Agradecemos el laboratorio O&#39;Bryan en la UIC para la evaluación experimental y la discusión crítica. Este trabajo fue apoyado por la American Heart Association Beca 11SDG5230003 al Centro GKC y Nacional para el Avance de la Ciencia Traslacional - UIC Centro de Ciencias de la clínica y traslacional Grant UL1TR000050.

1. Transfección celular <ol><li> Células de la placa el día antes de la transfección, plateando el menor número de células de inmunofluorescencia. <ol><li> Por inmunofluorescencia: en una placa de 6 pocillos, escudo cubreobjetos de vidrio (1 por pocillo) con 0,02% de gelatina a 37 ° C durante al menos 4 horas, se lava una vez con medio, y para cada pozo, placa 1 x 10 5 células HEK 293T las células en 2 ml de medio de crecimiento completo [medio de Eagle modificado de Dulbecco (DMEM) más 10% de FBS]. </li><li> Para citometría de flujo y análisis de transferencia Western: placa de 1,2 x 10 5 células HEK 293T / pocillo en 2 ml de medio de crecimiento completo en placa de 6 pocillos (5 x 10 células HEK 293T 0,3 en 0,5 ml de medio de crecimiento completo por pocillo en placas de 24 pocillos ). </li></ol></li><li> Preparar ADN para la transfección de acuerdo con el protocolo de fabricación: Effectene (Qiagen) se utiliza para inmunofluorescencia. TransIT-LT1 (Mirus) se utiliza para citometría de flujo y análisis de transferencia de Western. Cantidad de ADN usada se enumeran a continuación. <table border="1"><tbody><tr><td&gt; </td><td> Placa de 24 pocillos (ng) </td><td> Placa de 6 pocillos (ng) </td></tr><tr><td> CFP-vector </td><td> 10 </td><td> 50 </td></tr><tr><td> VN N-AKAP-Lbc </td><td> 200 </td><td> 1000 </td></tr><tr><td> VC N-PDE4D3-FL (longitud completa PDE4D3) </td><td> 2,5, 5, 10, 20, 40, 80 </td><td> 100 </td></tr><tr><td> VC-N-PDE4D3 UCR1 (un fragmento N-terminal de PDE4D3 que contiene el dominio UCR1) </td><td></td><td> 100 </td></tr><tr><td> VC-N-PDE4D3 UCR2 + CAT (un fragmento C-terminal de PDE4D3 que contiene los dominios UCR2 y catalítica) </td><td></td><td> 100 </td></tr></tbody></table> La transfección utilizando Effectene (6 pocillos): <ol><li> Añadir cantidad indicada de ADN plásmido + 4 l potenciador a 100 l de tampón CE, la mezcla, y se incuba durante 5 min a temperatura ambiente. </li><li> Añadir 5 l Effectene, mezclar e incubar durante 10 minutos atemperatura ambiente. Añadir gota a gota a las células. </li></ol> La transfección con tránsito LT1 (6-well/24-well): <ol><li> Añadir cantidad indicada de ADN plásmido a 250 μl/50 l de Opti-MEM medio libre de suero que en un tubo estéril. </li><li> Añadir TransIT-LT1 reactivos a la mezcla de ADN diluido y pipetear suavemente para mezclar. (Tránsito-LT1 Reactivo: relación DNA es de 3 l de tránsito LT1 reactivo por 1 g de ADN). </li><li> Incubar durante 30 minutos a temperatura ambiente y añadir, gota a gota a las células. </li></ol></li></ol> 2. Preparación de las células para citometría de flujo, Western Blot e inmunofluorescencia <ol><li> 24 h después de la transfección, compruebe fluorescencia al microscopio de epifluorescencia antes de recoger las células. </li><li> Preparación de las células para el análisis de citometría de flujo: <ol><li> Lavar las células con 0,5 ml / 2 ml de PBS enfriado en hielo para las placas 24-well/6-well. </li><li> Separar las células utilizando 50 μl/250 l 0,05% de tripsina. </li><li> Neutralizar la tripsina con 200 l / 1 ml de medio DMEM. </li><li> Collect 250 células l (tanto para la placa de 24 pocillos y 6 pocillos) por centrifugación a 500 xg durante 5 min, se utilizan las células restantes (1 ml) para análisis de transferencia Western. </li><li> Resuspender las células en 250 l de tampón FACS [PBS + 0,5% (w / v) de BSA + 2 mM de EDTA], almacenar en hielo para el análisis de citometría de flujo. Las células también pueden ser fijadas en