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Cepeda AP, Ninov M, Neef J, Parfentev I, Kusch K, Reisinger E, Jahn R, Moser T, Urlaub H. Proteomic Analysis Reveals the Composition of Glutamatergic Organelles of Auditory Inner Hair Cells. Mol Cell Proteomics 2024; 23:100704. [PMID: 38128648 PMCID: PMC10832297 DOI: 10.1016/j.mcpro.2023.100704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 11/08/2023] [Accepted: 12/18/2023] [Indexed: 12/23/2023] Open
Abstract
In the ear, inner hair cells (IHCs) employ sophisticated glutamatergic ribbon synapses with afferent neurons to transmit auditory information to the brain. The presynaptic machinery responsible for neurotransmitter release in IHC synapses includes proteins such as the multi-C2-domain protein otoferlin and the vesicular glutamate transporter 3 (VGluT3). Yet, much of this likely unique molecular machinery remains to be deciphered. The scarcity of material has so far hampered biochemical studies which require large amounts of purified samples. We developed a subcellular fractionation workflow combined with immunoisolation of VGluT3-containing membrane vesicles, allowing for the enrichment of glutamatergic organelles that are likely dominated by synaptic vesicles (SVs) of IHCs. We have characterized their protein composition in mice before and after hearing onset using mass spectrometry and confocal imaging and provide a fully annotated proteome with hitherto unidentified proteins. Despite the prevalence of IHC marker proteins across IHC maturation, the profiles of trafficking proteins differed markedly before and after hearing onset. Among the proteins enriched after hearing onset were VAMP-7, syntaxin-7, syntaxin-8, syntaxin-12/13, SCAMP1, V-ATPase, SV2, and PKCα. Our study provides an inventory of the machinery associated with synaptic vesicle-mediated trafficking and presynaptic activity at IHC ribbon synapses and serves as a foundation for future functional studies.
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Affiliation(s)
- Andreia P Cepeda
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Momchil Ninov
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany; Department of Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Jakob Neef
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience & Synaptic Nanophysiology Group Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Iwan Parfentev
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Kathrin Kusch
- Functional Auditory Genomics Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
| | - Ellen Reisinger
- Gene Therapy for Hearing Impairment and Deafness, Department for Otolaryngology, Head & Neck Surgery, University Hospital Tübingen, Tübingen, Germany
| | - Reinhard Jahn
- Laboratory of Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany.
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience & Synaptic Nanophysiology Group Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany.
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany; Department of Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany.
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Erickson JD, Kyllo T, Wulff H. Ca 2+-regulated expression of high affinity methylaminoisobutryic acid transport in hippocampal neurons inhibited by riluzole and novel neuroprotective aminothiazoles. Curr Res Physiol 2023; 6:100109. [PMID: 38107787 PMCID: PMC10724208 DOI: 10.1016/j.crphys.2023.100109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 09/13/2023] [Accepted: 09/27/2023] [Indexed: 12/19/2023] Open
Abstract
High affinity methylaminoisobutyric acid(MeAIB)/glutamine(Gln) transport activity regulated by neuronal firing occurs at the plasma membrane in mature rat hippocampal neuron-enriched cultures. Spontaneous Ca2+-regulated transport activity was similarly inhibited by riluzole, a benzothiazole anticonvulsant agent, and by novel naphthalenyl substituted aminothiazole derivatives such as SKA-378. Here, we report that spontaneous transport activity is stimulated by 4-aminopyridine (4-AP) and that phorbol-myristate acetate (PMA) increases high K+ stimulated transport activity that is inhibited by staurosporine. 4-AP-stimulated spontaneous and PMA-stimulated high K+-induced transport is not present at 7 days in vitro (DIV) and is maximal by DIV∼21. The relative affinity for MeAIB is similar for spontaneous and high K+-stimulated transport (Km ∼ 50 μM) suggesting that a single transporter is involved. While riluzole and SKA-378 inhibit spontaneous transport with equal potency (IC50 ∼ 1 μM), they exhibit decreased (∼3-5 X) potency for 4-AP-stimulated spontaneous transport. Interestingly, high K+-stimulated MeAIB transport displays lower and differential sensitivity to the two compounds. SKA-378-related halogenated derivatives of SKA-75 (SKA-219, SKA-377 and SKA-375) preferentially inhibit high K+-induced expression of MeAIB transport activity at the plasma membrane (IC50 < 25 μM), compared to SKA-75 and riluzole (IC50 > 100 μM). Ca2+-dependent spontaneous and high K+-stimulated MeAIB transport activity is blocked by ω-conotoxin MVIIC, ω-agatoxin IVA, ω-agatoxin TK (IC50 ∼ 500 nM) or cadmium ion (IC50 ∼ 20 μM) demonstrating that P/Q-type CaV channels that are required for activity-regulated presynaptic vesicular glutamate (Glu) release are also required for high-affinity MeAIB transport expression at the plasma membrane. We suggest that neural activity driven and Ca2+ dependent trafficking of the high affinity MeAIB transporter to the plasma membrane is a unique target to understand mechanisms of Glu/Gln recycling in synapses and acute neuroprotection against excitotoxic presynaptic Glu induced neural injury.
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Affiliation(s)
- Jeffrey D. Erickson
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health-New Orleans, New Orleans, LA, USA
| | - Thomas Kyllo
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health-New Orleans, New Orleans, LA, USA
| | - Heike Wulff
- Department of Pharmacology, School of Medicine, University of California-Davis, Davis, CA, USA
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Harsing LG, Timar J, Miklya I. Striking Neurochemical and Behavioral Differences in the Mode of Action of Selegiline and Rasagiline. Int J Mol Sci 2023; 24:13334. [PMID: 37686140 PMCID: PMC10487936 DOI: 10.3390/ijms241713334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 08/22/2023] [Accepted: 08/23/2023] [Indexed: 09/10/2023] Open
Abstract
Selegiline and rasagiline are two selective monoamine oxidase B (MAO-B) inhibitors used in the treatment of Parkinson's disease. In their clinical application, however, differences in L-dopa-sparing potencies have been observed. The aim of this study was to find neurochemical and behavioral explanations for the antiparkinsonian effects of these drugs. We found that selegiline possesses a dopaminergic enhancer effect: it stimulated the electrically induced [3H]dopamine release without influencing the resting [3H]dopamine release from rat striatal slices in 10-10-10-9 mol/L concentrations. Rasagiline added in 10-13 to 10-5 mol/L concentrations did not alter the resting or electrically stimulated [3H]dopamine release. Rasagiline (10-9 mol/L), however, suspended the stimulatory effect of selegiline on the electrically induced [3H]dopamine release. The trace amine-associated receptor 1 (TAAR1) antagonist EPPTB (10-8-10-7 mol/L) also inhibited the stimulatory effect of selegiline on [3H]dopamine release. The effect of selegiline in its enhancer dose (5.33 nmol/kg) against tetrabenazine-induced learning deficit measured in a shuttle box apparatus was abolished by a 5.84 nmol/kg dose of rasagiline. The selegiline metabolite (-)methamphetamine (10-9 mol/L) also exhibited enhancer activity on [3H]dopamine release. We have concluded that selegiline acts as an MAO-B inhibitor and a dopaminergic enhancer drug, and the latter relates to an agonist effect on TAAR1. In contrast, rasagiline is devoid of enhancer activity but may act as an antagonist on TAAR1.
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Affiliation(s)
| | | | - Ildiko Miklya
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Nagyvarad ter 4, 1089 Budapest, Hungary; (L.G.H.J.); (J.T.)
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Valverde-Salazar V, Ruiz-Gabarre D, García-Escudero V. Alzheimer's Disease and Green Tea: Epigallocatechin-3-Gallate as a Modulator of Inflammation and Oxidative Stress. Antioxidants (Basel) 2023; 12:1460. [PMID: 37507998 PMCID: PMC10376369 DOI: 10.3390/antiox12071460] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 07/05/2023] [Accepted: 07/17/2023] [Indexed: 07/30/2023] Open
Abstract
Alzheimer's disease (AD) is the most common cause of dementia, characterised by a marked decline of both memory and cognition, along with pathophysiological hallmarks including amyloid beta peptide (Aβ) accumulation, tau protein hyperphosphorylation, neuronal loss and inflammation in the brain. Additionally, oxidative stress caused by an imbalance between free radicals and antioxidants is considered one of the main risk factors for AD, since it can result in protein, lipid and nucleic acid damage and exacerbate Aβ and tau pathology. To date, there is a lack of successful pharmacological approaches to cure or even ameliorate the terrible impact of this disease. Due to this, dietary compounds with antioxidative and anti-inflammatory properties acquire special relevance as potential therapeutic agents. In this context, green tea, and its main bioactive compound, epigallocatechin-3-gallate (EGCG), have been targeted as a plausible option for the modulation of AD. Specifically, EGCG acts as an antioxidant by regulating inflammatory processes involved in neurodegeneration such as ferroptosis and microglia-induced cytotoxicity and by inducing signalling pathways related to neuronal survival. Furthermore, it reduces tau hyperphosphorylation and aggregation and promotes the non-amyloidogenic route of APP processing, thus preventing the formation of Aβ and its subsequent accumulation. Taken together, these results suggest that EGCG may be a suitable candidate in the search for potential therapeutic compounds for neurodegenerative disorders involving inflammation and oxidative stress, including Alzheimer's disease.
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Affiliation(s)
- Víctor Valverde-Salazar
- Department of Anatomy, Histology and Neuroscience, School of Medicine, Universidad Autónoma de Madrid, 28029 Madrid, Spain
| | - Daniel Ruiz-Gabarre
- Department of Anatomy, Histology and Neuroscience, School of Medicine, Universidad Autónoma de Madrid, 28029 Madrid, Spain
| | - Vega García-Escudero
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas, CIBERNED, 28031 Madrid, Spain
- Institute for Molecular Biology-IUBM, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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Feldthouse MG, Vyleta NP, Smith SM. PLC regulates spontaneous glutamate release triggered by extracellular calcium and readily releasable pool size in neocortical neurons. Front Cell Neurosci 2023; 17:1193485. [PMID: 37260580 PMCID: PMC10228687 DOI: 10.3389/fncel.2023.1193485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 04/26/2023] [Indexed: 06/02/2023] Open
Abstract
Introduction Dynamic physiological changes in brain extracellular calcium ([Ca2+]o) occur when high levels of neuronal activity lead to substantial Ca2+ entry via ion channels reducing local [Ca2+]o. Perturbations of the extracellular microenvironment that increase [Ca2+]o are commonly used to study how [Ca2+] regulates neuronal activity. At excitatory synapses, the Ca2+-sensing receptor (CaSR) and other G-protein coupled receptors link [Ca2+]o and spontaneous glutamate release. Phospholipase C (PLC) is activated by G-proteins and is hypothesized to mediate this process. Methods Patch-clamping cultured neocortical neurons, we tested how spontaneous glutamate release was affected by [Ca2+]o and inhibition of PLC activity. We used hypertonic sucrose (HS) to evaluate the readily releasable pool (RRP) and test if it was affected by inhibition of PLC activity. Results Spontaneous glutamate release substantially increased with [Ca2+]o, and inhibition of PLC activity, with U73122, abolished this effect. PLC-β1 is an abundant isoform in the neocortex, however, [Ca2+]o-dependent spontaneous release was unchanged in PLC-β1 null mutants (PLC-β1-/-). U73122 completely suppressed this response in PLC-β1-/- neurons, indicating that this residual [Ca2+]o-sensitivity may be mediated by other PLC isoforms. The RRP size was substantially reduced after incubation in U73122, but not U73343. Phorbol esters increased RRP size after PLC inhibition. Discussion Together these data point to a strong role for PLC in mediating changes in spontaneous release elicited by [Ca2+]o and other extracellular cues, possibly by modifying the size of the RRP.
