The authors thank Dr. Mike Ehlers and his laboratory members for originally demonstrating the protocol for subcellular fractionation of synaptic plasma membranes. We also thank Wendy Horsfall for management of the mouse colonies. This work was supported by operating grants from CIHR (AJR and AS).

Das folgende Protokoll entspricht den Richtlinien des Canadian Council der Tierpflege und wurde von der Fakultät für Medizin und Pharmazie Animal Care Committee an der Universität von Toronto genehmigt worden. 1. Bereiten Sie benötigten Reagenzien, wie in Tabelle 1 beschrieben, <ol><li> Hinzufügen Protease und Phosphatase (falls erforderlich) Inhibitoren für alle Saccharoselösungen, Puffer und ddH 2 O, die in Tabelle 1 angegebenen Konzentrationen. Wichtig: Führen alle Schritte bei 4 ° C und vor-kühlen alle Reagenzien und Ausrüstung vor dem Start des Experiments. Kennzeichnen Sie alle Rohre, einschließlich Ultrazentrifuge Rohre, mit Permanentmarker. </li></ol> 2. Präparation der entsprechende Hirnregion <ol><li> Opfern das Tier durch Genickbruch oder Enthauptung. Haus und einschläfern Tiere in Einklang mit den institutionellen und Regierungspolitik auf die Tierpflege. </li><li> Schnell zu entfernen the Gehirn aus dem Schädel und Platz auf einer gekühlten Dissektion Block. </li><li> Präparieren Sie die entsprechende Hirnregion aus frischem Gewebe und fahren Sie mit Schritt 3 fort. </li></ol> 3. Gewebehomogenisierung mit Motor Driven Glas-Teflon-Homogenisator <ol><li> Zeigen 50-100 mg (für SPM) oder 100-200 mg (PSD) des sezierten Gewebe in einem markierten 13 ml Polypropylen-Röhrchen mit 4 ml 0,32 M HEPES-gepufferte Saccharose-Lösung. Übertragen Sie die Probe in ein 15 ml Glas-Kegel Teflon Gewebemühle / Homogenisator, stellen Sie den Motorantrieb bis 900 Umdrehungen pro Minute (Stufe 7) und homogenisieren die Probe mit 12 Schlägen über einen Zeitraum von 30 Sekunden. Verwenden Sie eine andere Glas-Teflon-Homogenisator zwischen den Proben, oder spülen Sie den Homogenisator mit kaltem destilliertem Wasser zwischen den Proben und wischen Sie mit einem trockenen Kimwipe. HINWEIS: Bis zu 4 g Gewebe kann in 4 ml 0,32 M HEPES-gepufferten Saccharoselösung homogenisiert werden jedoch ratsam, weniger Gewebe verwenden, um die richtige Fraktionierung gewährleisten, ist es. </li><li> Übertragen Sie die Probe homogenisiert zurück to die gleiche 13 ml Polypropylen-Röhrchen. Reserve 100 ul Homogenat und bei -80 ° C für die anschließende Proteinquantifizierung und Western-Blot-Analyse des Gesamtproteinfraktion. </li></ol> 4. Zentrifugation bei niedriger Geschwindigkeit, um die Kernfraktion entfernen (Renditen Überstand S1) <ol><li> Zentrifuge das Homogenat in einem Festwinkelrotor bei 900 × g für 10 min bei 4 ° C ist. Den Überstand (S1) zu einem neuen, markierten 13-ml-Röhrchen und resuspendieren Kernfraktion Pellet (P1) in 500 ul 0,32 M HEPES-gepufferter Saccharose. HINWEIS: Die (P1) Fraktion kann bei -80 ° C gelagert und für die Western-Blot-Analyse der Kernfraktion benutzt werden. </li></ol> 5. Anreicherung des Crude Synaptosomale Fraktion (Pellet Renditen P2) <ol><li> Zentrifugieren der Überstand (S1) bei 10.000 × g für 15 min bei 4 ° C ist. Entfernen Sie den Überstand (S2) und Reserve 500 ul in einem Mikrozentrifugenröhrchen bei -80 ° C für die spätere Protein Quant speichernkation und Western-Blot-Analyse der cytosolischen / Licht Membranfraktion. Resuspendieren verbleibende rohe synaptosomale Fraktion Pellet (P2) in 1 ml 0,32 M HEPES-gepufferter Saccharose-Lösung und dann einen weiteren 3 ml 0,32 M HEPES-gepufferter Saccharose-Lösung. </li><li> Zentrifuge bei 10.000 x g für 15 min bei 4 ° C ist. Den Überstand (S2) und Reserve 500 ul in einem Mikrozentrifugenröhrchen bei -80 ° C für die anschließende Proteinquantifizierung und Western-Blot-Analyse der cytosolischen / Licht Membranfraktion zu speichern. Speichern Sie die gewaschene rohe synaptosomale Pellet (P2 &#39;) in der Polypropylen-Röhrchen. </li></ol> 6. Lysing (Hypoosmotische Shock) der rohen Synaptosomale Fraktion <ol><li> Lyse der rohe synaptosomale Pellet (P2 &#39;) in Polypropylenröhrchen durch Resuspendieren in 1 ml ddH 2 O. Fügen Sie weitere 3 ml ddH2O, Transfer zu einem Glas-Teflon-Gewebe-Homogenisator und homogenisieren von Hand mit 3 Schlägen. HINWEIS: Es ist wichtig,diesen Schritt so schnell wie möglich durchzuführen und schnell gehen Sie zu Schritt 6.2. </li><li> Übertragungs Proben aus dem Homogenisator in denselben 13 ml Polypropylenröhrchen und schnell einstellen Probe wieder auf 4 mM HEPES mit 16 ul 1 M HEPES-Lösung zum Mischen umgekehrt. </li><li> Drehen Proben bei 4 ° C für 30 Minuten, um eine vollständige Lyse sicherzustellen. </li></ol> 7. Anreicherung des