Este trabajo ha sido apoyado por becas de la Deutsche Forschungsgemeinschaft (DFG) BL567/3-1 y la Friedrich-Baur-Stiftung. Nos gustaría dar las gracias a Roger Y. Tsien, Howard Hughes Medical Institute Laboratorios de la Universidad de California, San Diego por darnos Tag-RFP-T2. Nosotros afortunadamente reconocemos David Baltimore, Instituto de Tecnología de California, Pasadena, y Didier Trono, de la Universidad de Ginebra, Ginebra, por brindarnos la lentiviral plásmidos FUGW y psPAX2/pMD2.G.

<ol>
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Los autores declaran que no tienen intereses financieros en competencia.

Las ventajas y desventajas del método TED se han discutido ampliamente en publicaciones recientes 34,35. En comparación con otros métodos descritos anteriormente, el TED evita el problema de la interrupción y la perfusión de las células. Por otra parte, dos aspectos deben ser enfatizado. El principio de TED para ER imágenes de calcio requiere de (1.) La expresión selectiva de una carboxilesterasa activo en el lumen del retículo endoplasmático con la ayuda de TED constructos vectoriales y (2.) La lib...

Con el fin de resolver las respuestas fisiológicas del calcio ER, hemos desarrollado una nueva estrategia para mejorar la captura de tintes sensibles calcio sintéticos en la sala de emergencias. El método permite la monitorización en tiempo real, directa, sin interrupciones del libre ER calcio en presencia de calcio extracelular. Función y señalización de calcio ER Señales de calcio se encuentran en diferentes tipos de células, por ejemplo células de músculo, neuronas y células gliales y su gama de funciones de la mediación de la contracción del músculo a una participación en la transmisión sináptica en el aprendizaje y la memoria 1,2. Los cambios en la concentración de calcio libre son de alto interés científico porque el calcio está implicado en la regulación de la transcripción de genes, la proliferación celular, la excitabilidad neuronal, muerte celular y otros eventos de señalización celular 1-7. Todas estas señales de calcio celulares están funcionalmente conectados y contribuyen a intracelular de calciotienda 8-10 dinámica. Una característica común entre todas las señales de calcio es el flujo de calcio entre el espacio extracelular, el citosol y los orgánulos, principalmente la sala de emergencia y las mitocondrias. Esto hace que los cambios dinámicos en la concentración de calcio dentro de estos orgánulos, los cuales son percibidos por los diferentes componentes de señalización. En general, la concentración de calcio en los rangos de ER entre 100 a 800 mM, en el citosol de la concentración de calcio es cerca de 100 nM, y en el espacio extracelular, la concentración es de alrededor de 1-2 mM. En consecuencia, hay una fuerza motriz química alta para el flujo de calcio hacia el citosol 2,9,10. Las señales de calcio derivados del ER más comúnmente investigados dependen de la estimulación de receptores acoplados a proteína G (GPCR), que a continuación, activan la fosfolipasa C (PLC). PLC a su vez produce inositol 1,4,5-trifosfato (IP 3) 1. Tras la unión de IP3 a su receptor (IP-3 Rec., Figura 1) en el ER-membrana, los iones de calcio son liberados desde el lumen del retículo endoplasmático. Históricamente, la liberación de calcio mediada por IP 3 de la ER fue el primero - aunque indirectamente - medido en células pancreáticas acinares por Streb et al en 1983 11.. Esta publicación sugirió por primera vez una cascada de señalización que implica la acetilcolina, la fosfolipasa C, y IP 3. Esta forma de liberación de calcio se denomina generalmente la liberación de calcio inducida por 3-IP (TIIE) (Figura 1). La activación de la quinasa dependiente de fosfolipasa Cγ por receptores tirosina quinasas vincula la acción de factores de crecimiento y factores neurotróficos para ER señalización de calcio después de IP3 elevación 12. Además de TIIE, elevación de calcio puede ser mediada por la entrada de calcio ionotrópicos, por ejemplo a través de los canales de calcio dependientes de voltaje (CA V), y la posterior liberación de