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Trovò L, Kouvaros S, Schwenk J, Fernandez-Fernandez D, Fritzius T, Rem PD, Früh S, Gassmann M, Fakler B, Bischofberger J, Bettler B. Synaptotagmin-11 facilitates assembly of a presynaptic signaling complex in post-Golgi cargo vesicles. EMBO Rep 2024; 25:2610-2634. [PMID: 38698221 PMCID: PMC11169412 DOI: 10.1038/s44319-024-00147-0] [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: 08/18/2023] [Revised: 04/11/2024] [Accepted: 04/12/2024] [Indexed: 05/05/2024] Open
Abstract
GABAB receptors (GBRs), the G protein-coupled receptors for GABA, regulate synaptic transmission throughout the brain. A main synaptic function of GBRs is the gating of Cav2.2-type Ca2+ channels. However, the cellular compartment where stable GBR/Cav2.2 signaling complexes form remains unknown. In this study, we demonstrate that the vesicular protein synaptotagmin-11 (Syt11) binds to both the auxiliary GBR subunit KCTD16 and Cav2.2 channels. Through these dual interactions, Syt11 recruits GBRs and Cav2.2 channels to post-Golgi vesicles, thus facilitating assembly of GBR/Cav2.2 signaling complexes. In addition, Syt11 stabilizes GBRs and Cav2.2 channels at the neuronal plasma membrane by inhibiting constitutive internalization. Neurons of Syt11 knockout mice exhibit deficits in presynaptic GBRs and Cav2.2 channels, reduced neurotransmitter release, and decreased GBR-mediated presynaptic inhibition, highlighting the critical role of Syt11 in the assembly and stable expression of GBR/Cav2.2 complexes. These findings support that Syt11 acts as a vesicular scaffold protein, aiding in the assembly of signaling complexes from low-abundance components within transport vesicles. This mechanism enables insertion of pre-assembled functional signaling units into the synaptic membrane.
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Affiliation(s)
- Luca Trovò
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | | | - Jochen Schwenk
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | | | | | | | - Simon Früh
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | - Martin Gassmann
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | - Bernd Fakler
- Institute of Physiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- CIBSS Center for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
- Center for Basics in NeuroModulation, Freiburg, Germany
| | | | - Bernhard Bettler
- Department of Biomedicine, University of Basel, Basel, Switzerland.
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2
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Inyushkin AN, Poletaev VS, Inyushkina EM, Kalberdin IS, Inyushkin AA. Irisin/BDNF signaling in the muscle-brain axis and circadian system: A review. J Biomed Res 2023; 38:1-16. [PMID: 38164079 PMCID: PMC10818175 DOI: 10.7555/jbr.37.20230133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Revised: 09/19/2023] [Accepted: 09/25/2023] [Indexed: 01/03/2024] Open
Abstract
In mammals, the timing of physiological, biochemical and behavioral processes over a 24-h period is controlled by circadian rhythms. To entrain the master clock located in the suprachiasmatic nucleus of the hypothalamus to a precise 24-h rhythm, environmental zeitgebers are used by the circadian system. This is done primarily by signals from the retina via the retinohypothalamic tract, but other cues like exercise, feeding, temperature, anxiety, and social events have also been shown to act as non-photic zeitgebers. The recently identified myokine irisin is proposed to serve as an entraining non-photic signal of exercise. Irisin is a product of cleavage and modification from its precursor membrane fibronectin type Ⅲ domain-containing protein 5 (FNDC5) in response to exercise. Apart from well-known peripheral effects, such as inducing the "browning" of white adipocytes, irisin can penetrate the blood-brain barrier and display the effects on the brain. Experimental data suggest that FNDC5/irisin mediates the positive effects of physical activity on brain functions. In several brain areas, irisin induces the production of brain-derived neurotrophic factor (BDNF). In the master clock, a significant role in gating photic stimuli in the retinohypothalamic synapse for BDNF is suggested. However, the brain receptor for irisin remains unknown. In the current review, the interactions of physical activity and the irisin/BDNF axis with the circadian system are reconceptualized.
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Affiliation(s)
- Alexey N. Inyushkin
- Department of Human & Animal Physiology, Samara National Research University, Samara 443011, Russia
| | - Vitalii S. Poletaev
- Department of Human & Animal Physiology, Samara National Research University, Samara 443011, Russia
| | - Elena M. Inyushkina
- Department of Human & Animal Physiology, Samara National Research University, Samara 443011, Russia
| | - Igor S. Kalberdin
- Department of Human & Animal Physiology, Samara National Research University, Samara 443011, Russia
| | - Andrey A. Inyushkin
- Department of Human & Animal Physiology, Samara National Research University, Samara 443011, Russia
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3
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Chang HF, Schirra C, Pattu V, Krause E, Becherer U. Lytic granule exocytosis at immune synapses: lessons from neuronal synapses. Front Immunol 2023; 14:1177670. [PMID: 37275872 PMCID: PMC10233144 DOI: 10.3389/fimmu.2023.1177670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Accepted: 05/09/2023] [Indexed: 06/07/2023] Open
Abstract
Regulated exocytosis is a central mechanism of cellular communication. It is not only the basis for neurotransmission and hormone release, but also plays an important role in the immune system for the release of cytokines and cytotoxic molecules. In cytotoxic T lymphocytes (CTLs), the formation of the immunological synapse is required for the delivery of the cytotoxic substances such as granzymes and perforin, which are stored in lytic granules and released via exocytosis. The molecular mechanisms of their fusion with the plasma membrane are only partially understood. In this review, we discuss the molecular players involved in the regulated exocytosis of CTL, highlighting the parallels and differences to neuronal synaptic transmission. Additionally, we examine the strengths and weaknesses of both systems to study exocytosis.
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4
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Lamanna J, Ferro M, Spadini S, Malgaroli A. Exploiting the molecular diversity of the synapse to investigate neuronal communication: A guide through the current toolkit. Eur J Neurosci 2022; 56:6141-6161. [PMID: 36239030 PMCID: PMC10100385 DOI: 10.1111/ejn.15848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 07/15/2022] [Accepted: 10/10/2022] [Indexed: 12/29/2022]
Abstract
Chemical synapses are tiny and overcrowded environments, deeply embedded inside brain tissue and enriched with thousands of protein species. Many efforts have been devoted to developing custom approaches for evaluating and modifying synaptic activity. Most of these methods are based on the engineering of one or more synaptic protein scaffolds used to target active moieties to the synaptic compartment or to manipulate synaptic functioning. In this review, we summarize the most recent methodological advances and provide a description of the involved proteins as well as the operation principle. Furthermore, we highlight their advantages and limitations in relation to studies of synaptic transmission in vitro and in vivo. Concerning the labelling methods, the most important challenge is how to extend the available approaches to the in vivo setting. On the other hand, for those methods that allow manipulation of synaptic function, this limit has been overcome using optogenetic approaches that can be more easily applied to the living brain. Finally, future applications of these methods to neuroscience, as well as new potential routes for development, are discussed.
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Affiliation(s)
- Jacopo Lamanna
- Center for Behavioral Neuroscience and Communication (BNC), Vita-Salute San Raffaele University, Milan, Italy.,Faculty of Psychology, Vita-Salute San Raffaele University, Milan, Italy
| | - Mattia Ferro
- Center for Behavioral Neuroscience and Communication (BNC), Vita-Salute San Raffaele University, Milan, Italy.,Department of Psychology, Sigmund Freud University, Milan, Italy
| | - Sara Spadini
- Center for Behavioral Neuroscience and Communication (BNC), Vita-Salute San Raffaele University, Milan, Italy.,Faculty of Psychology, Vita-Salute San Raffaele University, Milan, Italy
| | - Antonio Malgaroli
- Center for Behavioral Neuroscience and Communication (BNC), Vita-Salute San Raffaele University, Milan, Italy.,Faculty of Psychology, Vita-Salute San Raffaele University, Milan, Italy.,San Raffaele Turro, IRCCS Ospedale San Raffaele, Milan, Italy
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5
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Prestigio C, Ferrante D, Marte A, Romei A, Lignani G, Onofri F, Valente P, Benfenati F, Baldelli P. REST/NRSF drives homeostatic plasticity of inhibitory synapses in a target-dependent fashion. eLife 2021; 10:e69058. [PMID: 34855580 PMCID: PMC8639147 DOI: 10.7554/elife.69058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 11/22/2021] [Indexed: 12/31/2022] Open
Abstract
The repressor-element 1-silencing transcription/neuron-restrictive silencer factor (REST/NRSF) controls hundreds of neuron-specific genes. We showed that REST/NRSF downregulates glutamatergic transmission in response to hyperactivity, thus contributing to neuronal homeostasis. However, whether GABAergic transmission is also implicated in the homeostatic action of REST/NRSF is unknown. Here, we show that hyperactivity-induced REST/NRSF activation, triggers a homeostatic rearrangement of GABAergic inhibition, with increased frequency of miniature inhibitory postsynaptic currents (IPSCs) and amplitude of evoked IPSCs in mouse cultured hippocampal neurons. Notably, this effect is limited to inhibitory-onto-excitatory neuron synapses, whose density increases at somatic level and decreases in dendritic regions, demonstrating a complex target- and area-selectivity. The upscaling of perisomatic inhibition was occluded by TrkB receptor inhibition and resulted from a coordinated and sequential activation of the Npas4 and Bdnf gene programs. On the opposite, the downscaling of dendritic inhibition was REST-dependent, but BDNF-independent. The findings highlight the central role of REST/NRSF in the complex transcriptional responses aimed at rescuing physiological levels of network activity in front of the ever-changing environment.
