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  1. Article: Neuronal mTOR Outposts: Implications for Translation, Signaling, and Plasticity.

    Altas, Bekir / Romanowski, Andrea J / Bunce, Garrett W / Poulopoulos, Alexandros

    Frontiers in cellular neuroscience

    2022  Volume 16, Page(s) 853634

    Abstract: The kinase mTOR is a signaling hub for pathways that regulate cellular growth. In neurons, the subcellular localization of mTOR takes on increased significance. Here, we review findings on the localization of mTOR in axons and offer a perspective on how ... ...

    Abstract The kinase mTOR is a signaling hub for pathways that regulate cellular growth. In neurons, the subcellular localization of mTOR takes on increased significance. Here, we review findings on the localization of mTOR in axons and offer a perspective on how these may impact our understanding of nervous system development, function, and disease. We propose a model where mTOR accumulates in local foci we term mTOR outposts, which can be found in processes distant from a neuron's cell body. In this model, pathways that funnel through mTOR are gated by local outposts to spatially select and amplify local signaling. The presence or absence of mTOR outposts in a segment of axon or dendrite may determine whether regional mTOR-dependent signals, such as nutrient and growth factor signaling, register toward neuron-wide responses. In this perspective, we present the emerging evidence for mTOR outposts in neurons, their putative roles as spatial gatekeepers of signaling inputs, and the implications of the mTOR outpost model for neuronal protein synthesis, signal transduction, and synaptic plasticity.
    Language English
    Publishing date 2022-04-07
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2452963-1
    ISSN 1662-5102
    ISSN 1662-5102
    DOI 10.3389/fncel.2022.853634
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Biochemical Purification of Binding Partners of Synaptic Scaffold Proteins.

    Altas, Bekir / Jahn, Olaf / Kawabe, Hiroshi

    Methods in molecular biology (Clifton, N.J.)

    2017  Volume 1538, Page(s) 69–82

    Abstract: The chemical synapse displays specialized intercellular adhesion between pre- and potsynaptic plasma membranes mediated by synaptic cell adhesion proteins. In this asymmetric cell adhesion, pre- and postsynapses have their own unique functions; the ... ...

    Abstract The chemical synapse displays specialized intercellular adhesion between pre- and potsynaptic plasma membranes mediated by synaptic cell adhesion proteins. In this asymmetric cell adhesion, pre- and postsynapses have their own unique functions; the presynaptic terminal releases neurotransmitter, which diffuses through the synaptic cleft and is received by receptors accumulated at the postsynapse. Such distinct modes of actions of pre- and postsynapses in synaptic neurotransmission are the rate-limiting factors in signal processing in the brain, and thus protein-protein interactions within the pre- and postsynaptic scaffold are of particular importance for brain function by regulating the pre- and postsynaptic function. In the present paper, we outline a method to screen for binding partners of synaptic scaffold proteins biochemically.
    Language English
    Publishing date 2017
    Publishing country United States
    Document type Journal Article
    ISSN 1940-6029
    ISSN (online) 1940-6029
    DOI 10.1007/978-1-4939-6688-2_6
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Enhancing Precision and Efficiency of Cas9-Mediated Knockin Through Combinatorial Fusions of DNA Repair Proteins.

    Richardson, Ryan R / Steyert, Marilyn / Khim, Saovleak N / Crutcher, Garrett W / Brandenburg, Cheryl / Robertson, Colin D / Romanowski, Andrea J / Inen, Jeffrey / Altas, Bekir / Poulopoulos, Alexandros

    The CRISPR journal

    2023  Volume 6, Issue 5, Page(s) 447–461

    Abstract: Cas9 targets genomic loci with high specificity. For knockin with double-strand break repair, however, Cas9 often leads to unintended on-target knockout rather than intended edits. This imprecision is a barrier for ... ...

    Abstract Cas9 targets genomic loci with high specificity. For knockin with double-strand break repair, however, Cas9 often leads to unintended on-target knockout rather than intended edits. This imprecision is a barrier for direct
    MeSH term(s) Animals ; Mice ; CRISPR-Cas Systems/genetics ; Gene Editing ; CRISPR-Associated Protein 9/genetics ; DNA Repair/genetics ; DNA Breaks, Double-Stranded
    Chemical Substances CRISPR-Associated Protein 9 (EC 3.1.-)
    Language English
    Publishing date 2023-09-15
    Publishing country United States
    Document type Journal Article
    ZDB-ID 3017891-5
    ISSN 2573-1602 ; 2573-1599
    ISSN (online) 2573-1602
    ISSN 2573-1599
    DOI 10.1089/crispr.2023.0036
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Ultrastructural Correlates of Presynaptic Functional Heterogeneity in Hippocampal Synapses.

