department of Biological Science, Florida State University, Tallahassee, FL, United States
| | - Paul Q Trombley
- Program in Neuroscience, Florida State University, Tallahassee, FL, United States; Department of Biological Science, Florida State University, Tallahassee, FL, United States.
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7
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Gao M, Whitt JL, Huang S, Lee A, Mihalas S, Kirkwood A, Lee HK. Experience-dependent homeostasis of 'noise' at inhibitory synapses preserves information coding in adult visual cortex. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0156. [PMID: 28093550 DOI: 10.1098/rstb.2016.0156] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2016] [Indexed: 02/05/2023] Open
Abstract
Synapses are intrinsically 'noisy' in that neurotransmitter is occasionally released in the absence of an action potential. At inhibitory synapses, the frequency of action potential-independent release is orders of magnitude higher than that at excitatory synapses raising speculations that it may serve a function. Here we report that the frequency of action potential-independent inhibitory synaptic 'noise' (i.e. miniature inhibitory postsynaptic currents, mIPSCs) is highly regulated by sensory experience in visual cortex. Importantly, regulation of mIPSC frequency is so far the predominant form of functional plasticity at inhibitory synapses in adults during the refractory period for plasticity and is a locus of rapid non-genomic actions of oestrogen. Models predict that regulating the frequency of mIPSCs, together with the previously characterized synaptic scaling of miniature excitatory PSCs, allows homeostatic maintenance of both the mean and variance of inputs to a neuron, a necessary feature of probabilistic population codes. Furthermore, mIPSC frequency regulation allows preservation of the temporal profile of neural responses while homeostatically regulating the overall firing rate. Our results suggest that the control of inhibitory 'noise' allows adaptive maintenance of adult cortical function in tune with the sensory environment.This article is part of the themed issue 'Integrating Hebbian and homeostatic plasticity'.
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Affiliation(s)
- Ming Gao
- Solomon H. Snyder Department of Neuroscience, Zanvyl-Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Jessica L Whitt
- Solomon H. Snyder Department of Neuroscience, Zanvyl-Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Shiyong Huang
- Solomon H. Snyder Department of Neuroscience, Zanvyl-Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Angela Lee
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Stefan Mihalas
- Allen Institute for Brain Science, Seattle, WA 98103, USA
| | - Alfredo Kirkwood
- Solomon H. Snyder Department of Neuroscience, Zanvyl-Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Hey-Kyoung Lee
- Solomon H. Snyder Department of Neuroscience, Zanvyl-Krieger Mind/Brain Institute, Johns Hopkins University, Baltimore, MD 21218, USA .,Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD 21205, USA
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8
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Acute Stress Shapes Synaptic Inhibition within an Amygdala Microcircuit. J Neurosci 2017; 37:474-476. [PMID: 28100732 DOI: 10.1523/jneurosci.3145-16.2017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 12/05/2016] [Accepted: 12/09/2016] [Indexed: 11/21/2022] Open
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9
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Crawford DC, Kavalali ET. Molecular underpinnings of synaptic vesicle pool heterogeneity. Traffic 2015; 16:338-64. [PMID: 25620674 DOI: 10.1111/tra.12262] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 01/06/2015] [Indexed: 12/31/2022]
Abstract
Neuronal communication relies on chemical synaptic transmission for information transfer and processing. Chemical neurotransmission is initiated by synaptic vesicle fusion with the presynaptic active zone resulting in release of neurotransmitters. Classical models have assumed that all synaptic vesicles within a synapse have the same potential to fuse under different functional contexts. In this model, functional differences among synaptic vesicle populations are ascribed to their spatial distribution in the synapse with respect to the active zone. Emerging evidence suggests, however, that synaptic vesicles are not a homogenous population of organelles, and they possess intrinsic molecular differences and differential interaction partners. Recent studies have reported a diverse array of synaptic molecules that selectively regulate synaptic vesicles' ability to fuse synchronously and asynchronously in response to action potentials or spontaneously irrespective of action potentials. Here we discuss these molecular mediators of vesicle pool heterogeneity that are found on the synaptic vesicle membrane, on the presynaptic plasma membrane, or within the cytosol and consider some of the functional consequences of this diversity. This emerging molecular framework presents novel avenues to probe synaptic function and uncover how synaptic vesicle pools impact neuronal signaling.
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Affiliation(s)
- Devon C Crawford
- Department of Neuroscience, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9111, USA
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10
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Bajo M, Varodayan FP, Madamba SG, Robert AJ, Casal LM, Oleata CS, Siggins GR, Roberto M. IL-1 interacts with ethanol effects on GABAergic transmission in the mouse central amygdala. Front Pharmacol 2015; 6:49. [PMID: 25852553 PMCID: PMC4365713 DOI: 10.3389/fphar.2015.00049] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Accepted: 02/28/2015] [Indexed: 11/13/2022] Open
Abstract
Neuroinflammation is hypothesized to enhance alcohol consumption and contribute to the development of alcoholism. GABAergic transmission in the central amygdala (CeA) plays an important role in the transition to alcohol dependence. Therefore, we studied the effects of interleukin-1β (IL-1β), a proinflammatory cytokine mediating ethanol-induced neuroinflammation, and its interaction with ethanol on CeA GABAegic transmission in B6129SF2/J mice. We also assessed ethanol intake in B6129SF2/J mice. Intake with unlimited (24 h) ethanol access was 9.2–12.7 g/kg (3–15% ethanol), while limited (2 h) access produced an intake of 4.1 ± 0.5 g/kg (15% ethanol). In our electrophysiology experiments, we found that recombinant IL-1β (50 and 100 ng/ml) significantly decreased the amplitude of evoked inhibitory postsynaptic potentials (eIPSPs), with no significant effects on paired-pulse facilitation (PPF). IL-1β (50 ng/ml) had dual effects on spontaneous miniature inhibitory postsynaptic currents (mIPSCs): increasing mIPSC frequencies in most CeA neurons, but decreasing both mIPSC frequencies and amplitudes in a few cells. The IL-1β receptor antagonist (IL-1ra; 100 ng/ml) also had dual effects on mIPSCs and prevented the actions of IL-1β on mIPSC frequencies. These results suggest that IL-1β can alter CeA GABAergic transmission at pre- and postsynaptic sites. Ethanol (44 mM) significantly increased eIPSP amplitudes, decreased PPFs, and increased mIPSC frequencies. IL-1β did not alter ethanol’s enhancement of the eIPSP amplitude, but, in IL-1β-responsive neurons, the ethanol effects on mIPSC frequencies were lost. Overall, our data suggest that the IL-1 system is involved in basal GABAergic transmission and that IL-1β interacts with the ethanol-induced facilitation of CeA GABAergic transmission.