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Affiliation(s)
- Cosimo Prestigio
- Department of Experimental Medicine, University of GenovaGenovaItaly
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di TecnologiaGenovaItaly
| | - Daniele Ferrante
- Department of Experimental Medicine, University of GenovaGenovaItaly
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di TecnologiaGenovaItaly
| | - Antonella Marte
- Department of Experimental Medicine, University of GenovaGenovaItaly
| | - Alessandra Romei
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di TecnologiaGenovaItaly
| | - Gabriele Lignani
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, Queen Square HouseLondonUnited Kingdom
| | - Franco Onofri
- Department of Experimental Medicine, University of GenovaGenovaItaly
- IRCCS, Ospedale Policlinico San MartinoGenovaItaly
| | - Pierluigi Valente
- Department of Experimental Medicine, University of GenovaGenovaItaly
- IRCCS, Ospedale Policlinico San MartinoGenovaItaly
| | - Fabio Benfenati
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di TecnologiaGenovaItaly
- IRCCS, Ospedale Policlinico San MartinoGenovaItaly
| | - Pietro Baldelli
- Department of Experimental Medicine, University of GenovaGenovaItaly
- IRCCS, Ospedale Policlinico San MartinoGenovaItaly
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6
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Function of Drosophila Synaptotagmins in membrane trafficking at synapses. Cell Mol Life Sci 2021; 78:4335-4364. [PMID: 33619613 PMCID: PMC8164606 DOI: 10.1007/s00018-021-03788-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/29/2021] [Accepted: 02/09/2021] [Indexed: 12/13/2022]
Abstract
The Synaptotagmin (SYT) family of proteins play key roles in regulating membrane trafficking at neuronal synapses. Using both Ca2+-dependent and Ca2+-independent interactions, several SYT isoforms participate in synchronous and asynchronous fusion of synaptic vesicles (SVs) while preventing spontaneous release that occurs in the absence of stimulation. Changes in the function or abundance of the SYT1 and SYT7 isoforms alter the number and route by which SVs fuse at nerve terminals. Several SYT family members also regulate trafficking of other subcellular organelles at synapses, including dense core vesicles (DCV), exosomes, and postsynaptic vesicles. Although SYTs are linked to trafficking of multiple classes of synaptic membrane compartments, how and when they interact with lipids, the SNARE machinery and other release effectors are still being elucidated. Given mutations in the SYT family cause disorders in both the central and peripheral nervous system in humans, ongoing efforts are defining how these proteins regulate vesicle trafficking within distinct neuronal compartments. Here, we review the Drosophila SYT family and examine their role in synaptic communication. Studies in this invertebrate model have revealed key similarities and several differences with the predicted activity of their mammalian counterparts. In addition, we highlight the remaining areas of uncertainty in the field and describe outstanding questions on how the SYT family regulates membrane trafficking at nerve terminals.
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7
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Journey of brain-derived neurotrophic factor: from intracellular trafficking to secretion. Cell Tissue Res 2020; 382:125-134. [PMID: 32897423 DOI: 10.1007/s00441-020-03274-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 08/07/2020] [Indexed: 12/14/2022]
Abstract
Brain-derived neurotrophic factor (BDNF) is known to control a wide variety of brain functions, ranging from memory formation to food intake. However, since the BDNF levels are extremely low in the nervous system, the dynamics in neurons from intracellular trafficking to secretion is absolutely complicated; the understanding is not fully promoted. We here review the findings of those critical mechanisms from intracellular trafficking to the secretion of BDNF. Furthermore, to solve this issue, technological advances for the detection, measurement, and imaging of this growth factor are essential. We believe that this review helps the study of these complex but critical mechanisms of BDNF.
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8
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Radak Z, Suzuki K, Posa A, Petrovszky Z, Koltai E, Boldogh I. The systemic role of SIRT1 in exercise mediated adaptation. Redox Biol 2020; 35:101467. [PMID: 32086007 PMCID: PMC7284913 DOI: 10.1016/j.redox.2020.101467] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 02/07/2020] [Accepted: 02/13/2020] [Indexed: 12/30/2022] Open
Abstract
Cellular energy demands are readily changed during physical exercise resulting in adaptive responses by signaling proteins of metabolic processes, including the NAD+ dependent lysine deacetylase SIRT1. Regular exercise results in systemic adaptation that restores the level of SIRT1 in the kidney, liver, and brain in patients with neurodegenerative diseases, and thereby normalizes cellular metabolic processes to attenuate the severity of these diseases. In skeletal muscle, over-expression of SIRT1 results in enhanced numbers of myonuclei improves the repair process after injury and is actively involved in muscle hypertrophy by up-regulating anabolic and downregulating catabolic processes. The present review discusses the different views of SIRT1 dependent deacetylation of PGC-α.
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Affiliation(s)
- Zsolt Radak
- Research Institute of Sport Science, University of Physical Education, Budapest, Hungary; Faculty of Sport Sciences, Waseda University, Saitama, 359-1192, Japan; University of Szeged, Szeged, Hungary.
| | - Katsuhiko Suzuki
- Faculty of Sport Sciences, Waseda University, Saitama, 359-1192, Japan
| | | | | | - Erika Koltai
- Research Institute of Sport Science, University of Physical Education, Budapest, Hungary
| | - Istvan Boldogh
- Department of Microbiology and Immunology, University of Texas Medical Branch at Galveston, Galveston, TX, 77555, USA
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9
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Shimojo M, Madara J, Pankow S, Liu X, Yates J, Südhof TC, Maximov A. Synaptotagmin-11 mediates a vesicle trafficking pathway that is essential for development and synaptic plasticity. Genes Dev 2019; 33:365-376. [PMID: 30808661 PMCID: PMC6411015 DOI: 10.1101/gad.320077.118] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 12/21/2018] [Indexed: 11/25/2022]
Abstract
Shimojo et al. show that Synaptotagmin-11 is an essential component of a neuronal vesicular trafficking pathway that differs from the well-characterized synaptic vesicle trafficking pathway but is also essential for life. Synaptotagmin-11 (Syt11) is a Synaptotagmin isoform that lacks an apparent ability to bind calcium, phospholipids, or SNARE proteins. While human genetic studies have linked mutations in the Syt11 gene to schizophrenia and Parkinson's disease, the localization or physiological role of Syt11 remain unclear. We found that in neurons, Syt11 resides on abundant vesicles that differ from synaptic vesicles and resemble trafficking endosomes. These vesicles recycle via the plasma membrane in an activity-dependent manner, but their exocytosis is slow and desynchronized. Constitutive knockout mice lacking Syt11 died shortly after birth, suggesting Syt11-mediated membrane transport is required for survival. In contrast, selective ablation of Syt11 in excitatory forebrain neurons using a conditional knockout did not affect life span but impaired synaptic plasticity and memory. Syt11-deficient neurons displayed normal secretion of fast neurotransmitters and peptides but exhibited a reduction of long-term synaptic potentiation. Hence, Syt11 is an essential component of a neuronal vesicular trafficking pathway that differs from the well-characterized synaptic vesicle trafficking pathway but is also essential for life.
