Questo lavoro è stato sostenuto da sovvenzioni della Deutsche Forschungsgemeinschaft (DFG) BL567/3-1 e la Friedrich-Baur-Stiftung. Vorremmo ringraziare Roger Y. Tsien, Howard Hughes Medical Institute laboratori presso l&#39;Università della California, San Diego per averci fornito Tag-RFP-T2. Noi per fortuna riconosciamo David Baltimore, California Institute of Technology, Pasadena, e Didier Trono, Università di Ginevra, Ginevra, per averci fornito il lentiviral plasmidi FUGW e psPAX2/pMD2.G.

<ol>
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Gli autori dichiarano di non avere interessi finanziari in competizione.

I vantaggi e gli svantaggi del metodo di TED sono state ampiamente discusse in recenti pubblicazioni 34,35. Rispetto ad altri metodi sopra descritti, TED elude il problema di interrompere e perfusione delle cellule. Inoltre, due aspetti hanno bisogno di essere sottolineato. Il principio di TED per ER calcium imaging richiede (1.) L&#39;espressione mirata di un carbossilesterasi attiva nel lume ER con l&#39;aiuto del TED costrutti vettoriali e (2.) Il rilascio efficiente e preferenziale di bassa affinità sint...

Al fine di risolvere le risposte fisiologiche di calcio del ER, abbiamo sviluppato una nuova strategia per migliorare la cattura di calcio sintetici coloranti sensibili al pronto soccorso. Il metodo consente la diretta, senza interruzioni monitoraggio in tempo reale di libero ER calcio in presenza di calcio extracellulare. Funzione e segnalazione di calcio ER Segnali di calcio si trovano in diversi tipi di cellule, ad esempio-cellule muscolari, neuroni e cellule gliali e la loro gamma di funzioni di mediazione contrazione muscolare ad un coinvolgimento nella trasmissione sinaptica nell&#39;apprendimento e nella memoria di 1,2. Cambiamenti nella concentrazione di calcio libero sono di grande interesse scientifico perché il calcio è coinvolto nella regolazione della trascrizione genica, la proliferazione cellulare, eccitabilità neuronale, la morte cellulare e altri eventi di segnalazione cellulare 1-7. Tutti questi segnali di calcio cellulari sono funzionalmente collegati e contribuiscono a intracellulare di calcionegozio dinamiche 8-10. Una caratteristica comune a tutti i segnali di calcio è il flusso di calcio tra lo spazio extracellulare, citoplasma e organelli, soprattutto il ER e mitocondri. Questo provoca cambiamenti dinamici nella concentrazione di calcio all&#39;interno di questi organelli, che vengono rilevate dai diversi componenti di segnalamento. In generale, la concentrazione di calcio nelle gamme ER tra 100 a 800 pM, nel citosol della concentrazione di calcio è quasi 100 nM, e nello spazio extracellulare la concentrazione è di circa 1-2 mm. Pertanto, vi è una forza motrice elevato chimica per flusso di calcio verso il citosol 2,9,10. I segnali di calcio ER-derivati ​​più comunemente studiate dipendono dalla stimolazione dei recettori accoppiati alla proteina G (GPCR), che poi attivano la fosfolipasi C (PLC). PLC a sua volta produce inositolo 1,4,5-trifosfato (IP 3) 1. In seguito al legame di IP 3 alla sua receptor (IP 3-Rec, Figura 1) in ER-membrana, gli ioni calcio vengono rilasciati dal lume ER. Storicamente, IP rilascio di calcio 3-mediata dal pronto soccorso è stato il primo - anche se indirettamente - misurata in cellule pancreatiche acinose di Streb et al nel 1983 11.. Questa pubblicazione suggerito per la prima volta una cascata di segnalazione che coinvolge acetilcolina, fosfolipasi C, e IP 3. Questo modo di rilascio del calcio è generalmente definito IP rilascio del calcio 3-indotta (IiCR) (Figura 1). L&#39;attivazione della chinasi-dipendente della fosfolipasi Cγ da recettore tirosin chinasi link l&#39;azione di fattori di crescita e fattori neurotrofici di ER di calcio di segnalazione IP dopo 3 elevazione 12. Oltre a IiCR, elevazione di calcio può essere mediata da recettori ionotropici ingresso di calcio, per esempio attraverso i canali del calcio voltaggio-dipendenti (CA V), e il successivo rilascio di calcio di calcio indotta (CICR) di ryanodine rirecettori (RyR). IiCR e CICR sono fisiologicamente legati al negozio-Entry operato di calcio (SOCE). SOCE comprende l&#39;azione di STIM (stroma interagenti molecola), che è un sensore per il rilascio di calcio ER. STIM ha mostrato di stimolare l&#39;ingresso di calcio extracellulare attraverso canali potenziali transitori recettore (Trp) 13, Orai canali del calcio 14 e anche canali del calcio voltaggio-dipendenti 15 (Figura 1). Perdita di ER calcio viene salvato dinamicamente dall&#39;azione del Sarco-reticolo endoplasmatico calcio ATPasi (SERCA), che attivamente pompe indietro calcio nel ER. Bloccare il SERCA con farmaci come thapsigargin svela una continua perdita di calcio ER al compartimento citosolico. Questo calcio ER &quot;fuga&quot; è causato da ER intramembrane complessi del poro come il complesso proteico Sec61 16,17 (figura 1). Nel 1998, Berridge pubblicato un modello, il &quot;neurone all&#39;interno di un modello di neurone&quot;, which suggerisce un ruolo fisiologico principio della ER nell&#39;integrazione di calcio neuronale 5. Questo modello considera l&#39;esistenza di un sistema a membrana ER continuo formando una &quot;immagine&quot; intracellulare della membrana plasmatica neuronale 5. Questo sistema a membrana eucariotica binario è stato affermato di essere un prerequisito fondamentale per l&#39;integrazione temporale e spaziale dei segnali veloci e lenti di calcio nei neuroni. Segnali di calcio che si verificano sia in concomitanza o successivamente in diverse spine o dendriti del neurone stesso sono conferiti a soma o nucleo attraverso il pronto soccorso, dove vengono riassunte 5,18 della cellula. Quindi, la loro somma può avere effetto sul l&#39;eccitabilità del neurone, regolazione della trascrizione genica o l&#39;integrazione di cascate di segnalazione. Così, l&#39;ER sostiene l&#39;integrazione