Synaptosomale Membranfraktion (P3) <ol><li> Zentrifuge bei 25.000 x g für 20 min bei 4 ° C ist. Entfernen des rohen vesikulären Fraktion Stand (S3) und behalten sie in einem 5-ml-Röhrchen bei -80 ° C für die anschließende Proteinquantifizierung und Western-Blot-Analyse zu speichern. Resuspendieren synaptosomalen Membranfraktion (P3) in 1 ml 0,32 M HEPES-gepufferter Saccharose-Lösung. </li></ol> 8. Vorbereitung der diskontinuierlichen Saccharosegradienten <ol><li> Pipette genau 3,5 ml 1,2 M HEPES-gepufferter Saccharose-Lösung und exakt 3,0 ml von 1,0 M und 0,8 M HEPES-gepufferte Saccharose-Lösung in separate 6 ml Snap Cap Röhren. ANMERKUNG: Dies geschieht vor Messung der Volumina der Puffer, die verwendet werden, um den Saccharose-Gradienten bilden. Genaue Messung der Volumina ist wichtig, um sicherzustellen, dass die resultierenden Verläufe für Ultrazentrifugation ausgeglichen werden. </li><li> Mit einer Glaspasteurpipette und Birne, übertragen 1.2 M HEPES-gepufferten Saccharoselösung zu den 12 ml Polyallomer Ultrazentrifugenröhrchen. Schicht sorgfältig die 1,0 M HEPES-gepufferter Saccharose-Lösung auf der Oberseite der 1,2 M HEPES-gepufferter Saccharose-Lösung. Schließlich Schicht das 0,8 M HEPES-gepufferter Saccharose-Lösung auf der Oberseite der 1,0 M HEPES-gepufferter Saccharose-Lösung. Verwenden Sie eine frische Pasteur-Pipette für jedes Saccharose-Lösung und kümmern uns nicht um die Saccharose-Gradienten zu stören. Vibrationen von einer Bank oder Mikrowirbel wird die Integrität des Gradienten zu stören. </li><li> Verwendung einer Pasteur-Pipette resuspendiert Schicht die synaptosomale Membranfraktion (P3) auf der Oberseite des vorbereiteten diskontinuierlichen Saccharosegradienten.Stellen Sie sicher, dass die Gradienten durch Wiegen sie in den Eimer des Schwingbecherrotor ausgeglichen. Wenn die Eimer nicht ausgeglichen sind, verwenden Sie ein P200-Pipette vorsichtig hinzufügen 0,32 M HEPES-gepufferte Saccharose an die Spitze des Gradienten und das Gleichgewicht der Rotorschaufeln. </li></ol> 9. Fraktionierung der synaptischen Plasmamembran (SPM) <ol><li> Ultrazentrifuge in einem Schwingbecher-Rotor bei 150.000 × g für 2 h bei 4 ° C ist. Die Saccharose-Gradienten vorsichtig aus dem Eimer Ultrazentrifuge. Verwendung einer 18 G-Nadel und einer 1 ml-Spritze durchstoßen das Rohr an der Unterseite der 1,0 M / 1,2 M HEPES-gepufferter Saccharose-Lösung Interphase und zieht die synaptischen Plasmamembranschicht (SPM). </li><li> Notieren Sie sich die Lautstärke, die jedes SPM Probe in der 1 ml Spritze einnimmt. Legen Sie die gesammelten SPM Schicht in 3,5 ml dickwandigen Rohren Ultrazentrifuge, fügen Sie genau 2,5 Volumen 4 mM HEPES, um die Saccharose-Konzentration von 1,2 m bis 0,32 M. einstellen Sobald jeder Probe wurde einstellened auf 0,32 M Saccharose, mit 0,32 M HEPES-gepufferte Saccharose-Lösung das Gleichgewicht der Rohre. </li><li> Ultrazentrifuge in einem Festwinkelrotor bei 200.000 × g für 30 min bei 4 ° C ist. Entfernen und entsorgen Sie den Überstand. Resuspendieren synaptischen Plasmamembranpellet (SPM) in 300 ul 50 mM HEPES / 2 mM EDTA-Lösung. Proben bei -80 ° C bis zur Western-Blot verwendet. </li></ol> 10. Herstellung der postsynaptischen Dichte Fraktion (PSD) <ol><li> Auftauen SPM Proben auf Eis. </li><li> Machen Sie eine Lösung von 0,54% Triton X-100 in 50 mM HEPES / 2 mM EDTA-Lösung. </li><li> In einem 5 ml-Polystyrolröhrchen, kombinieren 2,7 ml Triton X-100 / HEPES / EDTA-Lösung und 300 ul SPM Fraktion und Drehen der Probe für 15 min bei 4 ° C </li><li> Übertragungs Proben zu 3,5 ml dickwandiger Rohre Ultrazentrifuge und Zentrifugenproben bei 32.000 × g für 20 min bei 4 ° C ist. </li><li> Reservieren Sie den Überstand (Triton X-100 löslichen Fraktion [TS]) und bei -80, ° C. HINWEIS: In dieser Stufe wird das Pellet stellt die &quot;PSD-1T&quot; Fraktion. Eine zweite Behandlung mit Reinigungsmittel ein &quot;PSD-2T&quot; Fraktion zu produzieren. Wenn eine PSD-1T-Fraktion gewünscht wird, gehen Sie zu Schritt 10.6. <ol><li> Um ein PSD-2T Fraktion produzieren, das Pellet in 3 ml 0,5% Triton X-100 in 50 mM HEPES / 2 mM EDTA-Lösung. Drehen Proben für 15 min bei 4 ° C ist. Zentrifugieren Sie die Proben bei 32.000 g für 20 min bei 4 ° C und gehen Sie zu Schritt 10.6. </li></ol></li><li> Überstand verwerfen und resuspendieren postsynaptischen (PSD) Pellet in 50 mM HEPES / 2 mM EDTA-Lösung. HINWEIS: Die Resuspension Volumen kann von der Größe der Pellets ab; ein Volumen von 50-75 ul empfohlen. Weil der PSD-Fraktion eine Waschmittel-unlöslichen Fraktion, ist es oft notwendig, 1-2 ul 0,5% SDS in den vollständigen Resuspendierung des Proteins zu ermöglichen. Proben bei -80 ° C bis zur Western-Blot verwendet. </li></ol>