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Affiliation(s)
- Michal Bajo
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute La Jolla, CA, USA
| | - Florence P Varodayan
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute La Jolla, CA, USA
| | - Samuel G Madamba
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute La Jolla, CA, USA
| | - Amanda J Robert
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute La Jolla, CA, USA
| | - Lindsey M Casal
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute La Jolla, CA, USA
| | - Christopher S Oleata
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute La Jolla, CA, USA
| | - George R Siggins
- Molecular and Cellular Neuroscience Department, The Scripps Research Institute La Jolla, CA, USA
| | - Marisa Roberto
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute La Jolla, CA, USA
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11
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Zhang P, Bannon NM, Ilin V, Volgushev M, Chistiakova M. Adenosine effects on inhibitory synaptic transmission and excitation-inhibition balance in the rat neocortex. J Physiol 2015; 593:825-41. [PMID: 25565160 DOI: 10.1113/jphysiol.2014.279901] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 11/28/2014] [Indexed: 12/20/2022] Open
Abstract
KEY POINTS Adenosine might be the most widespread neuromodulator in the brain, but its effects on inhibitory transmission in the neocortex are not understood. Here we report that adenosine suppresses inhibitory transmission to layer 2/3 pyramidal neurons via activation of presynaptic A1 receptors. We present evidence for functional A2A receptors, which have a weak modulatory effect on the A1-mediated suppression, at about 50% of inhibitory synapses at pyramidal neurons. Adenosine suppresses excitatory and inhibitory transmission to a different extent, and can change the excitation-inhibition balance at a set of synapses bidirectionally, but on average the balance was maintained during application of adenosine. These results suggest that changes of adenosine concentration may lead to differential modulation of excitatory-inhibitory balance in pyramidal neurons, and thus redistribution of local spotlights of activity in neocortical circuits, while preserving the balanced state of the whole network. ABSTRACT Adenosine might be the most widespread neuromodulator in the brain: as a metabolite of ATP it is present in every neuron and glial cell. However, how adenosine affects operation of neurons and networks in the neocortex is poorly understood, mostly because modulation of inhibitory transmission by adenosine has been so little studied. To clarify adenosine's role at inhibitory synapses, and in excitation-inhibition balance in pyramidal neurons, we recorded pharmacologically isolated inhibitory responses, compound excitatory-inhibitory responses and spontaneous events in layer 2/3 pyramidal neurons in slices from rat visual cortex. We show that adenosine (1-150 μm) suppresses inhibitory transmission to these neurons in a concentration-dependent and reversible manner. The suppression was mediated by presynaptic A1 receptors (A1Rs) because it was blocked by a selective A1 antagonist, DPCPX, and associated with changes of release indices: paired-pulse ratio, inverse coefficient of variation and frequency of miniature events. At some synapses (12 out of 24) we found evidence for A2ARs: their blockade led to a small but significant increase of the magnitude of adenosine-mediated suppression. This effect of A2AR blockade was not observed when A1Rs were blocked, suggesting that A2ARs do not have their own effect on transmission, but can modulate the A1R-mediated suppression. At both excitatory and inhibitory synapses, the magnitude of A1R-mediated suppression and A2AR-A1R interaction expressed high variability, suggesting high heterogeneity of synapses in the sensitivity to adenosine. Adenosine could change the balance between excitation and inhibition at a set of inputs to a neuron bidirectionally, towards excitation or towards inhibition. On average, however, these bidirectional changes cancelled each other, and the overall balance of excitation and inhibition was maintained during application of adenosine. These results suggest that changes of adenosine concentration may lead to differential modulation of excitatory-inhibitory balance in pyramidal neurons, and thus redistribution of local spotlights of activity in neocortical circuits, while preserving the balanced state of the whole network.
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Affiliation(s)
- Pei Zhang
- Department of Psychology, University of Connecticut, Storrs, CT, 06269, USA
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12
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Truckenbrodt S, Rizzoli SO. Spontaneous vesicle recycling in the synaptic bouton. Front Cell Neurosci 2014; 8:409. [PMID: 25538561 PMCID: PMC4259163 DOI: 10.3389/fncel.2014.00409] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 11/11/2014] [Indexed: 11/13/2022] Open
Abstract
The trigger for synaptic vesicle exocytosis is Ca2+, which enters the synaptic bouton following action potential stimulation. However, spontaneous release of neurotransmitter also occurs in the absence of stimulation in virtually all synaptic boutons. It has long been thought that this represents exocytosis driven by fluctuations in local Ca2+ levels. The vesicles responding to these fluctuations are thought to be the same ones that release upon stimulation, albeit potentially triggered by different Ca2+ sensors. This view has been challenged by several recent works, which have suggested that spontaneous release is driven by a separate pool of synaptic vesicles. Numerous articles appeared during the last few years in support of each of these hypotheses, and it has been challenging to bring them into accord. We speculate here on the origins of this controversy, and propose a solution that is related to developmental effects. Constitutive membrane traffic, needed for the biogenesis of vesicles and synapses, is responsible for high levels of spontaneous membrane fusion in young neurons, probably independent of Ca2+. The vesicles releasing spontaneously in such neurons are not related to other synaptic vesicle pools and may represent constitutively releasing vesicles (CRVs) rather than bona fide synaptic vesicles. In mature neurons, constitutive traffic is much dampened, and the few remaining spontaneous release events probably represent bona fide spontaneously releasing synaptic vesicles (SRSVs) responding to Ca2+ fluctuations, along with a handful of CRVs that participate in synaptic vesicle turnover.
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Affiliation(s)
- Sven Truckenbrodt
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Center, European Neuroscience Institute, Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain Göttingen, Germany ; International Max Planck Research School for Molecular Biology Göttingen, Germany
| | - Silvio O Rizzoli
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Center, European Neuroscience Institute, Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain Göttingen, Germany
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13
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Menezes FP, Rico EP, Da Silva RS. Tolerance to seizure induced by kainic acid is produced in a specific period of zebrafish development. Prog Neuropsychopharmacol Biol Psychiatry 2014; 55:109-12. [PMID: 24743104 DOI: 10.1016/j.pnpbp.2014.04.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 04/04/2014] [Accepted: 04/05/2014] [Indexed: 01/07/2023]
Abstract
During brain development, the electrical disturbance promoted by a seizure can have several consequences, because it can disturb a set of steps extremely regulated needed to the correct brain maturation. Animal modeling of seizure is invaluable to contribute to the mechanistic understanding of punctual seizure event, and those that triggered in an immature neural network could alter the mature brain physiology. In the present study we observed that the exposure to kainic acid diluted directly in water of zebrafish decreased the locomotor activity at 7 days post-fertilization (dpf) animals and increased at 15 dpf, despite the absence of more specific seizure features. Pre-exposure to kainic acid (500 μM) diluted in water at 7 dpf animals reduced the susceptibility to a second exposure 2 months later by intraperitoneal injection. The current data suggest that these different responses are associated with neuronal maturation process and open a question about the window of development that are crucial to long lasting effects related to seizure in this animal model.
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Affiliation(s)
- Fabiano Peres Menezes
- Laboratório de Neuroquímica e Psicofarmacologia, Departamento de Biologia Celular e Molecular, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Eduardo Pacheco Rico
- Programa de Pós-graduação em Bioquímica, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos 2600-Anexo, 90035-003 Porto Alegre, RS, Brazil; Instituto Nacional de Ciência e Tecnologia em Excitotoxicidade e Neuroproteção (INCT-EN), 90035-003 Porto Alegre, RS, Brazil
| | - Rosane Souza Da Silva
- Laboratório de Neuroquímica e Psicofarmacologia, Departamento de Biologia Celular e Molecular, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, RS, Brazil; Instituto Nacional de Ciência e Tecnologia Translacional em Medicina (INCT-TM), 90035-003, Porto Alegre, RS, Brazil.
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Ramirez DMO, Kavalali ET. The role of non-canonical SNAREs in synaptic vesicle recycling. CELLULAR LOGISTICS 2014; 2:20-27. [PMID: 22645707 PMCID: PMC3355972 DOI: 10.4161/cl.20114] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
An increasing number of studies suggest that distinct pools of synaptic vesicles drive specific forms of neurotransmission. Interspersed with these functional studies are analyses of the synaptic vesicle proteome which have consistently detected the presence of so-called “non-canonical” SNAREs that typically function in fusion and trafficking of other subcellular structures within the neuron. The recent identification of certain non-canonical vesicular SNAREs driving spontaneous (e.g., VAMP7 and vti1a) or evoked asynchronous (e.g., VAMP4) release integrates and corroborates existing data from functional and proteomic studies and implies that at least some complement of non-canonical SNAREs resident on synaptic vesicles function in neurotransmission. Here, we discuss the specific roles in neurotransmission of proteins homologous to each member of the classical neuronal SNARE complex consisting of synaptobrevin2, syntaxin-1 and SNAP-25.