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Affiliation(s)
- Masafumi Shimojo
- Department of Neuroscience, Scripps Research, La Jolla, California 92037, USA.,The Dorris Neuroscience, Scripps Research, La Jolla, California 92037, USA
| | - Joseph Madara
- Department of Neuroscience, Scripps Research, La Jolla, California 92037, USA.,The Dorris Neuroscience, Scripps Research, La Jolla, California 92037, USA
| | - Sandra Pankow
- Department of Molecular Medicine, Scripps Research, La Jolla, California 92037, USA
| | - Xinran Liu
- Department of Neuroscience, University of Texas Southwestern Medical Center at Dallas, Dallas 75235, Texas, USA
| | - John Yates
- Department of Molecular Medicine, Scripps Research, La Jolla, California 92037, USA
| | - Thomas C Südhof
- Department of Neuroscience, University of Texas Southwestern Medical Center at Dallas, Dallas 75235, Texas, USA.,Department of Molecular and Cellular Physiology, Stanford University, Palo Alto, California 94035, USA
| | - Anton Maximov
- Department of Neuroscience, Scripps Research, La Jolla, California 92037, USA.,The Dorris Neuroscience, Scripps Research, La Jolla, California 92037, USA.,Department of Neuroscience, University of Texas Southwestern Medical Center at Dallas, Dallas 75235, Texas, USA
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10
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Capture of Dense Core Vesicles at Synapses by JNK-Dependent Phosphorylation of Synaptotagmin-4. Cell Rep 2018; 21:2118-2133. [PMID: 29166604 PMCID: PMC5714612 DOI: 10.1016/j.celrep.2017.10.084] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 10/05/2017] [Accepted: 10/23/2017] [Indexed: 01/04/2023] Open
Abstract
Delivery of neurotrophins and neuropeptides via long-range trafficking of dense core vesicles (DCVs) from the cell soma to nerve terminals is essential for synapse modulation and circuit function. But the mechanism by which transiting DCVs are captured at specific sites is unknown. Here, we discovered that Synaptotagmin-4 (Syt4) regulates the capture and spatial distribution of DCVs in hippocampal neurons. We found that DCVs are highly mobile and undergo long-range translocation but switch directions only at the distal ends of axons, revealing a circular trafficking pattern. Phosphorylation of serine 135 of Syt4 by JNK steers DCV trafficking by destabilizing Syt4-Kif1A interaction, leading to a transition from microtubule-dependent DCV trafficking to capture at en passant presynaptic boutons by actin. Furthermore, neuronal activity increased DCV capture via JNK-dependent phosphorylation of the S135 site of Syt4. Our data reveal a mechanism that ensures rapid, site-specific delivery of DCVs to synapses. Syt4-bearing dense core vesicles in axons traffic continually in a circular pattern Phosphorylation of S135 of Syt4 by JNK destabilizes Syt4-Kif1A binding Destabilized Syt4-Kif1A binding promotes capture of vesicles at synapses by actin Neuronal activity increases vesicle capture via S135-dependent JNK phosphorylation
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11
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Urbina FL, Gomez SM, Gupton SL. Spatiotemporal organization of exocytosis emerges during neuronal shape change. J Cell Biol 2018; 217:1113-1128. [PMID: 29351997 PMCID: PMC5839795 DOI: 10.1083/jcb.201709064] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 11/17/2017] [Accepted: 12/14/2017] [Indexed: 12/12/2022] Open
Abstract
Urbina et al. use a new computer-vision image analysis tool and extended clustering statistics to demonstrate that the spatiotemporal distribution of constitutive VAMP2-mediated exocytosis is dynamic in developing neurons. The exocytosis pattern is modified by both developmental time and the guidance cue netrin-1, regulated differentially in the soma and neurites, and distinct from exocytosis in nonneuronal cells. Neurite elongation and branching in developing neurons requires plasmalemma expansion, hypothesized to occur primarily via exocytosis. We posited that exocytosis in developing neurons and nonneuronal cells would exhibit distinct spatiotemporal organization. We exploited total internal reflection fluorescence microscopy to image vesicle-associated membrane protein (VAMP)–pHluorin—mediated exocytosis in mouse embryonic cortical neurons and interphase melanoma cells, and developed computer-vision software and statistical tools to uncover spatiotemporal aspects of exocytosis. Vesicle fusion behavior differed between vesicle types, cell types, developmental stages, and extracellular environments. Experiment-based mathematical calculations indicated that VAMP2-mediated vesicle fusion supplied excess material for the plasma membrane expansion that occurred early in neuronal morphogenesis, which was balanced by clathrin-mediated endocytosis. Spatial statistics uncovered distinct spatiotemporal regulation of exocytosis in the soma and neurites of developing neurons that was modulated by developmental stage, exposure to the guidance cue netrin-1, and the brain-enriched ubiquitin ligase tripartite motif 9. In melanoma cells, exocytosis occurred less frequently, with distinct spatial clustering patterns.
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Affiliation(s)
- Fabio L Urbina
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Shawn M Gomez
- University of North Carolina at Chapel Hill/North Carolina State University Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill/North Carolina State University, Chapel Hill, NC
| | - Stephanie L Gupton
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC .,Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC.,Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC
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12
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Johnson KW, Herold KF, Milner TA, Hemmings HC, Platholi J. Sodium channel subtypes are differentially localized to pre- and post-synaptic sites in rat hippocampus. J Comp Neurol 2017; 525:3563-3578. [PMID: 28758202 PMCID: PMC5927368 DOI: 10.1002/cne.24291] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 07/24/2017] [Accepted: 07/25/2017] [Indexed: 12/16/2022]
Abstract
Voltage-gated Na+ channels (Nav ) modulate neuronal excitability, but the roles of the various Nav subtypes in specific neuronal functions such as synaptic transmission are unclear. We investigated expression of the three major brain Nav subtypes (Nav 1.1, Nav 1.2, Nav 1.6) in area CA1 and dentate gyrus of rat hippocampus. Using light and electron microscopy, we found labeling for all three Nav subtypes on dendrites, dendritic spines, and axon terminals, but the proportion of pre- and post-synaptic labeling for each subtype varied within and between subregions of CA1 and dentate gyrus. In the central hilus (CH) of the dentate gyrus, Nav 1.1 immunoreactivity was selectively expressed in presynaptic profiles, while Nav 1.2 and Nav 1.6 were expressed both pre- and post-synaptically. In contrast, in the stratum radiatum (SR) of CA1, Nav 1.1, Nav 1.2, and Nav 1.6 were selectively expressed in postsynaptic profiles. We next compared differences in Nav subtype expression between CH and SR axon terminals and between CH and SR dendrites and spines. Nav 1.1 and Nav 1.2 immunoreactivity was preferentially localized to CH axon terminals compared to SR, and in SR dendrites and spines compared to CH. No differences in Nav 1.6 immunoreactivity were found between axon terminals of CH and SR or between dendrites and spines of CH and SR. All Nav subtypes in both CH and SR were preferentially associated with asymmetric synapses rather than symmetric synapses. These findings indicate selective presynaptic and postsynaptic Nav expression in glutamatergic synapses of CH and SR supporting neurotransmitter release and synaptic plasticity.
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Affiliation(s)
| | - Karl F. Herold
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY
| | - Teresa A. Milner
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY
- Harold and Milliken Hatch Laboratory of Neuroendocrinology, The Rockefeller University, NY NY
| | - Hugh C. Hemmings
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY
- Department of Pharmacology, Weill Cornell Medicine, New York, NY
| | - Jimcy Platholi
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY
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13
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Robinson BJ, Stanisavljevic B, Silverman MA, Scalettar BA. Stochastic Subcellular Organization of Dense-Core Vesicles Revealed by Point Pattern Analysis. Biophys J 2017; 111:852-863. [PMID: 27558728 DOI: 10.1016/j.bpj.2016.07.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 06/20/2016] [Accepted: 07/05/2016] [Indexed: 12/20/2022] Open
Abstract
Dense-core vesicles (DCVs) are regulated secretory organelles found in many types of neurons. In neurons of the hippocampus, their cargo includes proteins that mediate several pivotal processes, including differentiation and synaptic plasticity. Motivated by interest in DCV distribution and its impact on cargo action, we have used fluorescence microscopy and statistical analysis to develop a quantitative model of the subcellular organization of DCVs in hippocampal neurons that are spontaneously active (their most prevalent state). We also have tested the functionally motivated hypothesis that these organelles are synaptically enriched. Variance-to-mean ratio, frequency distribution, and Moran's autocorrelation analyses reveal that DCV distribution along shafts, and within synapses, follows Poisson statistics, establishing that stochastically dictated organization sustains cargo function. Occupancy in boutons exceeds that at nearby extrasynaptic axonal sites by approximately threefold, revealing significant local presynaptic enrichment. Widespread stochastic organization is consistent with the emerging functional importance of synaptically and extrasynaptically localized DCVs. Presynaptic enrichment is consistent with the established importance of protecting presynaptic sites from depletion of DCV cargo. These results enhance understanding of the link between DCV organization and mechanisms of cargo action, and they reinforce the emerging theme that randomness is a prevalent aspect of synaptic organization and composition.
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Affiliation(s)
- Benjamin J Robinson
- Department of Physics, Lewis & Clark College, Portland, Oregon; Department of Mathematics, Lewis & Clark College, Portland, Oregon
| | - Bogdan Stanisavljevic
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Michael A Silverman
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Bethe A Scalettar
- Department of Physics, Lewis & Clark College, Portland, Oregon; Program in Biochemistry and Molecular Biology, Lewis & Clark College, Portland, Oregon.