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E., Chammas, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+lysosomal-associated+membrane+protein+LAMP-1+is+a+novel+differentiation+marker+for+HC11+mouse+mammary+epithelial+cells.">The lysosomal-associated membrane protein LAMP-1 is a novel differentiation marker for HC11 mouse mammary epithelial cells.</a> Differentiation. 61, 113-120 (1996).</li><li>Otera, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Peroxisomal+targeting+signal+receptor+Pex5p+interacts+with+cargoes+and+import+machinery+components+in+a+spatiotemporally+differentiated+manner:+conserved+Pex5p+WXXXF/Y+motifs+are+critical+for+matrix+protein+import.">Peroxisomal targeting signal receptor Pex5p interacts with cargoes and import machinery components in a spatiotemporally differentiated manner: conserved Pex5p WXXXF/Y motifs are critical for matrix protein import.</a> Mol Cell Biol. 22, 1639-1655 (2002).</li><li>Goubaeva, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+mitochondrial+connexin+43+regulates+apoptosis.">Cardiac mitochondrial connexin 43 regulates apoptosis.</a> Biochem Biophys Res Commun. 352, 97-103 (2007).</li><li>Lamers, K. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+S-100B,+neuron-specific+enolase+(NSE),+myelin+basic+protein+(MBP)+and+glial+fibrillary+acidic+protein+(GFAP)+in+cerebrospinal+fluid+(CSF)+and+blood+of+neurological+patients.">Protein S-100B, neuron-specific enolase (NSE), myelin basic protein (MBP) and glial fibrillary acidic protein (GFAP) in cerebrospinal fluid (CSF) and blood of neurological patients.</a> Brain Res Bull. 61, 261-264 (2003).</li><li>Arunachalam, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Munc18-1+is+critical+for+plasma+membrane+localization+of+syntaxin1+but+not+of+SNAP-25+in+PC12+cells.">Munc18-1 is critical for plasma membrane localization of syntaxin1 but not of SNAP-25 in PC12 cells.</a> Mol Biol Cell. 19, 722-734 (2008).</li><li>Brandstatter, J. H., Fletcher, E. L., Garner, C. C., Gundelfinger, E. D., Wassle, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+expression+of+the+presynaptic+cytomatrix+protein+bassoon+among+ribbon+synapses+in+the+mammalian+retina.">Differential expression of the presynaptic cytomatrix protein bassoon among ribbon synapses in the mammalian retina.</a> Eur J Neurosci. 11, 3683-3693 (1999).</li></ol>

The authors have no conflicts of interest to disclose.

Es gibt mehrere Schritte in der Prozedur, die entscheidend für ein erfolgreiches Ergebnis sind. In Schritt 3 ist es wichtig, dass ein gleichmäßiger Grad der Homogenisierung wird für jede Probe erreicht. Beim Homogenisieren Gewebe mit dem Motor angetrieben Homogenisator wird eine konstante Geschwindigkeit nicht nur für die Drehbewegung des Stößels, sondern auch mit der Anzahl von Hüben. Die Inkubationszeit bei der osmotischen Schock sollten präzise sein, da längere Homogenisierung oder Inkubation in der hypoton...