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15
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Revelo NH, Kamin D, Truckenbrodt S, Wong AB, Reuter-Jessen K, Reisinger E, Moser T, Rizzoli SO. A new probe for super-resolution imaging of membranes elucidates trafficking pathways. ACTA ACUST UNITED AC 2014; 205:591-606. [PMID: 24862576 PMCID: PMC4033769 DOI: 10.1083/jcb.201402066] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
mCLING is a novel membrane probe for the study of membrane trafficking with demonstrated value in both live and fixed cells across a wide range of biological systems. The molecular composition of the organelles involved in membrane recycling is difficult to establish as a result of the absence of suitable labeling tools. We introduce in this paper a novel probe, named membrane-binding fluorophore-cysteine-lysine-palmitoyl group (mCLING), which labels the plasma membrane and is taken up during endocytosis. It remains attached to membranes after fixation and permeabilization and can therefore be used in combination with immunostaining and super-resolution microscopy. We applied mCLING to mammalian-cultured cells, yeast, bacteria, primary cultured neurons, Drosophila melanogaster larval neuromuscular junctions, and mammalian tissue. mCLING enabled us to study the molecular composition of different trafficking organelles. We used it to address several questions related to synaptic vesicle recycling in the auditory inner hair cells from the organ of Corti and to investigate molecular differences between synaptic vesicles that recycle actively or spontaneously in cultured neurons. We conclude that mCLING enables the investigation of trafficking membranes in a broad range of preparations.
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Affiliation(s)
- Natalia H Revelo
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, GermanyDepartment of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany International Max Planck Research School for Neurosciences, 37077 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany
| | - Dirk Kamin
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, GermanyDepartment of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany
| | - Sven Truckenbrodt
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, GermanyDepartment of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany International Max Planck Research School for Molecular Biology, 37077 Göttingen, Germany
| | - Aaron B Wong
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany International Max Planck Research School for Neurosciences, 37077 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany
| | - Kirsten Reuter-Jessen
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany
| | - Ellen Reisinger
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany
| | - Tobias Moser
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany
| | - Silvio O Rizzoli
- Department of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, GermanyDepartment of Neuro- and Sensory Physiology; European Neuroscience Institute; and InnerEarLab and Molecular Biology of Cochlear Neurotransmission Group, Department of Otolaryngology; University Medical Center Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889 and Cluster of Excellence Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37099 Göttingen, Germany
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16
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Powell AD, Saintot PP, Gill KK, Bharathan A, Buck SC, Morris G, Jiruska P, Jefferys JGR. Reduced gamma oscillations in a mouse model of intellectual disability: a role for impaired repetitive neurotransmission? PLoS One 2014; 9:e95871. [PMID: 24800744 PMCID: PMC4011727 DOI: 10.1371/journal.pone.0095871] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 04/01/2014] [Indexed: 11/19/2022] Open
Abstract
Intellectual disability affects 2-3% of the population; mutations of the X-chromosome are a major cause of moderate to severe cases. The link between the molecular consequences of the mutation and impaired cognitive function remains unclear. Loss of function mutations of oligophrenin-1 (OPHN1) disrupt Rho-GTPase signalling. Here we demonstrate abnormal neurotransmission at CA3 synapses in hippocampal slices from Ophn1-/y mice, resulting from a substantial decrease in the readily releasable pool of vesicles. As a result, synaptic transmission fails at high frequencies required for oscillations associated with cognitive functions. Both spontaneous and KA-induced gamma oscillations were reduced in Ophn1-/y hippocampal slices. Spontaneous oscillations were rapidly rescued by inhibition of the downstream signalling pathway of oligophrenin-1. These findings suggest that the intellectual disability due to mutations of oligophrenin-1 results from a synaptopathy and consequent network malfunction, providing a plausible mechanism for the learning disabilities. Furthermore, they raise the prospect of drug treatments for affected individuals.
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Affiliation(s)
- Andrew D. Powell
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
- * E-mail:
| | - Pierre-Philippe Saintot
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Kalbinder K. Gill
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Ashtami Bharathan
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - S. Caroline Buck
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Gareth Morris
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Premysl Jiruska
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
- Department of Developmental Epileptology, Institute of Physiology, Academy of Sciences of Czech Republic, Prague, Czech Republic
- Department of Neurology, Charles University, 2 School of Medicine, Prague, Czech Republic
| | - John G. R. Jefferys
- School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
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17
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Abstract
Synaptic vesicle recycling is one of the best-studied cellular pathways. Many of the proteins involved are known, and their interactions are becoming increasingly clear. However, as for many other pathways, it is still difficult to understand synaptic vesicle recycling as a whole. While it is generally possible to point out how synaptic reactions take place, it is not always easy to understand what triggers or controls them. Also, it is often difficult to understand how the availability of the reaction partners is controlled: how the reaction partners manage to find each other in the right place, at the right time. I present here an overview of synaptic vesicle recycling, discussing the mechanisms that trigger different reactions, and those that ensure the availability of reaction partners. A central argument is that synaptic vesicles bind soluble cofactor proteins, with low affinity, and thus control their availability in the synapse, forming a buffer for cofactor proteins. The availability of cofactor proteins, in turn, regulates the different synaptic reactions. Similar mechanisms, in which one of the reaction partners buffers another, may apply to many other processes, from the biogenesis to the degradation of the synaptic vesicle.
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Affiliation(s)
- Silvio O Rizzoli
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen European Neuroscience Institute, Göttingen, Germany
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18
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Abstract
Our understanding of the molecular properties of kainate receptors and their involvement in synaptic physiology has progressed significantly over the last 30 years. A plethora of studies indicate that kainate receptors are important mediators of the pre- and postsynaptic actions of glutamate, although the mechanisms underlying such effects are still often a topic for discussion. Three clear fields related to their behavior have emerged: there are a number of interacting proteins that pace the properties of kainate receptors; their activity is unconventional since they can also signal through G proteins, behaving like metabotropic receptors; they seem to be linked to some devastating brain diseases. Despite the significant progress in their importance in brain function, kainate receptors remain somewhat puzzling. Here we examine discoveries linking these receptors to physiology and their probable implications in disease, in particular mood disorders, and propose some ideas to obtain a deeper understanding of these intriguing proteins.
