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Ringsevjen H, Egbenya DL, Bieler M, Davanger S, Hussain S. Activity-regulated cytoskeletal-associated protein (Arc) in presynaptic terminals and extracellular vesicles in hippocampal synapses. Front Mol Neurosci 2023; 16:1225533. [PMID: 38025262 PMCID: PMC10658193 DOI: 10.3389/fnmol.2023.1225533] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 10/06/2023] [Indexed: 12/01/2023] Open
Abstract
The activity-regulated cytoskeleton-associated protein (Arc/Arg3.1) is a neuron-specific immediate early gene (IEG) product. The protein regulates synaptic strength through modulation of spine density and morphology, AMPA receptor endocytosis, and as being part of a retrovirus-like inter-cellular communication mechanism. However, little is known about the detailed subsynaptic localization of the protein, and especially its possible presynaptic localization. In the present study, we provide novel electron microscopical data of Arc localization at hippocampal Schaffer collateral synapses in the CA1 region. The protein was found in both pre-and postsynaptic cytoplasm in a majority of synapses, associated with small vesicles. We also observed multivesicular body-like structures positive for Arc. Furthermore, the protein was located over the presynaptic active zone and the postsynaptic density. The relative concentration of Arc was 25% higher in the postsynaptic spine than in the presynaptic terminal. Notably, small extracellular vesicles labeled for Arc were detected in the synaptic cleft or close to the synapse, supporting a possible transsynaptic transmission of the protein in the brain.
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Affiliation(s)
- Håvard Ringsevjen
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Daniel Lawer Egbenya
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
- Department of Physiology, School of Medical Sciences, College of Health and Allied Sciences, University of Cape Coast, Cape Coast, Ghana
| | - Malte Bieler
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Svend Davanger
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Suleman Hussain
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
- Institute of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway
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SNARE protein VAMP-2, but not syntaxin-1, SNAP-25 and synaptotagmin 1, expressed in perisynaptic astrocytic processes in the CA1 area of the rat hippocampus. Neuroreport 2023; 34:75-80. [PMID: 36608162 DOI: 10.1097/wnr.0000000000001861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
OBJECTIVE Perisynaptic astrocytic processes have been suggested as sites for the regulated release of neuroactive substances. However, very little is known about the molecular properties of regulated exocytosis in these processes. Soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) proteins mediate synaptic vesicle exocytosis from neuronal cells and might be candidates for regulated exocytosis also from astrocytic processes. The expression of SNARE proteins in astrocytes, however, is not clarified. Thus, we aimed to investigate the localization and relative concentrations of neuronal SNARE proteins syntaxin-1, synaptosomal nerve-associated protein 25 (SNAP-25), vesicle-associated membrane protein 2 (VAMP-2) (synaptobrevin-2) and calcium sensor synaptotagmin 1 in perisynaptic astrocytic processes compared to nerve terminals and dendrites. METHODS We used quantitative immunogold electron microscopy of the rat hippocampus to investigate the localization and concentration of neuronal SNARE proteins. RESULTS As expected, analysis of the immunogold data revealed a lower labeling density of SNARE proteins in the perisynaptic astrocytic processes than in presynaptic terminals. The same was also true when compared to dendrites. Contrary to VAMP-2, labeling intensities for syntaxin-1, SNAP-25 and synaptotagmin 1 were not distinguishable from background labeling in the processes. The relative concentration of VAMP-2 stands out, as the mean perisynaptic astrocytic process concentration of the protein was only 68 % lower than in presynaptic terminals and still 32 % higher than in dendrites. VAMP-2 was associated with small vesicles in the processes. Some gold particles were located over the astrocytic plasma membrane. CONCLUSION VAMP-2 is expressed in perisynaptic astrocytic processes, with a concentration higher than in the dendrites. Our results are compatible with the role of VAMP-2 in exocytosis from perisynaptic astrocytic processes.
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Petralia RS, Wang YX. Review of Post-embedding Immunogold Methods for the Study of Neuronal Structures. Front Neuroanat 2021; 15:763427. [PMID: 34720893 PMCID: PMC8551803 DOI: 10.3389/fnana.2021.763427] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 09/28/2021] [Indexed: 01/03/2023] Open
Abstract
The post-embedding immunogold (PI) technique for immunolabeling of neuronal tissues utilizing standard thin-section transmission electron microscopy (TEM) continues to be a prime method for understanding the functional localization of key proteins in neuronal function. Its main advantages over other immunolabeling methods for thin-section TEM are (1) fairly accurate and quantifiable localization of proteins in cells; (2) double-labeling of sections using two gold particle sizes; and (3) the ability to perform multiple labeling for different proteins by using adjacent sections. Here we first review in detail a common method for PI of neuronal tissues. This method has two major parts. First, we describe the freeze-substitution embedding method: cryoprotected tissue is frozen in liquid propane via plunge-freezing, and is placed in a freeze-substitution instrument in which the tissue is embedded in Lowicryl at low temperatures. We highlight important aspects of freeze-substitution embedding. Then we outline how thin sections of embedded tissue on grids are labeled with a primary antibody and a secondary gold particle-conjugated antibody, and the particular problems encountered in TEM of PI-labeled sections. In the Discussion, we compare our method both to earlier PI methods and to more recent PI methods used by other laboratories. We also compare TEM immunolabeling using PI vs. various pre-embedding immunolabeling methods, especially relating to neuronal tissue.