Neuronen kommunizieren über Synapsen und die Qualität dieser Kommunikation wird durch Veränderungen in der Zusammensetzung der Proteine ​​an der Synapse weitgehend reguliert. Insbesondere die Proteine ​​in der postsynaptischen Dichte liegt in der neuronalen Kommunikation teilnehmen, die durch inniges Gerüst Neurotransmitter-Rezeptoren mit ihren Signalübertragungssysteme 1. Weiterhin sind dauerhafte Änderungen in der Stärke der synaptischen Wirksamkeit durch Zugabe oder Entfernung von Rezeptoren an der postsynaptischen Dichte 1-6 gesteuert. Daher ist die Isolierung und Quantifizierung der synaptischen Proteinen eine notwendige und nützliche Technik, um einen Einblick in die Möglichkeiten, die Nervenzellen reagieren auf Reize und verändern synaptischen Wirksamkeit 7 zu gewinnen. Dieser Artikel beschreibt eine übliche Technik, synaptischen Proteinen aus Hirngewebe von Nagern durch Ultrazentrifugation auf diskontinuierlichen Saccharose-Gradienten zu isolieren. Die synaptischen Plasmamembranfraktion angereichert und isoliert werden, basierend aufseine Dichte in Saccharose, die empirisch bestimmt worden ist, ähnlich zu 1,2 M Saccharose ist. Je nachdem welche biologischen Frage kann subzellulären Fraktionen durch kontinuierlichen oder diskontinuierlichen Gradienten von Saccharose oder Percoll getrennt werden. Kontinuierlichen Gradienten ermöglichen die Trennung von Proteinen in mehrere Fraktionen; Dies kann besonders nützlich sein, um die Co-Lokalisierung von Proteinen in einer gegebenen Fraktion 8 zeigen. Jedoch ist die Herstellung von kontinuierlichen Gradienten mühsamer und unnötig für viele Anwendungen. Diskontinuierlichen Gradienten vergleichsweise leichter herzustellen und kann verwendet werden, um Proteine ​​in wenigen, allgemein definierten Fraktionen zu trennen. Diskontinuierlichen Gradienten, der aus drei Schichten von Saccharose Erhöhung Molarität bestehen in großem Umfang verwendet, um Proteine, die mit den synaptischen Plasmamembran (SPM) zugeordnet isolieren. Diese synaptischen Plasmamembranfraktion kann weiter auf der postsynaptischen Dichte fractio verarbeitet werdenn (PSD) durch Detergensbehandlung und Isolierung der Waschmittel-unlöslichen Fraktion. Wenn dieses Verfahren wurde zuerst in den 1960er Jahren 9,10 beschrieben wurde Elektronenmikroskopie verwendet, um die Organellen und Membranen, die in etwa definieren die synaptischen Plasmamembran und postsynaptischen Dichte Fraktionen 9-14 demonstrieren. Diese Studien zeigten, die Aufnahme von prä-und postsynaptischen Membranen und synaptischen Vesikeln in der SPM-Fraktion; nach Detergens-Behandlung vor allem die Elektronendichte, waren postsynaptischen Dichten sichtbar. In dem Verfahren wird ein hypotonischen Schock verwendet, um aus dem Zellkörper 10 abzuklemmen die synaptischen Prozessen. Dieser Schritt nutzt die Tatsache, dass Mitochondrien sind resistenter gegen osmotischen Schock und intakt bleiben, so dass sie an der Unterseite des Saccharosegradienten (Figur 1) zu sedimentieren. Mit dem gleichen Anreicherungstechnik, waren die SPM und PSD-Fraktionen erste biochemischdurch Polyacrylamid-Gelelektrophorese und Sequenzierung der Hauptproteinkomponenten 15-17. Anschließend Western Blot-Analyse wurde verwendet, um zu detektieren und zu quantifizieren, die Pegel der synaptischen Proteinen und definieren diese Fraktionen weiter (Figur 2). Wir haben diese Technik in unseren Laboratorien verwendet, um Änderungen in der synaptischen Ebenen der Dopamin-Transporter, wenn das SLC6A3-Locus in der Maus 18 doppelt auftreten, zu quantifizieren. Wir haben auch diese Technik in NMDA-Rezeptor-defizienten Mäusen verwendet, um Synapse-spezifische Verringerung der Proteine, die Teil des DISC1 Interaktom 19 aufzudecken. Es ist aus Western-Blot-Analyse, die SPM Fraktionen enthalten synaptische Vesikel Membranproteine, Endosomen-Marker, mitochondriale Proteine, membranassoziierten synthetische Enzyme und Signaltransduktion Moleküle sowie als integrierte Komponenten der postsynaptischen Dichte und synaptischen Plasmamembranen 20-23. Even PSD Fraktionen Kontamination mit reichlich mitochondriale Proteine ​​und es kann notwendig, um einen zweiten Gradienten Sedimentation oder zusätzliche Reinigungsschritte durchzuführen, um diese 13 zu entfernen. Kürzlich wurde die quantitative Massenspektrometrie eine Liste von über 100 Proteinen in der postsynaptischen Dichte allein, sowie einen Hinweis auf die relative Menge dieser Komponenten 24,25 vorgesehen.

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preparation of synaptic plasma membrane and postsynaptic density proteins using a discontinuous sucrose gradient

Neuronale subzellulärer Fraktionierung Techniken erlauben die Quantifizierung von Proteinen, die in und aus der Synapse gehandelt werden. Wie ursprünglich in den späten 1960er Jahren beschrieben, können Proteine, die mit den synaptischen Plasmamembran assoziiert durch Ultrazentrifugation auf einem Saccharose-Dichtegradienten isoliert werden. Sobald synaptischen Membranen isoliert werden, kann der makromolekularen Komplex postsynaptischen Dichte bekannt anschließend aufgrund seiner Unlöslichkeit Reinigungsmittel isoliert werden. Die zur synaptischen Plasmamembranen und postsynaptischen Dichte Proteine ​​zu isolieren Techniken im Wesentlichen gleich bleiben nach 40 Jahren, und sind weit verbreitet in der aktuellen neurowissenschaftlichen Forschung. Dieser Artikel beschreibt die Fraktionierung von Proteinen mit der synaptischen Plasmamembran und postsynaptischen Dichte mit einem diskontinuierlichen Saccharosegradienten verbunden. Resultierenden Proteinpräparate eignen sich für Western-Blot-oder 2D-DIGE-Analyse.

Die Vorbereitung der Saccharosedichtegradienten sollten in einer klaren Trennung der drei Mol-Lösungen von Saccharose (0,8, 1,0 und 1,2 M Saccharose) führen. Siehe 3A ein Beispiel des Verlaufs bevor die Proteinprobe zugegeben. Wenn der Gradient zu viel im Voraus vorbereitet, oder wenn es auf einer Arbeitsfläche, mit Vibrationen von anderen Geräten hergestellt, wird der Gradient verglichen werden kann und korrekte Trennung nicht erreicht werden. Wenn eine klare Trennung der drei Lösungen nicht sicht...

Watch this Scientific Journal Video about Preparation of Synaptic Plasma Membrane and Postsynaptic Density Proteins Using a Discontinuous Sucrose Gradient at JoVE.com

Preparation of Synaptic Plasma Membrane and Postsynaptic Density Proteins Using a Discontinuous Sucrose Gradient

Dieser Artikel beschreibt die Anreicherung von Proteinen mit den synaptischen Plasmamembran durch Ultrazentrifugation auf einem diskontinuierlichen Saccharosegradienten verbunden. Die anschließende Herstellung der postsynaptischen Dichte Proteine ​​wird ebenfalls beschrieben. Proteinpräparate eignen sich für Western-Blot-oder 2D-DIGE-Analyse.