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19
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Chung C, Raingo J. Vesicle dynamics: how synaptic proteins regulate different modes of neurotransmission. J Neurochem 2013; 126:146-54. [PMID: 23517499 DOI: 10.1111/jnc.12245] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 03/05/2013] [Accepted: 03/18/2013] [Indexed: 01/09/2023]
Abstract
Central synapses operate neurotransmission in several modes: synchronous/fast neurotransmission (neurotransmitters release is tightly coupled to action potentials and fast), asynchronous neurotransmission (neurotransmitter release is slower and longer lasting), and spontaneous neurotransmission (where small amounts of neurotransmitter are released without being evoked by an action potential). A substantial body of evidence from the past two decades suggests that seemingly identical synaptic vesicles possess distinct propensities to fuse, thus selectively serving different modes of neurotransmission. In efforts to better understand the mechanism(s) underlying the different modes of synaptic transmission, many research groups found that synaptic vesicles used in different modes of neurotransmission differ by a number of synaptic proteins. Synchronous transmission with higher temporal fidelity to stimulation seems to require synaptotagmin 1 and complexin for its Ca²⁺ sensitivity, RIM proteins for closer location of synaptic vesicles (SV) to the voltage operated calcium channels (VGCC), and dynamin for SV retrieval. Asynchronous release does not seem to require functional synaptotagmin 1 as a calcium sensor or complexins, but the activity of dynamin is indispensible for its maintenance. On the other hand, the control of spontaneous neurotransmission remains less clear as deleting a number of essential synaptic proteins does not abolish this type of synaptic vesicle fusion. VGCC distance from the SV seems to have little control on spontaneous transmission, while there is an involvement of functional synaptic proteins including synaptotagmins and complexin. Recently, presynaptic deficits have been proposed to contribute to a number of pathological conditions including cognitive and mental disorders. In this review, we evaluate recent advances in understanding the regulatory mechanisms of synaptic vesicle dynamics and in understanding how different molecular substrates maintain selective modes of neurotransmission. We also highlight the implications of these studies in understanding pathological conditions.
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Affiliation(s)
- ChiHye Chung
- Department of Biological Sciences, Konkuk University, Seoul, South Korea
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20
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Staples J, Broadie K. The cell polarity scaffold Lethal Giant Larvae regulates synapse morphology and function. J Cell Sci 2013; 126:1992-2003. [PMID: 23444371 DOI: 10.1242/jcs.120139] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Lethal Giant Larvae (LGL) is a cytosolic cell polarity scaffold whose loss dominantly enhances neuromuscular junction (NMJ) synaptic overgrowth caused by loss of the Fragile X Mental Retardation Protein (FMRP). However, direct roles for LGL in NMJ morphological and functional development have not before been tested. Here, we use confocal imaging and two-electrode voltage-clamp electrophysiology at the Drosophila larval NMJ to define the synaptic requirements of LGL. We find that LGL is expressed both pre- and postsynaptically, where the scaffold localizes at the membrane on both sides of the synaptic interface. We show that LGL has a cell autonomous presynaptic role facilitating NMJ terminal branching and synaptic bouton formation. Moreover, loss of both pre- and postsynaptic LGL strongly decreases evoked neurotransmission strength, whereas the frequency and amplitude of spontaneous synaptic vesicle fusion events is increased. Cell-targeted RNAi and rescue reveals separable pre- and postsynaptic LGL roles mediating neurotransmission. We show that presynaptic LGL facilitates the assembly of active zone vesicle fusion sites, and that neuronally targeted rescue of LGL is sufficient to ameliorate increased synaptic vesicle cycling imaged with FM1-43 dye labeling. Postsynaptically, we show that loss of LGL results in a net increase in total glutamate receptor (GluR) expression, associated with the selective elevation of GluRIIB subunit-containing receptors. Taken together, these data indicate that the presynaptic LGL scaffold facilitates the assembly of active zone fusion sites to regulate synaptic vesicle cycling, and that the postsynaptic LGL scaffold modulates glutamate receptor composition and function.
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Affiliation(s)
- Jon Staples
- Department of Biological Sciences, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37212, USA
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21
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Intracellular Ca2+ stores and Ca2+ influx are both required for BDNF to rapidly increase quantal vesicular transmitter release. Neural Plast 2012; 2012:203536. [PMID: 22811938 PMCID: PMC3397209 DOI: 10.1155/2012/203536] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 05/29/2012] [Indexed: 12/22/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) is well known as a survival factor during brain development as well as a regulator of adult synaptic plasticity. One potential mechanism to initiate BDNF actions is through its modulation of quantal presynaptic transmitter release. In response to local BDNF application to CA1 pyramidal neurons, the frequency of miniature excitatory postsynaptic currents (mEPSC) increased significantly within 30 seconds; mEPSC amplitude and kinetics were unchanged. This effect was mediated via TrkB receptor activation and required both full intracellular Ca2+ stores as well as extracellular Ca2+. Consistent with a role of Ca2+-permeable plasma membrane channels of the TRPC family, the inhibitor SKF96365 prevented the BDNF-induced increase in mEPSC frequency. Furthermore, labeling presynaptic terminals with amphipathic styryl dyes and then monitoring their post-BDNF destaining in slice cultures by multiphoton excitation microscopy revealed that the increase in frequency of mEPSCs reflects vesicular fusion events. Indeed, BDNF application to CA3-CA1 synapses in TTX rapidly enhanced FM1-43 or FM2-10 destaining with a time course that paralleled the phase of increased mEPSC frequency. We conclude that BDNF increases mEPSC frequency by boosting vesicular fusion through a presynaptic, Ca2+-dependent mechanism involving TrkB receptors, Ca2+ stores, and TRPC channels.
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22
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Cornelisse LN, Tsivtsivadze E, Meijer M, Dijkstra TMH, Heskes T, Verhage M. Molecular machines in the synapse: overlapping protein sets control distinct steps in neurosecretion. PLoS Comput Biol 2012; 8:e1002450. [PMID: 22496630 PMCID: PMC3320570 DOI: 10.1371/journal.pcbi.1002450] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 02/14/2012] [Indexed: 11/18/2022] Open
Abstract
Activity regulated neurotransmission shapes the computational properties of a neuron and involves the concerted action of many proteins. Classical, intuitive working models often assign specific proteins to specific steps in such complex cellular processes, whereas modern systems theories emphasize more integrated functions of proteins. To test how often synaptic proteins participate in multiple steps in neurotransmission we present a novel probabilistic method to analyze complex functional data from genetic perturbation studies on neuronal secretion. Our method uses a mixture of probabilistic principal component analyzers to cluster genetic perturbations on two distinct steps in synaptic secretion, vesicle priming and fusion, and accounts for the poor standardization between different studies. Clustering data from 121 perturbations revealed that different perturbations of a given protein are often assigned to different steps in the release process. Furthermore, vesicle priming and fusion are inversely correlated for most of those perturbations where a specific protein domain was mutated to create a gain-of-function variant. Finally, two different modes of vesicle release, spontaneous and action potential evoked release, were affected similarly by most perturbations. This data suggests that the presynaptic protein network has evolved as a highly integrated supramolecular machine, which is responsible for both spontaneous and activity induced release, with a group of core proteins using different domains to act on multiple steps in the release process. Synapses, which are small structures where information is transmitted between neurons, are the functional units of computation in the brain implicated in information processing, learning and memory. In the last few years several genes that are expressed in synapses have been linked to brain disorders such as autism, depression and schizophrenia. However, good understanding of the molecular basis of these diseases requires more insight in the functional organization of the protein network. In the classic view proteins are involved in a specific step of a cellular process, whereas modern system theories suggest a more integrated and complex network where proteins can be involved in several steps. We have developed a method that allows comparison of high-end but low-throughput functional data from different genetic perturbation studies despite the poor standardization between studies. Our analysis shows that synaptic proteins are not restricted to a single function but that they are part of a highly integrated supramolecular machine, with overlapping protein sets being involved in distinct steps in neurotransmitter release. Further characterization of these complex protein network relations will be important for new drug design strategies.
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Affiliation(s)
- L Niels Cornelisse
- Functional Genomics, Center for Neurogenomics and Cognitive Research-CNCR, Department of Clinical Genetics, VUmc, Neuroscience Campus Amsterdam-NCA, VU University-VUA and VU University Medical Center-VUmc, Amsterdam, The Netherlands.