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Affiliation(s)
- Maya G. Feldthouse
- Section of Pulmonary and Critical Care Medicine and Research and Development, VA Portland Health Care System, Portland, OR, United States
| | - Nicholas P. Vyleta
- Division of Pulmonary and Critical Care Medicine, Oregon Health and Science University, Portland, OR, United States
| | - Stephen M. Smith
- Section of Pulmonary and Critical Care Medicine and Research and Development, VA Portland Health Care System, Portland, OR, United States
- Division of Pulmonary and Critical Care Medicine, Oregon Health and Science University, Portland, OR, United States
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Zhu F, Liu L, Li J, Liu B, Wang Q, Jiao R, Xu Y, Wang L, Sun S, Sun X, Younus M, Wang C, Hokfelt T, Zhang B, Gu H, Xu ZQD, Zhou Z. Cocaine increases quantal norepinephrine secretion through NET-dependent PKC activation in locus coeruleus neurons. Cell Rep 2022; 40:111199. [PMID: 35977516 DOI: 10.1016/j.celrep.2022.111199] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 04/20/2022] [Accepted: 07/20/2022] [Indexed: 11/25/2022] Open
Abstract
The norepinephrine neurons in locus coeruleus (LC-NE neurons) are essential for sleep arousal, pain sensation, and cocaine addiction. According to previous studies, cocaine increases NE overflow (the profile of extracellular NE level in response to stimulation) by blocking the NE reuptake. NE overflow is determined by NE release via exocytosis and reuptake through NE transporter (NET). However, whether cocaine directly affects vesicular NE release has not been directly tested. By recording quantal NE release from LC-NE neurons, we report that cocaine directly increases the frequency of quantal NE release through regulation of NET and downstream protein kinase C (PKC) signaling, and this facilitation of NE release modulates the activity of LC-NE neurons and cocaine-induced stimulant behavior. Thus, these findings expand the repertoire of mechanisms underlying the effects of cocaine on NE (pro-release and anti-reuptake), demonstrate NET as a release enhancer in LC-NE neurons, and provide potential sites for treatment of cocaine addiction.
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Affiliation(s)
- Feipeng Zhu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Lina Liu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China; Core Facilities Center, Departments of Neurobiology and Pathology, Beijing Key Laboratory of Neural Regeneration and Repair, Beijing Institute for Brain Disorders, Capital Medical University, Beijing 100069, China
| | - Jie Li
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Bing Liu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Qinglong Wang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Ruiying Jiao
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Yongxin Xu
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Lun Wang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Suhua Sun
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Xiaoxuan Sun
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Muhammad Younus
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Changhe Wang
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China
| | - Tomas Hokfelt
- Department of Neuroscience, Karolinska Institute, 171 71 Stockholm, Sweden
| | - Bo Zhang
- School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen 518055, China; Institute of Neurological and Psychiatric Disorders, Shenzhen Bay Laboratory, Shenzhen 518132, China.
| | - Howard Gu
- Department of Biological Chemistry and Pharmacology, Ohio State University College of Medicine, Columbus, OH 43210, USA.
| | - Zhi-Qing David Xu
- Core Facilities Center, Departments of Neurobiology and Pathology, Beijing Key Laboratory of Neural Regeneration and Repair, Beijing Institute for Brain Disorders, Capital Medical University, Beijing 100069, China.
| | - Zhuan Zhou
- State Key Laboratory of Membrane Biology and Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, College of Future Technology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China.
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Lu CW, Yeh KC, Chiu KM, Lee MY, Lin TY, Wang SJ. The Effect of Isosaponarin Derived from Wasabi Leaves on Glutamate Release in Rat Synaptosomes and Its Underlying Mechanism. Int J Mol Sci 2022; 23:ijms23158752. [PMID: 35955884 PMCID: PMC9368944 DOI: 10.3390/ijms23158752] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 08/05/2022] [Accepted: 08/05/2022] [Indexed: 11/23/2022] Open
Abstract
Excessive glutamate release is known to be involved in the pathogenesis of neurological diseases, and suppression of glutamate release from nerve terminals is considered to be a treatment strategy. In this study, we investigated whether isosaponarin, a flavone glycoside isolated from wasabi leaves, could affect glutamate release in rat cerebral cortex nerve terminals (synaptosomes). The release of glutamate was evoked by the K+ channel blocker 4-aminopyridine (4-AP) and measured by an online enzyme-coupled fluorimetric assay. Isosaponarin produced a concentration-dependent inhibition of 4-AP-evoked glutamate release with a half-maximum inhibition of release value of 22 μM. The inhibition caused by isosaponarin was prevented by eliminating extracellular Ca2+ or by using bafilomycin A1, an inhibitor of synaptic vesicle exocytosis. Isosaponarin decreased intrasynaptosomal rises in Ca2+ levels that were induced by 4-AP, without affecting the synaptosomal membrane potential. The isosaponarin-induced inhibition of glutamate release was significantly prevented in synaptosomes that were pretreated with a combination of the calcium channel blockers ω-conotoxin GVIA (N-type) and ω-agatoxin IVA (P/Q-types). The protein kinase C (PKC) pan-inhibitor GF109203X and the Ca2+-dependent PKC inhibitor Go6976 abolished the inhibition of glutamate release by isosaponarin, while the Ca2+-independent PKC inhibitor rottlerin did not show any effect. The results from immunoblotting assays also showed that isosaponarin lowered PKC, PKCα, synaptosomal-associated protein of 25 kDa (SNAP-25), and myristoylated alanine-rich C-kinase substrate (MARCKS) phosphorylation induced by 4-AP. In addition, FM1-43-labeled synaptic vesicles in synaptosomes showed that treatment with isosaponarin resulted in an attenuation of the 4-AP-induced decrease in fluorescence intensity that is consistent with glutamate release. Transmission electron microscopy of synaptosomes also provided evidence that isosaponarin altered the number of synaptic vesicles. These results indicate that isosaponarin suppresses the Ca2+-dependent PKC/SNAP-25 and MARCKS pathways in synaptosomes, causing a decrease in the number of available synaptic vesicles, which inhibits vesicular glutamate release from synaptosomes.
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Affiliation(s)
- Cheng-Wei Lu
- Department of Anesthesiology, Far-Eastern Memorial Hospital, New Taipei City 22060, Taiwan
- Department of Mechanical Engineering, Yuan Ze University, Taoyuan 32003, Taiwan
| | - Kun-Chieh Yeh
- School of Medicine, Fu Jen Catholic University, New Taipei City 24205, Taiwan
- Department of Surgery, Taoyuan Armed Forces General Hospital, Taoyuan 325208, Taiwan
- Department of Surgery, Fu Jen Catholic University Hospital, Fu Jen Catholic University, New Taipei City 24205, Taiwan
| | - Kuan-Ming Chiu
- Division of Cardiovascular Surgery, Cardiovascular Center, Far-Eastern Memorial Hospital, New Taipei City 22060, Taiwan
- Department of Electrical Engineering, Yuan Ze University, Taoyuan 32003, Taiwan
| | - Ming-Yi Lee
- Department of Medical Research, Far-Eastern Memorial Hospital, New Taipei 22060, Taiwan
| | - Tzu-Yu Lin
- Department of Anesthesiology, Far-Eastern Memorial Hospital, New Taipei City 22060, Taiwan
- Department of Mechanical Engineering, Yuan Ze University, Taoyuan 32003, Taiwan
- Correspondence: (T.-Y.L.); (S.-J.W.); Tel.: +886-2-8966-7000 (T.-Y.L.); +886-2-2905-3465 (S.-J.W.)
| | - Su-Jane Wang
- School of Medicine, Fu Jen Catholic University, New Taipei City 24205, Taiwan
- Research Center for Chinese Herbal Medicine, College of Human Ecology, Chang Gung University of Science and Technology, Taoyuan 33303, Taiwan
- Correspondence: (T.-Y.L.); (S.-J.W.); Tel.: +886-2-8966-7000 (T.-Y.L.); +886-2-2905-3465 (S.-J.W.)
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Enhancer Regulation of Dopaminergic Neurochemical Transmission in the Striatum. Int J Mol Sci 2022; 23:ijms23158543. [PMID: 35955676 PMCID: PMC9369307 DOI: 10.3390/ijms23158543] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 07/22/2022] [Accepted: 07/29/2022] [Indexed: 02/04/2023] Open
Abstract
The trace amine-associated receptor 1 (TAAR1) is a Gs protein-coupled, intracellularly located metabotropic receptor. Trace and classic amines, amphetamines, act as agonists on TAAR1; they activate downstream signal transduction influencing neurotransmitter release via intracellular phosphorylation. Our aim was to check the effect of the catecholaminergic activity enhancer compound ((−)BPAP, (R)-(−)-1-(benzofuran-2-yl)-2-propylaminopentane) on neurotransmitter release via the TAAR1 signaling. Rat striatal slices were prepared and the resting and electrical stimulation-evoked [3H]dopamine release was measured. The releaser (±)methamphetamine evoked non-vesicular [3H]dopamine release in a TAAR1-dependent manner, whereas (−)BPAP potentiated [3H]dopamine release with vesicular origin via TAAR1 mediation. (−)BPAP did not induce non-vesicular [3H]dopamine release. N-Ethylmaleimide, which inhibits SNARE core complex disassembly, potentiated the stimulatory effect of (−)BPAP on vesicular [3H]dopamine release. Subsequent analyses indicated that the dopamine-release stimulatory effect of (−)BPAP was due to an increase in PKC-mediated phosphorylation. We have hypothesized that there are two binding sites present on TAAR1, one for the releaser and one for the enhancer compounds, and they activate different PKC-mediated phosphorylation leading to the evoking of non-vesicular and vesicular dopamine release. (−)BPAP also increased VMAT2 operation enforcing vesicular [3H]dopamine accumulation and release. Vesicular dopamine release promoted by TAAR1 evokes activation of D2 dopamine autoreceptor-mediated presynaptic feedback inhibition. In conclusion, TAAR1 possesses a triggering role in both non-vesicular and vesicular dopamine release, and the mechanism of action of (−)BPAP is linked to the activation of TAAR1 and the signal transduction attached.
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Hanuscheck N, Thalman C, Domingues M, Schmaul S, Muthuraman M, Hetsch F, Ecker M, Endle H, Oshaghi M, Martino G, Kuhlmann T, Bozek K, van Beers T, Bittner S, von Engelhardt J, Vogt J, Vogelaar CF, Zipp F. Interleukin-4 receptor signaling modulates neuronal network activity. J Exp Med 2022; 219:213227. [PMID: 35587822 PMCID: PMC9123307 DOI: 10.1084/jem.20211887] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 12/13/2021] [Accepted: 04/29/2022] [Indexed: 11/25/2022] Open
Abstract
Evidence is emerging that immune responses not only play a part in the central nervous system (CNS) in diseases but may also be relevant for healthy conditions. We discovered a major role for the interleukin-4 (IL-4)/IL-4 receptor alpha (IL-4Rα) signaling pathway in synaptic processes, as indicated by transcriptome analysis in IL-4Rα–deficient mice and human neurons with/without IL-4 treatment. Moreover, IL-4Rα is expressed presynaptically, and locally available IL-4 regulates synaptic transmission. We found reduced synaptic vesicle pools, altered postsynaptic currents, and a higher excitatory drive in cortical networks of IL-4Rα–deficient neurons. Acute effects of IL-4 treatment on postsynaptic currents in wild-type neurons were mediated via PKCγ signaling release and led to increased inhibitory activity supporting the findings in IL-4Rα–deficient neurons. In fact, the deficiency of IL-4Rα resulted in increased network activity in vivo, accompanied by altered exploration and anxiety-related learning behavior; general learning and memory was unchanged. In conclusion, neuronal IL-4Rα and its presynaptic prevalence appear relevant for maintaining homeostasis of CNS synaptic function.