Vorbereitung der synaptischen Plasmamembran und Postsynaptische Dichte Proteinen mit einer diskontinuierlichen Saccharosegradienten

Neuronal subcellular fractionation techniques allow the quantification of proteins that are trafficked to and from the synapse. As originally described in ...

preparation-synaptic-plasma-membrane-postsynaptic-density-proteins

Research

JoVE Journal

Neuroscience

31.0K Aufrufe.  University of Toronto.  Dieser Artikel beschreibt die Anreicherung von Proteinen mit den synaptischen Plasmamembran durch Ultrazentrifugation auf einem diskontinuierlichen Saccharosegradienten verbunden. Die anschließende Herstellung der postsynaptischen Dichte Proteine ​​wird ebenfalls beschrieben. Proteinpräparate eignen sich für Western-Blot-oder 2D-DIGE-Analyse. 

Serie: Preparation of Synaptic Plasma Membrane and Postsynaptic Density Proteins Using a Discontinuous Sucrose Gradient

Studying Synaptic Vesicle Pools using Photoconversion of Styryl Dyes

The fusion of synaptic vesicles with the plasma membrane (exocytosis) is a required step in neurotransmitter release and neuronal communication. The vesicles are then retrieved from the plasma membrane (endocytosis) and grouped together with the general pool of vesicles within the nerve terminal, until they undergo a new exo- and endocytosis cycle (vesicle recycling). These processes have been studied using a variety of techniques such as electron microscopy, electrophysiology recordings, amperometry and capacitance measurements. Importantly, during the last two decades a number of fluorescently labeled markers emerged, allowing optical techniques to track vesicles in their recycling dynamics. One of the most commonly used markers is the styryl or FM dye 1; structurally, all FM dyes contain a hydrophilic head and a lipophilic tail connected through an aromatic ring and one or more double bonds (Fig. 1B). A classical FM dye experiment to label a pool of vesicles consists in bathing the preparation (Fig. 1Ai) with the dye during the stimulation of the nerve (electrically or with high K+). This induces vesicle recycling and the subsequent loading of the dye into recently endocytosed vesicles (Fig. 1Ai-iii). After loading the vesicles with dye, a second round of stimulation in a dye-free bath would trigger the FM release through exocytosis (Fig. 1Aiv-v), process that can be followed by monitoring the fluorescence intensity decrease (destaining).

Although FM dyes have contributed greatly to the field of vesicle recycling, it is not possible to determine the exact localization or morphology of individual vesicles by using conventional fluorescence microscopy. For that reason, we explain here how FM dyes can also be used as endocytic markers using electron microscopy, through photoconversion. The photoconversion technique exploits the property of fluorescent dyes to generate reactive oxygen species under intense illumination. Fluorescently labeled preparations are submerged in a solution containing diaminobenzidine (DAB) and illuminated. Reactive species generated by the dye molecules oxidize the DAB, which forms a stable, insoluble precipitate that has a dark appearance and can be easily distinguished in electron microscopy 2,3. As DAB is only oxidized in the immediate vicinity of fluorescent molecules (as the reactive oxygen species are short-lived), the technique ensures that only fluorescently labeled structures are going to contain the electron-dense precipitate. The technique thus allows the study of the exact location and morphology of actively recycling organelles.

FM dyes have been of invaluable help in the understanding of synaptic dynamics. FMs are normally followed under the fluorescent microscope during different stimulation conditions. However, photoconversion of FM dyes combined with electron microscopy allows the visualization of distinct synaptic vesicle pools, among other ultrastructure components, in synaptic boutons.

Studium synaptischer Vesikel Pools mit Photokonversion Styrylfarbstoffe

The fusion of synaptic vesicles with the plasma membrane (exocytosis) is a required step in neurotransmitter release and neuronal communication. The ...

Forschung

Neurowissenschaften

Membrane Potentials, Synaptic Responses, Neuronal Circuitry, Neuromodulation and Muscle Histology Using the Crayfish: Student Laboratory Exercises

The purpose of this report is to help develop an understanding of the effects caused by ion gradients across a biological membrane. Two aspects that influence a cell's membrane potential and which we address in these experiments are: (1) Ion concentration of K+ on the outside of the membrane, and (2) the permeability of the membrane to specific ions. The crayfish abdominal extensor muscles are in groupings with some being tonic (slow) and others phasic (fast) in their biochemical and physiological phenotypes, as well as in their structure; the motor neurons that innervate these muscles are correspondingly different in functional characteristics. We use these muscles as well as the superficial, tonic abdominal flexor muscle to demonstrate properties in synaptic transmission. In addition, we introduce a sensory-CNS-motor neuron-muscle circuit to demonstrate the effect of cuticular sensory stimulation as well as the influence of neuromodulators on certain aspects of the circuit. With the techniques obtained in this exercise, one can begin to answer many questions remaining in other experimental preparations as well as in physiological applications related to medicine and health. We have demonstrated the usefulness of model invertebrate preparations to address fundamental questions pertinent to all animals.

The experiments demonstrate an easy approach for students to gain experience in examining muscle structure, synaptic responses, the effects of ion gradients and permeability on membrane potentials. Also, a sensory-CNS-motor-muscle circuit is presented to show a means to test effects of compounds on a neuronal circuit.

Membranpotentiale, Synaptic Responses, neuronalen, Neuromodulation und Muscle Histologie Mit dem Crayfish: Schülerlabor Übungen

The purpose of this report is to help develop an understanding of the effects caused by ion gradients across a biological membrane. Two aspects that ...