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23
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Jiang E, Yan X, Weng HR. Glial glutamate transporter and glutamine synthetase regulate GABAergic synaptic strength in the spinal dorsal horn. J Neurochem 2012; 121:526-36. [PMID: 22339645 DOI: 10.1111/j.1471-4159.2012.07694.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Decreased GABAergic synaptic strength ('disinhibition') in the spinal dorsal horn is a crucial mechanism contributing to the development and maintenance of pathological pain. However, mechanisms leading to disinhibition in the spinal dorsal horn remain elusive. We investigated the role of glial glutamate transporters (GLT-1 and GLAST) and glutamine synthetase in maintaining GABAergic synaptic activity in the spinal dorsal horn. Electrically evoked GABAergic inhibitory post-synaptic currents (eIPSCs), spontaneous IPSCs (sIPSCs) and miniature IPSCs were recorded in superficial spinal dorsal horn neurons of spinal slices from young adult rats. We used (2S,3S)-3-[3-[4-(trifluoromethyl)benzoylamino]benzyloxy]aspartate (TFB-TBOA), to block both GLT-1 and GLAST and dihydrokainic acid to block only GLT-1. We found that blockade of both GLAST and GLT-1 and blockade of only GLT-1 in the spinal dorsal horn decreased the amplitude of GABAergic eIPSCs, as well as both the amplitude and frequency of GABAergic sIPSCs or miniature IPSCs. Pharmacological inhibition of glial glutamine synthetase had similar effects on both GABAergic eIPSCs and sIPSCs. We provided evidence demonstrating that the reduction in GABAergic strength induced by the inhibition of glial glutamate transporters is due to insufficient GABA synthesis through the glutamate-glutamine cycle between astrocytes and neurons. Thus, our results indicate that deficient glial glutamate transporters and glutamine synthetase significantly attenuate GABAergic synaptic strength in the spinal dorsal horn, which may be a crucial synaptic mechanism underlying glial-neuronal interactions caused by dysfunctional astrocytes in pathological pain conditions.
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Affiliation(s)
- Enshe Jiang
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia, USA
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24
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Ramirez DMO, Khvotchev M, Trauterman B, Kavalali ET. Vti1a identifies a vesicle pool that preferentially recycles at rest and maintains spontaneous neurotransmission. Neuron 2012; 73:121-34. [PMID: 22243751 DOI: 10.1016/j.neuron.2011.10.034] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/18/2011] [Indexed: 01/18/2023]
Abstract
Recent studies suggest that synaptic vesicles (SVs) giving rise to spontaneous neurotransmission are distinct from those that carry out evoked release. However, the molecular basis of this dichotomy remains unclear. Here, we focused on two noncanonical SNARE molecules, Vps10p-tail-interactor-1a (vti1a) and VAMP7, previously shown to reside on SVs. Using simultaneous multicolor imaging at individual synapses, we could show that compared to the more abundant vesicular SNARE synaptobrevin2, both vti1a and VAMP7 were reluctantly mobilized during activity. Vti1a, but not VAMP7, showed robust trafficking under resting conditions that could be partly matched by synaptobrevin2. Furthermore, loss of vti1a function selectively reduced high-frequency spontaneous neurotransmitter release detected postsynaptically. Expression of a truncated version of vti1a augmented spontaneous release more than full-length vti1a, suggesting that an autoinhibitory process regulates vti1a function. Taken together, these results support the premise that in its native form vti1a selectively maintains spontaneous neurotransmitter release.
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Affiliation(s)
- Denise M O Ramirez
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX 75390-9111, USA
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25
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26
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Synaptic reorganization of inhibitory hilar interneuron circuitry after traumatic brain injury in mice. J Neurosci 2011; 31:6880-90. [PMID: 21543618 DOI: 10.1523/jneurosci.0032-11.2011] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Functional plasticity of synaptic networks in the dentate gyrus has been implicated in the development of posttraumatic epilepsy and in cognitive dysfunction after traumatic brain injury, but little is known about potentially pathogenic changes in inhibitory circuits. We examined synaptic inhibition of dentate granule cells and excitability of surviving GABAergic hilar interneurons 8-13 weeks after cortical contusion brain injury in transgenic mice that express enhanced green fluorescent protein in a subpopulation of inhibitory neurons. Whole-cell voltage-clamp recordings in granule cells revealed a reduction in spontaneous and miniature IPSC frequency after head injury; no concurrent change in paired-pulse ratio was found in granule cells after paired electrical stimulation of the hilus. Despite reduced inhibitory input to granule cells, action potential and EPSC frequencies were increased in hilar GABA neurons from slices ipsilateral to the injury versus those from control or contralateral slices. Furthermore, increased excitatory synaptic activity was detected in hilar GABA neurons ipsilateral to the injury after glutamate photostimulation of either the granule cell or CA3 pyramidal cell layers. Together, these findings suggest that excitatory drive to surviving hilar GABA neurons is enhanced by convergent input from both pyramidal and granule cells, but synaptic inhibition of granule cells is not fully restored after injury. This rewiring of circuitry regulating hilar inhibitory neurons may reflect an important compensatory mechanism, but it may also contribute to network destabilization by increasing the relative impact of surviving individual interneurons in controlling granule cell excitability in the posttraumatic dentate gyrus.
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27
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Kavalali ET, Chung C, Khvotchev M, Leitz J, Nosyreva E, Raingo J, Ramirez DMO. Spontaneous neurotransmission: an independent pathway for neuronal signaling? Physiology (Bethesda) 2011; 26:45-53. [PMID: 21357902 DOI: 10.1152/physiol.00040.2010] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Recent findings suggest that spontaneous neurotransmission is a bona fide pathway for interneuronal signaling that operates independent of evoked transmission via distinct presynaptic as well as postsynaptic substrates. This article will examine the role of spontaneous release events in neuronal signaling by focusing on aspects that distinguish this process from evoked neurotransmission, and evaluate the mechanisms that may underlie this segregation.
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Affiliation(s)
- Ege T Kavalali
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, Texas, USA.
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28
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Use-dependent AMPA receptor block reveals segregation of spontaneous and evoked glutamatergic neurotransmission. J Neurosci 2011; 31:5378-82. [PMID: 21471372 DOI: 10.1523/jneurosci.5234-10.2011] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Earlier findings had suggested that spontaneous and evoked glutamate release activates non-overlapping populations of NMDA receptors. Here, we evaluated whether AMPA receptor populations activated by spontaneous and evoked release show a similar segregation. To track the receptors involved in spontaneous or evoked neurotransmission, we used a polyamine agent, philanthotoxin, that selectively blocks AMPA receptors lacking GluR2 subunits in a use-dependent manner. In hippocampal neurons obtained from GluR2-deficient mice, philanthotoxin application decreased AMPA-receptor-mediated spontaneous miniature EPSCs (AMPA-mEPSCs) down to 20% of their initial level within 5 min. In contrast, the same philanthotoxin application at rest decreased the subsequent AMPA-receptor-mediated evoked EPSCs (eEPSCs) only down to 80% of their initial value. A 10-min-long perfusion of philanthotoxin further decreased AMPA-eEPSC amplitudes to 60% of their initial magnitude, which remained substantially higher than the level of AMPA-mEPSC block achieved within 5 min. Finally, stimulation after removal of philanthotoxin resulted in reversal of AMPA-eEPSC block, verifying strict use dependence of philanthotoxin. These results support the notion that spontaneous and evoked neurotransmission activate distinct sets of AMPA receptors and bolster the hypothesis that synapses harbor separate microdomains of evoked and spontaneous signaling.