calcio inducida por calcio (CICR) por rianodina receptores (RyR). TIIE y el CICR están fisiológicamente vinculados a la entrada de calcio tienda que funciona (SOCE). SOCE incluye la acción de STIM (molécula interactuante estroma), que es un sensor para la liberación de calcio ER. STIM se ha demostrado que estimula la entrada de calcio extracelular a través de canales receptores de potencial transitorio (TRP) 13, Orai canales de calcio y hasta 14 canales de calcio dependientes del voltaje 15 (Figura 1). La pérdida de calcio ER es rescatado dinámicamente por la acción del retículo endoplásmico sarco-ATPasa de calcio (SERCA), que activa las bombas de calcio de nuevo en la sala de emergencias. El bloqueo de la SERCA con fármacos tales como tapsigargina presenta una pérdida continua de calcio ER para el compartimiento citosólico. Esta ER calcio &quot;fuga&quot; es causado por ER complejos de poro intramembrane tales como el complejo de proteína Sec61 16,17 (Figura 1). En 1998, Berridge publicó un modelo, la &quot;neurona dentro de un modelo de neurona&quot;, which sugiere un papel fisiológico principio de la ER en la integración de calcio neuronal 5. Este modelo considera la existencia de un sistema de membrana del RE continua que forma una &quot;imagen&quot; intracelular de la membrana plasmática neuronal 5. Este sistema de membranas eucariotas binario se afirma que es un requisito básico para la integración temporal y espacial de las señales de calcio rápidos y lentos en las neuronas. Señales de calcio que se producen ya sea concomitantemente o posteriormente en diferentes espinas o dendritas de la misma neurona se confieren al soma o núcleo a través de la sala de emergencias, en el que se resumen 5,18 de la célula. Entonces, su suma puede tener efectos sobre la excitabilidad de la neurona, la regulación de la transcripción de genes o la integración de cascadas de señalización. Por lo tanto, la sala de emergencias apoya la integración de las señales de calcio. Un requisito previo para este concepto es la continuidad de la ER en una sola célula, que ha sido reclamada por varios estudios y que se ha demostrado al menos para somato-dáreas endritic y corta distancia proyecciones axonales 19-21. Si hay continuidad ER dentro de proyecciones axonales largas es una cuestión de debate. Estrategias para medir el flujo de calcio libre sobre la membrana ER Señales de calcio se controlan con mayor frecuencia en el citosol 22,23. Por lo tanto, no puede ser distinguido fácilmente si Ca 2 + está fluyendo hacia el citosol a partir extracelular o intracelular de las tiendas 6,24. Para superar esta limitación, se han desarrollado estrategias metodológicas para la obtención de imágenes directas de calcio ER. En resumen, se utilizan las siguientes estrategias: (1) ER-dirigidos ingeniería genética de proteínas indicadores 25-27 de baja afinidad Ca 2 + indicadores basados ​​en la proteína utilizan la proteína aequorina bioluminiscente o GFP en combinación con una proteína de detección. Calcio. Estos Ca 2 + indicadores de ingeniería genética (Gecis) puedeser dirigidos a la sala de emergencia con la ayuda de un péptido señal y se mantienen activamente en el ER mediante un motivo de retención y recuperación. Común ER Ca 2 + indicadores de base en el principio de Cameleon y son el Cameleon YC4.3 26,28; Cameleon división YC7.3ER 29 y Cameleon D1 30. (2) Directo carga de colorante a base de esterasa AM-éster de baja afinidad Ca 2 + indicadores. 31,32 de los colorantes indicadores (Mag-Fura2-AM, Mag-Fluo4-AM o Fluo5N-AM)-derivados AM pasar el membranas biológicas en un estado lipofílica, calcio y minúsculas. Entonces, en el citosol, así como en la sala de emergencias, esterasas endógenas escindir el grupo de AM-éster y liberan el indicador de Ca 2 +, dejando tras de sí una cierta cantidad de colorante activo en el citosol y en la sala de emergencias. Por lo tanto, este enfoque es útil en condiciones de una alta concentración de calcio en la sala de emergencias, siempre y cuando la concentración de calcio citosólico se mantiene muy por debajo de la delímite de protección de los