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Affiliation(s)
- Ronald S. Petralia
- Advanced Imaging Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
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Lange F, Agüi-Gonzalez P, Riedel D, Phan NTN, Jakobs S, Rizzoli SO. Correlative fluorescence microscopy, transmission electron microscopy and secondary ion mass spectrometry (CLEM-SIMS) for cellular imaging. PLoS One 2021; 16:e0240768. [PMID: 33970908 PMCID: PMC8109779 DOI: 10.1371/journal.pone.0240768] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 04/13/2021] [Indexed: 11/24/2022] Open
Abstract
Electron microscopy (EM) has been employed for decades to analyze cell structure. To also analyze the positions and functions of specific proteins, one typically relies on immuno-EM or on a correlation with fluorescence microscopy, in the form of correlated light and electron microscopy (CLEM). Nevertheless, neither of these procedures is able to also address the isotopic composition of cells. To solve this, a correlation with secondary ion mass spectrometry (SIMS) would be necessary. SIMS has been correlated in the past to EM or to fluorescence microscopy in biological samples, but not to CLEM. We achieved this here, using a protocol based on transmission EM, conventional epifluorescence microscopy and nanoSIMS. The protocol is easily applied, and enables the use of all three technologies at high performance parameters. We suggest that CLEM-SIMS will provide substantial information that is currently beyond the scope of conventional correlative approaches.
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Affiliation(s)
- Felix Lange
- Research Group Mitochondrial Structure and Dynamics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- Clinic for Neurology, University Medical Center Göttingen, Göttingen, Germany
| | - Paola Agüi-Gonzalez
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Dietmar Riedel
- Laboratory of Electron Microscopy, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Nhu T. N. Phan
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Stefan Jakobs
- Research Group Mitochondrial Structure and Dynamics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- Clinic for Neurology, University Medical Center Göttingen, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
- * E-mail: (SJ); (SOR)
| | - Silvio O. Rizzoli
- Department of Neuro- and Sensory Physiology, University Medical Center Göttingen, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
- * E-mail: (SJ); (SOR)
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Kim HL, Riew TR, Park J, Lee Y, Kim IB. Correlative Light and Electron Microscopy Using Frozen Section Obtained Using Cryo-Ultramicrotomy. Int J Mol Sci 2021; 22:ijms22084273. [PMID: 33924132 PMCID: PMC8074315 DOI: 10.3390/ijms22084273] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 04/13/2021] [Accepted: 04/17/2021] [Indexed: 11/16/2022] Open
Abstract
Immuno-electron microscopy (Immuno-EM) is a powerful tool for identifying molecular targets with ultrastructural details in biological specimens. However, technical barriers, such as the loss of ultrastructural integrity, the decrease in antigenicity, or artifacts in the handling process, hinder the widespread use of the technique by biomedical researchers. We developed a method to overcome such challenges by combining light and electron microscopy with immunolabeling based on Tokuyasu's method. Using cryo-sectioned biological specimens, target proteins with excellent antigenicity were first immunolabeled for confocal analysis, and then the same tissue sections were further processed for electron microscopy, which provided a well-preserved ultrastructure comparable to that obtained using conventional electron microscopy. Moreover, this method does not require specifically designed correlative light and electron microscopy (CLEM) devices but rather employs conventional confocal and electron microscopes; therefore, it can be easily applied in many biomedical studies.
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Affiliation(s)
- Hong-Lim Kim
- Integrative Research Support Center, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea; (H.-L.K.); (J.P.); (Y.L.)
| | - Tae-Ryong Riew
- Department of Anatomy, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea;
| | - Jieun Park
- Integrative Research Support Center, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea; (H.-L.K.); (J.P.); (Y.L.)
| | - Youngchun Lee
- Integrative Research Support Center, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea; (H.-L.K.); (J.P.); (Y.L.)
| | - In-Beom Kim
- Integrative Research Support Center, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea; (H.-L.K.); (J.P.); (Y.L.)
- Department of Anatomy, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea;
- Catholic Neuroscience Institute, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Catholic Institute for Applied Anatomy, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
- Correspondence: ; Tel.: +82-2-2258-7263
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