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Affiliation(s)
- Nicholas Hanuscheck
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Carine Thalman
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Micaela Domingues
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Samantha Schmaul
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Muthuraman Muthuraman
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Florian Hetsch
- Institute for Pathophysiology, Focus Program Translational Neuroscience, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Manuela Ecker
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Heiko Endle
- Department of Molecular and Translational Neuroscience, Cluster of Excellence-Cellular Stress Response in Aging-Associated Diseases and Center of Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Mohammadsaleh Oshaghi
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Gianvito Martino
- Neuroimmunology Unit, Institute of Experimental Neurology, Division of Neuroscience, IRCCS San Raffaele Scientific Institute and Vita Salute San Raffaele University, Milan, Italy
| | - Tanja Kuhlmann
- Institute for Neuropathology, University Hospital Münster, Münster, Germany
| | - Katarzyna Bozek
- Center for Molecular Medicine, Faculty of Medicine and University Hospital Cologne; University of Cologne, Cologne, Germany
| | - Tim van Beers
- Molecular Cell Biology, Institute I of Anatomy, University of Cologne, Cologne, Germany
| | - Stefan Bittner
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Jakob von Engelhardt
- Institute for Pathophysiology, Focus Program Translational Neuroscience, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Johannes Vogt
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany.,Department of Molecular and Translational Neuroscience, Cluster of Excellence-Cellular Stress Response in Aging-Associated Diseases and Center of Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Christina Francisca Vogelaar
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Frauke Zipp
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine Main Neuroscience Network (rmn2), University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
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10
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Qin N, Chen Z, Xue R. A two-subpopulation model that reflects heterogeneity of large dense core vesicles in exocytosis. Cell Cycle 2022; 21:531-546. [PMID: 35067177 PMCID: PMC8942488 DOI: 10.1080/15384101.2022.2026576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Exocytosis of large dense core vesicles is responsible for hormone secretion in neuroendocrine cells. The population of primed vesicles ready to release upon cell excitation demonstrates large heterogeneity. However, there are currently no models that clearly reflect such heterogeneity. Here, we develop a novel model based on single vesicle release events from amperometry recordings of PC12 cells using carbon fiber microelectrode. In this model, releasable vesicles can be grouped into two subpopulations, namely, SP1 and SP2. SP1 vesicles replenish quickly, with kinetics of ~0.0368 s-1, but likely undergo slow fusion pore expansion (amperometric signals rise at ~2.5 pA/ms), while SP2 vesicles demonstrate slow replenishment (kinetics of ~0.0048 s-1) but prefer fast dilation of fusion pore, with an amperometric signal rising rate of ~9.1 pA/ms. Phorbol ester enlarges the size of SP2 partially via activation of protein kinase C and conveys SP1 vesicles into SP2. Inhibition of Rho GTPase-dependent actin rearrangement almost completely depletes SP2. We also propose that the phorbol ester-sensitive vesicle subpopulation (SP2) is analogous to the subset of superprimed synaptic vesicles in neurons. This model provides a meticulous description of the architecture of the readily releasable vesicle pool and elucidates the heterogeneity of the vesicle priming mechanism.
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Affiliation(s)
- Nan Qin
- Shanghai Key Laboratory of Maternal Fetal Medicine, Clinical and Translational Research Center of Shanghai First Maternity & Infant Hospital, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Zhixi Chen
- Shanghai Key Laboratory of Maternal Fetal Medicine, Clinical and Translational Research Center of Shanghai First Maternity & Infant Hospital, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Renhao Xue
- Shanghai Key Laboratory of Maternal Fetal Medicine, Clinical and Translational Research Center of Shanghai First Maternity & Infant Hospital, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China,CONTACT Renhao Xue Shanghai Key Laboratory of Maternal Fetal Medicine, Clinical and Translational Research Center of Shanghai First Maternity & Infant Hospital, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China
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11
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The redundancy and diversity between two novel PKC isotypes that regulate learning in Caenorhabditis elegans. Proc Natl Acad Sci U S A 2022; 119:2106974119. [PMID: 35027448 PMCID: PMC8784152 DOI: 10.1073/pnas.2106974119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2021] [Indexed: 11/18/2022] Open
Abstract
The nematode Caenorhabditis elegans learns the concentration of NaCl and moves toward the previously experienced concentration. In this behavior, the history of NaCl concentration change is reflected in the level of diacylglycerol and the activity of protein kinase C, PKC-1, in the gustatory sensory neuron ASER and determines the direction of migration. Here, through a genetic screen, we found that the activation of Gq protein compensates for the behavioral defect of the loss-of-function mutant of pkc-1 We found that Gq activation results in hyperproduction of diacylglycerol in ASER sensory neuron, which leads to recruitment of TPA-1, an nPKC isotype closely related to PKC-1. Unlike the pkc-1 mutants, loss of tpa-1 did not obviously affect migration directions in the conventional learning assay. This difference was suggested to be due to cooperative functions of the C1 and C2-like domains of the nPKC isotypes. Furthermore, we investigated how the compensatory capability of tpa-1 contributes to learning and found that learning was less robust in the context of cognitive decline or environmental perturbation in tpa-1 mutants. These results highlight how two nPKC isotypes contribute to the learning system.
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12
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Hsu SK, Hung CF, Yang HC, Weng JR, Wang SJ. TCD, a triterpenoid isolated from wild bitter gourd, reduces synaptosomal release of glutamate and protects against kainic acid-induced neuronal death. Food Funct 2021; 11:9858-9867. [PMID: 33089839 DOI: 10.1039/d0fo02039g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
3β,7β,25-Trihydroxycucurbita-5,23(E)-dien-19-al (TCD) is a triterpenoid isolated from wild bitter gourd that is a common tropical vegetable with neuroprotective effects. Because excessive glutamate release is a major cause of neuronal damage in various neurological disorders, the aims of this study were to examine the effect of TCD on glutamate release in vitro and to examine the effect of TCD in vivo. In rat cerebrocortical synaptosomes, TCD reduced 4-aminopyridine (4-AP)-stimulated glutamate release and Ca2+ concentration elevation, but had no effect on plasma membrane potential. TCD-mediated inhibition of 4-AP-induced glutamate release was dependent on the presence of extracellular calcium; persisted in the presence of the glutamate transporter inhibitor dl-TBOA, P/Q-type Ca2+ channel blocker ω-agatoxin IVA, and intracellular Ca2+-releasing inhibitors dantrolene and CGP37157; and was blocked by the vesicular transporter inhibitor bafilomycin A1 and the N-type Ca2+ channel blocker ω-conotoxin GVIA. Molecular docking studies have demonstrated that TCD binds to N-type Ca2+ channels. TCD-mediated inhibition of 4-AP-induced glutamate release was abolished by the Ca2+-dependent protein kinase C (PKC) inhibitor Go6976, but was unaffected by the Ca2+-independent PKC inhibitor rottlerin. Furthermore, TCD considerably reduced the phosphorylation of PKC, PKCα, and myristoylated alanine-rich C kinase substrate, a major presynaptic substrate for PKC. In a rat model of kainic acid (KA)-induced excitotoxicity, TCD pretreatment substantially attenuated KA-induced neuronal death in the CA3 hippocampal region. These results suggest that TCD inhibits synaptosomal glutamate release by suppressing N-type Ca2+ channels and PKC activity and exerts protective effects against KA-induced excitotoxicity in vivo.
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Affiliation(s)
- Szu Kai Hsu
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan.
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13
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Jia Q, Sieburth D. Mitochondrial hydrogen peroxide positively regulates neuropeptide secretion during diet-induced activation of the oxidative stress response. Nat Commun 2021; 12:2304. [PMID: 33863916 PMCID: PMC8052458 DOI: 10.1038/s41467-021-22561-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 03/17/2021] [Indexed: 12/17/2022] Open
Abstract
Mitochondria play a pivotal role in the generation of signals coupling metabolism with neurotransmitter release, but a role for mitochondrial-produced ROS in regulating neurosecretion has not been described. Here we show that endogenously produced hydrogen peroxide originating from axonal mitochondria (mtH2O2) functions as a signaling cue to selectively regulate the secretion of a FMRFamide-related neuropeptide (FLP-1) from a pair of interneurons (AIY) in C. elegans. We show that pharmacological or genetic manipulations that increase mtH2O2 levels lead to increased FLP-1 secretion that is dependent upon ROS dismutation, mitochondrial calcium influx, and cysteine sulfenylation of the calcium-independent PKC family member PKC-1. mtH2O2-induced FLP-1 secretion activates the oxidative stress response transcription factor SKN-1/Nrf2 in distal tissues and protects animals from ROS-mediated toxicity. mtH2O2 levels in AIY neurons, FLP-1 secretion and SKN-1 activity are rapidly and reversibly regulated by exposing animals to different bacterial food sources. These results reveal a previously unreported role for mtH2O2 in linking diet-induced changes in mitochondrial homeostasis with neuropeptide secretion.
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Affiliation(s)
- Qi Jia
- PIBBS program, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Derek Sieburth
- Department of Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
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14
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Perez DM. α 1-Adrenergic Receptors in Neurotransmission, Synaptic Plasticity, and Cognition. Front Pharmacol 2020; 11:581098. [PMID: 33117176 PMCID: PMC7553051 DOI: 10.3389/fphar.2020.581098] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 09/11/2020] [Indexed: 12/14/2022] Open
Abstract
α1-adrenergic receptors are G-Protein Coupled Receptors that are involved in neurotransmission and regulate the sympathetic nervous system through binding and activating the neurotransmitter, norepinephrine, and the neurohormone, epinephrine. There are three α1-adrenergic receptor subtypes (α1A, α1B, α1D) that are known to play various roles in neurotransmission and cognition. They are related to two other adrenergic receptor families that also bind norepinephrine and epinephrine, the β- and α2-, each with three subtypes (β1, β2, β3, α2A, α2B, α2C). Previous studies assessing the roles of α1-adrenergic receptors in neurotransmission and cognition have been inconsistent. This was due to the use of poorly-selective ligands and many of these studies were published before the characterization of the cloned receptor subtypes and the subsequent development of animal models. With the availability of more-selective ligands and the development of animal models, a clearer picture of their role in cognition and neurotransmission can be assessed. In this review, we highlight the significant role that the α1-adrenergic receptor plays in regulating synaptic efficacy, both short and long-term synaptic plasticity, and its regulation of different types of memory. We will also present evidence that the α1-adrenergic receptors, and particularly the α1A-adrenergic receptor subtype, are a potentially good target to treat a wide variety of neurological conditions with diminished cognition.