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14
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Zhang W, Daly KM, Liang B, Zhang L, Li X, Li Y, Lin DT. BDNF rescues prefrontal dysfunction elicited by pyramidal neuron-specific DTNBP1 deletion in vivo. J Mol Cell Biol 2017; 9:117-131. [PMID: 27330059 DOI: 10.1093/jmcb/mjw029] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 05/16/2016] [Indexed: 01/15/2023] Open
Abstract
Dystrobrevin-binding protein 1 (Dtnbp1) is one of the earliest identified schizophrenia susceptibility genes. Reduced expression of DTNBP1 is commonly found in brain areas of schizophrenic patients. Dtnbp1-null mutant mice exhibit abnormalities in behaviors and impairments in neuronal activities. However, how diminished DTNBP1 expression contributes to clinical relevant features of schizophrenia remains to be illustrated. Here, using a conditional Dtnbp1 knockout mouse line, we identified an in vivo schizophrenia-relevant function of DTNBP1 in pyramidal neurons of the medial prefrontal cortex (mPFC). We demonstrated that DTNBP1 elimination specifically in pyramidal neurons of the mPFC impaired mouse pre-pulse inhibition (PPI) behavior and reduced perisomatic GABAergic synapses. We further revealed that loss of DTNBP1 in pyramidal neurons diminished activity-dependent secretion of brain-derived neurotrophic factor (BDNF). Finally, we showed that chronic BDNF infusion in the mPFC fully rescued both GABAergic synaptic dysfunction and PPI behavioral deficit induced by DTNBP1 elimination from pyramidal neurons. Our findings highlight brain region- and cell type-specific functions of DTNBP1 in the pathogenesis of schizophrenia, and underscore BDNF restoration as a potential therapeutic strategy for schizophrenia.
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Affiliation(s)
- Wen Zhang
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Kathryn M Daly
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Bo Liang
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Lifeng Zhang
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Xuan Li
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Yun Li
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Da-Ting Lin
- Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 333 Cassell Drive, Baltimore, MD 21224, USA.,The Jackson Laboratory, 600 Main Street, Bar Harbor, ME 04609, USA.,The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA
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15
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Signaling by FGF Receptor 2, Not FGF Receptor 1, Regulates Myelin Thickness through Activation of ERK1/2-MAPK, Which Promotes mTORC1 Activity in an Akt-Independent Manner. J Neurosci 2017; 37:2931-2946. [PMID: 28193689 DOI: 10.1523/jneurosci.3316-16.2017] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 01/06/2017] [Accepted: 02/01/2017] [Indexed: 12/21/2022] Open
Abstract
FGF signaling has emerged as a significant "late-stage" regulator of myelin thickness in the CNS, independent of oligodendrocyte differentiation. Therefore, it is critically important to identify the specific FGF receptor type and its downstream signaling molecules in oligodendrocytes to obtain better insights into the regulatory mechanisms of myelin growth. Here, we show that FGF receptor type 2 (FGFR2) is highly enriched at the paranodal loops of myelin. Conditional ablation of this receptor-type, but not FGF receptor type 1 (FGFR1), resulted in attenuation of myelin growth, expression of major myelin genes, key transcription factor Myrf and extracellular signal-regulated protein kinase 1 and 2 (ERK1/2) activity. This was rescued by upregulating ERK1/2 activity in these mice, strongly suggesting that ERK1/2 are key transducers of FGFR2 signals for myelin growth. However, given that the PI3K/Akt/mechanistic target of rapamycin (mTOR) pathway is also known to regulate myelin thickness, we examined FGFR2-deficient mice for the expression of key signaling molecules in this pathway. A significant downregulation of p-mTOR, p-Raptor, and p-S6RP was observed, which was restored to normal by elevating ERK1/2 activity in these mice. Similar downregulation of these molecules was observed in ERK1/2 knock-out mice. Interestingly, since p-Akt levels remained largely unchanged in these mice, it suggests a mechanism of mTORC1 activation by ERK1/2 in an Akt-independent manner in oligodendrocytes. Taken together, these data support a model in which FGFs, possibly from axons, activate FGFR2 in the oligodendrocyte/myelin compartment to increase ERK1/2 activation, which ultimately targets Myrf, as well as converges with the PI3K/Akt/mTOR pathway at the level of mTORC1, working together to drive the growth of the myelin sheath, thus increasing myelin thickness.SIGNIFICANCE STATEMENT It is well accepted that myelin is a biologically active membrane in active communication with the axons. However, the axonal signals, the receptors on myelin, and the integration of intracellular signaling pathways emanating downstream from these receptors that drive the growth of the myelin sheath remain poorly understood in the CNS. This study brings up the intriguing possibility that FGF receptor 2, in the oligodendrocyte/myelin compartment, may be one such signal. Importantly, it provides compelling evidence linking FGFR2 with the ERK1/2-MAPK pathway, which converges with the PI3K/Akt/mTOR (mechanistic target of rapamycin) pathway at the level of mTORC1 and also regulates the transcription factor Myrf, together providing a mechanistic framework for regulating both the transcriptional and translational machinery required for the proper growth of the myelin sheath.
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Releasing Mechanism of Neurotrophic Factors via Polysialic Acid. VITAMINS AND HORMONES 2017; 104:89-112. [DOI: 10.1016/bs.vh.2016.11.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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17
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Yuan Q, Yang F, Xiao Y, Tan S, Husain N, Ren M, Hu Z, Martinowich K, Ng JS, Kim PJ, Han W, Nagata KI, Weinberger DR, Je HS. Regulation of Brain-Derived Neurotrophic Factor Exocytosis and Gamma-Aminobutyric Acidergic Interneuron Synapse by the Schizophrenia Susceptibility Gene Dysbindin-1. Biol Psychiatry 2016; 80:312-322. [PMID: 26386481 DOI: 10.1016/j.biopsych.2015.08.019] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 08/12/2015] [Accepted: 08/12/2015] [Indexed: 10/23/2022]
Abstract
BACKGROUND Genetic variations in dystrobrevin binding protein 1 (DTNBP1 or dysbindin-1) have been implicated as risk factors in the pathogenesis of schizophrenia. The encoded protein dysbindin-1 functions in the regulation of synaptic activity and synapse development. Intriguingly, a loss of function mutation in Dtnbp1 in mice disrupted both glutamatergic and gamma-aminobutyric acidergic transmission in the cerebral cortex; pyramidal neurons displayed enhanced excitability due to reductions in inhibitory synaptic inputs. However, the mechanism by which reduced dysbindin-1 activity causes inhibitory synaptic deficits remains unknown. METHODS We investigated the role of dysbindin-1 in the exocytosis of brain-derived neurotrophic factor (BDNF) from cortical excitatory neurons, organotypic brain slices, and acute slices from dysbindin-1 mutant mice and determined how this change in BDNF exocytosis transsynaptically affected the number of inhibitory synapses formed on excitatory neurons via whole-cell recordings, immunohistochemistry, and live-cell imaging using total internal reflection fluorescence microscopy. RESULTS A decrease in dysbindin-1 reduces the exocytosis of BDNF from cortical excitatory neurons, and this reduction in BDNF exocytosis transsynaptically resulted in reduced inhibitory synapse numbers formed on excitatory neurons. Furthermore, application of exogenous BDNF rescued the inhibitory synaptic deficits caused by the reduced dysbindin-1 level in both cultured cortical neurons and slice cultures. CONCLUSIONS Taken together, our results demonstrate that these two genes linked to risk for schizophrenia (BDNF and dysbindin-1) function together to regulate interneuron development and cortical network activity. This evidence supports the investigation of the association between dysbindin-1 and BDNF in humans with schizophrenia.
