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Konietzny A, Wegmann S, Mikhaylova M. The endoplasmic reticulum puts a new spin on synaptic tagging. Trends Neurosci 2023; 46:32-44. [PMID: 36428191 DOI: 10.1016/j.tins.2022.10.012] [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: 08/18/2022] [Revised: 10/12/2022] [Accepted: 10/31/2022] [Indexed: 11/23/2022]
Abstract
The heterogeneity of the endoplasmic reticulum (ER) makes it a versatile platform for a broad range of homeostatic processes, ranging from calcium regulation to synthesis and trafficking of proteins and lipids. It is not surprising that neurons use this organelle to fine-tune synaptic properties and thereby provide specificity to synaptic inputs. In this review, we discuss the mechanisms that enable activity-dependent ER recruitment into dendritic spines, with a focus on molecular mechanisms that mediate transport and retention of the ER in spines. The role of calcium signaling in spine ER, synaptopodin 'tagging' of active synapses, and the formation of the spine apparatus (SA) are highlighted. Finally, we discuss the role of liquid-liquid phase separation as a possible driving force in these processes.
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Affiliation(s)
- Anja Konietzny
- AG Optobiology, Institute of Biology, Humboldt Universität zu Berlin, Berlin, Germany; Guest Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Susanne Wegmann
- German Center for Neurodegenerative Diseases (DZNE), Berlin, Germany
| | - Marina Mikhaylova
- AG Optobiology, Institute of Biology, Humboldt Universität zu Berlin, Berlin, Germany; Guest Group 'Neuronal Protein Transport', Center for Molecular Neurobiology, ZMNH, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
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2
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Dubes S, Soula A, Benquet S, Tessier B, Poujol C, Favereaux A, Thoumine O, Letellier M. miR
‐124‐dependent tagging of synapses by synaptopodin enables input‐specific homeostatic plasticity. EMBO J 2022; 41:e109012. [PMID: 35875872 PMCID: PMC9574720 DOI: 10.15252/embj.2021109012] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 06/11/2022] [Accepted: 06/27/2022] [Indexed: 12/26/2022] Open
Abstract
Homeostatic synaptic plasticity is a process by which neurons adjust their synaptic strength to compensate for perturbations in neuronal activity. Whether the highly diverse synapses on a neuron respond uniformly to the same perturbation remains unclear. Moreover, the molecular determinants that underlie synapse‐specific homeostatic synaptic plasticity are unknown. Here, we report a synaptic tagging mechanism in which the ability of individual synapses to increase their strength in response to activity deprivation depends on the local expression of the spine‐apparatus protein synaptopodin under the regulation of miR‐124. Using genetic manipulations to alter synaptopodin expression or regulation by miR‐124, we show that synaptopodin behaves as a “postsynaptic tag” whose translation is derepressed in a subpopulation of synapses and allows for nonuniform homeostatic strengthening and synaptic AMPA receptor stabilization. By genetically silencing individual connections in pairs of neurons, we demonstrate that this process operates in an input‐specific manner. Overall, our study shifts the current view that homeostatic synaptic plasticity affects all synapses uniformly to a more complex paradigm where the ability of individual synapses to undergo homeostatic changes depends on their own functional and biochemical state.
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Affiliation(s)
- Sandra Dubes
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
| | - Anaïs Soula
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
| | - Sébastien Benquet
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
| | - Béatrice Tessier
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
| | - Christel Poujol
- University of Bordeaux CNRS INSERM Bordeaux Imaging Center BIC UMS 3420, US 4 Bordeaux France
| | - Alexandre Favereaux
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
| | - Olivier Thoumine
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
| | - Mathieu Letellier
- University of Bordeaux CNRS Interdisciplinary Institute for Neuroscience UMR 5297 Bordeaux France
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3
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Gobbo F, Cattaneo A. Neuronal Activity at Synapse Resolution: Reporters and Effectors for Synaptic Neuroscience. Front Mol Neurosci 2020; 13:572312. [PMID: 33192296 PMCID: PMC7609880 DOI: 10.3389/fnmol.2020.572312] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Accepted: 08/31/2020] [Indexed: 12/15/2022] Open
Abstract
The development of methods for the activity-dependent tagging of neurons enabled a new way to tackle the problem of engram identification at the cellular level, giving rise to groundbreaking findings in the field of memory studies. However, the resolution of activity-dependent tagging remains limited to the whole-cell level. Notably, events taking place at the synapse level play a critical role in the establishment of new memories, and strong experimental evidence shows that learning and synaptic plasticity are tightly linked. Here, we provide a comprehensive review of the currently available techniques that enable to identify and track the neuronal activity with synaptic spatial resolution. We also present recent technologies that allow to selectively interfere with specific subsets of synapses. Lastly, we discuss how these technologies can be applied to the study of learning and memory.