Quantitative Analysis of Synaptic Vesicle Pool Replenishment in Cultured Cerebellar Granule Neurons using FM Dyes

After neurotransmitter release in central nerve terminals, SVs are rapidly retrieved by endocytosis. Retrieved SVs are then refilled with neurotransmitter and rejoin the recycling pool, defined as SVs that are available for exocytosis1,2. The recycling pool can generally be subdivided into two distinct pools - the readily releasable pool (RRP) and the reserve pool (RP). As their names imply, the RRP consists of SVs that are immediately available for fusion while RP SVs are released only during intense stimulation1,2. It is important to have a reliable assay that reports the differential replenishment of these SV pools in order to understand 1) how SVs traffic after different modes of endocytosis (such as clathrin-dependent endocytosis and activity-dependent bulk endocytosis) and 2) the mechanisms controlling the mobilisation of both the RRP and RP in response to different stimuli.
FM dyes are routinely employed to quantitatively report SV turnover in central nerve terminals3-8. They have a hydrophobic hydrocarbon tail that allows reversible partitioning in the lipid bilayer, and a hydrophilic head group that blocks passage across membranes. The dyes have little fluorescence in aqueous solution, but their quantum yield increases dramatically when partitioned in membrane9. Thus FM dyes are ideal fluorescent probes for tracking actively recycling SVs. The standard protocol for use of FM dye is as follows. First they are applied to neurons and are taken up during endocytosis (Figure 1). After non-internalised dye is washed away from the plasma membrane, recycled SVs redistribute within the recycling pool. These SVs are then depleted using unloading stimuli (Figure 1). Since FM dye labelling of SVs is quantal10, the resulting fluorescence drop is proportional to the amount of vesicles released. Thus, the recycling and fusion of SVs generated from the previous round of endocytosis can be reliably quantified.
Here, we present a protocol that has been modified to obtain two additional elements of information. Firstly, sequential unloading stimuli are used to differentially unload the RRP and the RP, to allow quantification of the replenishment of specific SV pools. Secondly, each nerve terminal undergoes the protocol twice. Thus, the response of the same nerve terminal at S1 can be compared against the presence of a test substance at phase S2 (Figure 2), providing an internal control. This is important, since the extent of SV recycling across different nerve terminals is highly variable11.
Any adherent primary neuronal cultures may be used for this protocol, however the plating density, solutions and stimulation conditions are optimised for cerebellar granule neurons (CGNs)12,13.

A live fluorescence imaging technique to quantify the replenishment and mobilisation of specific synaptic vesicle (SV) pools in central nerve terminals is described. Two rounds of SV recycling are monitored in the same nerve terminals providing an internal control.

Quantitative Analyse der synaptischen Vesikel Pool Replenishment in Cultured Cerebellar Nervenzellen Granulat mit FM Dyes

After neurotransmitter release in central nerve terminals, SVs are rapidly retrieved by endocytosis.  Retrieved SVs are then refilled with ...

Preparation of Synaptoneurosomes from Mouse Cortex using a Discontinuous Percoll-Sucrose Density Gradient

Synaptoneurosomes (SNs) are obtained after homogenization and fractionation of mouse brain cortex. They are resealed vesicles or isolated terminals that break away from axon terminals when the cortical tissue is homogenized. The SNs retain pre- and postsynaptic characteristics, which makes them useful in the study of synaptic transmission. They retain the molecular machinery used in neuronal signaling and are capable of uptake, storage, and release of neurotransmitters.
The production and isolation of active SNs can be problematic using medias like Ficoll, which can be cytotoxic and require extended centrifugation due to high density, and filtration and centrifugation methods, which can result in low activity due to mechanical damage of the SNs. However, the use of discontinuous Percoll-sucrose density gradients to isolate SNs provides a rapid method to produce good yields of translationally active SNs. The Percoll-sucrose gradient method is quick and gentle as it employs isotonic conditions, has fewer and shorter centrifugation spins and avoids centrifugation steps that pellet SNs and cause mechanical damage.

A method to prepare translationally active, intact synaptoneurosomes (SNs) from mouse brain cortex is described. The method uses a discontinuous Percoll-sucrose density gradient allowing for the quick preparation of active SNs.

Vorbereitung der Synaptoneurosomen von Maus Cortex mit einem diskontinuierlichen Percoll-Saccharose-Dichtegradienten

Synaptoneurosomes (SNs) are obtained after homogenization and fractionation of mouse brain cortex. They are resealed vesicles or isolated terminals that ...

A General Method for Evaluating Incubation of Sucrose Craving in Rats

For someone on a food-restricted diet, food craving in response to food-paired cues may serve as a key behavioral transition point between abstinence and relapse to food taking 1. Food craving conceptualized in this way is akin to drug craving in response to drug-paired cues. A rich literature has been developed around understanding the behavioral and neurobiological determinants of drug craving; we and others have been focusing recently on translating techniques from basic addiction research to better understand addiction-like behaviors related to food 2-4.
As done in previous studies of drug craving, we examine sucrose craving behavior by utilizing a rat model of relapse. In this model, rats self-administer either drug or food in sessions over several days. In a session, lever responding delivers the reward along with a tone+light stimulus. Craving behavior is then operationally defined as responding in a subsequent session where the reward is not available. Rats will reliably respond for the tone+light stimulus, likely due to its acquired conditioned reinforcing properties 5. This behavior is sometimes referred to as sucrose seeking or cue reactivity. In the present discussion we will use the term "sucrose craving" to subsume both of these constructs.
In the past decade, we have focused on how the length of time following reward self-administration influences reward craving. Interestingly, rats increase responding for the reward-paired cue over the course of several weeks of a period of forced-abstinence. This "incubation of craving" is observed in rats that have self-administered either food or drugs of abuse 4,6. This time-dependent increase in craving we have identified in the animal model may have great potential relevance to human drug and food addiction behaviors.
Here we present a protocol for assessing incubation of sucrose craving in rats. Variants of the procedure will be indicated where craving is assessed as responding for a discrete sucrose-paired cue following extinction of lever pressing within the sucrose self-administration context (Extinction without cues) or as responding for sucrose-paired cues in a general extinction context (Extinction with cues).