dei segnali di calcio. Una condizione per questo concetto è la continuità della ER in una singola cella, che è stato rivendicato da diversi studi e che è stato dimostrato almeno per somato-daree endritic e breve distanza proiezioni assonali 19-21. Che ci sia continuità ER entro lunghe proiezioni assonale è una questione di dibattito. Strategie per misurare il flusso di calcio gratis su membrana ER Segnali di calcio sono più frequentemente monitorati nel citosol 22,23. Pertanto, non può essere distinto facilmente se Ca 2 + fluisce nel citosol da extracellulare o da riserve intracellulari 6,24. Per superare questa limitazione, sono state sviluppate strategie metodologiche per l&#39;imaging diretto di calcio ER. In sintesi, le seguenti strategie da utilizzare sono: (1) ER-mirati geneticamente proteine ​​indicatori 25-27 a base di proteine ​​a bassa affinità Ca 2 + indicatori utilizzano la proteina bioluminescente aequorina o GFP in combinazione con una proteina di rilevamento. Calcio. Queste Ca 2 + indicatori geneticamente (GeCIS) puòessere mirati al pronto soccorso con l&#39;aiuto di un peptide segnale e sono tenute attivamente al pronto soccorso con una ritenzione e motivo recupero. Comune ER Ca 2 + indicatori di base sul principio Cameleon e sono il Cameleon YC4.3 26,28; Cameleon spaccatura YC7.3ER 29, e Cameleon D1 30. (2) colorante diretto carico esterasi a base di AM-estere a bassa affinità Ca 2 + indicatori 31,32. Dell&#39;indicatore di coloranti (Mag-Fura2-AM, Mag-Fluo4-AM o Fluo5N-AM)-derivati ​​AM passare il membrane biologiche in una lipofila, Stato di calcio-insensitive. Poi, nel citosol, nonché in ER, esterasi endogene fendere del gruppo AM-estere e rilasciano l&#39;indicatore di Ca 2 +, lasciando una certa quantità di colorante attivo nel citosol e nel ER. Pertanto, questo approccio è utile in condizioni di una concentrazione elevata di calcio in ER finché la concentrazione di calcio citosolico rimane ben al di sotto delimite di protezione degli indicatori a bassa affinità, in particolare durante segnali di calcio caratteristici (per esempio nM a basse pM). (3) loading AM-estere in associazione con permeabilizzazione della membrana plasmatica 32. Qualsiasi residuo + citosolico indicatore Ca 2 viene rimosso mediante permeabilizzazione della membrana plasmatica con piccole quantità di un detergente &quot;neutro&quot; (ad es saponina) in un tampone intracellulare artificiale. Così, le membrane intracellulari possono essere stimolate, ad esempio con IP 3 nel buffer intracellulare, direttamente attraverso &quot;pori&quot; nella membrana plasmatica. (4) Dialisi del citosol in configurazione whole-cell e misure simultanee di Ca 2 + nel lume ER e il citosol 32,33. Una cella viene prima caricato con una bassa affinità Ca 2 + indicatore (ad esempio Mag-Fura2- AM, raziometrico, luce UV). In seguito, con l&#39;aiuto di una pipetta di patch, qualsiasi residuo cytosolic Ca + indicatore a bassa affinità 2 viene dializzato dal citosol con un tampone contenente un Ca 2 + indicatore ad alta affinità (es. Fluo-3, luce visibile). Questa strategia consente la registrazione simultanea di segnali derivati ​​citosolici e ER. (5) Targeted-esterasi indotta colorante carico 8,34. Un carbossilesterasi (CES) è mirato a lume del ER e fornisce una elevata attività di esterasi intrappolamento efficiente del modulo AM-estere di bassa affinità Ca 2 + indicatori. Mirata-esterasi indotta colorante di caricamento (TED) Per migliorare il targeting di bassa affinità Ca 2 + indicatori per l&#39;ER lumen, TED è stato sviluppato. TED richiede la sovraespressione di un ER carbossilesterasi topo mirata (CES2) (Figura 2), che si ottiene tramite costrutti di espressione. Cellule esprimenti un CES-costrutto ricombinante vengono incubate con il modulo AM-estere di un calcio nelgnalazione colorante (Fluo5N-AM, la Figura 2). Poi, in ER, il colorante viene convertito al Ca 2 + sensibile, membrana impermeabile Ca 2 + indicatore complesso (Fluo5N/Ca 2 +) dall&#39;attività elevata esterasi, quindi intrappolando il colorante in una concentrazione elevata nel lume ER 8 , 34. Il metodo è particolarmente utile per indagare ER calcio-release tramite i IiCR-percorsi per esempio tramite metabotropici purinergici-o glutammato recettori, 8,34 e visualizzare ER deplezione di calcio attraverso &quot;canali di perdite&quot; direttamente, per esempio, dopo il blocco del SERCA 17 , 34. Per la nostra esperienza la bassa affinità Ca 2 + indicatore Fluo5N-AM è attualmente il miglior indicatore disponibile per l&#39;utilizzo con la strategia di caricamento TED colorante. Fluo5N-AM ha una bassa affinità per il Ca 2 + (costante di dissociazione K D ~ 90 pM, Figura 2), è quasi non fluorescente nella sua AM-forma, ma fornisce alta emissione di fluorescenza upon calcium 8,34 vincolante. Il Fluo5N/Ca 2 + complesso può essere eccitato con una sorgente luminosa standard di ~ 490 nm, che corrisponde a coloranti standard come FITC, Alexa 488, o eGFP. Segnali di calcio citosolico raggiungono appena un concentrazione nell&#39;intervallo pM bassa e sono quindi appena rilevati dal Fluo5N nel citosol 35. Per migliorare la prestazione TED, sono stati sviluppati diversi costrutti vettore ricombinante (Figura 3). In origine, vettori TED base alla sequenza codificante di CES2 (Refseq numero adesione NM_145603, CES2c) e migliori prestazioni TED si osserva con espressione stabile del CES costrutti. Nuovi TED vettori esprimono un elemento centrale della CES2 fusa alla proteina fluorescente rossa TagRFP-T2 36. Questi vettori hanno il vantaggio che possono essere utilizzati per identificare cellule trasdotte e di utilizzare la fluorescenza rossa come controllo interno per la normalizzazione dei cambiamenti in Fluo5N/Ca 2 + fluorescenza. La fluorescenza rossa offre anche la possibilità di visualizzare la distribuzione strutturale del ER e cambiamenti nelle dinamiche ER in condizioni di stimolazione.