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Affiliation(s)
- Francesco Gobbo
- Bio@SNS Laboratory of Biology, Scuola Normale Superiore, Pisa, Italy
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Antonino Cattaneo
- Bio@SNS Laboratory of Biology, Scuola Normale Superiore, Pisa, Italy
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Ostroff LE, Watson DJ, Cao G, Parker PH, Smith H, Harris KM. Shifting patterns of polyribosome accumulation at synapses over the course of hippocampal long-term potentiation. Hippocampus 2018; 28:416-430. [PMID: 29575288 DOI: 10.1002/hipo.22841] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 02/28/2018] [Accepted: 03/11/2018] [Indexed: 11/09/2022]
Abstract
Hippocampal long-term potentiation (LTP) is a cellular memory mechanism. For LTP to endure, new protein synthesis is required immediately after induction and some of these proteins must be delivered to specific, presumably potentiated, synapses. Local synthesis in dendrites could rapidly provide new proteins to synapses, but the spatial distribution of translation following induction of LTP is not known. Here, we quantified polyribosomes, the sites of local protein synthesis, in CA1 stratum radiatum dendrites and spines from postnatal day 15 rats. Hippocampal slices were rapidly fixed at 5, 30, or 120 min after LTP induction by theta-burst stimulation (TBS). Dendrites were reconstructed through serial section electron microscopy from comparable regions near the TBS or control electrodes in the same slice, and in unstimulated hippocampus that was perfusion-fixed in vivo. At 5 min after induction of LTP, polyribosomes were elevated in dendritic shafts and spines, especially near spine bases and in spine heads. At 30 min, polyribosomes remained elevated only in spine bases. At 120 min, both spine bases and spine necks had elevated polyribosomes. Polyribosomes accumulated in spines with larger synapses at 5 and 30 min, but not at 120 min. Small spines, meanwhile, proliferated dramatically by 120 min, but these largely lacked polyribosomes. The number of ribosomes per polyribosome is variable and may reflect differences in translation regulation. In dendritic spines, but not shafts, there were fewer ribosomes per polyribosome in the slice conditions relative to in vivo, but this recovered transiently in the 5 min LTP condition. Overall, our data show that LTP induces a rapid, transient upregulation of large polyribosomes in larger spines, and a persistent upregulation of small polyribosomes in the bases and necks of small spines. This is consistent with local translation supporting enlargement of potentiated synapses within minutes of LTP induction.
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Affiliation(s)
- Linnaea E Ostroff
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269
| | - Deborah J Watson
- Department of Neuroscience, Center for Learning and Memory, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78731
| | - Guan Cao
- Department of Neuroscience, Center for Learning and Memory, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78731
| | - Patrick H Parker
- Department of Neuroscience, Center for Learning and Memory, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78731
| | - Heather Smith
- Department of Neuroscience, Center for Learning and Memory, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78731
| | - Kristen M Harris
- Department of Neuroscience, Center for Learning and Memory, Institute for Neuroscience, University of Texas at Austin, Austin, Texas 78731
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Pastuzyn ED, Day CE, Kearns RB, Kyrke-Smith M, Taibi AV, McCormick J, Yoder N, Belnap DM, Erlendsson S, Morado DR, Briggs JAG, Feschotte C, Shepherd JD. The Neuronal Gene Arc Encodes a Repurposed Retrotransposon Gag Protein that Mediates Intercellular RNA Transfer. Cell 2018; 172:275-288.e18. [PMID: 29328916 PMCID: PMC5884693 DOI: 10.1016/j.cell.2017.12.024] [Citation(s) in RCA: 286] [Impact Index Per Article: 47.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 08/15/2017] [Accepted: 12/18/2017] [Indexed: 12/25/2022]
Abstract
The neuronal gene Arc is essential for long-lasting information storage in the mammalian brain, mediates various forms of synaptic plasticity, and has been implicated in neurodevelopmental disorders. However, little is known about Arc's molecular function and evolutionary origins. Here, we show that Arc self-assembles into virus-like capsids that encapsulate RNA. Endogenous Arc protein is released from neurons in extracellular vesicles that mediate the transfer of Arc mRNA into new target cells, where it can undergo activity-dependent translation. Purified Arc capsids are endocytosed and are able to transfer Arc mRNA into the cytoplasm of neurons. These results show that Arc exhibits similar molecular properties to retroviral Gag proteins. Evolutionary analysis indicates that Arc is derived from a vertebrate lineage of Ty3/gypsy retrotransposons, which are also ancestors to retroviruses. These findings suggest that Gag retroelements have been repurposed during evolution to mediate intercellular communication in the nervous system.
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Affiliation(s)
- Elissa D Pastuzyn
- Department of Neurobiology and Anatomy, The University of Utah, Salt Lake City, UT, USA
| | - Cameron E Day
- Department of Neurobiology and Anatomy, The University of Utah, Salt Lake City, UT, USA
| | - Rachel B Kearns
- Department of Neurobiology and Anatomy, The University of Utah, Salt Lake City, UT, USA
| | - Madeleine Kyrke-Smith
- Department of Neurobiology and Anatomy, The University of Utah, Salt Lake City, UT, USA
| | - Andrew V Taibi
- Department of Neurobiology and Anatomy, The University of Utah, Salt Lake City, UT, USA
| | - John McCormick
- Department of Human Genetics, The University of Utah, Salt Lake City, UT, USA
| | - Nathan Yoder
- Department of Neurobiology and Anatomy, The University of Utah, Salt Lake City, UT, USA
| | - David M Belnap
- Department of Biochemistry, The University of Utah, Salt Lake City, UT, USA; Department of Biology, The University of Utah, Salt Lake City, UT, USA
| | - Simon Erlendsson
- Department of Biology, University of Copenhagen, Copenhagen, Denmark; MRC Laboratory of Molecular Biology, Cambridge, UK
| | | | | | - Cédric Feschotte
- Department of Human Genetics, The University of Utah, Salt Lake City, UT, USA
| | - Jason D Shepherd
- Department of Neurobiology and Anatomy, The University of Utah, Salt Lake City, UT, USA; Department of Biochemistry, The University of Utah, Salt Lake City, UT, USA.
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