Responding for food or drug-paired cues increases over the course of a period of abstinence and this may relate to an increased susceptibility to relapse behaviors. Here we detail a procedure for evaluating this "incubation of craving" in rats that have self-administered sucrose.

Eine allgemeine Methode zur Bewertung der Inkubation von Saccharose Craving in Ratten

For someone on a food-restricted diet, food craving in response to food-paired cues may serve as a key behavioral transition point between abstinence and ...

Lateral Diffusion and Exocytosis of Membrane Proteins in Cultured Neurons Assessed using Fluorescence Recovery and Fluorescence-loss Photobleaching

Membrane proteins such as receptors and ion channels undergo active trafficking in neurons, which are highly polarised and morphologically complex. This directed trafficking is of fundamental importance to deliver, maintain or remove synaptic proteins.
Super-ecliptic pHluorin (SEP) is a pH-sensitive derivative of eGFP that has been extensively used for live cell imaging of plasma membrane proteins1-2. At low pH, protonation of SEP decreases photon absorption and eliminates fluorescence emission. As most intracellular trafficking events occur in compartments with low pH, where SEP fluorescence is eclipsed, the fluorescence signal from SEP-tagged proteins is predominantly from the plasma membrane where the SEP is exposed to a neutral pH extracellular environment. When illuminated at high intensity SEP, like every fluorescent dye, is irreversibly photodamaged (photobleached)3-5. Importantly, because low pH quenches photon absorption, only surface expressed SEP can be photobleached whereas intracellular SEP is unaffected by the high intensity illumination6-10. 
FRAP (fluorescence recovery after photobleaching) of SEP-tagged proteins is a convenient and powerful technique for assessing protein dynamics at the plasma membrane. When fluorescently tagged proteins are photobleached in a region of interest (ROI) the recovery in fluorescence occurs due to the movement of unbleached SEP-tagged proteins into the bleached region. This can occur via lateral diffusion and/or from exocytosis of non-photobleached receptors supplied either by de novo synthesis or recycling (see Fig. 1). The fraction of immobile and mobile protein can be determined and the mobility and kinetics of the diffusible fraction can be interrogated under basal and stimulated conditions such as agonist application or neuronal activation stimuli such as NMDA or KCl application8,10. 
We describe photobleaching techniques designed to selectively visualize the recovery of fluorescence attributable to exocytosis. Briefly, an ROI is photobleached once as with standard FRAP protocols, followed, after a brief recovery, by repetitive bleaching of the flanking regions. This 'FRAP-FLIP' protocol, developed in our lab, has been used to characterize AMPA receptor trafficking at dendritic spines10, and is applicable to a wide range of trafficking studies to evaluate the intracellular trafficking and exocytosis.

This report describes the use of live cell imaging and photobleach techniques to determine the surface expression, transport pathways and trafficking kinetics of exogenously expressed, pH-sensitive GFP-tagged proteins at the plasma membrane of neurons.

Laterale Diffusion und Exozytose von Membranproteinen in kultivierten Neuronen Veranlagte mit Fluorescence Recovery-und Fluoreszenz-Verlust Photobleaching

Membrane proteins such as receptors and ion channels undergo active trafficking in neurons, which are highly polarised and morphologically complex. This ...

Post-embedding Immunogold Labeling of Synaptic Proteins in Hippocampal Slice Cultures

Immunoelectron microscopy is a powerful tool to study biological molecules at the subcellular level. Antibodies coupled to electron-dense markers such as colloidal gold can reveal the localization and distribution of specific antigens in various tissues1. The two most widely used techniques are pre-embedding and post-embedding techniques. In pre-embedding immunogold-electron microscopy (EM) techniques, the tissue must be permeabilized to allow antibody penetration before it is embedded. These techniques are ideal for preserving structures but poor penetration of the antibody (often only the first few micrometers) is a considerable drawback2. The post-embedding labeling methods can avoid this problem because labeling takes place on sections of fixed tissues where antigens are more easily accessible. Over the years, a number of modifications have improved the post-embedding methods to enhance immunoreactivity and to preserve ultrastructure3-5.
Tissue fixation is a crucial part of EM studies. Fixatives chemically crosslink the macromolecules to lock the tissue structures in place. The choice of fixative affects not only structural preservation but also antigenicity and contrast. Osmium tetroxide (OsO4), formaldehyde, and glutaraldehyde have been the standard fixatives for decades, including for central nervous system (CNS) tissues that are especially prone to structural damage during chemical and physical processing. Unfortunately, OsO4 is highly reactive and has been shown to mask antigens6, resulting in poor and insufficient labeling. Alternative approaches to avoid chemical fixation include freezing the tissues. But these techniques are difficult to perform and require expensive instrumentation. To address some of these problems and to improve CNS tissue labeling, Phend et al. replaced OsO4 with uranyl acetate (UA) and tannic acid (TA), and successfully introduced additional modifications to improve the sensitivity of antigen detection and structural preservation in brain and spinal cord tissues7. We have adopted this osmium-free post-embedding method to rat brain tissue and optimized the immunogold labeling technique to detect and study synaptic proteins.
We present here a method to determine the ultrastructural localization of synaptic proteins in rat hippocampal CA1 pyramidal neurons. We use organotypic hippocampal cultured slices. These slices maintain the trisynaptic circuitry of the hippocampus, and thus are especially useful for studying synaptic plasticity, a mechanism widely thought to underlie learning and memory. Organotypic hippocampal slices from postnatal day 5 and 6 mouse/rat pups can be prepared as described previously8, and are especially useful to acutely knockdown or overexpress exogenous proteins. We have previously used this protocol to characterize neurogranin (Ng), a neuron-specific protein with a critical role in regulating synaptic function8,9 . We have also used it to characterize the ultrastructural localization of calmodulin (CaM) and Ca2+/CaM-dependent protein kinase II (CaMKII)10. As illustrated in the results, this protocol allows good ultrastructural preservation of dendritic spines and efficient labeling of Ng to help characterize its distribution in the spine8. Furthermore, the procedure described here can have wide applicability in studying many other proteins involved in neuronal functions.