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Affiliation(s)
- Qiang Yuan
- Molecular Neurophysiology Laboratory, Signature Program in Neuroscience and Behavioral Disorders, Duke-National University of Singapore Graduate Medical School, Singapore, Singapore
| | - Feng Yang
- Lieber Institute for Brain Development, Johns Hopkins Medical Campus, Baltimore, Maryland
| | - Yixin Xiao
- Molecular Neurophysiology Laboratory, Signature Program in Neuroscience and Behavioral Disorders, Duke-National University of Singapore Graduate Medical School, Singapore, Singapore
| | - Shawn Tan
- Molecular Neurophysiology Laboratory, Signature Program in Neuroscience and Behavioral Disorders, Duke-National University of Singapore Graduate Medical School, Singapore, Singapore
| | - Nilofer Husain
- Molecular Neurophysiology Laboratory, Signature Program in Neuroscience and Behavioral Disorders, Duke-National University of Singapore Graduate Medical School, Singapore, Singapore
| | - Ming Ren
- Lieber Institute for Brain Development, Johns Hopkins Medical Campus, Baltimore, Maryland
| | - Zhonghua Hu
- Lieber Institute for Brain Development, Johns Hopkins Medical Campus, Baltimore, Maryland
| | - Keri Martinowich
- Lieber Institute for Brain Development, Johns Hopkins Medical Campus, Baltimore, Maryland
| | - Julia S Ng
- Molecular Neurophysiology Laboratory, Signature Program in Neuroscience and Behavioral Disorders, Duke-National University of Singapore Graduate Medical School, Singapore, Singapore
| | - Paul J Kim
- Molecular Neurophysiology Laboratory, Signature Program in Neuroscience and Behavioral Disorders, Duke-National University of Singapore Graduate Medical School, Singapore, Singapore
| | - Weiping Han
- Singapore Bioimaging Consortium, Singapore, Singapore
| | - Koh-Ichi Nagata
- Institute for Developmental Research, Aichi Human Service Center, Kasugai, Japan
| | - Daniel R Weinberger
- Lieber Institute for Brain Development, Johns Hopkins Medical Campus, Baltimore, Maryland
| | - H Shawn Je
- Molecular Neurophysiology Laboratory, Signature Program in Neuroscience and Behavioral Disorders, Duke-National University of Singapore Graduate Medical School, Singapore, Singapore; Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
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18
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Gonzalez A, Moya-Alvarado G, Gonzalez-Billaut C, Bronfman FC. Cellular and molecular mechanisms regulating neuronal growth by brain-derived neurotrophic factor. Cytoskeleton (Hoboken) 2016; 73:612-628. [PMID: 27223597 DOI: 10.1002/cm.21312] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/20/2016] [Accepted: 05/23/2016] [Indexed: 12/31/2022]
Abstract
Brain-derived neurotrophic factor (BDNF) and its receptors TrkB and p75 regulate dendritic and axonal growth during development and maintenance of the mature nervous system; however, the cellular and molecular mechanisms underlying this process are not fully understood. In recent years, several advances have shed new light on the processes behind the regulation of BDNF-mediated structural plasticity including control of neuronal transcription, local translation of proteins, and regulation of cytoskeleton and membrane dynamics. In this review, we summarize recent advances in the field of BDNF signaling in neurons to induce neuronal growth. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Andres Gonzalez
- MINREB and Center for Ageing and Regeneration (CARE UC), Faculty of Biological Sciences, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Guillermo Moya-Alvarado
- MINREB and Center for Ageing and Regeneration (CARE UC), Faculty of Biological Sciences, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Christian Gonzalez-Billaut
- Laboratory of Cell and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile and Geroscience Center for Brain Health and Metabolism, Santiago, Chile
| | - Francisca C Bronfman
- MINREB and Center for Ageing and Regeneration (CARE UC), Faculty of Biological Sciences, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.
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19
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Kuzniewska B, Nader K, Dabrowski M, Kaczmarek L, Kalita K. Adult Deletion of SRF Increases Epileptogenesis and Decreases Activity-Induced Gene Expression. Mol Neurobiol 2016; 53:1478-1493. [PMID: 25636686 PMCID: PMC4789231 DOI: 10.1007/s12035-014-9089-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 12/29/2014] [Indexed: 11/27/2022]
Abstract
Although the transcription factor serum response factor (SRF) has been suggested to play a role in activity-dependent gene expression and mediate plasticity-associated structural changes in the hippocampus, no unequivocal evidence has been provided for its role in brain pathology, such as epilepsy. A genome-wide program of activity-induced genes that are regulated by SRF also remains unknown. In the present study, we show that the inducible and conditional deletion of SRF in the adult mouse hippocampus increases the epileptic phenotype in the kainic acid model of epilepsy, reflected by more severe and frequent seizures. Moreover, we observe a robust decrease in activity-induced gene transcription in SRF knockout mice. We characterize the genetic program controlled by SRF in neurons and using functional annotation, we find that SRF target genes are associated with synaptic plasticity and epilepsy. Several of these SRF targets function as regulators of inhibitory or excitatory balance and the structural plasticity of neurons. Interestingly, mutations in those SRF targets have found to be associated with such human neuropsychiatric disorders, as autism and intellectual disability. We also identify novel direct SRF targets in hippocampus: Npas4, Gadd45g, and Zfp36. Altogether, our data indicate that proteins that are highly upregulated by neuronal stimulation, identified in the present study as SRF targets, may function as endogenous protectors against overactivation. Thus, the lack of these effector proteins in SRF knockout animals may lead to uncontrolled excitation and eventually epilepsy.
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Affiliation(s)
- Bozena Kuzniewska
- Laboratory of Neurobiology, Nencki Institute, 3 Pasteur Street, Warsaw, Poland
| | - Karolina Nader
- Laboratory of Neurobiology, Nencki Institute, 3 Pasteur Street, Warsaw, Poland
| | - Michal Dabrowski
- Laboratory of Bioinformatics, Neurobiology Center, Nencki Institute, 3 Pasteur Street, Warsaw, Poland
| | - Leszek Kaczmarek
- Laboratory of Neurobiology, Nencki Institute, 3 Pasteur Street, Warsaw, Poland
| | - Katarzyna Kalita
- Laboratory of Neurobiology, Nencki Institute, 3 Pasteur Street, Warsaw, Poland.
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20
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Abstract
The majority of studies of the living cell rely on capturing images using fluorescence microscopy. Unfortunately, for centuries, diffraction of light was limiting the spatial resolution in the optical microscope: structural and molecular details much finer than about half the wavelength of visible light (~200 nm) could not be visualized, imposing significant limitations on this otherwise so promising method. The surpassing of this resolution limit in far-field microscopy is currently one of the most momentous developments for studying the living cell, as the move from microscopy to super-resolution microscopy or 'nanoscopy' offers opportunities to study problems in biophysical and biomedical research at a new level of detail. This review describes the principles and modalities of present fluorescence nanoscopes, as well as their potential for biophysical and cellular experiments. All the existing nanoscopy variants separate neighboring features by transiently preparing their fluorescent molecules in states of different emission characteristics in order to make the features discernible. Usually these are fluorescent 'on' and 'off' states causing the adjacent molecules to emit sequentially in time. Each of the variants can in principle reach molecular spatial resolution and has its own advantages and disadvantages. Some require specific transitions and states that can be found only in certain fluorophore subfamilies, such as photoswitchable fluorophores, while other variants can be realized with standard fluorescent labels. Similar to conventional far-field microscopy, nanoscopy can be utilized for dynamical, multi-color and three-dimensional imaging of fixed and live cells, tissues or organisms. Lens-based fluorescence nanoscopy is poised for a high impact on future developments in the life sciences, with the potential to help solve long-standing quests in different areas of scientific research.
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21
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Eagleson KL, Lane CJ, McFadyen-Ketchum L, Solak S, Wu HH, Levitt P. Distinct intracellular signaling mediates C-MET regulation of dendritic growth and synaptogenesis. Dev Neurobiol 2016; 76:1160-81. [PMID: 26818605 DOI: 10.1002/dneu.22382] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 12/11/2015] [Accepted: 01/13/2016] [Indexed: 12/14/2022]
Abstract
Hepatocyte growth factor (HGF) activation of the MET receptor tyrosine kinase influences multiple neurodevelopmental processes. Evidence from human imaging and mouse models shows that, in the forebrain, disruptions in MET signaling alter circuit formation and function. One likely means of modulation is by controlling neuron maturation. Here, we examined the signaling mechanisms through which MET exerts developmental effects in the neocortex. In situ hybridization revealed that hgf is located near MET-expressing neurons, including deep neocortical layers and periventricular zones. Western blot analyses of neocortical crude membranes demonstrated that HGF-induced MET autophosphorylation peaks during synaptogenesis, with a striking reduction in activation between P14 and P17 just before pruning. In vitro analysis of postnatal neocortical neurons assessed the roles of intracellular signaling following MET activation. There is rapid, HGF-induced phosphorylation of MET, ERK1/2, and Akt that is accompanied by two major morphological changes: increases in total dendritic growth and synapse density. Selective inhibition of each signaling pathway altered only one of the two distinct events. MAPK/ERK pathway inhibition significantly reduced the HGF-induced increase in dendritic length, but had no effect on synapse density. In contrast, inhibition of the PI3K/Akt pathway reduced HGF-induced increases in synapse density, with no effect on dendritic length. The data reveal a key role for MET activation during the period of neocortical neuron growth and synaptogenesis, with distinct biological outcomes mediated via discrete MET-linked intracellular signaling pathways in the same neurons. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1160-1181, 2016.