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29
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Calfa G, Hablitz JJ, Pozzo-Miller L. Network hyperexcitability in hippocampal slices from Mecp2 mutant mice revealed by voltage-sensitive dye imaging. J Neurophysiol 2011; 105:1768-84. [PMID: 21307327 PMCID: PMC3075283 DOI: 10.1152/jn.00800.2010] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Accepted: 02/03/2011] [Indexed: 11/22/2022] Open
Abstract
Dysfunctions of neuronal and network excitability have emerged as common features in disorders associated with intellectual disabilities, autism, and seizure activity, all common clinical manifestations of Rett syndrome (RTT), a neurodevelopmental disorder caused by loss-of-function mutations in the transcriptional regulator methyl-CpG-binding protein 2 (MeCP2). Here, we evaluated the consequences of Mecp2 mutation on hippocampal network excitability, as well as synapse structure and function using a combination of imaging and electrophysiological approaches in acute slices. Imaging the amplitude and spatiotemporal spread of neuronal depolarizations with voltage-sensitive dyes (VSD) revealed that the CA1 and CA3 regions of hippocampal slices from symptomatic male Mecp2 mutant mice are highly hyperexcitable. However, only the density of docked synaptic vesicles and the rate of release from the readily releasable pool are impaired in Mecp2 mutant mice, while synapse density and morphology are unaffected. The differences in network excitability were not observed in surgically isolated CA1 minislices, and blockade of GABAergic inhibition enhanced VSD signals to the same extent in Mecp2 mutant and wild-type mice, suggesting that network excitability originates in area CA3. Indeed, extracellular multiunit recordings revealed a higher level of spontaneous firing of CA3 pyramidal neurons in slices from symptomatic Mecp2 mutant mice. The neuromodulator adenosine reduced the amplitude and spatiotemporal spread of VSD signals evoked in CA1 of Mecp2 mutant slices to wild-type levels, suggesting its potential use as an anticonvulsant in RTT individuals. The present results suggest that hyperactive CA3 pyramidal neurons contribute to hippocampal dysfunction and possibly to limbic seizures observed in Mecp2 mutant mice and RTT individuals.
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Affiliation(s)
- Gaston Calfa
- Department of Neurobiology, Civitan International Research Center, The University of Alabama at Birmingham, Birmingham, AL 35294-2182, USA
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Ramirez DM, Kavalali ET. Differential regulation of spontaneous and evoked neurotransmitter release at central synapses. Curr Opin Neurobiol 2011; 21:275-82. [PMID: 21334193 PMCID: PMC3092808 DOI: 10.1016/j.conb.2011.01.007] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Accepted: 01/25/2011] [Indexed: 12/20/2022]
Abstract
Recent studies have begun to scrutinize the presynaptic machinery and vesicle populations that give rise to action potential evoked and spontaneous forms of neurotransmitter release. In several cases this work produced unexpected results which lend support to the notion that regulation, mechanisms, postsynaptic targets and possibly presynaptic origins of evoked and spontaneous neurotransmitter release differ. Furthermore, the list of regulatory pathways that impact spontaneous and evoked release in a divergent manner is rapidly growing. These findings challenge our classical views on the relationship between evoked and spontaneous neurotransmission. In contrast to the well-characterized neuromodulatory pathways that equally suppress or augment all forms of neurotransmitter release, molecular substrates specifically controlling spontaneous release remain unclear. In this review, we outline possible mechanisms that may underlie the differential regulation of distinct forms of neurotransmission and help demultiplex complex neuronal signals and generate parallel signaling events at their postsynaptic targets.
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Affiliation(s)
- Denise M.O. Ramirez
- Department of Neuroscience UT Southwestern Medical Center, Dallas, TX 75390-9111, USA
| | - Ege T. Kavalali
- Department of Neuroscience UT Southwestern Medical Center, Dallas, TX 75390-9111, USA
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390-9111, USA
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31
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The same synaptic vesicles drive active and spontaneous release. Nat Neurosci 2011; 13:1454-6. [PMID: 21102450 DOI: 10.1038/nn.2690] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Accepted: 10/12/2010] [Indexed: 11/08/2022]
Abstract
Synaptic vesicles release neurotransmitter both actively (on stimulation) and spontaneously (at rest). It has been assumed that identical vesicles use both modes of release; however, recent evidence has challenged this view. Using several assays (FM dye imaging, pHluorin imaging and antibody-labeling of synaptotagmin) in neuromuscular preparations from Drosophila, frog and mouse, as well as rat cultured neurons, we found that the same vesicles participate in active and spontaneous release.
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Wang ZW. Origin of quantal size variation and high-frequency miniature postsynaptic currents at the Caenorhabditis elegans neuromuscular junction. J Neurosci Res 2010; 88:3425-32. [PMID: 20722072 PMCID: PMC3058485 DOI: 10.1002/jnr.22468] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2010] [Revised: 04/26/2010] [Accepted: 06/20/2010] [Indexed: 11/08/2022]
Abstract
The neuromuscular junction (NMJ) of Caenorhabditis elegans has proved to be a very useful model synapse for investigating molecular mechanisms of synaptic transmission. Intriguingly, miniature postsynaptic currents (minis) at this synapse occur at an unusually high frequency (50-90 Hz in wild-type worms) and show large variation in quantal size (from <10 pA to >200 pA). It is important to understand the cellular and molecular bases for these properties of minis in order to interpret electrophysiological data from this synapse properly. Existing data suggest that several factors may contribute to the high frequency and quantal size variation, including 1) the establishment of multiple NMJs with each body-wall muscle cell, 2) diversity of postsynaptic receptors (two acetylcholine receptors and one GABA receptor), 3) association of one presynaptic site with several body-wall muscle cells, 4) effects of Ca(2+) at the presynaptic site, and 5) a possibly elevated (less negative) resting membrane potential in motoneurons. Neither the frequency nor the quantal size of minis is affected by electrical coupling of body-wall muscle cells. Furthermore, quantal size variation is not due to synchronized multivesicular release. Analyses of the C. elegans NMJ may lead to a better understanding of the mechanisms controlling the frequency and quantal size of minis of other synapses as well.
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Affiliation(s)
- Zhao-Wen Wang
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030-3401, USA.
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Xue L, Wu LG. Post-tetanic potentiation is caused by two signalling mechanisms affecting quantal size and quantal content. J Physiol 2010; 588:4987-94. [PMID: 21041528 DOI: 10.1113/jphysiol.2010.196964] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
A high-frequency action potential train induces post-tetanic potentiation (PTP) of transmission at many synapses by increasing the intra-terminal calcium concentration, which may increase the quantal content by activation of protein kinase C (PKC). A recent study found that an increase of the mEPSC size, caused by compound vesicle fusion, parallels PTP, suggesting that the quantal size increase also contributes to the PTP generation. However, the strength of this suggestion is somewhat undermined by recent studies suggesting that vesicles responsible for spontaneous and evoked EPSCs may originate from different pools. Furthermore, it is unclear whether the quantal size increase is also mediated by PKC. The present work addressed these issues at a large calyx of Held synapse. We found that PTP was caused by both a PKC-dependent increase of the quantal content and a PKC-independent increase of the quantal size. In addition, we found that mEPSCs and EPSCs were subjected to similar up- and down-regulation, which verifies the basic assumption of quantal analysis--the same mechanism controls the quantal size of spontaneous and evoked release. This verification supports the use of quantal analysis at central synapses. However, unlike the traditional quantal analysis that attributes the quantal size change to a postsynaptic mechanism, the present work, together with one of our previous studies, suggests that the quantal size increase is caused by a presynaptic mechanism, the compound fusion among vesicles that forms large compound vesicles.