    Maus, Lydia / Lee, ChoongKu / Altas, Bekir / Sertel, Sinem M / Weyand, Kirsten / Rizzoli, Silvio O / Rhee, JeongSeop / Brose, Nils / Imig, Cordelia / Cooper, Benjamin H

    Cell reports

    2020  Volume 30, Issue 11, Page(s) 3632–3643.e8

    Abstract: Although similar in molecular composition, synapses can exhibit strikingly distinct functional transmitter release and plasticity characteristics. To determine whether ultrastructural differences co-define this functional heterogeneity, we combine ... ...

    Abstract Although similar in molecular composition, synapses can exhibit strikingly distinct functional transmitter release and plasticity characteristics. To determine whether ultrastructural differences co-define this functional heterogeneity, we combine hippocampal organotypic slice cultures, high-pressure freezing, freeze substitution, and 3D-electron tomography to compare two functionally distinct synapses: hippocampal Schaffer collateral and mossy fiber synapses. We find that mossy fiber synapses, which exhibit a lower release probability and stronger short-term facilitation than Schaffer collateral synapses, harbor lower numbers of docked synaptic vesicles at active zones and a second pool of possibly tethered vesicles in their vicinity. Our data indicate that differences in the ratio of docked versus tethered vesicles at active zones contribute to distinct functional characteristics of synapses.
    MeSH term(s) Animals ; Cyclic AMP/metabolism ; Excitatory Postsynaptic Potentials ; Hippocampus/physiology ; Hippocampus/ultrastructure ; Mice, Inbred C57BL ; Mice, Knockout ; Mossy Fibers, Hippocampal/physiology ; Mossy Fibers, Hippocampal/ultrastructure ; Neurotransmitter Agents/metabolism ; Organ Culture Techniques ; Presynaptic Terminals/physiology ; Presynaptic Terminals/ultrastructure ; Secretory Vesicles/physiology ; Secretory Vesicles/ultrastructure ; Synapses/physiology ; Synapses/ultrastructure ; Synaptic Vesicles/ultrastructure ; Tissue Fixation
    Chemical Substances Neurotransmitter Agents ; Cyclic AMP (E0399OZS9N)
    Language English
    Publishing date 2020-04-12
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2649101-1
    ISSN 2211-1247 ; 2211-1247
    ISSN (online) 2211-1247
    ISSN 2211-1247
    DOI 10.1016/j.celrep.2020.02.083
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Nedd4-2-dependent regulation of astrocytic Kir4.1 and Connexin43 controls neuronal network activity.

    Altas, Bekir / Rhee, Hong-Jun / Ju, Anes / Solís, Hugo Cruces / Karaca, Samir / Winchenbach, Jan / Kaplan-Arabaci, Oykum / Schwark, Manuela / Ambrozkiewicz, Mateusz C / Lee, ChungKu / Spieth, Lena / Wieser, Georg L / Chaugule, Viduth K / Majoul, Irina / Hassan, Mohamed A / Goel, Rashi / Wojcik, Sonja M / Koganezawa, Noriko / Hanamura, Kenji /
    Rotin, Daniela / Pichler, Andrea / Mitkovski, Miso / de Hoz, Livia / Poulopoulos, Alexandros / Urlaub, Henning / Jahn, Olaf / Saher, Gesine / Brose, Nils / Rhee, JeongSeop / Kawabe, Hiroshi

    The Journal of cell biology

    2023  Volume 223, Issue 1

    Abstract: Nedd4-2 is an E3 ubiquitin ligase in which missense mutation is related to familial epilepsy, indicating its critical role in regulating neuronal network activity. However, Nedd4-2 substrates involved in neuronal network function have yet to be ... ...