indicadores de baja afinidad, en particular durante las señales de calcio características (por ejemplo nM a mM bajas). (3) de carga AM-éster en combinación con permeabilización de la membrana plasmática 32. Cualquier + indicador restante citosólica de Ca 2 se elimina mediante permeabilización de la membrana de plasma con pequeñas cantidades de un detergente &quot;suave&quot; (por ejemplo, saponina) en un tampón intracelular artificial. Por lo tanto, las membranas intracelulares pueden ser estimuladas, por ejemplo, con IP 3 en el tampón intracelular, directamente a través de &quot;poros&quot; en la membrana plasmática. (4) Diálisis del citosol bajo configuración de célula y las mediciones simultáneas de Ca 2 + en el lumen del RE y el citosol 32,33. Una celda se carga por primera vez con una baja afinidad Ca 2 + indicador (por ejemplo, Mag-Fura2- AM, radiométrico, la luz ultravioleta). Después, con la ayuda de una pipeta de parche, cualquier cyt restanteCa + Indicador de baja afinidad 2 osolic se dializa fuera del citosol con un tampón que contiene un indicador de Ca 2 + de alta afinidad (por ejemplo, Fluo-3, la luz visible). Esta estrategia permite la grabación simultánea de señales derivadas citosólicas y ER. (5) Targeted-esterasa inducida colorante de carga 8,34. Un carboxilesterasa (CES) se dirige al lumen del ER y proporciona una alta actividad de esterasa para la captura eficiente de la forma de AM-éster de baja afinidad Ca 2 + indicadores. Inducida Targeted-esterasa colorante de carga (TED) Para mejorar la focalización de baja afinidad Ca 2 + indicadores a la luz del RE, TED se ha desarrollado. TED requiere la sobreexpresión de una carboxilesterasa ER dirigido ratón (CES2) (Figura 2), que se consigue a través de construcciones de expresión. Las células que expresan un CES-constructo recombinante se incuban con la forma de AM-éster de un calcio enindicador colorante (Fluo5N-AM, la Figura 2). A continuación, en la sala de emergencias, el colorante se convierte en el Ca 2 + sensibles, membrana impermeable Ca 2 + complejo indicador (Fluo5N/Ca 2 +) por la alta actividad de esterasa, por lo tanto atrapando el colorante en una alta concentración en el lumen del RE 8 , 34. El método es especialmente útil para investigar-ER liberación de calcio a través de las vías de TIIE-por ejemplo a través de metabotrópicos purinérgicos-o receptores de glutamato, 8,34 y para visualizar el agotamiento de calcio ER a través de &quot;canales de fugas&quot; directamente, por ejemplo, después del bloqueo de la SERCA 17 , 34. Para nuestra experiencia, la baja afinidad de Ca 2 + indicador Fluo5N-AM es actualmente el mejor indicador disponible para su uso con la estrategia de carga TED tinte. Fluo5N-AM tiene una baja afinidad por Ca 2 + (constante de disociación K D ~ 90 mM, Figura 2), es casi no fluorescente en su AM-forma, pero ofrece una alta emisión de fluorescencia a calciu8,34 m vinculante. El Fluo5N/Ca 2 + complejo puede ser excitado con una fuente de luz estándar de ~ 490 nm, que corresponde a los tintes estándar tales como FITC, Alexa 488, o eGFP. Señales de calcio citosólico apenas alcanzan una concentración en el rango de baja mu M y por lo tanto apenas se detectaron por Fluo5N en el citosol 35. Para mejorar el funcionamiento del TED, se han desarrollado varias construcciones de vectores recombinantes (Figura 3). Originalmente, los vectores de TED basado en la secuencia de codificación de CES2 (Refseq número de acceso NM_145603, CES2c) y mejor funcionamiento del TED se observa con expresión estable de construcciones de CES. Nuevos vectores TED expresan un elemento central de CES2 fusionado a la proteína roja fluorescente TagRFP-T2 36. Estos vectores tienen la ventaja de que pueden ser utilizados para identificar las células transducidas y para utilizar la fluorescencia roja como un control interno para la normalización de los cambios en Fluo5N/Ca 2 + fluorescencia. La fluorescencia de color rojo también ofrece la posibilidad de visualizar la distribución estructural de la sala de emergencia y los cambios en la dinámica de ER en condiciones de estimulación.