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Affiliation(s)
- Kathie L Eagleson
- Department of Pediatrics, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Christianne J Lane
- Department of Preventive Medicine, Division of Biostatistics, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Lisa McFadyen-Ketchum
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Sara Solak
- Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Hsiao-Huei Wu
- Department of Pediatrics, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California
| | - Pat Levitt
- Department of Pediatrics, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California.,Institute for the Developing Mind, The Saban Research Institute, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California
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22
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Sednev MV, Belov VN, Hell SW. Fluorescent dyes with large Stokes shifts for super-resolution optical microscopy of biological objects: a review. Methods Appl Fluoresc 2015; 3:042004. [DOI: 10.1088/2050-6120/3/4/042004] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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23
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McDole B, Isgor C, Pare C, Guthrie K. BDNF over-expression increases olfactory bulb granule cell dendritic spine density in vivo. Neuroscience 2015. [PMID: 26211445 DOI: 10.1016/j.neuroscience.2015.07.056] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Olfactory bulb granule cells (GCs) are axon-less, inhibitory interneurons that regulate the activity of the excitatory output neurons, the mitral and tufted cells, through reciprocal dendrodendritic synapses located on GC spines. These contacts are established in the distal apical dendritic compartment, while GC basal dendrites and more proximal apical segments bear spines that receive glutamatergic inputs from the olfactory cortices. This synaptic connectivity is vital to olfactory circuit function and is remodeled during development, and in response to changes in sensory activity and lifelong GC neurogenesis. Manipulations that alter levels of the neurotrophin brain-derived neurotrophic factor (BDNF) in vivo have significant effects on dendritic spine morphology, maintenance and activity-dependent plasticity for a variety of CNS neurons, yet little is known regarding BDNF effects on bulb GC spine maturation or maintenance. Here we show that, in vivo, sustained bulbar over-expression of BDNF in transgenic mice produces a marked increase in GC spine density that includes an increase in mature spines on their apical dendrites. Morphometric analysis demonstrated that changes in spine density were most notable in the distal and proximal apical domains, indicating that multiple excitatory inputs are potentially modified by BDNF. Our results indicate that increased levels of endogenous BDNF can promote the maturation and/or maintenance of dendritic spines on GCs, suggesting a role for this factor in modulating GC functional connectivity within adult olfactory circuitry.
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Affiliation(s)
- B McDole
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, United States
| | - C Isgor
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, United States
| | - C Pare
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, United States
| | - K Guthrie
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, United States.
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24
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SNAREs Controlling Vesicular Release of BDNF and Development of Callosal Axons. Cell Rep 2015; 11:1054-66. [PMID: 25959820 DOI: 10.1016/j.celrep.2015.04.032] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 03/11/2015] [Accepted: 04/14/2015] [Indexed: 11/22/2022] Open
Abstract
At presynaptic active zones, exocytosis of neurotransmitter vesicles (SVs) is driven by SNARE complexes that recruit Syb2 and SNAP25. However, it remains unknown which SNAREs promote the secretion of neuronal proteins, including those essential for circuit development and experience-dependent plasticity. Here we demonstrate that Syb2 and SNAP25 mediate the vesicular release of BDNF in axons and dendrites of cortical neurons, suggesting these SNAREs act in multiple spatially segregated secretory pathways. Remarkably, axonal secretion of BDNF is also strongly regulated by SNAP47, which interacts with SNAP25 but appears to be dispensable for exocytosis of SVs. Cell-autonomous ablation of SNAP47 disrupts the layer-specific branching of callosal axons of projection cortical neurons in vivo, and this phenotype is recapitulated by ablation of BDNF or its receptor, TrkB. Our results provide insights into the molecular mechanisms of protein secretion, and they define the functions of SNAREs in BDNF signaling and regulation of neuronal connectivity.
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25
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Abstract
The endogenous cannabinoid (endocannabinoid) system is an important regulator of synaptic function. Endocannabinoids acutely modulate inhibitory and excitatory transmission, and also mediate long-term depression at GABAergic and glutamatergic synapses. Typically, endocannabinoid synthesis and release is stimulated by depolarization-induced calcium influx and/or activation of phospholipase-C (PLC) signaling triggered by mGluR activation. Recently it has been shown that brain-derived neurotrophic factor (BDNF) can also induce endocannabinoid release. Although there is growing evidence for cross-talk between BDNF and endocannabinoid signaling, little is known about the functional relevance of these interactions. In the present studies, we examined BDNF - endocannabinoid interactions in regulating activity-dependent long-term depression at inhibitory synapses (iLTD). We found that theta burst stimulation (TBS) in layer 2/3 of mouse somatosensory cortical slices can induce a form of endocannabinoid-mediated iLTD that is independent of metabotropic glutamate receptor (mGluR) activation. This endocannabinoid-dependent iLTD, however, requires endogenous BDNF-trkB signaling, as it is blocked by a trk tyrosine kinase inhibitor and by a trkB receptor antagonist, and also requires activation of diacylglycerol lipase (DAG-lipase, DGL). In addition, endocannabinoid-mediated iLTD can be induced by combining a subthreshold concentration of exogenous BDNF with weak TBS stimulation that by itself is insufficient to induce iLTD. Taken together, our results suggest that TBS can induce the release of endogenous BDNF, which triggers DGL-dependent endocannabinoid mobilization and cannabinoid receptor-dependent iLTD at layer 2/3 cortical synapses.
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26
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Abstract
Synaptic vesicles release their vesicular contents to the extracellular space by Ca(2+)-triggered exocytosis. The Ca(2+)-triggered exocytotic process is regulated by synaptotagmin (Syt), a vesicular Ca(2+)-binding C2 domain protein. Synaptotagmin 1 (Syt1), the most studied major isoform among 16 Syt isoforms, mediates Ca(2+)-triggered synaptic vesicle exocytosis by interacting with the target membranes and SNARE/complexin complex. In synapses of the central nervous system, synaptobrevin 2, a major vesicular SNARE protein, forms a ternary SNARE complex with the plasma membrane SNARE proteins, syntaxin 1 and SNAP25. The affinities of Ca(2+)-dependent interactions between Syt1 and its targets (i.e., SNARE complexes and membranes) are well correlated with the efficacies of the corresponding exocytotic processes. Therefore, different SNARE protein isoforms and membrane lipids, which interact with Syt1 with various affinities, are capable of regulating the efficacy of Syt1-mediated exocytosis. Otoferlin, another type of vesicular C2 domain protein that binds to the membrane in a Ca(2+)-dependent manner, is also involved in the Ca(2+)-triggered synaptic vesicle exocytosis in auditory hair cells. However, the functions of otoferlin in the exocytotic process are not well understood. In addition, at least five different types of synaptic vesicle proteins such as synaptic vesicle protein 2, cysteine string protein α, rab3, synapsin, and a group of proteins containing four transmembrane regions, which includes synaptophysin, synaptogyrin, and secretory carrier membrane protein, are involved in modulating the exocytotic process by regulating the formation and trafficking of synaptic vesicles.
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Affiliation(s)
- Ok-Ho Shin
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas
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27
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Terauchi A, Timmons KM, Kikuma K, Pechmann Y, Kneussel M, Umemori H. Selective synaptic targeting of the excitatory and inhibitory presynaptic organizers FGF22 and FGF7. J Cell Sci 2014; 128:281-92. [PMID: 25431136 DOI: 10.1242/jcs.158337] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Specific formation of excitatory and inhibitory synapses is crucial for proper functioning of the brain. Fibroblast growth factor 22 (FGF22) and FGF7 are postsynaptic-cell-derived presynaptic organizers necessary for excitatory and inhibitory presynaptic differentiation, respectively, in the hippocampus. For the establishment of specific synaptic networks, these FGFs must localize to appropriate synaptic locations - FGF22 to excitatory and FGF7 to inhibitory postsynaptic sites. Here, we show that distinct motor and adaptor proteins contribute to intracellular microtubule transport of FGF22 and FGF7. Excitatory synaptic targeting of FGF22 requires the motor proteins KIF3A and KIF17 and the adaptor protein SAP102 (also known as DLG3). By contrast, inhibitory synaptic targeting of FGF7 requires the motor KIF5 and the adaptor gephyrin. Time-lapse imaging shows that FGF22 moves with SAP102, whereas FGF7 moves with gephyrin. These results reveal the basis of selective targeting of the excitatory and inhibitory presynaptic organizers that supports their different synaptogenic functions. Finally, we found that knockdown of SAP102 or PSD95 (also known as DLG4), which impairs the differentiation of excitatory synapses, alters FGF7 localization, suggesting that signals from excitatory synapses might regulate inhibitory synapse formation by controlling the distribution of the inhibitory presynaptic organizer.