<table border="1">
	 <tbody>
 <tr>
 <td>Name of Reagent/Material</td>
 <td>Company</td>
 <td>Catalogue Number</td>
 <td>Comments</td>
 </tr>
 <tr>
 <td>(S)-3,5-DHPG (Dihydroxyphenylglycine)</td>
 <td>Tocris</td>
 <td>0805</td>
 <td></td>
 </tr>
 <tr>
 <td>5';-ATP-Na2, ATP disodium salt hydrate</td>
 <td>Sigma</td>
 <td>A26209-1G</td>
 <td></td>
 </tr>
 <tr>
 <td>B-27 supplement,50x</td>
 <td>Invitrogen</td>
 <td>17504-044</td>
 <td></td>
 </tr>
 <tr>
 <td>Carbamoylcholine chloride (Charbachol)</td>
 <td>Sigma</td>
 <td>C4382-1g</td>
 <td></td>
 </tr>
 <tr>
 <td>Cyclopiazonic acid (CPA)</td>
 <td>Ascent scientific</td>
 <td>Asc-300</td>
 <td></td>
 </tr>
 <tr>
 <td>Dimethylsulfoxide (DMSO)</td>
 <td>Sigma</td>
 <td>D2650</td>
 <td></td>
 </tr>
 <tr>
 <td>DMEM with Glutamax</td>
 <td>Invitrogen-Gibco</td>
 <td>31966-047</td>
 <td></td>
 </tr>
 <tr>
 <td>Dulbecco's PBS without Ca/Mg 1x</td>
 <td>PAA</td>
 <td>H15-002</td>
 <td></td>
 </tr>
 <tr>
 <td>Fetal calf serum</td>
 <td>Invitrogen-Gibco</td>
 <td>10270-106</td>
 <td></td>
 </tr>
 <tr>
 <td>Fluo-5N-AM, 10 x 50 &mu;g</td>
 <td>Invitrogen</td>
 <td>F14204</td>
 <td></td>
 </tr>
 <tr>
 <td>Glutamate</td>
 <td>Ascent scientific</td>
 <td>Asc-049</td>
 <td></td>
 </tr>
 <tr>
 <td>Glutamax</td>
 <td>Invitrogen</td>
 <td>35050-038</td>
 <td></td>
 </tr>
 <tr>
 <td>Ham's F12 nutrients mixture</td>
 <td>Invitrogen-Gibco</td>
 <td>21765-029</td>
 <td></td>
 </tr>
 <tr>
 <td>Hank's BSS(1x) without Ca,without Mg, with Phenol Red, HBSS</td>
 <td>PAA Laboratories</td>
 <td>H15-010</td>
 <td></td>
 </tr>
 <tr>
 <td>Horse serum</td>
 <td>SHD3250YK</td>
 <td>Linearis</td>
 <td></td>
 </tr>
 <tr>
 <td>Ionomycin Ca2+ salt</td>
 <td>Ascent scientific</td>
 <td>Asc-116</td>
 <td></td>
 </tr>
 <tr>
 <td>murine EGF </td>
 <td>PreproTech</td>
 <td>315-09</td>
 <td></td>
 </tr>
 <tr>
 <td>N2 supplement 100x</td>
 <td>Invitrogen</td>
 <td>17502-048</td>
 <td></td>
 </tr>
 <tr>
 <td>Neurobasal medium</td>
 <td>Invitrogen-Gibco</td>
 <td>21103-049</td>
 <td></td>
 </tr>
 <tr>
 <td>Pluronic F127, low UV absorbance,2g</td>
 <td>Invitrogen</td>
 <td>P6867</td>
 <td></td>
 </tr>
 <tr>
 <td>Poly-DL-ornithine hydrobromide PORN</td>
 <td>Sigma</td>
 <td>P8638</td>
 <td></td>
 </tr>
 <tr>
 <td>Poly-D-lysine hydrobromide</td>
 <td>Sigma</td>
 <td>P7280</td>
 <td></td>
 </tr>
 <tr>
 <td>Poly-L-Lysin</td>
 <td>Sigma</td>
 <td>P2636</td>
 <td></td>
 </tr>
 <tr>
 <td>Thapsigargin</td>
 <td>Calbiochem</td>
 <td>586005-1mg</td>
 <td></td>
 </tr>
 <tr>
 <td>TryLE Express</td>
 <td>Invitrogen</td>
 <td>12605-028</td>
 <td></td>
 </tr>
 <tr>
 <td>Trypsin</td>
 <td>Worthington</td>
 <td>LS-003707</td>
 <td></td>
 </tr>
 <tr>
 <td>Trypsininhibitor from Glycine MAX (soybean)</td>
 <td>Sigma</td>
 <td>T6522</td>
 <td></td>
 </tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>Materials</td>
 </tr>
 <tr>
 <td>Confocal system: inverted laser scanning microscope: FV1000 with IX81</td>
 <td>Olympus</td>
 <td></td>
 <td>user-specific configuration</td>
 </tr>
 <tr>
 <td>Confocal system: laser combiner FV10 and diode lasers (405, 473, 559, 635)</td>
 <td>Olympus</td>
 <td></td>
 <td>user-specific configuration</td>
 </tr>
 <tr>
 <td>Confocal system: scan head FV10-SPD with spectraldetector</td>
 <td>Olympus</td>
 <td></td>
 <td>user-specific configuration</td>
 </tr>
 <tr>
 <td>Heater controller TC-344B</td>
 <td>Warner Instruments</td>
 <td>64-0101</td>
 <td>to control in line solution heater</td>
 </tr>
 <tr>
 <td>NIH ImageJ software</td>
 <td>WS Rasband, ImageJ, US National Institutes of Health, <a href="http://rsb.info.nih.gov/ij/" target="_blank">http://rsb.info.nih.gov/ij/</a>, 1997--2006</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Objective: UAPON20XW340 NA 0,7 WD 0,35</td>
 <td>Olympus</td>
 <td>N2709100</td>
 <td></td>
 </tr>
 <tr>
 <td>Objective: UPLFLN40XO</td>
 <td>Olympus</td>
 <td>N1478700</td>
 <td></td>
 </tr>
 <tr>
 <td>Objective: UPLSAPO60XO/1.35, WD=0.15</td>
 <td>Olympus</td>
 <td>N1480700</td>
 <td></td>
 </tr>
 <tr>
 <td>Perfusion chamber, inverse</td>
 <td>custom-made</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Perfusion chamber, RC-49FS</td>
 <td>Warner Instruments</td>
 <td>W4 64-1709 </td>
 <td></td>
 </tr>
 <tr>
 <td>Perfusion tube: PT-49</td>
 <td>Warner Instruments</td>
 <td>64-1730</td>
 <td>for perfusion</td>
 </tr>
 <tr>
 <td>Peristaltic pump MiniPlus 3 (4 channels)</td>
 <td>Gilson</td>
 <td>n.a. </td>
 <td>perfusion pump</td>
 </tr>
 <tr>
 <td>Single inline solution heater SH-27B</td>
 <td>Warner Instruments</td>
 <td>64-0102</td>
 <td>controlled by heater controller</td>
 </tr>
 <tr>
 <td>Suction tubes: ST3R</td>
 <td>Warner Instruments</td>
 <td>64-1407</td>
 <td>for perfusion</td>
 </tr>
 <tr>
 <td>Heating insert: Tempocontrol 37-2 digital 2-channel</td>
 <td>Pecon</td>
 <td>n.a. </td>
 <td></td>
 </tr>
	 </tbody>
 </table>