paraformaldehído al 1% (en PBS) si el análisis de citometría de flujo no será inmediata. </li></ol></li><li> Preparación de las células para el análisis de Western blot: lleva a cabo en paralelo con la preparación de células para el análisis de citometría de flujo. <ol><li> Lavar las células 1 vez con 2 ml de PBS enfriado en hielo, lisar las células mediante la adición de 100 l de tampón de lisis celular [10 mM de tampón de fosfato de sodio, pH 6,95, 150 mM de NaCl, 5 mM de EDTA, 5 mM EGTA, 1% de Triton X-100] . </li><li> Recoger lisado de células por centrifugación durante 10 min a 21.000 xg a 4 ° C. </li><li> Cuantificar la concentración de proteína mediante el ensayo de proteínas Bradford, cargar la misma cantidad de proteína por carril para SDS-PAGE y transferencia a nitrocelulosa para inmunotransferencia. </li></ol&gt; </li><li> Preparación de las células para inmunofluorescencia. <ol><li> Lavar las células 3 veces con 2 ml de PBS, fijar las células en 1 ml de paraformaldehído al 3,7% (en PBS) durante 10 min a temperatura ambiente, a continuación, lavar 3 veces con 2 ml de PBS durante 5 min. </li><li> Monte cubreobjetos sobre un portaobjetos de vidrio, utilizando medio de montaje. Selle los bordes cubreobjetos utilizando esmalte de uñas si es necesario. </li><li> Guarde las diapositivas a 4 ° C antes del examen. </li></ol></li></ol> 3. Citometría de flujo y microscopía de inmunofluorescencia <ol><li> La citometría de flujo se realizó utilizando un Beckman Coulter Cian ADP, equipada con 488 nm, 405 nm, 642 nm y los láseres de estado sólido. Cumbre software se utiliza para la adquisición y análisis. <ol><li> Calibrar citómetro de flujo usando perlas estándar. </li><li> Terreno dispersión frontal (FSC) / Inclinación de lado de dispersión (SSC) en una escala lineal para la población de células vivas de puerta. </li><li> Terreno FSC / tensión ancho de pulso de la población de células vivas no agregada gating. </li><li> Terreno count/FL6 (PPC fluorescence, 405 nm) en una escala logarítmica para las células PPC-positivos en vivo no agregadas de activación periódica. </li><li> Terreno count/FL1 (YFP fluorescencia, 488 nm) en una escala logarítmica de la intensidad BiFC. </li><li> Ejecutar las muestras negativas YFP-PPC-doble, ajuste FSC, SSC, FL1 y FL6 foto tubo multiplicador (PMT) para ajustar la tensión de umbral para cada señal. </li><li> Ejecute un solo positivo (tanto YFP y PPC + +) muestras para futuras compensaciones fuera de línea </li><li> Adquirir al menos 10.000 eventos cerradas (células no agregadas en vivo PPC +) para su análisis. </li></ol></li><li> La inmunofluorescencia se realizó con un LSM 510 microscopio confocal Zeiss Nota:. Es importante tener todas las configuraciones (como el zoom, pinhole, la ganancia del detector, amplificador de desplazamiento, tamaño, velocidad de exploración, exploración de la media, y la potencia del láser) consistente entre muestras para comparación adecuada de todos los datos. </li></ol> 4. Análisis de Datos (realizó utilizando el software Summit) <ol><li> Configurar el protocolo de análisis similar a la de acquisition con la selección adecuada: Puerta 1 en gráfico de puntos de FSC / SSC para las células vivas. Puerta 2 de FSC / ancho de pulso de la puerta 1 para las células vivas no agregados. Puerta 3 en el recuento / PPC de la puerta 3 de la PPC no agregada + células vivas. </li><li> Compensar YFP y PPC señal usando + y PPC + células positivas individuales YFP. </li><li> Vuelva a determinar las líneas de corte para las células CFP / YFP-positivo. </li><li> Export YFP intensidad media de fluorescencia (MFI) de PPC + células a Excel de datos de trazado. </li><li> Normalizar YFP IMF a los niveles de expresión de AKAP-Lbc, PDE4D3, y control de carga α-tubulina, según se determinó por Western blot. </li></ol>