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Affiliation(s)
- Lei Xue
- National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Bldg 35, Bethesda, MD 20892, USA
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Denker A, Rizzoli SO. Synaptic vesicle pools: an update. Front Synaptic Neurosci 2010; 2:135. [PMID: 21423521 PMCID: PMC3059705 DOI: 10.3389/fnsyn.2010.00135] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2010] [Accepted: 08/02/2010] [Indexed: 12/04/2022] Open
Abstract
During the last few decades synaptic vesicles have been assigned to a variety of functional and morphological classes or “pools”. We have argued in the past (Rizzoli and Betz, 2005) that synaptic activity in several preparations is accounted for by the function of three vesicle pools: the readily releasable pool (docked at active zones and ready to go upon stimulation), the recycling pool (scattered throughout the nerve terminals and recycling upon moderate stimulation), and finally the reserve pool (occupying most of the vesicle clusters and only recycling upon strong stimulation). We discuss here the advancements in the vesicle pool field which took place in the ensuing years, focusing on the behavior of different pools under both strong stimulation and physiological activity. Several new findings have enhanced the three-pool model, with, for example, the disparity between recycling and reserve vesicles being underlined by the observation that the former are mobile, while the latter are “fixed”. Finally, a number of altogether new concepts have also evolved such as the current controversy on the identity of the spontaneously recycling vesicle pool.
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Affiliation(s)
- Annette Denker
- European Neuroscience Institute, DFG Center for Molecular Physiology of the Brain Göttingen, Germany
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Exogenous Glutamate-Induced Modulation of Neurosecretory Process in Nerve Terminals Obtained from the Rat Brain. NEUROPHYSIOLOGY+ 2010. [DOI: 10.1007/s11062-010-9135-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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36
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Acute dynamin inhibition dissects synaptic vesicle recycling pathways that drive spontaneous and evoked neurotransmission. J Neurosci 2010; 30:1363-76. [PMID: 20107062 DOI: 10.1523/jneurosci.3427-09.2010] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Synapses maintain synchronous, asynchronous, and spontaneous forms of neurotransmission that are distinguished by their Ca(2+) dependence and time course. Despite recent advances in our understanding of the mechanisms that underlie these three forms of release, it remains unclear whether they originate from the same vesicle population or arise from distinct vesicle pools with diverse propensities for release. Here, we used a reversible inhibitor of dynamin, dynasore, to dissect the vesicle pool dynamics underlying the three forms of neurotransmitter release in hippocampal GABAergic inhibitory synapses. In dynasore, evoked synchronous release and asynchronous neurotransmission detected after activity showed marked and unrecoverable depression within seconds. In contrast, spontaneous release remained intact after intense stimulation in dynasore or during prolonged (approximately 1 h) application of dynasore at rest, suggesting that separate recycling pathways maintain evoked and spontaneous synaptic vesicle trafficking. In addition, simultaneous imaging of spectrally separable styryl dyes revealed that, in a given synapse, vesicles that recycle spontaneously and in response to activity do not mix. These findings suggest that evoked synchronous and asynchronous release originate from the same vesicle pool that recycles rapidly in a dynamin-dependent manner, whereas a distinct vesicle pool sustains spontaneous release independent of dynamin activation. This result lends additional support to the notion that synapses harbor distinct vesicle populations with divergent release properties that maintain independent forms of neurotransmission.
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Surviving hilar somatostatin interneurons enlarge, sprout axons, and form new synapses with granule cells in a mouse model of temporal lobe epilepsy. J Neurosci 2009; 29:14247-56. [PMID: 19906972 DOI: 10.1523/jneurosci.3842-09.2009] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In temporal lobe epilepsy, seizures initiate in or near the hippocampus, which frequently displays loss of neurons, including inhibitory interneurons. It is unclear whether surviving interneurons function normally, are impaired, or develop compensatory mechanisms. We evaluated GABAergic interneurons in the hilus of the dentate gyrus of epileptic pilocarpine-treated GIN mice, specifically a subpopulation of somatostatin interneurons that expresses enhanced green fluorescence protein (GFP). GFP-immunocytochemistry and stereological analyses revealed substantial loss of GFP-positive hilar neurons (GPHNs) but increased GFP-positive axon length per dentate gyrus in epileptic mice. Individual biocytin-labeled GPHNs in hippocampal slices from epileptic mice also had larger somata, more axon in the molecular layer, and longer dendrites than controls. Dual whole-cell patch recording was used to test for monosynaptic connections from hilar GPHNs to granule cells. Unitary IPSCs (uIPSCs) recorded in control and epileptic mice had similar average rise times, amplitudes, charge transfers, and decay times. However, the probability of finding monosynaptically connected pairs and evoking uIPSCs was 2.6 times higher in epileptic mice compared to controls. Together, these findings suggest that surviving hilar somatostatin interneurons enlarge, extend dendrites, sprout axon collaterals in the molecular layer, and form new synapses with granule cells. These epilepsy-related changes in cellular morphology and connectivity may be mechanisms for surviving hilar interneurons to inhibit more granule cells and compensate for the loss of vulnerable interneurons.
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Bullock WM, Bolognani F, Botta P, Valenzuela CF, Perrone-Bizzozero NI. Schizophrenia-like GABAergic gene expression deficits in cerebellar Golgi cells from rats chronically exposed to low-dose phencyclidine. Neurochem Int 2009; 55:775-82. [PMID: 19651169 DOI: 10.1016/j.neuint.2009.07.010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Revised: 07/22/2009] [Accepted: 07/27/2009] [Indexed: 12/21/2022]
Abstract
One of the most consistent findings in schizophrenia is the decreased expression of the GABA synthesizing enzymes GAD(67) and GAD(65) in specific interneuron populations. This dysfunction is observed in distributed brain regions including the prefrontal cortex, hippocampus, and cerebellum. In an effort to understand the mechanisms for this GABA deficit, we investigated the effect of the N-methyl-D-aspartate receptor (NMDAR) antagonist phencyclidine (PCP), which elicits schizophrenia-like symptoms in both humans and animal models, in a chronic, low-dose exposure paradigm. Adult rats were given PCP at a dose of 2.58 mg/kg/day i.p. for a month, after which levels of various GABAergic cell mRNAs and other neuromodulators were examined in the cerebellum by qRT-PCR. Administration of PCP decreased the expression of GAD(67), GAD(65), and the presynaptic GABA transporter GAT-1, and increased GABA(A) receptor subunits similar to those seen in patients with schizophrenia. Additionally, we found that the mRNA levels of two Golgi cell selective NMDAR subunits, NR2B and NR2D, were decreased in PCP-treated rats. Furthermore, we localized the deficits in GAD(67) expression solely to these interneurons. Slice electrophysiological studies showed that spontaneous firing of Golgi cells was reduced by acute exposure to low-dose PCP, suggesting that these neurons are particularly vulnerable to NMDA receptor antagonism. In conclusion, our results demonstrate that chronic exposure to low levels of PCP in rats mimics the GABAergic alterations reported in the cerebellum of patients with schizophrenia (Bullock et al., 2008. Am. J. Psychiatry 165, 1594-1603), further supporting the validity of this animal model.