direct imaging of er calcium with targeted-esterase induced dye loading (ted)

Visualizzazione delle dinamiche di calcio è importante per capire il ruolo del calcio nella fisiologia cellulare. Per esaminare le dinamiche del calcio, fluorescenti Ca 2 + indictors sintetici sono diventati popolari. Qui mostriamo TED (= colorante carico mirato-esterasi indotto), un metodo per migliorare il rilascio di Ca 2 + pigmenti indicatori nel lume ER di tipi cellulari. Ad oggi, TED è stato utilizzato in linee cellulari, cellule gliali e neuroni in vitro. Basi TED su efficiente, ricombinante di mira di un&#39;attività ad alto carbossilesterasi al lume ER utilizzando vettori costrutti che esprimono carbossilesterasi (CES). Le ultime vettori TED contengono un elemento centrale della CES2 fuso ad una proteina fluorescente rossa, consentendo in tal modo l&#39;imaging simultaneo a due colori. La dinamica del calcio libero in ER vengono esposte in un unico colore, mentre la corrispondente struttura di ER appare in rosso. All&#39;inizio del procedimento, le cellule vengono trasdotte con un lentivirus. Successivamente, le cellule infette ari seminati su vetrini per consentire finalmente l&#39;imaging cellulare dal vivo. Poi, le cellule viventi sono incubate con l&#39;estere acetossimetil (AM-estere) sotto forma di bassa affinità Ca 2 + indicatori, per esempio Fluo5N-AM, Mag-Fluo4-AM, o Mag-Fura2-AM. L&#39;attività esterasi nei unirà ER off catene laterali idrofobiche dal modulo AM del + indicatore Ca 2 e una idrofila colorante fluorescente / Ca 2 + complesso è formato e intrappolato in ER lumen. Dopo il colorante di caricamento, le cellule vengono analizzate con un microscopio confocale a scansione laser invertito. Le cellule sono continuamente perfusi con soluzioni di Ringer-like e le dinamiche del calcio ER sono direttamente visualizzati da time-lapse imaging. Rilascio del calcio dal RE è identificato da una diminuzione della intensità di fluorescenza in regioni di interesse, mentre il riempimento del negozio calcio ER produce un aumento di intensità di fluorescenza. Infine, la variazione di intensità fluorescente nel tempo è determinata mediante calcolo di Af / F 0.