<ol>
	<li>Collura, V., Boissy, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+protein-protein+complexes+to+interactomics.">From protein-protein complexes to interactomics.</a> Subcell Biochem. 43, 135-183 (2007).</li><li>Stumpf, M. P., 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=Estimating+the+size+of+the+human+interactome.">Estimating the size of the human interactome.</a> Proc. Natl. Acad. Sci. U.S.A. 105, 6959-6964 (2008).</li><li>Shekhawat, S. S., Ghosh, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Split-protein+systems:+beyond+binary+protein-protein+interactions.">Split-protein systems: beyond binary protein-protein interactions.</a> Curr. Opin. Chem. Biol. 15, 789-797 (2011).</li><li>Dwane, S., Kiely, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tools+used+to+study+how+protein+complexes+are+assembled+in+signaling+cascades.">Tools used to study how protein complexes are assembled in signaling cascades.</a> Bioeng. Bugs. 2, 247-259 (2011).</li><li>Piehler, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+methodologies+for+measuring+protein+interactions+in+vivo+and+in+vitro.">New methodologies for measuring protein interactions in vivo and in vitro.</a> Curr. Opin. Struct. Biol. 15, 4-14 (2005).</li><li>Kerppola, T. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+and+implementation+of+bimolecular+fluorescence+complementation+(BiFC)+assays+for+the+visualization+of+protein+interactions+in+living+cells.">Design and implementation of bimolecular fluorescence complementation (BiFC) assays for the visualization of protein interactions in living cells.</a> Nat. Protoc. 1, 1278-1286 (2006).</li><li>Shyu, Y. J., Suarez, C. D., Hu, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualization+of+ternary+complexes+in+living+cells+by+using+a+BiFC-based+FRET+assay.">Visualization of ternary complexes in living cells by using a BiFC-based FRET assay.</a> Nat. Protoc. 3, 1693-1702 (2008).</li><li>Wong, K. A., O'Bryan, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bimolecular+fluorescence+complementation.">Bimolecular fluorescence complementation.</a> J. Vis. Exp. (50), e2643 (2011).</li><li>Sugarbaker, E. V., Thornthwaite, J. T., Temple, W. T., Ketcham, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow+cytometry:+general+principles+and+applications+to+selected+studies+in+tumor+biology.">Flow cytometry: general principles and applications to selected studies in tumor biology.</a> Int. Adv. Surg. Oncol. 2, 125-153 (1979).</li><li>Koshy, S., Alizadeh, P., Timchenko, L. T., Beeton, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+measurement+of+GLUT4+translocation+to+the+plasma+membrane+by+flow+cytometry.">Quantitative measurement of GLUT4 translocation to the plasma membrane by flow cytometry.</a> J. Vis. Exp. (45), e2429 (2010).</li><li>Smith, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Basic+confocal+microscopy.">Basic confocal microscopy.</a> Curr. Protoc. Mol. Biol. Chapter 14 (Unit 14), 11 (2008).</li><li>Westwick, J. K., Lamerdin, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improving+drug+discovery+with+contextual+assays+and+cellular+systems+analysis.">Improving drug discovery with contextual assays and cellular systems analysis.</a> Methods Mol. Biol. 756, 61-73 (2011).</li><li>Kilpatrick, L. E., Holliday, N. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissecting+the+pharmacology+of+G+protein-coupled+receptor+signaling+complexes+using+bimolecular+fluorescence+complementation.">Dissecting the pharmacology of G protein-coupled receptor signaling complexes using bimolecular fluorescence complementation.</a> Methods Mol. Biol. 897, 109-138 (2012).</li></ol>

Los autores declaran que no tienen intereses financieros en competencia.