    Abstract Nedd4-2 is an E3 ubiquitin ligase in which missense mutation is related to familial epilepsy, indicating its critical role in regulating neuronal network activity. However, Nedd4-2 substrates involved in neuronal network function have yet to be identified. Using mouse lines lacking Nedd4-1 and Nedd4-2, we identified astrocytic channel proteins inwardly rectifying K+ channel 4.1 (Kir4.1) and Connexin43 as Nedd4-2 substrates. We found that the expression of Kir4.1 and Connexin43 is increased upon conditional deletion of Nedd4-2 in astrocytes, leading to an elevation of astrocytic membrane ion permeability and gap junction activity, with a consequent reduction of γ-oscillatory neuronal network activity. Interestingly, our biochemical data demonstrate that missense mutations found in familial epileptic patients produce gain-of-function of the Nedd4-2 gene product. Our data reveal a process of coordinated astrocytic ion channel proteostasis that controls astrocyte function and astrocyte-dependent neuronal network activity and elucidate a potential mechanism by which aberrant Nedd4-2 function leads to epilepsy.
    MeSH term(s) Animals ; Humans ; Mice ; Astrocytes ; Cell Membrane Permeability ; Connexin 43/genetics ; Mutation, Missense ; Proteostasis ; Potassium Channels, Inwardly Rectifying/genetics ; Nedd4 Ubiquitin Protein Ligases/genetics ; Epilepsy
    Chemical Substances Connexin 43 ; Kcnj10 (channel) ; GJA1 protein, mouse ; Nedd4 protein, mouse (EC 2.3.2.26) ; Potassium Channels, Inwardly Rectifying ; Nedd4 Ubiquitin Protein Ligases (EC 2.3.2.26)
    Language English
    Publishing date 2023-11-30
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 218154-x
    ISSN 1540-8140 ; 0021-9525
    ISSN (online) 1540-8140
    ISSN 0021-9525
    DOI 10.1083/jcb.201902050
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Region-Specific Phosphorylation Determines Neuroligin-3 Localization to Excitatory Versus Inhibitory Synapses.

    Altas, Bekir / Tuffy, Liam P / Patrizi, Annarita / Dimova, Kalina / Soykan, Tolga / Brandenburg, Cheryl / Romanowski, Andrea J / Whitten, Julia R / Robertson, Colin D / Khim, Saovleak N / Crutcher, Garrett W / Ambrozkiewicz, Mateusz C / Yagensky, Oleksandr / Krueger-Burg, Dilja / Hammer, Matthieu / Hsiao, He-Hsuan / Laskowski, Pawel R / Dyck, Lydia / Puche, Adam C /
    Sassoè-Pognetto, Marco / Chua, John J E / Urlaub, Henning / Jahn, Olaf / Brose, Nils / Poulopoulos, Alexandros

    Biological psychiatry

    2023  

    Abstract: Background: Neuroligin-3 is a postsynaptic adhesion molecule involved in synapse development and function. It is implicated in rare, monogenic forms of autism, and its shedding is critical to the tumor microenvironment of gliomas. While other members of ...

    Abstract Background: Neuroligin-3 is a postsynaptic adhesion molecule involved in synapse development and function. It is implicated in rare, monogenic forms of autism, and its shedding is critical to the tumor microenvironment of gliomas. While other members of the neuroligin family exhibit synapse-type specificity in localization and function through distinct interactions with postsynaptic scaffold proteins, the specificity of neuroligin-3 synaptic localization remains largely unknown.
    Methods: We investigated the synaptic localization of neuroligin-3 across regions in mouse and human brain samples after validating antibody specificity in knockout animals. We raised a phospho-specific neuroligin antibody and used phosphoproteomics, cell-based assays, and in utero CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/Cas9) knockout and gene replacement to identify mechanisms that regulate neuroligin-3 localization to distinct synapse types.
    Results: Neuroligin-3 exhibits region-dependent synapse specificity, largely localizing to excitatory synapses in cortical regions and inhibitory synapses in subcortical regions of the brain in both mice and humans. We identified specific phosphorylation of cortical neuroligin-3 at a key binding site for recruitment to inhibitory synapses, while subcortical neuroligin-3 remained unphosphorylated. In vitro, phosphomimetic mutation of that site disrupted neuroligin-3 association with the inhibitory postsynaptic scaffolding protein gephyrin. In vivo, phosphomimetic mutants of neuroligin-3 localized to excitatory postsynapses, while phospho-null mutants localized to inhibitory postsynapses.
    Conclusions: These data reveal an unexpected region-specific pattern of neuroligin-3 synapse specificity, as well as a phosphorylation-dependent mechanism that regulates its recruitment to either excitatory or inhibitory synapses. These findings add to our understanding of how neuroligin-3 is involved in conditions that may affect the balance of excitation and inhibition.
    Language English
    Publishing date 2023-12-27
    Publishing country United States
    Document type Journal Article
    ZDB-ID 209434-4
    ISSN 1873-2402 ; 0006-3223
    ISSN (online) 1873-2402
    ISSN 0006-3223
    DOI 10.1016/j.biopsych.2023.12.020
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  7. Article ; Online: Formation and Maintenance of Functional Spines in the Absence of Presynaptic Glutamate Release.