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Affiliation(s)
- Dianne M Perez
- The Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, OH, United States
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15
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Huson V, Meijer M, Dekker R, Ter Veer M, Ruiter M, van Weering JR, Verhage M, Cornelisse LN. Post-tetanic potentiation lowers the energy barrier for synaptic vesicle fusion independently of Synaptotagmin-1. eLife 2020; 9:55713. [PMID: 32831174 PMCID: PMC7500951 DOI: 10.7554/elife.55713] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 08/23/2020] [Indexed: 11/13/2022] Open
Abstract
Previously, we showed that modulation of the energy barrier for synaptic vesicle fusion boosts release rates supralinearly (Schotten, 2015). Here we show that mouse hippocampal synapses employ this principle to trigger Ca2+-dependent vesicle release and post-tetanic potentiation (PTP). We assess energy barrier changes by fitting release kinetics in response to hypertonic sucrose. Mimicking activation of the C2A domain of the Ca2+-sensor Synaptotagmin-1 (Syt1), by adding a positive charge (Syt1D232N) or increasing its hydrophobicity (Syt14W), lowers the energy barrier. Removing Syt1 or impairing its release inhibitory function (Syt19Pro) increases spontaneous release without affecting the fusion barrier. Both phorbol esters and tetanic stimulation potentiate synaptic strength, and lower the energy barrier equally well in the presence and absence of Syt1. We propose a model where tetanic stimulation activates Syt1-independent mechanisms that lower the energy barrier and act additively with Syt1-dependent mechanisms to produce PTP by exerting multiplicative effects on release rates.
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Affiliation(s)
- Vincent Huson
- Department of Functional Genomics, Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam University Medical Center- Location VUmc, Amsterdam, Netherlands
| | - Marieke Meijer
- Department of Functional Genomics, Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam University Medical Center- Location VUmc, Amsterdam, Netherlands
| | - Rien Dekker
- Department of Functional Genomics, Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam University Medical Center- Location VUmc, Amsterdam, Netherlands
| | - Mirelle Ter Veer
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam, Netherlands
| | - Marvin Ruiter
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam, Netherlands
| | - Jan Rt van Weering
- Department of Functional Genomics, Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam University Medical Center- Location VUmc, Amsterdam, Netherlands
| | - Matthijs Verhage
- Department of Functional Genomics, Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam University Medical Center- Location VUmc, Amsterdam, Netherlands.,Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, Amsterdam, Netherlands
| | - Lennart Niels Cornelisse
- Department of Functional Genomics, Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam University Medical Center- Location VUmc, Amsterdam, Netherlands
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16
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Heterosynaptic Plasticity in Cortical Interneurons. J Neurosci 2020; 40:1793-1794. [PMID: 32102906 DOI: 10.1523/jneurosci.2567-19.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Revised: 01/22/2020] [Accepted: 01/27/2020] [Indexed: 11/21/2022] Open
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17
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Bekkers JM. Autaptic Cultures: Methods and Applications. Front Synaptic Neurosci 2020; 12:18. [PMID: 32425765 PMCID: PMC7203343 DOI: 10.3389/fnsyn.2020.00018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Accepted: 04/01/2020] [Indexed: 11/13/2022] Open
Abstract
Neurons typically form daisy chains of synaptic connections with other neurons, but they can also form synapses with themselves. Although such self-synapses, or autapses, are comparatively rare in vivo, they are surprisingly common in dissociated neuronal cultures. At first glance, autapses in culture seem like a mere curiosity. However, by providing a simple model system in which a single recording electrode gives simultaneous access to the pre- and postsynaptic compartments, autaptic cultures have proven to be invaluable in facilitating important and elegant experiments in the area of synaptic neuroscience. Here, I provide detailed protocols for preparing and recording from autaptic cultures (also called micro-island or microdot cultures). Variations on the basic procedure are presented, as well as practical tips for optimizing the outcomes. I also illustrate the utility of autaptic cultures by reviewing the types of experiments that have used them over the past three decades. These examples serve to highlight the power and elegance of this simple model system, and will hopefully inspire new experiments for the interrogation of synaptic function.
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Affiliation(s)
- John M Bekkers
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia
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18
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Ruiter M, Houy S, Engholm-Keller K, Graham ME, Sørensen JB. SNAP-25 phosphorylation at Ser187 is not involved in Ca 2+ or phorbolester-dependent potentiation of synaptic release. Mol Cell Neurosci 2019; 102:103452. [PMID: 31794878 DOI: 10.1016/j.mcn.2019.103452] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 10/13/2019] [Accepted: 11/29/2019] [Indexed: 11/25/2022] Open
Abstract
SNAP-25, one of the three SNARE-proteins responsible for synaptic release, can be phosphorylated by Protein Kinase C on Ser-187, close to the fusion pore. In neuroendocrine cells, this phosphorylation event potentiates vesicle recruitment into releasable pools, whereas the consequences of phosphorylation for synaptic release remain unclear. We mutated Ser-187 and expressed two mutants (S187C and S187E) in the context of the SNAP-25B-isoform in SNAP-25 knockout glutamatergic autaptic neurons. Whole-cell patch clamp recordings were performed to assess the effect of Ser-187 phosphorylation on synaptic transmission. Blocking phosphorylation by expressing the S187C mutant did not affect synapse density, basic evoked or spontaneous neurotransmission, the readily-releasable pool size or its Ca2+-independent or Ca2+-dependent replenishment. Furthermore, it did not affect the response to phorbol esters, which activate PKC. Expressing S187C in the context of the SNAP-25A isoform also did not affect synaptic transmission. Strikingly, the - potentially phosphomimetic - mutant S187E reduced spontaneous release and release probability, with the largest effect seen in the SNAP-25B isoform, showing that a negative charge in this position is detrimental for neurotransmission, in agreement with electrostatic fusion triggering. During the course of our experiments, we found that higher SNAP-25B expression levels led to decreased paired pulse potentiation, probably due to higher release probabilities. Under these conditions, the potentiation of evoked EPSCs by phorbol esters was followed by a persistent down-regulation, probably due to a ceiling effect. In conclusion, our results indicate that phosphorylation of Ser-187 in SNAP-25 is not involved in modulation of synaptic release by Ca2+ or phorbol esters.
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Affiliation(s)
- Marvin Ruiter
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3C, 2200 Copenhagen N, Denmark
| | - Sébastien Houy
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3C, 2200 Copenhagen N, Denmark
| | - Kasper Engholm-Keller
- Synapse Proteomics Group, Children's Medical Research Institute, The University of Sydney, 214 Hawkesbury Road, Westmead NSW 2145, New South Wales, Australia; Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
| | - Mark E Graham
- Synapse Proteomics Group, Children's Medical Research Institute, The University of Sydney, 214 Hawkesbury Road, Westmead NSW 2145, New South Wales, Australia
| | - Jakob B Sørensen
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3C, 2200 Copenhagen N, Denmark.
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19
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Su IC, Hung CF, Lin CN, Huang SK, Wang SJ. Cycloheterophyllin Inhibits the Release of Glutamate from Nerve Terminals of the Rat Hippocampus. Chem Res Toxicol 2019; 32:1591-1598. [PMID: 31264847 DOI: 10.1021/acs.chemrestox.9b00121] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The effect of cycloheterophyllin, a prenylflavone isolated from Artocarpus heteophyllus, on glutamate release was studied in the rat hippocampus using synaptosome and slice preparations. In rat hippocampal synaptosomes, cycloheterophyllin inhibited 4-aminopyridine (4-AP)-evoked glutamate release and elevation of intrasynaptosomal calcium levels. The inhibitory effect of cycloheterophyllin on 4-AP-evoked glutamate release was prevented in the presence of the vesicular transporter inhibitor, the N- and P/Q-type calcium channel blocker, and the protein kinase C (PKC) inhibitor but was insensitive to the intracellular Ca2+ release inhibitors, the protein kinase A inhibitor, and the mitogen-activated/extracellular signal-regulated kinase inhibitor. Western blotting data in synaptosomes also showed that cycloheterophyllin significantly decreased the level of phosphorylation of PKC. In addition, cycloheterophyllin decreased the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) without influencing the amplitude of sEPSCs and glutamate-activated currents in hippocampal slices, supporting a presynaptic action. Together, these results suggest that cycloheterophyllin inhibits presynaptic glutamate release by suppressing N- and P/Q-type calcium channel and PKC activity in the rat hippocampus.
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Affiliation(s)
- I Chang Su
- School of Medicine , Fu Jen Catholic University , No. 510, Chung-Cheng Road , Hsin-Chuang, New Taipei City 24205 , Taiwan.,Division of Neurosurgery, Department of Surgery , Cathay General Hospital , Taipei City , Taiwan 106
| | - Chi Feng Hung
- School of Medicine , Fu Jen Catholic University , No. 510, Chung-Cheng Road , Hsin-Chuang, New Taipei City 24205 , Taiwan
| | - Chun Nan Lin
- College of Pharmacy , Kaoshiung Medical University , Kaohsiung , Taiwan 807
| | - Shu Kuei Huang
- Department of Anesthesiology , Far-Eastern Memorial Hospital , Pan-Chiao District , New Taipei City 22060 , Taiwan
| | - Su Jane Wang
- School of Medicine , Fu Jen Catholic University , No. 510, Chung-Cheng Road , Hsin-Chuang, New Taipei City 24205 , Taiwan.,Research Center for Chinese Herbal Medicine, College of Human Ecology , Chang Gung University of Science and Technology , Taoyuan City , Taiwan 333
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20
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Lu CW, Hung CF, Lin TY, Hsieh TY, Wang SJ. Allicin Inhibits Glutamate Release from Rat Cerebral Cortex Nerve Terminals Through Suppressing Ca2+ Influx and Protein Kinase C Activity. J Med Food 2019; 22:696-702. [DOI: 10.1089/jmf.2018.4337] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Affiliation(s)
- Cheng-Wei Lu
- Department of Anesthesiology, Far-Eastern Memorial Hospital, New Taipei City, Taiwan
- Department of Mechanical Engineering, Yuan Ze University, Taoyuan City, Taiwan
| | - Chi-Feng Hung
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan
| | - Tzu-Yu Lin
- Department of Anesthesiology, Far-Eastern Memorial Hospital, New Taipei City, Taiwan
- Department of Mechanical Engineering, Yuan Ze University, Taoyuan City, Taiwan
| | - Ting Yang Hsieh
- P.H.D. Program in Nutrition and Food Science, Fu Jen Catholic University, New Taipei City, Taiwan
| | - Su Jane Wang
- School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan
- Research Center for Chinese Herbal Medicine, College of Human Ecology, Chang Gung University of Science and Technology, Taoyuan City, Taiwan
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21
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Guzman GA, Guzman RE, Jordan N, Hidalgo P. A Tripartite Interaction Among the Calcium Channel α 1- and β-Subunits and F-Actin Increases the Readily Releasable Pool of Vesicles and Its Recovery After Depletion. Front Cell Neurosci 2019; 13:125. [PMID: 31130843 PMCID: PMC6509170 DOI: 10.3389/fncel.2019.00125] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 03/13/2019] [Indexed: 11/13/2022] Open
Abstract
Neurotransmitter release is initiated by the influx of Ca2+via voltage-gated calcium channels. The accessory β-subunit (CaVβ) of these channels shapes synaptic transmission by associating with the pore-forming subunit (CaVα1) and up-regulating presynaptic calcium currents. Besides CaVα1, CaVβ interacts with several partners including actin filaments (F-actin). These filaments are known to associate with synaptic vesicles (SVs) at the presynaptic terminals and support their translocation within different pools, but the role of CaVβ/F-actin association on synaptic transmission has not yet been explored. We here study how CaVβ4, the major calcium channel β isoform in mamalian brain, modifies synaptic transmission in concert with F-actin in cultured hippocampal neurons. We analyzed the effect of exogenous CaVβ4 before and after pharmacological disruption of the actin cytoskeleton and dissected calcium channel-dependent and -independent functions by comparing the effects of the wild-type subunit with the one bearing a double mutation that impairs binding to CaVα1. We found that exogenously expressed wild-type CaVβ4 enhances spontaneous and depolarization-evoked excitatory postsynaptic currents (EPSCs) without altering synaptogenesis. CaVβ4 increases the size of the readily releasable pool (RRP) of SVs at resting conditions and accelerates their recovery after depletion. The enhanced neurotransmitter release induced by CaVβ4 is abolished upon disruption of the actin cytoskeleton. The CaVα1 association-deficient CaVβ4 mutant associates with actin filaments, but neither alters postsynaptic responses nor the time course of the RRP recovery. Furthermore, this mutant protein preserves the ability to increase the RRP size. These results indicate that the interplay between CaVβ4 and F-actin also support the recruitment of SVs to the RRP in a CaVα1-independent manner. Our studies show an emerging role of CaVβ in determining SV maturation toward the priming state and its replenishment after release. We envision that this subunit plays a role in coupling exocytosis to endocytosis during the vesicle cycle.