Questo protocollo fornisce un approccio non distruttivo per l&#39;imaging diretto di libera ER calcio. Bassa affinità sintetica Ca 2 + indicatori vengono rilasciati e intrappolati nel lume ER con l&#39;aiuto di un ER mirati, attività enzimatica esterasi ricombinante. Migliorata caricamento delle Ca 2 + indicatore coloranti al pronto soccorso lume consente una rappresentazione diretta e veloce di ER calcio negozio dinamiche. Tipi di cellule per TED <p class="jove_cont...

Watch this Scientific Journal Video about Direct Imaging of ER Calcium with Targeted-Esterase Induced Dye Loading TED at JoVE.com

Direct Imaging of ER Calcium with Targeted-Esterase Induced Dye Loading TED

Mirata-esterasi indotta colorante di caricamento (TED) supporta l&#39;analisi delle dinamiche di calcio intracellulare negozio di imaging di fluorescenza. Il metodo basa sul targeting di un carbossilesterasi ricombinante al reticolo endoplasmatico (ER), dove migliora la smascheramento locale di sintetico a bassa affinità Ca<sup&gt; 2 +</sup&gt; Indicatore di coloranti in ER lumen.

Imaging diretta di calcio ER con Targeted-esterasi Induced Loading Dye (TED)

Visualization of calcium dynamics is important to understand the role of calcium in cell physiology. To examine calcium dynamics, synthetic fluorescent ...

direct-imaging-er-calcium-with-targeted-esterase-induced-dye-loading

Research

JoVE Journal

Biology

Direct Imaging of ER Calcium with Targeted-Esterase Induced Dye Loading (TED)

19.1K Views.  University of Wuerzburg. Mirata-esterasi indotta colorante di caricamento (TED) supporta l'analisi delle dinamiche di calcio intracellulare negozio di imaging di fluorescenza. Il metodo basa sul targeting di un carbossilesterasi ricombinante al reticolo endoplasmatico (ER), dove migliora la smascheramento locale di sintetico a bassa affinità Ca 2 + Indicatore di coloranti in ER lumen.

Video: Direct Imaging of ER Calcium with Targeted-Esterase Induced Dye Loading TED

Loading Drosophila Nerve Terminals with Calcium Indicators

Calcium plays many roles in the nervous system but none more impressive than as the trigger for neurotransmitter release, and none more profound than as the messenger essential for the synaptic plasticity that supports learning and memory. To further elucidate the molecular underpinnings of Ca2+-dependent synaptic mechanisms, a model system is required that is both genetically malleable and physiologically accessible. Drosophila melanogaster provides such a model. In this system, genetically-encoded fluorescent indicators are available to detect Ca2+ changes in nerve terminals. However, these indicators have limited sensitivity to Ca2+ and often show a non-linear response. Synthetic fluorescent indicators are better suited for measuring the rapid Ca2+ changes associated with nerve activity. Here we demonstrate a technique for loading dextran-conjugated synthetic Ca2+ indicators into live nerve terminals in Drosophila larvae. Particular emphasis is placed on those aspects of the protocol most critical to the technique's success, such as how to avoid static electricity discharges along the isolated nerves, maintaining the health of the preparation during extended loading periods, and ensuring axon survival by providing Ca2+ to promote sealing of severed axon endings. Low affinity dextran-conjugated Ca2+-indicators, such as fluo-4 and rhod, are available which show a high signal-to-noise ratio while minimally disrupting presynaptic Ca2+ dynamics. Dextran-conjugation helps prevent Ca2+ indicators being sequestered into organelles such as mitochondria. The loading technique can be applied equally to larvae, embryos and adults.

Calcium is a ubiquitous messenger in the nervous system, essential for triggering neurotransmitter release and changes in synaptic strength. Here we demonstrate a technique for loading Ca2+-indicators into Drosophila nerve terminals. We also demonstrate fabrication of the required apparatus and emphasize points critical for the technique's success.

Caricamento terminazioni nervose Drosophila con gli indicatori di calcio

Calcium plays many roles in the nervous system but none more impressive than as the trigger for neurotransmitter release, and none more profound than as ...

Ricerca

Biologia

In Vivo 2-Photon Calcium Imaging in Layer 2/3 of Mice

To understand network dynamics of microcircuits in the neocortex, it is essential to simultaneously record the activity of a large number of neurons . In-vivo two-photon calcium imaging is the only method that allows one to record the activity of a dense neuronal population with single-cell resolution . The method consists in implanting a cranial imaging window, injecting a fluorescent calcium indicator dye that can be taken up by large numbers of neurons and finally recording the activity of neurons with time lapse calcium imaging using an in-vivo two photon microscope. Co-injection of astrocyte-specific dyes allows one to differentiate neurons from astrocytes. The technique can be performed in mice expressing fluorescent molecules in specific subpopulations of neurons to better understand the network interactions of different groups of cells.

To understand network dynamics of microcircuits in the neocortex, it is essential to simultaneously record the activity of a large number of neurons . In-vivo two-photon calcium imaging is the only method that allows one to record the activity of a dense neuronal population with single-cell resolution .