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Affiliation(s)
- Akiko Terauchi
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
| | - Kendall M Timmons
- Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
| | - Koto Kikuma
- Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
| | - Yvonne Pechmann
- Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Falkenried 94, D-20251 Hamburg, Germany
| | - Matthias Kneussel
- Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Falkenried 94, D-20251 Hamburg, Germany
| | - Hisashi Umemori
- Department of Neurology, F.M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
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28
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Retrograde BMP signaling modulates rapid activity-dependent synaptic growth via presynaptic LIM kinase regulation of cofilin. J Neurosci 2014; 34:4371-81. [PMID: 24647957 DOI: 10.1523/jneurosci.4943-13.2014] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The Drosophila neuromuscular junction (NMJ) is capable of rapidly budding new presynaptic varicosities over the course of minutes in response to elevated neuronal activity. Using live imaging of synaptic growth, we characterized this dynamic process and demonstrated that rapid bouton budding requires retrograde bone morphogenic protein (BMP) signaling and local alteration in the presynaptic actin cytoskeleton. BMP acts during development to provide competence for rapid synaptic growth by regulating the levels of the Rho-type guanine nucleotide exchange factor Trio, a transcriptional output of BMP-Smad signaling. In a parallel pathway, we find that the BMP type II receptor Wit signals through the effector protein LIM domain kinase 1 (Limk) to regulate bouton budding. Limk interfaces with structural plasticity by controlling the activity of the actin depolymerizing protein Cofilin. Expression of constitutively active or inactive Cofilin in motor neurons demonstrates that increased Cofilin activity promotes rapid bouton formation in response to elevated synaptic activity. Correspondingly, the overexpression of Limk, which inhibits Cofilin, inhibits bouton budding. Live imaging of the presynaptic F-actin cytoskeleton reveals that activity-dependent bouton addition is accompanied by the formation of new F-actin puncta at sites of synaptic growth. Pharmacological disruption of actin turnover inhibits bouton budding, indicating that local changes in the actin cytoskeleton at pre-existing boutons precede new budding events. We propose that developmental BMP signaling potentiates NMJs for rapid activity-dependent structural plasticity that is achieved by muscle release of retrograde signals that regulate local presynaptic actin cytoskeletal dynamics.
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Deák F. Neuronal vesicular trafficking and release in age-related cognitive impairment. J Gerontol A Biol Sci Med Sci 2014; 69:1325-30. [PMID: 24809352 DOI: 10.1093/gerona/glu061] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Aging is a common major risk factor for many neurological disorders resulting in cognitive impairment and neurodegeneration including Parkinson's and Alzheimer's diseases. Novel results from the fields of molecular neuroscience and aging research provide evidence for a link between decline of various cognitive, executive functions and changes in neuronal mechanisms of intracellular trafficking and regulated vesicle release processes in the aging nervous system. In this Perspective, we review these recent findings and formulate a hypothesis on how cargo delivery to the synapses and the release of neurotrophic factors may be involved in maintaining learning and memory capabilities during healthy aging and present examples on how defects of those disrupt normal cognition. We provide an overview of emerging new concepts and approaches that will significantly advance our understanding of the aging brain and pathophysiology of dementia. This knowledge will be instrumental in defining drug targets and designing novel therapeutic strategies.
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Affiliation(s)
- Ferenc Deák
- Reynolds Oklahoma Center on Aging, Department of Geriatric Medicine, University of Oklahoma Health Sciences Center.
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Liu H, Bai H, Hui E, Yang L, Evans CS, Wang Z, Kwon SE, Chapman ER. Synaptotagmin 7 functions as a Ca2+-sensor for synaptic vesicle replenishment. eLife 2014; 3:e01524. [PMID: 24569478 PMCID: PMC3930910 DOI: 10.7554/elife.01524] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Synaptotagmin (syt) 7 is one of three syt isoforms found in all metazoans; it is ubiquitously expressed, yet its function in neurons remains obscure. Here, we resolved Ca(2+)-dependent and Ca(2+)-independent synaptic vesicle (SV) replenishment pathways, and found that syt 7 plays a selective and critical role in the Ca(2+)-dependent pathway. Mutations that disrupt Ca(2+)-binding to syt 7 abolish this function, suggesting that syt 7 functions as a Ca(2+)-sensor for replenishment. The Ca(2+)-binding protein calmodulin (CaM) has also been implicated in SV replenishment, and we found that loss of syt 7 was phenocopied by a CaM antagonist. Moreover, we discovered that syt 7 binds to CaM in a highly specific and Ca(2+)-dependent manner; this interaction requires intact Ca(2+)-binding sites within syt 7. Together, these data indicate that a complex of two conserved Ca(2+)-binding proteins, syt 7 and CaM, serve as a key regulator of SV replenishment in presynaptic nerve terminals. DOI: http://dx.doi.org/10.7554/eLife.01524.001.
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Affiliation(s)
- Huisheng Liu
- Department of Neuroscience, Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, United States
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Tratnjek L, Zivin M, Glavan G. Up-regulation of Synaptotagmin IV within amyloid plaque-associated dystrophic neurons in Tg2576 mouse model of Alzheimer's disease. Croat Med J 2014; 54:419-28. [PMID: 24170720 PMCID: PMC3816566 DOI: 10.3325/cmj.2013.54.419] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
AIM To investigate the involvement of the vesicular membrane trafficking regulator Synaptotagmin IV (Syt IV) in Alzheimer's disease pathogenesis and to define the cell types containing increased levels of Syt IV in the β-amyloid plaque vicinity. METHODS Syt IV protein levels in wild type (WT) and Tg2576 mice cortex were determined by Western blot analysis and immunohistochemistry. Co-localization studies using double immunofluorescence staining for Syt IV and markers for astrocytes (glial fibrillary acidic protein), microglia (major histocompatibility complex class II), neurons (neuronal specific nuclear protein), and neurites (neurofilaments) were performed in WT and Tg2576 mouse cerebral cortex. RESULTS Western blot analysis showed higher Syt IV levels in Tg2576 mice cortex than in WT cortex. Syt IV was found only in neurons. In plaque vicinity, Syt IV was up-regulated in dystrophic neurons. The Syt IV signal was not up-regulated in the neurons of Tg2576 mice cortex without plaques (resembling the pre-symptomatic conditions). CONCLUSIONS Syt IV up-regulation within dystrophic neurons probably reflects disrupted vesicular transport or/and impaired protein degradation occurring in Alzheimer's disease and is probably a consequence but not the cause of neuronal degeneration. Hence, Syt IV up-regulation and/or its accumulation in dystrophic neurons may have adverse effects on the survival of the affected neuron.
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Affiliation(s)
- Larisa Tratnjek
- Gordana Glavan, Laboratory for Brain Research, Institute of Pathophysiology, Medical Faculty, Zaloska 4, Ljubljana 1000, Slovenia,
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Marosi K, Mattson MP. BDNF mediates adaptive brain and body responses to energetic challenges. Trends Endocrinol Metab 2014; 25:89-98. [PMID: 24361004 PMCID: PMC3915771 DOI: 10.1016/j.tem.2013.10.006] [Citation(s) in RCA: 339] [Impact Index Per Article: 33.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Revised: 10/14/2013] [Accepted: 10/24/2013] [Indexed: 01/05/2023]
Abstract
Emerging findings suggest that brain-derived neurotrophic factor (BDNF) serves widespread roles in regulating energy homeostasis by controlling patterns of feeding and physical activity, and by modulating glucose metabolism in peripheral tissues. BDNF mediates the beneficial effects of energetic challenges such as vigorous exercise and fasting on cognition, mood, cardiovascular function, and on peripheral metabolism. By stimulating glucose transport and mitochondrial biogenesis BDNF bolsters cellular bioenergetics and protects neurons against injury and disease. By acting in the brain and periphery, BDNF increases insulin sensitivity and parasympathetic tone. Genetic factors, a 'couch potato' lifestyle, and chronic stress impair BDNF signaling, and this may contribute to the pathogenesis of metabolic syndrome. Novel BDNF-focused interventions are being developed for obesity, diabetes, and neurological disorders.
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Affiliation(s)
- Krisztina Marosi
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, USA
| | - Mark P Mattson
- Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, Baltimore, MD, USA; Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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34
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The activity-dependent transcription factor NPAS4 regulates domain-specific inhibition. Nature 2013; 503:121-5. [PMID: 24201284 DOI: 10.1038/nature12743] [Citation(s) in RCA: 208] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 10/09/2013] [Indexed: 11/08/2022]
Abstract
A heterogeneous population of inhibitory neurons controls the flow of information through a neural circuit. Inhibitory synapses that form on pyramidal neuron dendrites modulate the summation of excitatory synaptic potentials and prevent the generation of dendritic calcium spikes. Precisely timed somatic inhibition limits both the number of action potentials and the time window during which firing can occur. The activity-dependent transcription factor NPAS4 regulates inhibitory synapse number and function in cell culture, but how this transcription factor affects the inhibitory inputs that form on distinct domains of a neuron in vivo was unclear. Here we show that in the mouse hippocampus behaviourally driven expression of NPAS4 coordinates the redistribution of inhibitory synapses made onto a CA1 pyramidal neuron, simultaneously increasing inhibitory synapse number on the cell body while decreasing the number of inhibitory synapses on the apical dendrites. This rearrangement of inhibition is mediated in part by the NPAS4 target gene brain derived neurotrophic factor (Bdnf), which specifically regulates somatic, and not dendritic, inhibition. These findings indicate that sensory stimuli, by inducing NPAS4 and its target genes, differentially control spatial features of neuronal inhibition in a way that restricts the output of the neuron while creating a dendritic environment that is permissive for plasticity.