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Affiliation(s)
- Gustavo A Guzman
- Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, Jülich, Germany
| | - Raul E Guzman
- Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, Jülich, Germany
| | - Nadine Jordan
- Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, Jülich, Germany
| | - Patricia Hidalgo
- Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, Jülich, Germany.,Institute of Biochemistry, Heinrich-Heine University, Düsseldorf, Germany
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22
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Lazarevic V, Yang Y, Ivanova D, Fejtova A, Svenningsson P. Riluzole attenuates the efficacy of glutamatergic transmission by interfering with the size of the readily releasable neurotransmitter pool. Neuropharmacology 2018; 143:38-48. [PMID: 30222983 DOI: 10.1016/j.neuropharm.2018.09.021] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 08/11/2018] [Accepted: 09/12/2018] [Indexed: 01/02/2023]
Abstract
Riluzole is a potent neuroprotective agent which primarily inhibits excitatory neurotransmission interfering with presynaptic release, uptake and postsynaptic actions of glutamate by mechanisms that are not well understood. Riluzole and related prodrugs with improved blood brain barrier penetrance, are shown to be effective for the treatment of amyotrophic lateral sclerosis, ataxias, epilepsy and mood disorders. Our study was undertaken to decipher molecular and subcellular mechanisms of riluzole's antiglutamatergic effect, particularly focusing on presynaptic active zone structure and function. Applying multifarious live cell imaging techniques and amperometric glutamate recordings, we measured the impact of riluzole on presynaptic activity, synaptic vesicle recycling and glutamate release. Our in vitro and in vivo data revealed a unique mechanism whereby riluzole reduces the efficacy of glutamatergic transmission by selectively lowering the size of the readily releasable pool. This effect was correlated with the inhibition of protein kinase C-dependent Munc18-1 phosphorylation which is known to interfere with neurotransmitter release.
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Affiliation(s)
- Vesna Lazarevic
- Translational Neuropharmacology, Department of Clinical Neuroscience, Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden.
| | - Yunting Yang
- Translational Neuropharmacology, Department of Clinical Neuroscience, Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden
| | - Daniela Ivanova
- RG Presynaptic Plasticity, Leibniz Institute for Neurobiology, Magdeburg, Germany
| | - Anna Fejtova
- RG Presynaptic Plasticity, Leibniz Institute for Neurobiology, Magdeburg, Germany; Molecular Psychiatry, Department of Psychiatry and Psychotherapy, University Hospital, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany
| | - Per Svenningsson
- Translational Neuropharmacology, Department of Clinical Neuroscience, Center for Molecular Medicine, Karolinska Institute, Stockholm, Sweden
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SNAP-25 phosphorylation at Ser187 regulates synaptic facilitation and short-term plasticity in an age-dependent manner. Sci Rep 2017; 7:7996. [PMID: 28801590 PMCID: PMC5554206 DOI: 10.1038/s41598-017-08237-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 07/10/2017] [Indexed: 11/18/2022] Open
Abstract
Neurotransmitter release is mediated by the SNARE complex, but the role of its phosphorylation has scarcely been elucidated. Although PKC activators are known to facilitate synaptic transmission, there has been a heated debate on whether PKC mediates facilitation of neurotransmitter release through phosphorylation. One of the SNARE proteins, SNAP-25, is phosphorylated at the residue serine-187 by PKC, but its physiological significance has been unclear. To examine these issues, we analyzed mutant mice lacking the phosphorylation of SNAP-25 serine-187 and found that they exhibited reduced release probability and enhanced presynaptic short-term plasticity, suggesting that not only the release process, but also the dynamics of synaptic vesicles was regulated by the phosphorylation. Furthermore, it has been known that the release probability changes with development, but the precise mechanism has been unclear, and we found that developmental changes in release probability of neurotransmitters were regulated by the phosphorylation. These results indicate that SNAP-25 phosphorylation developmentally facilitates neurotransmitter release but strongly inhibits presynaptic short-term plasticity via modification of the dynamics of synaptic vesicles in presynaptic terminals.
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Trexler AJ, Taraska JW. Regulation of insulin exocytosis by calcium-dependent protein kinase C in beta cells. Cell Calcium 2017; 67:1-10. [PMID: 29029784 DOI: 10.1016/j.ceca.2017.07.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 12/27/2022]
Abstract
The control of insulin release from pancreatic beta cells helps ensure proper blood glucose level, which is critical for human health. Protein kinase C has been shown to be one key control mechanism for this process. After glucose stimulation, calcium influx into beta cells triggers exocytosis of insulin-containing dense-core granules and activates protein kinase C via calcium-dependent phospholipase C-mediated generation of diacylglycerol. Activated protein kinase C potentiates insulin release by enhancing the calcium sensitivity of exocytosis, likely by affecting two main pathways that could be linked: (1) the reorganization of the cortical actin network, and (2) the direct phosphorylation of critical exocytotic proteins such as munc18, SNAP25, and synaptotagmin. Here, we review what is currently known about the molecular mechanisms of protein kinase C action on each of these pathways and how these effects relate to the control of insulin release by exocytosis. We identify remaining challenges in the field and suggest how these challenges might be addressed to advance our understanding of the regulation of insulin release in health and disease.
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Affiliation(s)
- Adam J Trexler
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States
| | - Justin W Taraska
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, United States.
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Ren L, Pour MD, Majdi S, Li X, Malmberg P, Ewing AG. Zinc Regulates Chemical-Transmitter Storage in Nanometer Vesicles and Exocytosis Dynamics as Measured by Amperometry. Angew Chem Int Ed Engl 2017; 56:4970-4975. [PMID: 28319311 PMCID: PMC5540326 DOI: 10.1002/anie.201700095] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Indexed: 01/12/2023]
Abstract
We applied electrochemical techniques with nano-tip electrodes to show that micromolar concentrations of zinc not only trigger changes in the dynamics of exocytosis, but also vesicle content in a model cell line. The vesicle catecholamine content in PC12 cells is significantly decreased after 100 μm zinc treatment, but, catecholamine release during exocytosis remains nearly the same. This contrasts with the number of molecules stored in the exocytosis vesicles, which decreases, and we find that the amount of catecholamine released from zinc-treated cells reaches nearly 100 % content expelled. Further investigation shows that zinc slows down exocytotic release. Our results provide the missing link between zinc and the regulation of neurotransmitter release processes, which might be important in memory formation and storage.
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Affiliation(s)
- Lin Ren
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Masoumeh Dowlatshahi Pour
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
- National Center for Imaging Mass Spectrometry, Chalmers University of Technology and Gothenburg University, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Soodabeh Majdi
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Xianchan Li
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Per Malmberg
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
- National Center for Imaging Mass Spectrometry, Chalmers University of Technology and Gothenburg University, Kemivägen 10, 412 96, Gothenburg, Sweden
| | - Andrew G Ewing
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemivägen 10, 412 96, Gothenburg, Sweden
- National Center for Imaging Mass Spectrometry, Chalmers University of Technology and Gothenburg University, Kemivägen 10, 412 96, Gothenburg, Sweden
- Department of Chemistry and Molecular Biology, University of Gothenburg, Kemivägen 10, 412 96, Gothenburg, Sweden
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Ren L, Pour MD, Majdi S, Li X, Malmberg P, Ewing AG. Zinc Regulates Chemical-Transmitter Storage in Nanometer Vesicles and Exocytosis Dynamics as Measured by Amperometry. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201700095] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Lin Ren
- Department of Chemistry and Chemical Engineering; Chalmers University of Technology; Kemivägen 10 412 96 Gothenburg Sweden
| | - Masoumeh Dowlatshahi Pour
- Department of Chemistry and Chemical Engineering; Chalmers University of Technology; Kemivägen 10 412 96 Gothenburg Sweden
- National Center for Imaging Mass Spectrometry; Chalmers University of Technology and Gothenburg University; Kemivägen 10 412 96 Gothenburg Sweden
| | - Soodabeh Majdi
- Department of Chemistry and Molecular Biology; University of Gothenburg; Kemivägen 10 412 96 Gothenburg Sweden
| | - Xianchan Li
- Department of Chemistry and Molecular Biology; University of Gothenburg; Kemivägen 10 412 96 Gothenburg Sweden
| | - Per Malmberg
- Department of Chemistry and Chemical Engineering; Chalmers University of Technology; Kemivägen 10 412 96 Gothenburg Sweden
- National Center for Imaging Mass Spectrometry; Chalmers University of Technology and Gothenburg University; Kemivägen 10 412 96 Gothenburg Sweden
| | - Andrew G. Ewing
- Department of Chemistry and Chemical Engineering; Chalmers University of Technology; Kemivägen 10 412 96 Gothenburg Sweden
- National Center for Imaging Mass Spectrometry; Chalmers University of Technology and Gothenburg University; Kemivägen 10 412 96 Gothenburg Sweden
- Department of Chemistry and Molecular Biology; University of Gothenburg; Kemivägen 10 412 96 Gothenburg Sweden
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Phosphorylation of synaptotagmin-1 controls a post-priming step in PKC-dependent presynaptic plasticity. Proc Natl Acad Sci U S A 2016; 113:5095-100. [PMID: 27091977 DOI: 10.1073/pnas.1522927113] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Presynaptic activation of the diacylglycerol (DAG)/protein kinase C (PKC) pathway is a central event in short-term synaptic plasticity. Two substrates, Munc13-1 and Munc18-1, are essential for DAG-induced potentiation of vesicle priming, but the role of most presynaptic PKC substrates is not understood. Here, we show that a mutation in synaptotagmin-1 (Syt1(T112A)), which prevents its PKC-dependent phosphorylation, abolishes DAG-induced potentiation of synaptic transmission in hippocampal neurons. This mutant also reduces potentiation of spontaneous release, but only if alternative Ca(2+) sensors, Doc2A/B proteins, are absent. However, unlike mutations in Munc13-1 or Munc18-1 that prevent DAG-induced potentiation, the synaptotagmin-1 mutation does not affect paired-pulse facilitation. Furthermore, experiments to probe vesicle priming (recovery after train stimulation and dual application of hypertonic solutions) also reveal no abnormalities. Expression of synaptotagmin-2, which lacks a seven amino acid sequence that contains the phosphorylation site in synaptotagmin-1, or a synaptotagmin-1 variant with these seven residues removed (Syt1(Δ109-116)), supports normal DAG-induced potentiation. These data suggest that this seven residue sequence in synaptotagmin-1 situated in the linker between the transmembrane and C2A domains is inhibitory in the unphosphorylated state and becomes permissive of potentiation upon phosphorylation. We conclude that synaptotagmin-1 phosphorylation is an essential step in PKC-dependent potentiation of synaptic transmission, acting downstream of the two other essential DAG/PKC substrates, Munc13-1 and Munc18-1.