In Vivo 2-Photon Imaging di calcio a livello 2 / 3 dei topi

To understand network dynamics of microcircuits in the neocortex, it is essential to simultaneously record the activity of a large number of neurons .  ...

Calcium Imaging of Cortical Neurons using Fura-2 AM

Calcium imaging is a common technique that is useful for measuring calcium signals in cultured cells. Calcium imaging techniques take advantage of calcium indicator dyes, which are BAPTA-based organic molecules that change their spectral properties in response to the binding of Ca2+ ions. Calcium indicator dyes fall into two categories, ratio-metric dyes like Fura-2 and Indo-1 and single-wavelength dyes like Fluo-4. Ratio-metric dyes change either their excitation or their emission spectra in response to calcium, allowing the concentration of intracellular calcium to be determined from the ratio of fluorescence emission or excitation at distinct wavelengths.  The main advantage of using ratio-metric dyes over single wavelength probes is that the ratio signal is independent of the dye concentration, illumination intensity, and optical path length allowing the concentration of intracellular calcium to be determined independently of these artifacts. One of the most common calcium indicators is Fura-2, which has an emission peak at 505 nM and changes its excitation peak from 340 nm to 380 nm in response to calcium binding.  Here we describe the use of Fura-2 to measure intracellular calcium elevations in neurons and other excitable cells.

Calcium signals play a key role in many cellular processes including gene expression, survival and differentiation. Here we demonstrate how to perform calcium imaging using Fura-2 AM. Calcium imaging is a valuable tool to study the regulation of intracellular calcium in real time and its regulation of signaling cascades.

Imaging di calcio di neuroni corticali usando Fura-02:00

Calcium imaging is a common technique that is useful for measuring calcium signals in cultured cells. Calcium imaging techniques take advantage of calcium ...

Assembly, Loading, and Alignment of an Analytical Ultracentrifuge Sample Cell

The analytical ultracentrifuge (AUC) is a powerful biophysical tool that allows us to record macromolecular sedimentation profiles during high speed centrifugation. When properly planned and executed, an AUC sedimentation velocity or sedimentation equilibrium experiment can reveal a great deal about a protein in regards to size and shape, sample purity, sedimentation coefficient, oligomerization states and protein-protein interactions.
This technique, however, requires a rigorous level of technical attention. Sample cells hold a sectored center piece sandwiched between two window assemblies. They are sealed with a torque pressure of around 120-140 in/lbs. Reference buffer and sample are loaded into the centerpiece sectors and then after sealing, the cells are precisely aligned into a titanium rotor so that the optical detection systems scan both sample and reference buffer in the same radial path midline through each centerpiece sector while rotating at speeds of up to 60, 000 rpm and under very high vacuum
Not only is proper sample cell assembly critical, sample cell components are very expensive and must be properly cared for to ensure they are in optimum working condition in order to avoid leaks and breakage during experiments. Handle windows carefully, for even the slightest crack or scratch can lead to breakage in the centrifuge. The contact between centerpiece and windows must be as tight as possible; i.e. no Newton s rings should be visible after torque pressure is applied. Dust, lint, scratches and oils on either the windows or the centerpiece all compromise this contact and can very easily lead to leaking of solutions from one sector to another or leaking out of the centerpiece all together. Not only are precious samples lost, leaking of solutions during an experiment will cause an imbalance of pressure in the cell that often leads to broken windows and centerpieces. In addition, plug gaskets and housing plugs must be securely in place to avoid solutions being pulled out of the centerpiece sector through the loading holes by the high vacuum in the centrifuge chamber. Window liners and gaskets must be free of breaks and cracks that could cause movement resulting in broken windows.
This video will demonstrate our procedures of sample cell assembly, torque, loading and rotor alignment to help minimize component damage, solution leaking and breakage during the perfect AUC experiment.

The analytical ultracentrifuge (AUC) sample cell holds sample and reference buffer and during experiments and is exposed to high vacuum and rotor speeds up to 60,000 rpm. This video will demonstrate the rigorous attention to detail necessary for assembly, loading and alignment of this very important component of an AUC experiment.

Assemblaggio, carico, allineamento e di una cella analitica del campione Ultracentrifuga

The analytical ultracentrifuge (AUC) is a powerful biophysical tool that allows us to record macromolecular sedimentation profiles during high speed ...

Live Cell Calcium Imaging Combined with siRNA Mediated Gene Silencing Identifies Ca2+ Leak Channels in the ER Membrane and their Regulatory Mechanisms

In mammalian cells, the endoplasmic reticulum (ER) plays a key role in protein biogenesis as well as in calcium signalling1. The heterotrimeric Sec61 complex in the ER membrane provides an aqueous path for newly-synthesized polypeptides into the lumen of the ER. Recent work from various laboratories suggested that this heterotrimeric complex may also form transient Ca2+ leak channels2-8. The key observation for this notion was that release of nascent polypeptides from the ribosome and Sec61 complex by puromycin leads to transient release of Ca2+ from the ER. Furthermore, it had been observed in vitro that the ER luminal protein BiP is involved in preventing ion permeability at the level of the Sec61 complex9,10. We have established an experimental system that allows us to directly address the role of the Sec61 complex as potential Ca2+ leak channel and to characterize its putative regulatory mechanisms11-13. This system combines siRNA mediated gene silencing and live cell Ca2+ imaging13. Cells are treated with siRNAs that are directed against the coding and untranslated region (UTR), respectively, of the SEC61A1 gene or a negative control siRNA. In complementation analysis, the cells are co-transfected with an IRES-GFP vector that allows the siRNA-resistant expression of the wildtype SEC61A1 gene. Then the cells are loaded with the ratiometric Ca2+-indicator FURA-2 to monitor simultaneously changes in the cytosolic Ca2+ concentration in a number of cells via a fluorescence microscope. The continuous measurement of cytosolic Ca2+ also allows the evaluation of the impact of various agents, such as puromycin, small molecule inhibitors, and thapsigargin on Ca2+ leakage. This experimental system gives us the unique opportunities to i) evaluate the contribution of different ER membrane proteins to passive Ca2+ efflux from the ER in various cell types, ii) characterize the proteins and mechanisms that limit this passive Ca2+ efflux, and iii) study the effects of disease linked mutations in the relevant components.