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Pre- and postsynaptic twists in BDNF secretion and action in synaptic plasticity. Neuropharmacology 2013; 76 Pt C:610-27. [PMID: 23791959 DOI: 10.1016/j.neuropharm.2013.05.043] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 05/12/2013] [Accepted: 05/14/2013] [Indexed: 12/30/2022]
Abstract
Overwhelming evidence collected since the early 1990's strongly supports the notion that BDNF is among the key regulators of synaptic plasticity in many areas of the mammalian central nervous system. Still, due to the extremely low expression levels of endogenous BDNF in most brain areas, surprisingly little data i) pinpointing pre- and postsynaptic release sites, ii) unraveling the time course of release, and iii) elucidating the physiological levels of synaptic activity driving this secretion are available. Likewise, our knowledge regarding pre- and postsynaptic effects of endogenous BDNF at the single cell level in mediating long-term potentiation still is sparse. Thus, our review will discuss the data currently available regarding synaptic BDNF secretion in response to physiologically relevant levels of activity, and will discuss how endogenously secreted BDNF affects synaptic plasticity, giving a special focus on spike timing-dependent types of LTP and on mossy fiber LTP. We will attempt to open up perspectives how the remaining challenging questions regarding synaptic BDNF release and action might be addressed by future experiments. This article is part of the Special Issue entitled 'BDNF Regulation of Synaptic Structure, Function, and Plasticity'.
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Larimore J, Ryder PV, Kim KY, Ambrose LA, Chapleau C, Calfa G, Gross C, Bassell GJ, Pozzo-Miller L, Smith Y, Talbot K, Park IH, Faundez V. MeCP2 regulates the synaptic expression of a Dysbindin-BLOC-1 network component in mouse brain and human induced pluripotent stem cell-derived neurons. PLoS One 2013; 8:e65069. [PMID: 23750231 PMCID: PMC3672180 DOI: 10.1371/journal.pone.0065069] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 04/22/2013] [Indexed: 02/06/2023] Open
Abstract
Clinical, epidemiological, and genetic evidence suggest overlapping pathogenic mechanisms between autism spectrum disorder (ASD) and schizophrenia. We tested this hypothesis by asking if mutations in the ASD gene MECP2 which cause Rett syndrome affect the expression of genes encoding the schizophrenia risk factor dysbindin, a subunit of the biogenesis of lysosome-related organelles complex-1 (BLOC-1), and associated interacting proteins. We measured mRNA and protein levels of key components of a dysbindin interaction network by, quantitative real time PCR and quantitative immunohistochemistry in hippocampal samples of wild-type and Mecp2 mutant mice. In addition, we confirmed results by performing immunohistochemistry of normal human hippocampus and quantitative qRT-PCR of human inducible pluripotent stem cells (iPSCs)-derived human neurons from Rett syndrome patients. We defined the distribution of the BLOC-1 subunit pallidin in human and mouse hippocampus and contrasted this distribution with that of symptomatic Mecp2 mutant mice. Neurons from mutant mice and Rett syndrome patients displayed selectively reduced levels of pallidin transcript. Pallidin immunoreactivity decreased in the hippocampus of symptomatic Mecp2 mutant mice, a feature most prominent at asymmetric synapses as determined by immunoelectron microcopy. Pallidin immunoreactivity decreased concomitantly with reduced BDNF content in the hippocampus of Mecp2 mice. Similarly, BDNF content was reduced in the hippocampus of BLOC-1 deficient mice suggesting that genetic defects in BLOC-1 are upstream of the BDNF phenotype in Mecp2 deficient mice. Our results demonstrate that the ASD-related gene Mecp2 regulates the expression of components belonging to the dysbindin interactome and these molecular differences may contribute to synaptic phenotypes that characterize Mecp2 deficiencies and ASD.
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Affiliation(s)
- Jennifer Larimore
- Department of Biology, Agnes Scott College, Decatur, Georgia, United States of America
| | - Pearl V. Ryder
- Cell Biology, Emory University, Atlanta, Georgia, United States of America
| | - Kun-Yong Kim
- Department of Genetics, Yale Stem Cell Center, Yale School of Medicine, New Haven, Connecticut, United States of America
| | - L. Alex Ambrose
- Department of Biology, Agnes Scott College, Decatur, Georgia, United States of America
| | - Christopher Chapleau
- Department of Neurobiology, The University of Alabama, Birmingham, Alabama, United States of America
| | - Gaston Calfa
- Department of Neurobiology, The University of Alabama, Birmingham, Alabama, United States of America
| | - Christina Gross
- Cell Biology, Emory University, Atlanta, Georgia, United States of America
| | - Gary J. Bassell
- Cell Biology, Emory University, Atlanta, Georgia, United States of America
| | - Lucas Pozzo-Miller
- Department of Neurobiology, The University of Alabama, Birmingham, Alabama, United States of America
| | - Yoland Smith
- Department of Neurology, Emory University, Atlanta, Georgia, United States of America
- Yerkes National Primate Center, Emory University, Atlanta, Georgia, United States of America
| | - Konrad Talbot
- Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - In-Hyun Park
- Department of Genetics, Yale Stem Cell Center, Yale School of Medicine, New Haven, Connecticut, United States of America
| | - Victor Faundez
- Cell Biology, Emory University, Atlanta, Georgia, United States of America
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Fluorescence nanoscopy. Methods and applications. J Chem Biol 2013; 6:97-120. [PMID: 24432127 DOI: 10.1007/s12154-013-0096-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 05/05/2013] [Indexed: 12/30/2022] Open
Abstract
Fluorescence nanoscopy refers to the experimental techniques and analytical methods used for fluorescence imaging at a resolution higher than conventional, diffraction-limited, microscopy. This review explains the concepts behind fluorescence nanoscopy and focuses on the latest and promising developments in acquisition techniques, labelling strategies to obtain highly detailed super-resolved images and in the quantitative methods to extract meaningful information from them.
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38
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Petoukhov E, Fernando S, Mills F, Shivji F, Hunter D, Krieger C, Silverman MA, Bamji SX. Activity-dependent secretion of progranulin from synapses. J Cell Sci 2013; 126:5412-21. [DOI: 10.1242/jcs.132076] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The secreted growth factor progranulin (PGRN) has been shown to be important for regulating neuronal survival and outgrowth, as well as synapse formation and function. Mutations in the PGRN gene that result in PGRN haploinsufficiency have been identified as a major cause of frontotemporal dementia (FTD). Here we demonstrate that PGRN is colocalized with dense-core vesicle markers and is co-transported with brain-derived neurotrophic factor (BDNF) within axons and dendrites of cultured hippocampal neurons in both anterograde and retrograde directions. We also show that PGRN is secreted in an activity-dependent manner from synaptic and extrasynaptic sites, and that the temporal profiles of secretion are distinct in axons and dendrites. Neuronal activity is also shown to increase the recruitment of PGRN to synapses and to enhance the density of PGRN clusters along axons. Finally, treatment of neurons with recombinant PGRN is shown to increase synapse density, while decreasing the size of the presynaptic compartment and specifically the number of synaptic vesicles per synapse. Together, this indicates that activity-dependent secretion of PGRN can regulate synapse number and structure.
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Crish SD, Dapper JD, MacNamee SE, Balaram P, Sidorova TN, Lambert WS, Calkins DJ. Failure of axonal transport induces a spatially coincident increase in astrocyte BDNF prior to synapse loss in a central target. Neuroscience 2012; 229:55-70. [PMID: 23159315 DOI: 10.1016/j.neuroscience.2012.10.069] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 10/04/2012] [Accepted: 10/24/2012] [Indexed: 01/07/2023]
Abstract
Failure of anterograde transport to distal targets in the brain is a common feature of neurodegenerative diseases. We have demonstrated in rodent models of glaucoma, the most common optic neuropathy, early loss of anterograde transport along the retinal ganglion cell (RGC) projection to the superior colliculus (SC) is retinotopic and followed by a period of persistence of RGC axon terminals and synapses through unknown molecular pathways. Here we use the DBA/2J mouse model of hereditary glaucoma and an acute rat model to demonstrate that retinotopically focal transport deficits in the SC are accompanied by a spatially coincident increase in brain-derived neurotrophic factor (BDNF), especially in hypertrophic astrocytes. These neurochemical changes occur prior to loss of RGC synapses in the DBA/2J SC. In contrast to BDNF protein, levels of Bdnf mRNA decreased with transport failure, even as mRNA encoding synaptic structures remained unchanged. In situ hybridization signal for Bdnf mRNA was the strongest in SC neurons, and labeling for the immature precursor pro-BDNF was very limited. Subcellular fractionation of SC indicated that membrane-bound BDNF decreased with age in the DBA/2J, while BDNF released from vesicles remained high. These results suggest that in response to diminished axonal function, activated astrocytes in the brain may sequester mature BDNF released from target neurons to counter stressors that otherwise would challenge survival of projection synapses.
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Affiliation(s)
- S D Crish
- The Vanderbilt Eye Institute, Vanderbilt University Medical Center, 11425 Langford Medical Research Building IV, 2213 Garland Avenue, Nashville, TN 37232, USA.
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