BiFC es un método simple y sensible para estudiar la interacción proteína-proteína. Este método no se puede utilizar para identificar nuevas interacciones proteína-proteína, sin embargo, es especialmente conveniente para confirmar la interacción proteína-proteína dentro de las células y para estudiar las propiedades funcionales, tales como la localización subcelular de complejos de proteínas, mapeo de sitios de interacción proteína-proteína, y para la detección de pequeñas moléculas / péptidos que pu...

650.000 interacciones proteína-proteína se estima que existen en el interactome humana, jugando un papel crítico en el mantenimiento de las funciones celulares normales 1,2. Además de co-inmunoprecipitación (co-IP), el estándar de oro para el estudio de la interacción proteína-proteína a partir de lisado de células, varios ensayos de complementación de fragmentos de proteínas (PCA) se han desarrollado para mejorar la sensibilidad en la detección de la interacción proteína-proteína dentro de las células 3. Las técnicas incluyen la transferencia de energía por resonancia de Förster (FRET), la transferencia de energía de resonancia de bioluminiscencia (BRET) y complementación bimolecular de fluorescencia (BiFC) 4,5. BiFC se basa en la asociación facilitado de dos fragmentos de una proteína fluorescente (aquí usamos Venus; una variante YFP) que están cada uno fusionado a un potencial socio de interacción de proteínas (en este ejemplo utilizamos AKAP-Lbc y PDE4D3). La interacción de las dos proteínas de interés dentro de las células resultados en la fluorescencia funcional, que se pueden visualizar por fmicroscopía luorescence utilizando ya sea células vivas o fijas 6,7,8. En comparación con otros PCAs, BiFC es sensible y técnicamente menos exigente, con potencial para estudiar la localización celular en células vivas. Un inconveniente importante de esta técnica, sin embargo es que una vez formado, el complejo proteína fluorescente puede no ser revertida. Por lo tanto, no es un buen método para estudiar la interacción proteína-proteína dinámico. En este trabajo, utilizamos BiFC para asignar los sitios de interacción de PDE4D3 con AKAP-Lbc controlando la intensidad de fluorescencia de Venus. En comparación con el análisis tradicional utilizando microscopía de fluorescencia, que es mucho tiempo y mano de obra intensiva (si no se lleva a cabo utilizando maquinaria de alto rendimiento automatizado), citometría de flujo proporciona un análisis cuantitativo sencillo de miles de células en una población heterogénea durante un corto período de tiempo 9, 10. Aquí, mediante la realización de una comparación lado a lado de análisis de citometría de flujo-BiFC tradicional y co-IP, se demuestra que las dos métodos de proporcionar información comparable, sin embargo, el flujo de análisis de citometría de BiFC consume menos tiempo y utiliza menos material que puede ser más útil cuando las células de interés son limitados.

<table border="1">
	<tbody>
		<tr>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>REAGENTS</td>
		</tr>
		<tr>
			<td>Dulbecco's modified Eagle's media (DMEM)</td>
			<td>Invitrogen</td>
			<td>11965-092</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Penicilin-Streptomycin (pen/strep), 100x</td>
			<td>Invitrogen</td>
			<td>15070-063</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS)</td>
			<td>Invitrogen</td>
			<td>16000-044</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Anti-Flag antibody</td>
			<td>Sigma</td>
			<td>M2, F1804</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Anti-HA antibody</td>
			<td>Covance</td>
			<td>16B12, MMS-101R</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>&alpha;-tubulin</td>
			<td>Sigma</td>
			<td>DM1A, T9026</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Anti-GFP antibody</td>
			<td>Clontech</td>
			<td>632569</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Cell culture plates, 6-well tissue culture treated</td>
			<td>Thermo Fisher Scientific</td>
			<td>130184</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>HEK 293T cells</td>
			<td>ATCC</td>
			<td>CRL-11268</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Maxiprep plasmid purification kit, high speed</td>
			<td>Qiagen</td>
			<td>12663</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Dulbecco's Phosphate-buffered saline (DPBS), sterile 1x</td>
			<td>Invitrogen</td>
			<td>14190-144</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Trypsin-EDTA, 0.05% (w/v)</td>
			<td>Gibco</td>
			<td>25300</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Polystyrene round-bottom tubes for FACS staining</td>
			<td>BD Biosciences</td>
			<td>352052</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Fisher Scientific</td>
			<td>S74337MF</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Prolong gold antifade reagent with DAPI</td>
			<td>Invitrogen</td>
			<td>P-36931</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Superfrost plus Microscope slides</td>
			<td>Fisher Scientific</td>
			<td>12-550-15</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Fisherfinest premium cover glass</td>
			<td>Fisher Scientific</td>
			<td>12-548-5P</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>EQUIPMENT</td>
		</tr>
		<tr>
			<td>CO2 air-jacketed Incubator</td>
			<td>NuAIR DH autoflow</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Confocal microscope LSM510 META</td>
			<td>Carl Zeiss, Inc</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Electrophoresis and transfer unit</td>
			<td>Biorad</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Cyan ADP Flow Cytometer</td>
			<td>Beckman Coulter</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