Live Cell Calcium Imaging Combined with siRNA Mediated Gene Silencing Identifies Ca2+ Leak Channels in the ER Membrane and their Regulatory Mechanisms

The endoplasmic reticulum plays a key role in protein biogenesis and in calcium homeostasis. We have established an experimental system that allows us to address the role of Ca2+ leak channels and to characterize their putative regulatory mechanisms. This system involves siRNA mediated gene silencing and live cell Ca2+ imaging.

Vivere Imaging calcio cella Combinato con il silenziamento del gene mediata siRNA Identifica Ca 2 + Canali di perdite nella membrana ER e nei relativi meccanismi regolatori

In mammalian cells, the endoplasmic reticulum (ER) plays a key role in protein biogenesis as well as in calcium signalling1. The heterotrimeric Sec61 ...

Expression and Purification of Virus-like Particles for Vaccination

Virus-like particles (VLPs) and subviral particles (SVPs) are an alternative approach to viral vaccine design that offers the advantages of increased biosafety and stability over use of live pathogens. Non-infectious and self-assembling, VLPs are used to present structural proteins as immunogens, bypassing the need for live pathogens or recombinant viral vectors for antigen delivery. In this article, we demonstrate the different stages of VLP design and development for future applications in preclinical animal testing. The procedure includes the following stages: selection of antigen, expression of antigen in cell line of choice, purification of VLPs/SVPs, and quantification for antigen dosing. We demonstrate use of both mammalian and insect cell lines for expression of our antigens and demonstrate how methodologies differ in yield. The methodology presented may apply to a variety of pathogens and can be achieved by substituting the antigens with immunogenic structural proteins of the user&#39;s microorganism of interest. VLPs and SVPs assist with antigen characterization and selection of the best vaccine candidates.

Here, we present a protocol for synthesizing virus-like particles using either baculovirus or mammalian expression systems, and ultracentrifugation purification. This highly customizable approach is used to identify viral antigens as vaccine targets in a safe and flexible manner.

Espressione e purificazione di particelle virus-simili per la vaccinazione

Virus-like particles (VLPs) and subviral particles (SVPs) are an alternative approach to viral vaccine design that offers the advantages of increased ...

Monitoring ER/SR Calcium Release with the Targeted Ca2+ Sensor CatchER+

Intracellular calcium (Ca2+) transients evoked by extracellular stimuli initiate a multitude of biological processes in living organisms. At the center of intracellular calcium release are the major intracellular calcium storage organelles, the endoplasmic reticulum (ER) and the more specialized sarcoplasmic reticulum (SR) in muscle cells. The dynamic release of calcium from these organelles is mediated by the ryanodine receptor (RyR) and the inositol 1,4,5-triphosphate receptor (IP3R) with refilling occurring through the sarco/endoplasmic reticulum calcium ATPase (SERCA) pump. A genetically encoded calcium sensor (GECI) called CatchER was created to monitor the rapid calcium release from the ER/SR. Here, the detailed protocols for the transfection and expression of the improved, ER/SR-targeted GECI CatchER+ in HEK293 and C2C12 cells and its application in monitoring IP3R, RyR, and SERCA pump-mediated calcium transients in HEK293 cells using fluorescence microscopy is outlined. The receptor agonist or inhibitor of choice is dispersed in the chamber solution and the intensity changes are recorded in real time. With this method, a decrease in ER calcium is seen with RyR activation with 4-chloro-m-cresol (4-cmc), the indirect activation of IP3R with adenosine triphosphate (ATP), and inhibition of the SERCA pump with cyclopiazonic acid (CPA). We also discuss protocols for determining the in situ Kd and quantifying basal [Ca2+] in C2C12 cells. In summary, these protocols, used in conjunction with CatchER+, can elicit receptor mediated calcium release from the ER with future application in studying ER/SR calcium related pathologies.

Monitoring ER/SR Calcium Release with the Targeted Ca2+ Sensor CatchER+

We present protocols for the application of our targeted genetically-encoded calcium indicator (GECI) CatchER+ for monitoring rapid calcium transients in the endoplasmic/sarcoplasmic reticulum (ER/SR) of HEK293 and skeletal muscle C2C12 cells using real-time fluorescence microscopy. A protocol for the in situ Kd measurement and calibration is also discussed.

Monitoraggio del rilascio di Calcio di ER / SR con la Targeted Ca<sup&gt; 2+</sup&gt; Sensore CatchER<sup&gt; +</sup

Intracellular calcium (Ca2+) transients evoked by extracellular stimuli initiate a multitude of biological processes in living organisms. At the center of ...