    Sigler, Albrecht / Oh, Won Chan / Imig, Cordelia / Altas, Bekir / Kawabe, Hiroshi / Cooper, Benjamin H / Kwon, Hyung-Bae / Rhee, Jeong-Seop / Brose, Nils

    Neuron

    2017  Volume 94, Issue 2, Page(s) 304–311.e4

    Abstract: Dendritic spines are the major transmitter reception compartments of glutamatergic synapses in most principal neurons of the mammalian brain and play a key role in the function of nerve cell circuits. The formation of functional spine synapses is thought ...

    Abstract Dendritic spines are the major transmitter reception compartments of glutamatergic synapses in most principal neurons of the mammalian brain and play a key role in the function of nerve cell circuits. The formation of functional spine synapses is thought to be critically dependent on presynaptic glutamatergic signaling. By analyzing CA1 pyramidal neurons in mutant hippocampal slice cultures that are essentially devoid of presynaptic transmitter release, we demonstrate that the formation and maintenance of dendrites and functional spines are independent of synaptic glutamate release.
    MeSH term(s) Animals ; Calcium/metabolism ; Dendrites/metabolism ; Dendritic Spines/metabolism ; Glutamic Acid/metabolism ; Hippocampus/metabolism ; Mice ; Signal Transduction/physiology ; Synapses/metabolism ; Synapses/physiology
    Chemical Substances Glutamic Acid (3KX376GY7L) ; Calcium (SY7Q814VUP)
    Language English
    Publishing date 2017-04-19
    Publishing country United States
    Document type Journal Article
    ZDB-ID 808167-0
    ISSN 1097-4199 ; 0896-6273
    ISSN (online) 1097-4199
    ISSN 0896-6273
    DOI 10.1016/j.neuron.2017.03.029
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  8. Book ; Online ; Thesis: Roles of the Nedd4 Family E3 Ligases in Glial Function and Nerve Cell Development

    Altas, Bekir [Verfasser] / Brose, Nils [Akademischer Betreuer] / Stegmüller, Judith [Gutachter] / Goerlich, Dirk [Gutachter]

    2017  

    Author's details Bekir Altas ; Gutachter: Judith Stegmüller, Dirk Goerlich ; Betreuer: Nils Brose
    Keywords Biowissenschaften, Biologie ; Life Science, Biology
    Subject code sg570
    Language English
    Publisher Niedersächsische Staats- und Universitätsbibliothek Göttingen
    Publishing place Göttingen
    Document type Book ; Online ; Thesis
    Database Digital theses on the web

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  9. Article: BDNF enhances spontaneous and activity-dependent neurotransmitter release at excitatory terminals but not at inhibitory terminals in hippocampal neurons.

    Shinoda, Yo / Ahmed, Saheeb / Ramachandran, Binu / Bharat, Vinita / Brockelt, David / Altas, Bekir / Dean, Camin

    Frontiers in synaptic neuroscience

    2014  Volume 6, Page(s) 27

    Abstract: Brain-derived neurotrophic factor (BDNF) is widely reported to enhance synaptic vesicle (SV) exocytosis and neurotransmitter release. But it is still unclear whether BDNF enhances SV recycling at excitatory terminals only, or at both excitatory and ... ...