<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)

Visualización de la dinámica de calcio es importante para entender el papel del calcio en la fisiología celular. Para examinar la dinámica del calcio, fluorescentes Ca 2 + indicadores sintéticos se han vuelto populares. Aquí demostramos TED (= carga de colorante inducida dirigido-esterasa), un método para mejorar la liberación de Ca 2 + colorantes indicadores en el lumen del retículo endoplasmático de diferentes tipos de células. Hasta la fecha, el TED se utilizó en líneas celulares, células gliales y neuronas in vitro. Bases TED en eficiencia, recombinante orientación de una actividad de alto carboxilesterasa al lumen ER usando vectores construcciones que carboxilesterasas expresos (CES). Los últimos vectores TED contienen un elemento central de CES2 fusionado a una proteína fluorescente de color rojo, lo que permite simultánea de imágenes de dos colores. La dinámica de calcio libre en el ER se obtuvieron imágenes en un solo color, mientras que la estructura ER correspondiente aparece en rojo. Al comienzo del procedimiento, las células son transducidas con un lentivirus. Posteriormente, las células infectadas unare sembraron en cubreobjetos para finalmente permitir imágenes de células vivas. Entonces, las células vivas se incuban con el éster de acetoximetilo (AM-éster) de forma de baja afinidad Ca 2 + indicadores, por ejemplo Fluo5N-AM, Mag-Fluo4-AM, o Mag-Fura2-AM. La actividad esterasa en los unirá ER frente cadenas laterales hidrófobas de la forma de AM de la Ca 2 + indicador y un colorante fluorescente / Ca 2 + complejo hidrófilo se forma y atrapado en el lumen del RE. Después de colorante de carga, las células se analizaron en un microscopio de barrido láser confocal invertido. Las células se sometieron a perfusión continua con soluciones de Ringer-como y la dinámica del calcio ER son directamente visualizada por time-lapse. La liberación de calcio desde el RE se identifica por una disminución en la intensidad de fluorescencia en las regiones de interés, mientras que la recarga de la tienda de calcio ER produce un aumento en la intensidad de fluorescencia. Por último, el cambio en la intensidad de fluorescencia con el tiempo se determina mediante el cálculo de Delta F / F 0.

Este protocolo proporciona un enfoque no-perjudicial para la imagen directa de la libre ER calcio. De baja afinidad sintética Ca 2 + indicadores son liberados y atrapados en el lumen del RE con la ayuda de un ER específica, actividad de la enzima esterasa recombinante. Mejora de la carga de la Ca 2 + indicador tintes para el ER lumen permite una imagen directa y rápida de la dinámica de la tienda calcio ER. Tipos de células de TED La viabi...

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

Targeted-esterasa inducida colorante de carga (TED) es compatible con el análisis de la dinámica del almacén de calcio intracelular por imágenes de fluorescencia. El método basa en la orientación de un carboxilesterasa recombinante para el retículo endoplásmico (ER), donde mejora el desenmascaramiento local del sintético de baja afinidad Ca<sup&gt; 2 +</sup&gt; Tintes indicadores en el lumen del RE.

Direct Imaging de calcio ER con Targeted-esterasa inducida colorante de carga (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 vistas.  University of Wuerzburg. Targeted-esterasa inducida colorante de carga (TED) es compatible con el análisis de la dinámica del almacén de calcio intracelular por imágenes de fluorescencia. El método basa en la orientación de un carboxilesterasa recombinante para el retículo endoplásmico (ER), donde mejora el desenmascaramiento local del sintético de baja afinidad Ca 2 + Tintes indicadores en el lumen del RE.

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.

Cargando Drosophila terminales nerviosas con indicadores de 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 ...

Investigación

Biología

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 .

En Vivo 2-Photon imágenes de calcio en la capa 2 / 3 de los ratones

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.

Imagen de calcio de las neuronas corticales con Fura-2 a.m.

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.

Concentración, la carga, y la alineación de una célula de ultracentrifugación analítica de muestras

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.

Imágenes en vivo del calcio celular combinado con el silenciamiento de genes mediada por siRNA Identifica Ca 2 + Canales de fugas en la membrana del ER y sus mecanismos de regulación

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.

Expresión y purificación de partículas similares al virus para la Vacunación

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.

Seguimiento de la liberación de calcio ER / SR con el Ca<sup&gt; 2+</sup&gt; Sensor de Captura<supUnesdoc.unesco.org unesdoc.unesco.org</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

Filamentos intermedios y microtúbulos con microscopía de reconstrucción óptica estocástica directo 2-dimensional de imágenes

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.

Recuperación de fluorescencia Tras Fotoblanqueo de amarillo fluorescente proteína Tagged p62 en estructuras Aggresome inducida por

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.

Imagen de la dinámica del calcio en subpoblaciones de células de islotes pancreáticos de ratón

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