Imaging Intermediate Filaments and Microtubules with 2-dimensional Direct Stochastic Optical Reconstruction Microscopy

The cytoskeleton, composed of actin microfilaments, microtubules, and intermediate filaments (IF), plays a key role in the control of cell shape, polarity, and motility. The organization of the actin and microtubule networks has been extensively studied but that of IFs is not yet fully characterized. IFs have an average diameter of 10 nm and form a network extending throughout the cell cytoplasm. They are physically associated with actin and microtubules through molecular motors and cytoskeletal linkers. This tight association is at the heart of the regulatory mechanisms that ensure the coordinated regulation of the three cytoskeletal networks required for most cell functions. It is therefore crucial to visualize IFs alone and also together with each of the other cytoskeletal networks. However, IF networks are extremely dense in most cell types, especially in glial cells, which makes its resolution very difficult to achieve with standard fluorescence microscopy (lateral resolution of ~250 nm). Direct STochastic Optical Reconstruction Microscopy (dSTORM) is a technique allowing a gain in lateral resolution of one order of magnitude. Here, we show that lateral dSTORM resolution is sufficient to resolve the dense organization of the IF networks and, in particular, of IF bundles surrounding microtubules. Such tight association is likely to participate in the coordinated regulation of these two networks and may, explain how vimentin IFs template and stabilize microtubule organization as well as could influence microtubule dependent vesicular trafficking. More generally, we show how the observation of two cytoskeletal components with dual-color dSTORM technique brings new insight into their mutual interaction.

The overall goal of this methodology is to give the optimal experimental conditions from sample preparation to image acquisition and reconstruction in order to perform 2D dual color dSTORM images of microtubules and intermediate filaments in fixed cells

I filamenti intermedi e microtubuli con microscopia di ricostruzione ottico stocastico diretto 2-dimensionale di imaging

The cytoskeleton, composed of actin microfilaments, microtubules, and intermediate filaments (IF), plays a key role in the control of cell shape, ...

Fluorescence Recovery after Photobleaching of Yellow Fluorescent Protein Tagged p62 in Aggresome-like Induced Structures

Fluorescence recovery after photobleaching (FRAP)&#160;is a microscopy technique that can be used to quantify protein mobility in live cells. In a typical FRAP experiment, steady-state fluorescence is observed by repeated imaging with low-intensity laser light. Subsequently, the fluorescent molecules are rapidly and irreversibly impaired via brief exposure to high-intensity laser light. Information about protein mobility is obtained by monitoring the recovery of fluorescence. We used FRAP to determine the mobility of p62 in aggresome-like induced structures (ALIS) in murine macrophages after stimulation with lipopolysaccharide (LPS). Because many existing FRAP protocols are either incomplete or complex, our goal was to provide a comprehensive, practical, and straightforward step-by-step protocol for FRAP experiments with live cells. Here, we describe RAW264.7 macrophage transfection with yellow fluorescent protein-p62 (YFP-p62), induction of ALIS by exposing the cells to LPS, and a step-by-step method for collecting prebleach and postbleach FRAP images and data analysis. Finally, we discuss important factors to consider when conducting a FRAP experiment.

We describe a comprehensive and practical protocol for fluorescence recovery after photobleaching experiments with live cells. Although the protocol was used to measure the mobility of yellow fluorescent protein-tagged p62 in aggresome-like induced structures, it can be applied to a variety of microscopy systems and fluorescent proteins.

Recupero di fluorescenza dopo Photobleaching di giallo fluorescente proteine Tagged p62 in Aggresome-come le strutture indotta

Fluorescence recovery after photobleaching (FRAP)&#160;is a microscopy technique that can be used to quantify protein mobility in live cells. In a typical ...

Imaging Calcium Dynamics in Subpopulations of Mouse Pancreatic Islet Cells

Pancreatic islet hormones regulate blood glucose homeostasis. Changes in blood glucose induce oscillations of cytosolic calcium in pancreatic islet cells that trigger secretion of three main hormones: insulin (from &#946;-cells), glucagon (&#945;-cells) and somatostatin (&#948;-cells). &#946;-Cells, which make up the majority of islet cells and are electrically coupled to each other, respond to the glucose stimulus as one single entity. The excitability of the minor subpopulations, &#945;-cells and &#948;-cells (making up around 20% (30%) and 4% (10%) of the total rodent1 (human2) islet cell numbers, respectively) is less predictable and is therefore of special interest.
Calcium sensors are delivered into the peripheral layer of cells within the isolated islet. The islet or a group of islets is then immobilized and imaged using a fluorescence microscope. The choice of the imaging mode is between higher throughput (wide-field) and better spatial resolution (confocal). Conventionally, laser scanning confocal microscopy is used for imaging tissue, as it provides the best separation of the signal between the neighboring cells. A wide-field system can be utilized too, if the contaminating signal from the dominating population of &#946;-cells is minimized.
Once calcium dynamics in response to specific stimuli have been recorded, data are expressed in numerical form as fluorescence intensity vs. time, normalized to the initial fluorescence and baseline-corrected, to remove the effects linked to bleaching of the fluorophore. Changes in the spike frequency or partial area under the curve (pAUC) are computed vs. time, to quantify the observed effects. pAUC is more sensitive and quite robust whereas spiking frequency provides more information on the mechanism of calcium increase.
Minor cell subpopulations can be identified using functional responses to marker compounds, such as adrenaline and ghrelin, that induce changes in cytosolic calcium in a specific populations of islet cells.

Here, we present a protocol for imaging and quantifying calcium dynamics in heterogeneous cell populations, such as pancreatic islet cells. Fluorescent reporters are delivered into the peripheral layer of cells within the islet, which is then immobilized and imaged, and per-cell analysis of the dynamics of fluorescence intensity is performed.

Imaging calcio Dynamics in sottopopolazioni di cellule di islet pancreatica del topo

Pancreatic islet hormones regulate blood glucose homeostasis. Changes in blood glucose induce oscillations of cytosolic calcium in pancreatic islet cells ...