flow cytometric analysis of bimolecular fluorescence complementation: a high throughput quantitative method to study protein-protein interaction

Entre los métodos para el estudio de la interacción proteína-proteína dentro de las células, complementación bimolecular de fluorescencia (BiFC) es relativamente simple y sensible. BiFC se basa en la producción de fluorescencia utilizando dos fragmentos no fluorescentes de una proteína fluorescente (Venus, una variante de la proteína fluorescente amarilla, se utiliza aquí). Fragmentos de Venus no fluorescentes (VN y VC) se fusionan a dos proteínas que interactúan (en este caso, AKAP-Lbc y PDE4D3), produciendo fluorescencia debido a la interacción VN-AKAP-Lbc-VC-PDE4D3 y la formación de una proteína fluorescente funcional dentro de las células. BiFC proporciona información sobre la localización subcelular de complejos de proteínas y la fuerza de las interacciones de proteínas basado en la intensidad de fluorescencia. Sin embargo, el análisis mediante microscopía BiFC para cuantificar la fuerza de la interacción proteína-proteína es mucho tiempo y es algo subjetivo debido a la heterogeneidad en la expresión de proteínas y la interacción. Por citometría de flujo de acoplamientoanálisis con metodología BiFC, la BiFC señal de la interacción proteína-proteína fluorescente se puede medir con precisión para una gran cantidad de células en un corto período de tiempo. Aquí, demostramos una aplicación de esta metodología para mapear regiones en PDE4D3 que se requieren para la interacción con AKAP-Lbc. Esta metodología de alto rendimiento se puede aplicar a la detección de factores que regulan la interacción proteína-proteína.

AKAP-Lbc y PDE4D3 construcciones (Figura 1B) se fusionaron a VN y fragmentos de VC, respectivamente. Interacción de AKAP-Lbc y PDE4D3 resultados funcionales en YFP fluorescencia (Figura 1A). Aquí se utiliza el método BiFC para asignar sitios AKAP-Lbc vinculantes en PDE4D3. Aguas arriba región conservada 1 (UCR1), región aguas arriba conservada 2 (UCR2) y la región catalítica (CAT) se conservan entre las proteínas de la familia de PDE4, por lo tanto, de longitud completa (FL), UC...

Watch this Scientific Journal Video about Flow Cytometric Analysis of Bimolecular Fluorescence Complementation: A High Throughput Quantitative Method to Study Protein-protein Interaction at JoVE.com

Flow Cytometric Analysis of Bimolecular Fluorescence Complementation: A High Throughput Quantitative Method to Study Protein-protein Interaction

Análisis citométrico de flujo de Complementación fluorescencia bimolecular proporciona un método cuantitativo de alto rendimiento para estudiar la interacción proteína-proteína. Esta metodología se puede aplicar a los sitios de unión de proteínas y de mapeo para los factores que regulan la interacción proteína-proteína de cribado.

El análisis por citometría de Complementación fluorescencia Bimolecular: A High Throughput Método cuantitativo para estudiar la interacción proteína-proteína

Among methods to study protein-protein interaction inside cells, Bimolecular Fluorescence Complementation (BiFC) is relatively simple and sensitive. BiFC ...

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18.3K vistas.  University of Illinois at Chicago. Análisis citométrico de flujo de Complementación fluorescencia bimolecular proporciona un método cuantitativo de alto rendimiento para estudiar la interacción proteína-proteína. Esta metodología se puede aplicar a los sitios de unión de proteínas y de mapeo para los factores que regulan la interacción proteína-proteína de cribado.