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Affiliation(s)
- W Michael Bullock
- Department of Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
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40
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Hablitz JJ, Mathew SS, Pozzo-Miller L. GABA vesicles at synapses: are there 2 distinct pools? Neuroscientist 2009; 15:218-24. [PMID: 19436074 DOI: 10.1177/1073858408326431] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Fast synaptic inhibition in the neocortex is mediated by the neurotransmitter GABA, acting on GABA( A) receptors. Neurotransmitters, including GABA, are stored in synaptic vesicles at presynaptic nerve terminals. A long-held assumption has been that evoked and spontaneous neurotransmissions draw on the same pools of vesicles. We review the evidence from FM1-43 studies supporting the contention that at least 2 distinct pools of GABA vesicles are present at inhibitory synapses in the rat neocortex. FM1-43 uptake during spontaneous vesicle endocytosis labels a vesicle pool within neocortical inhibitory nerve terminals that is released much more slowly ("reluctant" pool) than those vesicles loaded by electrical stimulation of afferent fibers or hyperkalemic solutions. These multiple pools may play diverse roles in such processes as long-term depression and/or potentiating of inhibitory synaptic transmission, homeostatic plasticity of inhibitory activity, or developmental changes in inhibitory synaptic transmission.
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Affiliation(s)
- John J Hablitz
- Department of Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama.
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41
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Fredj NB, Burrone J. A resting pool of vesicles is responsible for spontaneous vesicle fusion at the synapse. Nat Neurosci 2009; 12:751-8. [PMID: 19430474 PMCID: PMC2738656 DOI: 10.1038/nn.2317] [Citation(s) in RCA: 173] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Accepted: 03/20/2009] [Indexed: 11/15/2022]
Abstract
Synapses relay information through the release of neurotransmitters stored in presynaptic vesicles. The identity, kinetics and location of the vesicle pools that are mobilized by neuronal activity have been studied using a variety of techniques. We created a genetically encoded probe, biosyn, which consists of a biotinylated VAMP2 expressed at presynaptic terminals. We exploited the high-affinity interaction between streptavidin and biotin to label biosyn with fluorescent streptavidin during vesicle fusion. This approach allowed us to tag vesicles sequentially to visualize and establish the identity of presynaptic pools. Using this technique, we were able to distinguish between two different pools of vesicles in rat hippocampal neurons: one that was released in response to presynaptic activity and another, distinct vesicle pool that spontaneously fused with the plasma membrane. We found that the spontaneous vesicles belonged to a 'resting pool' that is normally not mobilized by neuronal activity and whose function was previously unknown.
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Affiliation(s)
- Naila Ben Fredj
- MRC Centre for Developmental Neurobiology, King's College London, London, UK
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Proximity of excitatory and inhibitory axon terminals adjacent to pyramidal cell bodies provides a putative basis for nonsynaptic interactions. Proc Natl Acad Sci U S A 2009; 106:9878-83. [PMID: 19487685 DOI: 10.1073/pnas.0900330106] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Although pyramidal cells are the main excitatory neurons in the cerebral cortex, it has recently been reported that they can evoke inhibitory postsynaptic currents in neighboring pyramidal neurons. These inhibitory effects were proposed to be mediated by putative axo-axonic excitatory synapses between the axon terminals of pyramidal cells and perisomatic inhibitory axon terminals [Ren M, Yoshimura Y, Takada N, Horibe S, Komatsu Y (2007) Science 316:758-761]. However, the existence of this type of axo-axonic synapse was not found using serial section electron microscopy. Instead, we observed that inhibitory axon terminals synapsing on pyramidal cell bodies were frequently apposed by terminals that established excitatory synapses with neighbouring dendrites. We propose that a spillover of glutamate from these excitatory synapses can activate the adjacent inhibitory axo-somatic terminals.
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Grilli M, Zappettini S, Raiteri L, Marchi M. Nicotinic and muscarinic cholinergic receptors coexist on GABAergic nerve endings in the mouse striatum and interact in modulating GABA release. Neuropharmacology 2008; 56:610-4. [PMID: 19027759 DOI: 10.1016/j.neuropharm.2008.10.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 10/27/2008] [Accepted: 10/30/2008] [Indexed: 10/21/2022]
Abstract
Muscarinic cholinergic receptors (mAChRs) and nicotinic cholinergic receptors (nAChRs) regulating GABA release from striatal nerve endings were studied by monitoring release of previously accumulated [(3)H]GABA or endogenous GABA from superfused mouse striatal synaptosomes. Oxotremorine inhibited the release of [(3)H]GABA elicited by depolarization with 4-aminopyridine (4-AP), an effect antagonized by atropine. Agonists at nAChRs, including the alpha(4)beta(2)( *) subunit-selective RJR2403, provoked the release of [(3)H]GABA as well as of the endogenous transmitter; these effects also were prevented by oxotremorine and pilocarpine suggesting coexpression of functional mAChRs and alpha(4)beta(2)( *) nAChRs on GABAergic nerve endings. The inhibitory effects of oxotremorine on the release of [(3)H]GABA evoked by 4-AP or by RJR2403 were: (i) prevented by the M(2)/M(4) mAChR antagonist himbacine; (ii) insensitive to the M2 antagonist AFDX116; (iii) blocked by the selective M(4) mAChR antagonists MT3, thus indicating the involvement of receptors of the M(4) subtype. In conclusion, in the corpus striatum, acetylcholine released from cholinergic interneurons can activate alpha(4)beta(2)( *) nAChRs mediating release of GABA; this evoked release can be negatively modulated by M(4) mAChRs coexpressed on the same GABAergic terminals.
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Affiliation(s)
- Massimo Grilli
- Department of Experimental Medicine, Pharmacology Section, University of Genoa, Viale Cembrano 4, 16148 Genova, Italy
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Schubert T, Kerschensteiner D, Eggers ED, Misgeld T, Kerschensteiner M, Lichtman JW, Lukasiewicz PD, Wong ROL. Development of presynaptic inhibition onto retinal bipolar cell axon terminals is subclass-specific. J Neurophysiol 2008; 100:304-16. [PMID: 18436633 DOI: 10.1152/jn.90202.2008] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Synaptic integration is modulated by inhibition onto the dendrites of postsynaptic cells. However, presynaptic inhibition at axonal terminals also plays a critical role in the regulation of neurotransmission. In contrast to the development of inhibitory synapses onto dendrites, GABAergic/glycinergic synaptogenesis onto axon terminals has not been widely studied. Because retinal bipolar cells receive subclass-specific patterns of GABAergic and glycinergic presynaptic inhibition, they are a good model for studying the development of inhibition at axon terminals. Here, using whole cell recording methods and transgenic mice in which subclasses of retinal bipolar cells are labeled, we determined the temporal sequence and patterning of functional GABAergic and glycinergic input onto the major subclasses of bipolar cells. We found that the maturation of GABAergic and glycinergic synapses onto the axons of rod bipolar cells (RBCs), on-cone bipolar cells (ON-CBCs) and off-cone bipolar cells (OFF-CBCs) were temporally distinct: spontaneous chloride-mediated currents are present in RBCs earlier in development compared with ON- and OFF-CBC, and RBCs receive GABAergic and glycinergic input simultaneously, whereas in OFF-CBCs, glycinergic transmission emerges before GABAergic transmission. Because on-CBCs show little inhibitory activity, GABAergic and glycinergic events could not be pharmacologically distinguished for these bipolar cells. The balance of GABAergic and glycinergic input that is unique to RBCs and OFF-CBCs is established shortly after the onset of synapse formation and precedes visual experience. Our data suggest that presynaptic modulation of glutamate transmission from bipolar cells matures rapidly and is differentially coordinated for GABAergic and glycinergic synapses onto distinct bipolar cell subclasses.
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Affiliation(s)
- Timm Schubert
- Department of Biological Structure, University of Washington, Seattle, Washington 98195-7420, USA
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