    Abstract Brain-derived neurotrophic factor (BDNF) is widely reported to enhance synaptic vesicle (SV) exocytosis and neurotransmitter release. But it is still unclear whether BDNF enhances SV recycling at excitatory terminals only, or at both excitatory and inhibitory terminals. In the present study, in a direct comparison using cultured rat hippocampal neurons, we demonstrate that BDNF enhances both spontaneous and activity-dependent neurotransmitter release from excitatory terminals, but not from inhibitory terminals. BDNF treatment for 5 min or 48 h increased both spontaneous and activity-induced anti-synaptotagmin1 (SYT1) antibody uptake at excitatory terminals marked with vGluT1. Conversely, BDNF treatment did not enhance spontaneous or activity-induced uptake of anti-SYT1 antibodies in inhibitory terminals marked with vGAT. Time-lapse imaging of FM1-43 dye destaining in excitatory and inhibitory terminals visualized by post-hoc immunostaining of vGluT1 and vGAT also showed the same result: The rate of spontaneous and activity-induced destaining was increased by BDNF at excitatory synapses, but not at inhibitory synapses. These data demonstrate that BDNF enhances SV exocytosis in excitatory but not inhibitory terminals. Moreover, BDNF enhanced evoked SV exocytosis, even if vesicles were loaded under spontaneous vesicle recycling conditions. Thus, BDNF enhances both spontaneous and activity-dependent neurotransmitter release on both short and long time-scales, by the same mechanism.
    Language English
    Publishing date 2014-11-10
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2592086-8
    ISSN 1663-3563
    ISSN 1663-3563
    DOI 10.3389/fnsyn.2014.00027
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: The murine ortholog of Kaufman oculocerebrofacial syndrome protein Ube3b regulates synapse number by ubiquitinating Ppp3cc.

    Ambrozkiewicz, Mateusz C / Borisova, Ekaterina / Schwark, Manuela / Ripamonti, Silvia / Schaub, Theres / Smorodchenko, Alina / Weber, A Ioana / Rhee, Hong Jun / Altas, Bekir / Yilmaz, Rüstem / Mueller, Susanne / Piepkorn, Lars / Horan, Stephen T / Straussberg, Rachel / Zaqout, Sami / Jahn, Olaf / Dere, Ekrem / Rosário, Marta / Boehm-Sturm, Philipp /
    Borck, Guntram / Willig, Katrin I / Rhee, JeongSeop / Tarabykin, Victor / Kawabe, Hiroshi

    Molecular psychiatry

    2020  Volume 26, Issue 6, Page(s) 1980–1995

    Abstract: Kaufman oculocerebrofacial syndrome (KOS) is a severe autosomal recessive disorder characterized by intellectual disability, developmental delays, microcephaly, and characteristic dysmorphisms. Biallelic mutations of UBE3B, encoding for a ubiquitin ... ...

    Abstract Kaufman oculocerebrofacial syndrome (KOS) is a severe autosomal recessive disorder characterized by intellectual disability, developmental delays, microcephaly, and characteristic dysmorphisms. Biallelic mutations of UBE3B, encoding for a ubiquitin ligase E3B are causative for KOS. In this report, we characterize neuronal functions of its murine ortholog Ube3b and show that Ube3b regulates dendritic branching in a cell-autonomous manner. Moreover, Ube3b knockout (KO) neurons exhibit increased density and aberrant morphology of dendritic spines, altered synaptic physiology, and changes in hippocampal circuit activity. Dorsal forebrain-specific Ube3b KO animals show impaired spatial learning, altered social interactions, and repetitive behaviors. We further demonstrate that Ube3b ubiquitinates the catalytic γ-subunit of calcineurin, Ppp3cc, the overexpression of which phenocopies Ube3b loss with regard to dendritic spine density. This work provides insights into the molecular pathologies underlying intellectual disability-like phenotypes in a genetically engineered mouse model.
    MeSH term(s) Animals ; Calcineurin ; Dendritic Spines ; Eye Abnormalities ; Facies ; Intellectual Disability/genetics ; Limb Deformities, Congenital ; Mice ; Mice, Knockout ; Microcephaly/genetics ; Mutation/genetics ; Synapses ; Ubiquitin-Protein Ligases/genetics
    Chemical Substances Ubiquitin-Protein Ligases (EC 2.3.2.27) ; Calcineurin (EC 3.1.3.16)
    Language English
    Publishing date 2020-04-06
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1330655-8
    ISSN 1476-5578 ; 1359-4184
    ISSN (online) 1476-5578
    ISSN 1359-4184
    DOI 10.1038/s41380-020-0714-8
    Database MEDical Literature Analysis and Retrieval System OnLINE

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