Video: Flow Cytometric Analysis of Bimolecular Fluorescence Complementation: A High Throughput Quantitative Method to Study Protein-protein Interaction

A Neuronal and Astrocyte Co-Culture Assay for High Content Analysis of Neurotoxicity

High Content Analysis (HCA) assays combine cells and detection reagents with automated imaging and powerful image analysis algorithms, allowing measurement of multiple cellular phenotypes within a single assay. In this study, we utilized HCA to develop a novel assay for neurotoxicity. Neurotoxicity assessment represents an important part of drug safety evaluation, as well as being a significant focus of environmental protection efforts. Additionally, neurotoxicity is also a well-accepted in vitro marker of the development of neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Recently, the application of HCA to neuronal screening has been reported. By labeling neuronal cells with &beta;III-tubulin, HCA assays can provide high-throughput, non-subjective, quantitative measurements of parameters such as neuronal number, neurite count and neurite length, all of which can indicate neurotoxic effects. However, the role of astrocytes remains unexplored in these models. Astrocytes have an integral role in the maintenance of central nervous system (CNS) homeostasis, and are associated with both neuroprotection and neurodegradation when they are activated in response to toxic substances or disease states. GFAP is an intermediate filament protein expressed predominantly in the astrocytes of the CNS. Astrocytic activation (gliosis) leads to the upregulation of GFAP, commonly accompanied by astrocyte proliferation and hypertrophy. This process of reactive gliosis has been proposed as an early marker of damage to the nervous system. The traditional method for GFAP quantitation is by immunoassay. This approach is limited by an inability to provide information on cellular localization, morphology and cell number. We determined that HCA could be used to overcome these limitations and to simultaneously measure multiple features associated with gliosis - changes in GFAP expression, astrocyte hypertrophy, and astrocyte proliferation - within a single assay. In co-culture studies, astrocytes have been shown to protect neurons against several types of toxic insult and to critically influence neuronal survival. Recent studies have suggested that the use of astrocytes in an in vitro neurotoxicity test system may prove more relevant to human CNS structure and function than neuronal cells alone. Accordingly, we have developed an HCA assay for co-culture of neurons and astrocytes, comprised of protocols and validated, target-specific detection reagents for profiling &beta;III-tubulin and glial fibrillary acidic protein (GFAP). This assay enables simultaneous analysis of neurotoxicity, neurite outgrowth, gliosis, neuronal and astrocytic morphology and neuronal and astrocytic development in a wide variety of cellular models, representing a novel, non-subjective, high-throughput assay for neurotoxicity assessment. The assay holds great potential for enhanced detection of neurotoxicity and improved productivity in neuroscience research and drug discovery.

This article describes a novel protocol and reagent set designed for sensitive measurement of neurotoxic effects of compounds and treatments on co-cultures of neurons and astrocytes using high content analysis. Results demonstrate that high content analysis represents an exciting novel technology for neurotoxicity assessment.

A neuronales y astrocitos Co-cultivo de ensayo para el análisis de alto contenido de neurotoxicidad

High Content Analysis (HCA) assays combine cells and detection reagents with automated imaging and powerful image analysis algorithms, allowing ...

Investigación

Biología

A high-throughput method to globally study the organelle morphology in S. cerevisiae

High-throughput methods to examine protein localization or organelle morphology is an effective tool for studying protein interactions and can help achieve an comprehensive understanding of molecular pathways. In Saccharomyces cerevisiae, with the development of the non-essential gene deletion array, we can globally study the morphology of different organelles like the endoplasmic reticulum (ER) and the mitochondria using GFP (or variant)-markers in different gene backgrounds. However, incorporating GFP markers in each single mutant individually is a labor-intensive process. Here, we describe a procedure that is routinely used in our laboratory. By using a robotic system to handle high-density yeast arrays and drug selection techniques, we can significantly shorten the time required and improve reproducibility. In brief, we cross a GFP-tagged mitochondrial marker (Apc1-GFP) to a high-density array of 4,672 nonessential gene deletion mutants by robotic replica pinning.  Through diploid selection, sporulation, germination and dual marker selection, we recover both alleles. As a result, each haploid single mutant contains Apc1-GFP incorporated at its genomic locus. Now, we can study the morphology of mitochondria in all non-essential mutant background. Using this high-throughput approach, we can conveniently study and delineate the pathways and genes involved in the inheritance and the formation of organelles in a genome-wide setting.