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Activation of Brain L-glutamate Decarboxylase 65 Isoform (GAD65) by Phosphorylation at Threonine 95 (T95). Mol Neurobiol 2016; 54:866-873. [DOI: 10.1007/s12035-015-9633-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 12/15/2015] [Indexed: 11/26/2022]
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Ortinski PI, Briand LA, Pierce RC, Schmidt HD. Cocaine-seeking is associated with PKC-dependent reduction of excitatory signaling in accumbens shell D2 dopamine receptor-expressing neurons. Neuropharmacology 2015; 92:80-9. [PMID: 25596492 PMCID: PMC4346508 DOI: 10.1016/j.neuropharm.2015.01.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 11/25/2014] [Accepted: 01/07/2015] [Indexed: 01/11/2023]
Abstract
Stimulation of D1-like dopamine receptors (D1DRs) or D2-like dopamine receptors (D2DRs) in the nucleus accumbens (NAc) shell reinstates cocaine seeking in rats, an animal model of relapse. D2DRs and D1DRs activate protein kinase C (PKC) and recent studies indicate that activation of PKC in the NAc plays an important role in the reinstatement of drug seeking induced by a systemic cocaine priming injection. In the present study, pharmacological inhibition of PKC in the NAc shell attenuated cocaine seeking induced by intra-accumbens shell microinjection of a D2DR agonist, but not a D1DR agonist. D1DRs and D2DRs are primarily expressed on different accumbens medium spiny (MSN) neurons. Neuronal signaling and activity were assessed in these two populations of NAc neurons with transgenic mice expressing fluorescent labels under the control of D1DR and D2DR promoters. Following the extinction of cocaine self-administration, bath application of a PKC inhibitor produced similar effects on single evoked excitatory and inhibitory post-synaptic currents in D1DR- and D2DR-positive MSNs in the NAc shell. However, inhibition of PKC preferentially improved the ability of excitatory, but not inhibitory, synapses to sustain responding to brief train of stimuli specifically in D2DR-positive MSNs. This effect did not appear to involve modulation of presynaptic release mechanisms. Taken together, these findings indicate that the reinstatement of cocaine seeking is at least partially due to D2DR-dependent increases in PKC signaling in the NAc shell, which reduce excitatory synaptic efficacy in D2DR-expressing MSNs.
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Affiliation(s)
- Pavel I Ortinski
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC 29209, USA
| | - Lisa A Briand
- Department of Psychology, Temple University, Philadelphia, PA 19122, USA
| | - R Christopher Pierce
- Center for Neurobiology and Behavior, Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Heath D Schmidt
- Center for Neurobiology and Behavior, Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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Synaptic vesicle pools: Principles, properties and limitations. Exp Cell Res 2015; 335:150-6. [PMID: 25814361 DOI: 10.1016/j.yexcr.2015.03.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 03/14/2015] [Indexed: 11/21/2022]
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The role of Pak-interacting exchange factor-β phosphorylation at serines 340 and 583 by PKCγ in dopamine release. J Neurosci 2014; 34:9268-80. [PMID: 25009260 DOI: 10.1523/jneurosci.4278-13.2014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Protein kinase C (PKC) has been implicated in the control of neurotransmitter release. The AS/AGU rat, which has a nonsense mutation in PKCγ, shows symptoms of parkinsonian syndrome, including dopamine release impairments in the striatum. Here, we found that the AS/AGU rat is PKCγ-knock-out (KO) and that PKCγ-KO mice showed parkinsonian syndrome. However, the PKCγ substrates responsible for the regulated exocytosis of dopamine in vivo have not yet been elucidated. To identify the PKCγ substrates involved in dopamine release, we used PKCγ-KO mice and a phosphoproteome analysis. We found 10 candidate phosphoproteins that had decreased phosphorylation levels in the striatum of PKCγ-KO mice. We focused on Pak-interacting exchange factor-β (βPIX), a Cdc42/Rac1 guanine nucleotide exchange factor, and found that PKCγ directly phosphorylates βPIX at Ser583 and indirectly at Ser340 in cells. Furthermore, we found that PKC phosphorylated βPIX in vivo. Classical PKC inhibitors and βPIX knock-down (KD) significantly suppressed Ca(2+)-evoked dopamine release in PC12 cells. Wild-type βPIX, and not the βPIX mutants Ser340 Ala or Ser583 Ala, fully rescued the decreased dopamine release by βPIX KD. Double KD of Cdc42 and Rac1 decreased dopamine release from PC12 cells. These findings indicate that the phosphorylation of βPIX at Ser340 and Ser583 has pivotal roles in Ca(2+)-evoked dopamine release in the striatum. Therefore, we propose that PKCγ positively modulates dopamine release through β2PIX phosphorylation. The PKCγ-βPIX-Cdc42/Rac1 phosphorylation axis may provide a new therapeutic target for the treatment of parkinsonian syndrome.
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Cijsouw T, Weber JP, Broeke JH, Broek JAC, Schut D, Kroon T, Saarloos I, Verhage M, Toonen RF. Munc18-1 redistributes in nerve terminals in an activity- and PKC-dependent manner. ACTA ACUST UNITED AC 2014; 204:759-75. [PMID: 24590174 PMCID: PMC3941046 DOI: 10.1083/jcb.201308026] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
PKC-dependent dynamic control of Munc18-1 levels enables individual synapses to tune their output during periods of activity. Munc18-1 is a soluble protein essential for synaptic transmission. To investigate the dynamics of endogenous Munc18-1 in neurons, we created a mouse model expressing fluorescently tagged Munc18-1 from the endogenous munc18-1 locus. We show using fluorescence recovery after photobleaching in hippocampal neurons that the majority of Munc18-1 trafficked through axons and targeted to synapses via lateral diffusion together with syntaxin-1. Munc18-1 was strongly expressed at presynaptic terminals, with individual synapses showing a large variation in expression. Axon–synapse exchange rates of Munc18-1 were high: during stimulation, Munc18-1 rapidly dispersed from synapses and reclustered within minutes. Munc18-1 reclustering was independent of syntaxin-1, but required calcium influx and protein kinase C (PKC) activity. Importantly, a PKC-insensitive Munc18-1 mutant did not recluster. We show that synaptic Munc18-1 levels correlate with synaptic strength, and that synapses that recruit more Munc18-1 after stimulation have a larger releasable vesicle pool. Hence, PKC-dependent dynamic control of Munc18-1 levels enables individual synapses to tune their output during periods of activity.
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Affiliation(s)
- Tony Cijsouw
- Department of Functional Genomics and Clinical Genetics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, Netherlands
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The "memory kinases": roles of PKC isoforms in signal processing and memory formation. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 122:31-59. [PMID: 24484697 DOI: 10.1016/b978-0-12-420170-5.00002-7] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The protein kinase C (PKC) isoforms, which play an essential role in transmembrane signal conduction, can be viewed as a family of "memory kinases." Evidence is emerging that they are critically involved in memory acquisition and maintenance, in addition to their involvement in other functions of cells. Deficits in PKC signal cascades in neurons are one of the earliest abnormalities in the brains of patients suffering from Alzheimer's disease. Their dysfunction is also involved in several other types of memory impairments, including those related to emotion, mental retardation, brain injury, and vascular dementia/ischemic stroke. Inhibition of PKC activity leads to a reduced capacity of many types of learning and memory, but may have therapeutic values in treating substance abuse or aversive memories. PKC activators, on the other hand, have been shown to possess memory-enhancing and antidementia actions. PKC pharmacology may, therefore, represent an attractive area for developing effective cognitive drugs for the treatment of many types of memory disorders and dementias.
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Neuropeptide y gates a stress-induced, long-lasting plasticity in the sympathetic nervous system. J Neurosci 2013; 33:12705-17. [PMID: 23904607 DOI: 10.1523/jneurosci.3132-12.2013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Acute stress evokes the fight-or-flight reflex, which via release of the catecholamine hormones affects the function of every major organ. Although the reflex is transient, it has lasting consequences that produce an exaggerated response when stress is reexperienced. How this change is encoded is not known. We investigated whether the reflex affects the adrenal component of the sympathetic nervous system, a major branch of the stress response. Mice were briefly exposed to the cold-water forced swim test (FST) which evoked an increase in circulating catecholamines. Although this hormonal response was transient, the FST led to a long-lasting increase in the catecholamine secretory capacity measured amperometrically from chromaffin cells and in the expression of tyrosine hydroxylase. A variety of approaches indicate that these changes are regulated postsynaptically by neuropeptide Y (NPY), an adrenal cotransmitter. Using immunohistochemistry, RT-PCR, and NPY(GFP) BAC mice, we find that NPY is synthesized by all chromaffin cells. Stress failed to increase secretory capacity in NPY knock-out mice. Genetic or pharmacological interference with NPY and Y1 (but not Y2 or Y5) receptor signaling attenuated the stress-induced change in tyrosine hydroxylase expression. These results indicate that, under basal conditions, adrenal signaling is tonically inhibited by NPY, but stress overrides this autocrine negative feedback loop. Because acute stress leads to a lasting increase in secretory capacity in vivo but does not alter sympathetic tone, these postsynaptic changes appear to be an adaptive response. We conclude that the sympathetic limb of the stress response exhibits an activity-dependent form of long-lasting plasticity.
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Giuliani FA, Escudero C, Casas S, Bazzocchini V, Yunes R, Laconi MR, Cabrera R. Allopregnanolone and puberty: modulatory effect on glutamate and GABA release and expression of 3α-hydroxysteroid oxidoreductase in the hypothalamus of female rats. Neuroscience 2013; 243:64-75. [PMID: 23562943 DOI: 10.1016/j.neuroscience.2013.03.053] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 02/26/2013] [Accepted: 03/26/2013] [Indexed: 02/07/2023]
Abstract
The hypothalamic release of glutamate and GABA regulates neurosecretory functions that may control the onset of puberty. This release may be influenced by neurosteroids such as allopregnanolone. Using superfusion experiments we examined the role of allopregnanolone on the K(+)-evoked and basal [(3)H]-glutamate and [(3)H]-GABA release from mediobasal hypothalamus and anterior preoptic area in prepubertal, vaginal opening and pubertal (P) rats and evaluated its modulatory effect on GABAA and NMDA (N-methyl-d-aspartic acid) receptors. Also, we examined the hypothalamic activity and mRNA expression of 3α-hydroxysteroid oxidoreductase (3α-HSOR) - enzyme that synthesizes allopregnanolone - using a spectrophotometric method and RT-PCR, respectively. Allopregnanolone increased both the K(+)-evoked [(3)H]-glutamate and [(3)H]-GABA release in P rats, being the former effect mediated by the modulation of NMDA receptors - as was reverted by Mg(2+) and by the NMDA receptor antagonist AP-7 and the latter by the modulation of NMDA and GABAA receptors - as was reverted by Mg(2+) and the GABAA receptor antagonist bicuculline. The neurosteroid also increased the basal release of [(3)H]-glutamate in VO rats in an effect that was dependent on the modulation of NMDA receptors as was reverted by Mg(2+). On the other hand we show that allopregnanolone reduced the basal release of [(3)H]-GABA in P rats although we cannot elucidate the precise mechanism by which the neurosteroid exerted this latter effect. The enzymatic activity and the mRNA expression of 3α-HSOR were both increased in P rats regarding the other two studied stages of sexual development. These results suggest an important physiological function of allopregnanolone in the hypothalamus of the P rat where it might be involved in the 'fine tuning' of neurosecretory functions related to the biology of reproduction of the female rats.