The localization and distribution of proteins provide important information for understanding their cellular functions. The superior spatial resolution of electron microscopy (EM) can be used to determine the subcellular localization of a given antigen following immunohistochemistry. For tissues of the central nervous system (CNS), preserving structural integrity while maintaining antigenicity has been especially difficult in EM studies. Here, we adopt a procedure that has been used to preserve structures and antigens in the CNS to study and characterize synaptic proteins in rat hippocampal CA1 pyramidal neurons.

Post-Einbettung Immunogoldmarkierung der synaptischen Proteine ​​in Hippocampusschnitt Kulturen

Immunoelectron microscopy is a powerful tool to study biological molecules at the subcellular level. Antibodies coupled to electron-dense markers such as ...

Deriving the Time Course of Glutamate Clearance with a Deconvolution Analysis of Astrocytic Transporter Currents

The highest density of glutamate transporters in the brain is found in astrocytes. Glutamate transporters couple the movement of glutamate across the membrane with the co-transport of 3 Na+ and 1 H+ and the counter-transport of 1 K+. The stoichiometric current generated by the transport process can be monitored with whole-cell patch-clamp recordings from astrocytes. The time course of the recorded current is shaped by the time course of the glutamate concentration profile to which astrocytes are exposed, the kinetics of glutamate transporters, and the passive electrotonic properties of astrocytic membranes. Here we describe the experimental and analytical methods that can be used to record glutamate transporter currents in astrocytes and isolate the time course of glutamate clearance from all other factors that shape the waveform of astrocytic transporter currents. The methods described here can be used to estimate the lifetime of flash-uncaged and synaptically-released glutamate at astrocytic membranes in any region of the central nervous system during health and disease.

We describe an analytical method to estimate the lifetime of glutamate at astrocytic membranes from electrophysiological recordings of glutamate transporter currents in astrocytes.

Die Ableitung der zeitliche Verlauf der Glutamate Ausverkauf mit Dekonvolutionsanalyse von Astrozytäre Transporter Currents

The highest density of glutamate transporters in the brain is found in astrocytes. Glutamate transporters couple the movement of glutamate across the ...

The Neuromuscular Junction: Measuring Synapse Size, Fragmentation and Changes in Synaptic Protein Density Using Confocal Fluorescence Microscopy

The neuromuscular junction (NMJ) is the large, cholinergic relay synapse through which mammalian motor neurons control voluntary muscle contraction. Structural changes at the NMJ can result in neurotransmission failure, resulting in weakness, atrophy and even death of the muscle fiber. Many studies have investigated how genetic modifications or disease can alter the structure of the mouse NMJ. Unfortunately, it can be difficult to directly compare findings from these studies because they often employed different parameters and analytical methods. Three protocols are described here. The first uses maximum intensity projection confocal images to measure the area of acetylcholine receptor (AChR)-rich postsynaptic membrane domains at the endplate and the area of synaptic vesicle staining in the overlying presynaptic nerve terminal. The second protocol compares the relative intensities of immunostaining for synaptic proteins in the postsynaptic membrane. The third protocol uses Fluorescence Resonance Energy Transfer (FRET) to detect changes in the packing of postsynaptic AChRs at the endplate. The protocols have been developed and refined over a series of studies. Factors that influence the quality and consistency of results are discussed and normative data are provided for NMJs in healthy young adult mice.

The neuromuscular junction (NMJ) is altered in a variety of conditions that can sometimes culminate in synaptic failure. This report describes fluorescence microscope-based methods to quantify such structural changes.

Der neuromuskulären Synapse: Mess Synapse Größe, Fragmentierung und Veränderungen der synaptischen Protein Dichte Mit der konfokalen Fluoreszenzmikroskopie

The neuromuscular junction (NMJ) is the large, cholinergic relay synapse through which mammalian motor neurons control voluntary muscle contraction. ...

Simultaneous Two-photon In Vivo Imaging of Synaptic Inputs and Postsynaptic Targets in the Mouse Retrosplenial Cortex

This video shows the craniotomy procedure that allows chronic imaging of neurons in the mouse retrosplenial cortex (RSC) using in vivo two-photon microscopy in Thy1-GFP transgenic mouse line. This approach creates a possibility to investigate the correlation of behavioural manipulations with changes in neuronal morphology in vivo.
The cranial window implantation procedure was considered to be limited only to the easily accessible cortex regions such as the barrel field. Our approach allows visualization of neurons in the highly vascularized RSC. RSC is an important element of the brain circuit responsible for spatial memory, previously deemed to be problematic for in vivo two-photon imaging.
The cranial window implantation over the RSC is combined with an injection of mCherry-expressing recombinant adeno-associated virus (rAAVmCherry) into the dorsal hippocampus. The expressed mCherry spreads out to axonal projections from the hippocampus to RSC, enabling the visualization of changes in both presynaptic axonal boutons and postsynaptic dendritic spines in the cortex. 
This technique allows long-term monitoring of experience-dependent structural plasticity in RSC.

Simultaneous Two-photon In Vivo Imaging of Synaptic Inputs and Postsynaptic Targets in the Mouse Retrosplenial Cortex

This video shows the craniotomy procedure that allows chronic imaging of neurons in mouse retrosplenial cortex using in vivo two photon microscopy in Thy1-GFP transgenic line. This approach is combined with injection of mCherry-expressing adeno-associated virus into dorsal hippocampus. These techniques allow long-term monitoring of experience-dependent structural plasticity in RSC.

Die gleichzeitige Zwei-Photonen<em&gt; In Vivo</em&gt; Imaging der synaptischen Eingänge und Postsynaptische Targets in der Maus retrosplenialen Cortex