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Affiliation(s)
- F A Giuliani
- Instituto de Investigaciones Biomédicas (INBIOMED), Universidad de Mendoza, IMBECU-CONICET, Paseo Dr. Emilio Descotte 720, 5500 Mendoza, Argentina
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Mechanisms underlying induction of LTP-associated changes in short-term dynamics of transmission at immature synapses. Neuropharmacology 2012; 67:494-502. [PMID: 23246530 DOI: 10.1016/j.neuropharm.2012.11.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Revised: 11/21/2012] [Accepted: 11/25/2012] [Indexed: 01/11/2023]
Abstract
While the activity-dependent mechanisms guiding functional maturation of synaptic transmission postsynaptically are well characterized, less is known about the corresponding presynaptic mechanisms. Here we show that during the first postnatal week, a subset of CA3-CA1 synapses express postsynaptically induced LTP that is tightly associated with a robust decrease in synaptic facilitation, consistent with an increase in release probability (P(r)). The loss of facilitation is readily induced by physiologically relevant pairing protocols at immature synapses and is dependent on activation of NMDA-receptors but not L-type calcium channels. The putative pre- and postsynaptic components of neonatal LTP were distinguished in their downstream signaling requirements, PKC activity being selectively needed for the decrease in facilitation but not for synaptic potentiation per se. These data suggest that maturation of glutamatergic synapses involves a critical period during which presynaptic function is highly susceptible to activity-dependent regulation via a PKC-dependent mechanism.
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Crawford DC, Jiang X, Taylor A, Moulder KL, Mennerick S. Differential requirement for protein synthesis in presynaptic unmuting and muting in hippocampal glutamate terminals. PLoS One 2012; 7:e51930. [PMID: 23272190 PMCID: PMC3521764 DOI: 10.1371/journal.pone.0051930] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Accepted: 11/14/2012] [Indexed: 12/17/2022] Open
Abstract
Synaptic function and plasticity are crucial for information processing within the nervous system. In glutamatergic hippocampal neurons, presynaptic function is silenced, or muted, after strong or prolonged depolarization. This muting is neuroprotective, but the underlying mechanisms responsible for muting and its reversal, unmuting, remain to be clarified. Using cultured rat hippocampal neurons, we found that muting induction did not require protein synthesis; however, slow forms of unmuting that depend on protein kinase A (PKA), including reversal of depolarization-induced muting and forskolin-induced unmuting of basally mute synapses, required protein synthesis. In contrast, fast unmuting of basally mute synapses by phorbol esters was protein synthesis-independent. Further studies of recovery from depolarization-induced muting revealed that protein levels of Rim1 and Munc13-1, which mediate vesicle priming, correlated with the functional status of presynaptic terminals. Additionally, this form of unmuting was prevented by both transcription and translation inhibitors, so proteins are likely synthesized de novo after removal of depolarization. Phosphorylated cyclic adenosine monophosphate response element-binding protein (pCREB), a nuclear transcription factor, was elevated after recovery from depolarization-induced muting, consistent with a model in which PKA-dependent mechanisms, possibly including pCREB-activated transcription, mediate slow unmuting. In summary, we found that protein synthesis was required for slower, PKA-dependent unmuting of presynaptic terminals, but it was not required for muting or a fast form of unmuting. These results clarify some of the molecular mechanisms responsible for synaptic plasticity in hippocampal neurons and emphasize the multiple mechanisms by which presynaptic function is modulated.
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Affiliation(s)
- Devon C. Crawford
- Graduate Program in Neuroscience, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Department of Psychiatry, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Xiaoping Jiang
- Department of Psychiatry, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Amanda Taylor
- Department of Psychiatry, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Krista L. Moulder
- Department of Psychiatry, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Steven Mennerick
- Department of Psychiatry, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri, United States of America
- * E-mail:
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Laudes T, Meis S, Munsch T, Lessmann V. Impaired transmission at corticothalamic excitatory inputs and intrathalamic GABAergic synapses in the ventrobasal thalamus of heterozygous BDNF knockout mice. Neuroscience 2012; 222:215-27. [DOI: 10.1016/j.neuroscience.2012.07.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Revised: 06/27/2012] [Accepted: 07/02/2012] [Indexed: 01/08/2023]
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Abstract
Synaptic vesicles release neurotransmitter at chemical synapses, thus initiating the flow of information in neural networks. To achieve this, vesicles undergo a dynamic cycle of fusion and retrieval to maintain the structural and functional integrity of the presynaptic terminals in which they reside. Moreover, compelling evidence indicates these vesicles differ in their availability for release and mobilization in response to stimuli, prompting classification into at least three different functional pools. Ongoing studies of the molecular and cellular bases for this heterogeneity attempt to link structure to physiology and clarify how regulation of vesicle pools influences synaptic strength and presynaptic plasticity. We discuss prevailing perspectives on vesicle pools, the role they play in shaping synaptic transmission, and the open questions that challenge current understanding.
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Affiliation(s)
- AbdulRasheed A Alabi
- Department of Molecular and Cellular Physiology, Stanford Institute for Neuro-Innovation and Translational Neurosciences, Stanford Medical School, Stanford, California 94305, USA
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Trkov S, Stenovec M, Kreft M, Potokar M, Parpura V, Davletov B, Zorec R. Fingolimod--a sphingosine-like molecule inhibits vesicle mobility and secretion in astrocytes. Glia 2012; 60:1406-16. [PMID: 22639011 PMCID: PMC3675637 DOI: 10.1002/glia.22361] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 05/03/2012] [Indexed: 12/22/2022]
Abstract
In the brain, astrocytes signal to the neighboring cells by the release of chemical messengers (gliotransmitters) via regulated exocytosis. Recent studies uncovered a potential role of signaling lipids in modulation of exocytosis. Hence, we investigated whether sphingosine and the structural analog fingolimod/FTY720, a recently introduced therapeutic for multiple sclerosis, affect (i) intracellular vesicle mobility and (ii) vesicle cargo discharge from cultured rat astrocytes. Distinct types of vesicles, peptidergic, glutamatergic, and endosomes/lysosomes, were fluorescently prelabeled by cell transfection with plasmids encoding atrial natriuretic peptide tagged with mutant green fluorescent protein and vesicular glutamate transporter tagged with enhanced green fluorescent protein or by LysoTracker staining, respectively. The confocal and total internal reflection fluorescence microscopies were used to monitor vesicle mobility in the cytoplasm and near the basal plasma membrane, respectively. Sphingosine and FTY720, but not the membrane impermeable lipid analogs, dose-dependently attenuated vesicle mobility in the subcellular regions studied, and significantly inhibited stimulated exocytotic peptide and glutamate release. We conclude that in astrocytes, cell permeable sphingosine-like lipids affect regulated exocytosis by attenuating vesicle mobility, thereby preventing effective vesicle access/interaction with the plasma membrane docking/release sites.
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Affiliation(s)
- Saša Trkov
- Celica d.o.o., Biomedical Center, Technology Park 24, Ljubljana, Slovenia
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41
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Morales KA, Igumenova TI. Synergistic effect of Pb(2+) and phosphatidylinositol 4,5-bisphosphate on C2 domain-membrane interactions. Biochemistry 2012; 51:3349-60. [PMID: 22475207 DOI: 10.1021/bi201850h] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Ca(2+)-responsive C2 domains are peripheral membrane modules that target their host proteins to anionic membranes upon binding Ca(2+) ions. Several C2 domain-containing proteins, such as protein kinase C isoenzymes (PKCs), have been identified as molecular targets of Pb(2+), a known environmental toxin. We demonstrated previously that the C2 domain from PKCα (C2α) binds Pb(2+) with high affinity and undergoes membrane insertion in the Pb(2+)-complexed form. The objective of this work was to determine the effect of phosphatidylinositol 4,5-bisphosphate (PIP(2)) on the C2α-Pb(2+) interactions. Using nuclear magnetic resonance (NMR) experiments, we show that Pb(2+) and PIP(2) synergistically enhance each other's affinity for C2α. Moreover, the affinity of C2α for PIP(2) increases upon progressive saturation of the metal-binding sites. Combining the NMR data with the results of protein-to-membrane Förster resonance energy transfer and vesicle sedimentation experiments, we demonstrate that PIP(2) can influence two aspects of C2α-Pb(2+)-membrane interactions: the affinity of C2α for Pb(2+) and the association of Pb(2+) with the anionic sites on the membrane. Both factors may contribute to the toxic effect of Pb(2+) resulting from the aberrant modulation of PKCα activity. Finally, we propose a mechanism for Pb(2+) outcompeting Ca(2+) from membrane-bound C2α.
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Affiliation(s)
- Krystal A Morales
- Department of Biochemistry and Biophysics, Texas A&M University, 300 Olsen Boulevard, College Station, TX 77843-2128, USA
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42
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Straub SG, Sharp GWG. Evolving insights regarding mechanisms for the inhibition of insulin release by norepinephrine and heterotrimeric G proteins. Am J Physiol Cell Physiol 2012; 302:C1687-98. [PMID: 22492651 DOI: 10.1152/ajpcell.00282.2011] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Norepinephrine has for many years been known to have three major effects on the pancreatic β-cell which lead to the inhibition of insulin release. These are activation of K(+) channels to hyperpolarize the cell and prevent the gating of voltage-dependent Ca(2+) channels that increase intracellular Ca(2+) concentration ([Ca(2+)](i)) and trigger release; inhibition of adenylyl cyclases, thus preventing the augmentation of stimulated insulin release by cyclic AMP; and a "distal" effect that occurs downstream of increased [Ca(2+)](i) to inhibit exocytosis. All three are mediated by the pertussis toxin (PTX)-sensitive heterotrimeric Gi and Go proteins. The distal inhibitory effect on exocytosis is now known to be due to the binding of G protein βγ subunits to the synaptosomal-associated protein of 25 kDa (SNAP-25) on the soluble NSF attachment protein receptor (SNARE) complex. Recent studies have uncovered two more actions of norepinephrine on the β-cell: 1) retardation of the refilling of the readily releasable granule pool after it has been discharged, an action that is mediated by Gαi(1) and/or Gαi(2); and 2) inhibition of endocytosis that is mediated by Gz. Of importance also are new findings that Gαo regulates the number of docked granules in the β-cell, and that Gαo(2) maintains a tonic inhibitory influence on secretion. The latter provides another explanation as to why PTX, which blocks the effect of Gαo(2), was initially called "islet activating protein." Finally, there is clear evidence that overexpression of α(2A)-adrenergic receptors in β-cells can cause type 2 diabetes.
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Affiliation(s)
- Susanne G Straub
- Department of Molecular Medicine, Cornell University, Ithaca, New York 14853-6401, USA
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Sun MK, Alkon DL. Activation of protein kinase C isozymes for the treatment of dementias. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2012; 64:273-302. [PMID: 22840750 DOI: 10.1016/b978-0-12-394816-8.00008-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Memories are much more easily impaired than improved. Dementias, a lasting impairment of memory function, occur in a variety of cognitive disorders and become more clinically dominant as the population ages. Protein kinase C is one of the "cognitive kinases," and plays an essential role in both memory acquisition and maintenance. Deficits in protein kinase C (PKC) signal cascades in neurons represent one of the earliest changes in the brains of patients with Alzheimer's disease (AD) and other types of memory impairment, including those related to cerebral ischemia and ischemic stroke. Inhibition or impairment of PKC activity results in compromised learning and memory, whereas an appropriate activation of certain PKC isozymes leads to an enhancement of learning and memory and/or antidementic effects. In preclinical studies, PKC activators have been shown to increase the expression and activity of PKC isozymes, thereby restoring PKC signaling and downstream activity, including stimulation of neurotrophic activity, synaptic/structural remodeling, and synaptogenesis in the hippocampus and related cortical areas. PKC activators also reduce the accumulation of neurotoxic amyloid and tau protein hyperphosphorylation and support anti-apoptotic processes in the brain. These observations strongly suggest that PKC pharmacology may represent an attractive area for the development of effective cognition-enhancing therapeutics for the treatment of dementias.
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Affiliation(s)
- Miao-Kun Sun
- Blanchette Rockefeller Neurosciences Institute, Morgantown, WV, USA
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Bhattacharyya BJ, Wilson SM, Jung H, Miller RJ. Altered neurotransmitter release machinery in mice deficient for the deubiquitinating enzyme Usp14. Am J Physiol Cell Physiol 2011; 302:C698-708. [PMID: 22075695 DOI: 10.1152/ajpcell.00326.2010] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Homozygous ataxic mice (ax(J)) express reduced levels of the deubiquitinating enzyme Usp14. They develop severe tremors by 2-3 wk of age, followed by hindlimb paralysis, and death by 6-8 wk. While changes in the ubiquitin proteasome system often result in the accumulation of ubiquitin protein aggregates and neuronal loss, these pathological markers are not observed in the ax(J) mice. Instead, defects in neurotransmission were observed in both the central and peripheral nervous systems of ax(J) mice. We have now identified several new alterations in peripheral neurotransmission in the ax(J) mice. Using the two-microelectrode voltage clamp technique on diaphragm muscles of ax(J) mice, we observed that under normal neurotransmitter release conditions ax(J) mice lacked paired-pulse facilitation and exhibited a frequency-dependent increase in rundown of the end plate current at high-frequency stimulation (HFS). Combined electrophysiology and styryl dye staining revealed a significant reduction in quantal content during the initial and plateau portions of the HFS train. In addition, uptake of styryl dyes (FM dye) during HFS demonstrated that the size of the readily releasable vesicle pool was significantly reduced. Destaining rates for styryl dyes suggested that ax(J) neuromuscular junctions are unable to mobilize a sufficient number of vesicles during times of intense activity. These results imply that ax(J) nerve terminals are unable to recruit a sufficient number of vesicles to keep pace with physiological rates of transmitter release. Therefore, ubiquitination of synaptic proteins appears to play an important role in the normal operation of the neurotransmitter release machinery and in regulating the size of pools of synaptic vesicles.
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Affiliation(s)
- Bula J Bhattacharyya
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University, Chicago, IL 60611, USA
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UNC-73/trio RhoGEF-2 activity modulates Caenorhabditis elegans motility through changes in neurotransmitter signaling upstream of the GSA-1/Galphas pathway. Genetics 2011; 189:137-51. [PMID: 21750262 DOI: 10.1534/genetics.111.131227] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Rho-family GTPases play regulatory roles in many fundamental cellular processes. Caenorhabditis elegans UNC-73 RhoGEF isoforms function in axon guidance, cell migration, muscle arm extension, phagocytosis, and neurotransmission by activating either Rac or Rho GTPase subfamilies. Multiple differentially expressed UNC-73 isoforms contain a Rac-specific RhoGEF-1 domain, a Rho-specific RhoGEF-2 domain, or both domains. The UNC-73E RhoGEF-2 isoform is activated by the G-protein subunit Gαq and is required for normal rates of locomotion; however, mechanisms of UNC-73 and Rho pathway regulation of locomotion are not clear. To better define UNC-73 function in the regulation of motility we used cell-specific and inducible promoters to examine the temporal and spatial requirements of UNC-73 RhoGEF-2 isoform function in mutant rescue experiments. We found that UNC-73E acts within peptidergic neurons of mature animals to regulate locomotion rate. Although unc-73 RhoGEF-2 mutants have grossly normal synaptic morphology and weak resistance to the acetylcholinesterase inhibitor aldicarb, they are significantly hypersensitive to the acetylcholine receptor agonist levamisole, indicating alterations in acetylcholine neurotransmitter signaling. Consistent with peptidergic neuron function, unc-73 RhoGEF-2 mutants exhibit a decreased level of neuropeptide release from motor neuron dense core vesicles (DCVs). The unc-73 locomotory phenotype is similar to those of rab-2 and unc-31, genes with distinct roles in the DCV-mediated secretory pathway. We observed that constitutively active Gαs pathway mutations, which compensate for DCV-mediated signaling defects, rescue unc-73 RhoGEF-2 and rab-2 lethargic movement phenotypes. Together, these data suggest UNC-73 RhoGEF-2 isoforms are required for proper neurotransmitter signaling and may function in the DCV-mediated neuromodulatory regulation of locomotion rate.
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Luk CC, Naruo H, Prince D, Hassan A, Doran SA, Goldberg JI, Syed NI. A novel form of presynaptic CaMKII-dependent short-term potentiation between Lymnaea neurons. Eur J Neurosci 2011; 34:569-77. [PMID: 21749498 DOI: 10.1111/j.1460-9568.2011.07784.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Short-term plasticity is thought to form the basis for working memory, the cellular mechanisms of which are the least understood in the nervous system. In this study, using in vitro reconstructed synapses between the identified Lymnaea neuron visceral dorsal 4 (VD4) and left pedal dorsal 1 (LPeD1), we demonstrate a novel form of short-term potentiation (STP) which is 'use'- but not time-dependent, unlike most previously defined forms of short-term synaptic plasticity. Using a triple-cell configuration we demonstrate for the first time that a single presynaptic neuron can reliably potentiate both inhibitory and excitatory synapses. We further demonstrate that, unlike previously described forms of STP, the synaptic potentiation between Lymnaea neurons does not involve postsynaptic receptor sensitization or presynaptic residual calcium. Finally, we provide evidence that STP at the VD4-LPeD1 synapse requires presynaptic calcium/calmodulin dependent kinase II (CaMKII). Taken together, our study identifies a novel form of STP which may provide the basis for both short- and long-term potentiation, in the absence of any protein synthesis-dependent steps, and involve CaMKII activity exclusively in the presynaptic cell.
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Affiliation(s)
- Collin C Luk
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Alberta, Canada
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Martín R, Bartolomé-Martín D, Torres M, Sánchez-Prieto J. Non-additive potentiation of glutamate release by phorbol esters and metabotropic mGlu7 receptor in cerebrocortical nerve terminals. J Neurochem 2011; 116:476-85. [DOI: 10.1111/j.1471-4159.2010.07134.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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48
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Abstract
Endocrine pituitary cells are neuronlike; they express numerous voltage-gated sodium, calcium, potassium, and chloride channels and fire action potentials spontaneously, accompanied by a rise in intracellular calcium. In some cells, spontaneous electrical activity is sufficient to drive the intracellular calcium concentration above the threshold for stimulus-secretion and stimulus-transcription coupling. In others, the function of these action potentials is to maintain the cells in a responsive state with cytosolic calcium near, but below, the threshold level. Some pituitary cells also express gap junction channels, which could be used for intercellular Ca(2+) signaling in these cells. Endocrine cells also express extracellular ligand-gated ion channels, and their activation by hypothalamic and intrapituitary hormones leads to amplification of the pacemaking activity and facilitation of calcium influx and hormone release. These cells also express numerous G protein-coupled receptors, which can stimulate or silence electrical activity and action potential-dependent calcium influx and hormone release. Other members of this receptor family can activate calcium channels in the endoplasmic reticulum, leading to a cell type-specific modulation of electrical activity. This review summarizes recent findings in this field and our current understanding of the complex relationship between voltage-gated ion channels, ligand-gated ion channels, gap junction channels, and G protein-coupled receptors in pituitary cells.
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Affiliation(s)
- Stanko S Stojilkovic
- Program in Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Building 49, Room 6A-36, 49 Convent Drive, Bethesda, Maryland 20892-4510, USA.
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49
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Abstract
Presynaptic stimulation stochastically recruits transmission according to the release probability (P(r)) of synapses. The majority of central synapses have relatively low P(r), which includes synapses that are completely quiescent presynaptically. The presence of presynaptically dormant versus active terminals presumably increases synaptic malleability when conditions demand synaptic strengthening or weakening, perhaps by triggering second messenger signals. However, whether modulator-mediated potentiation involves recruitment of transmission from dormant terminals remains unclear. Here, by combining electrophysiological and fluorescence imaging approaches, we uncovered rapid presynaptic awakening by select synaptic modulators. A phorbol ester phorbol 12,13-dibutyrate (PDBu) (a diacylglycerol analog), but not forskolin (an adenylyl cyclase activator) or elevated extracellular calcium, recruited neurotransmission from presynaptically dormant synapses. This effect was not dependent on protein kinase C activation. After PDBu-induced awakening, these previously dormant terminals had a synaptic P(r) spectrum similar to basally active synapses naive to PDBu treatment. Dormant terminals did not seem to have properties of nascent or immature synapses, judged by NR2B NMDAR (NMDA receptor) receptor subunit contribution after PDBu-stimulated awakening. Strikingly, synapses rendered inactive by prolonged depolarization, unlike basally dormant synapses, were not awakened by PDBu. These results suggest that the initial release competence of synapses can dictate the acute response to second messenger modulation, and the results suggest multiple pathways to presynaptic dormancy and awakening.
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50
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Zhao Y, Fang Q, Straub SG, Lindau M, Sharp GWG. Noradrenaline inhibits exocytosis via the G protein βγ subunit and refilling of the readily releasable granule pool via the α(i1/2) subunit. J Physiol 2010; 588:3485-98. [PMID: 20643776 DOI: 10.1113/jphysiol.2010.190090] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The molecular mechanisms responsible for the 'distal' effect by which noradrenaline (NA) blocks exocytosis in the β-cell were examined by whole-cell and cell-attached patch clamp capacitance measurements in INS 832/13 β-cells. NA inhibited Ca(2+)-evoked exocytosis by reducing the number of exocytotic events, without modifying vesicle size. Fusion pore properties also were unaffected. NA-induced inhibition of exocytosis was abolished by a high level of Ca(2+) influx, by intracellular application of antibodies against the G protein subunit Gβ and was mimicked by the myristoylated βγ-binding/activating peptide mSIRK. NA-induced inhibition was also abolished by treatment with BoNT/A, which cleaves the C-terminal nine amino acids of SNAP-25, and also by a SNAP-25 C-terminal-blocking peptide containing the BoNT/A cleavage site. These data indicate that inhibition of exocytosis by NA is downstream of increased [Ca(2+)](i) and is mediated by an interaction between Gβγ and the C-terminus of SNAP-25, as is the case for inhibition of neurotransmitter release. Remarkably, in the course of this work, a novel effect of NA was discovered. NA induced a marked retardation of the rate of refilling of the readily releasable pool (RRP) of secretory granules. This retardation was specifically abolished by a Gα(i1/2) blocking peptide demonstrating that the effect is mediated via activation of Gα(i1) and/or Gα(i2).
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Affiliation(s)
- Ying Zhao
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853-6401, USA
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