GFP-fusion proteins are widely used to visualize organelles by confocal microscopy. However, screening for mutations that affect the morphology of organelles generally requires individual mutagenesis and is time consuming. Here, we demonstrate a method to simultaneously incorporate organelle-GFP markers in almost 5,000 non-essential genes in yeast.

Un método de alto rendimiento a nivel mundial para estudiar la morfología orgánulo en S. cerevisiae

High-throughput methods to examine protein localization or organelle morphology is an effective tool for studying protein interactions and can help ...

Bimolecular Fluorescence Complementation (BiFC) Assay for Protein-Protein Interaction in Onion Cells Using the Helios Gene Gun

Investigation of gene function in diverse organisms relies on knowledge of how the gene products interact with each other in their normal cellular environment. The Bimolecular Fluorescence Complementation (BiFC) Assay1 allows researchers to visualize protein-protein interactions in living cells and has become an essential research tool. This assay is based on the facilitated association of two fragments of a fluorescent protein (GFP) that are each fused to a potential interacting protein partner. The interaction of the two protein partners would facilitate the association of the N-terminal and C-terminal fragment of GFP, leading to fluorescence. For plant researchers, onion epidermal cells are an ideal experimental system for conducting the BiFC assay because of the ease in obtaining and preparing onion tissues and the direct visualization of fluorescence with minimal background fluorescence. The Helios Gene Gun (BioRad) is commonly used for bombarding plasmid DNA into onion cells. We demonstrate the use of Helios Gene Gun to introduce plasmid constructs for two interacting Arabidopsis thaliana transcription factors, SEUSS (SEU) and LEUNIG HOMOLOG (LUH)2 and the visualization of their interactions mediated by BiFC in onion epidermal cells.

Bimolecular Fluorescence Complementation BiFC Assay for Protein-Protein Interaction in Onion Cells Using the Helios Gene Gun

This article illustrates how to properly use the BioRad Helios Gene Gun to introduce plasmid DNA into onion epidermal cells and how to test for protein-protein interactions in onion cells based on the principle of Bimolecular Fluorescence Complementation (BiFC)

Bimolecular complementación de fluorescencia (BiFC) Ensayo de interacción proteína-proteína en las células de cebolla con la pistola de genes Helios

Investigation of gene function in diverse organisms relies on knowledge of how the gene products interact with each other in their normal cellular ...

Bimolecular Fluorescence Complementation

Defining the subcellular distribution of signaling complexes is imperative to understanding the output from that complex. Conventional methods such as immunoprecipitation do not provide information on the spatial localization of complexes. In contrast, BiFC monitors the interaction and subcellular compartmentalization of protein complexes. In this method, a fluororescent protein is split into amino- and carboxy-terminal non-fluorescent fragments which are then fused to two proteins of interest. Interaction of the proteins results in reconstitution of the fluorophore (Figure 1)1,2. A limitation of BiFC is that once the fragmented fluorophore is reconstituted the complex is irreversible3. This limitation is advantageous in detecting transient or weak interactions, but precludes a kinetic analysis of complex dynamics. An additional caveat is that the reconstituted flourophore requires 30min to mature and fluoresce, again precluding the observation of real time interactions4. BiFC is a specific example of the protein fragment complementation assay (PCA) which employs reporter proteins such as green fluorescent protein variants (BiFC), dihydrofolate reductase, b-lactamase, and luciferase to measure protein:protein interactions5,6. Alternative methods to study protein:protein interactions in cells include fluorescence co-localization and F&ouml;rster resonance energy transfer (FRET)7. For co-localization, two proteins are individually tagged either directly with a fluorophore or by indirect immunofluorescence. However, this approach leads to high background of non-interacting proteins making it difficult to interpret co-localization data. In addition, due to the limits of resolution of confocal microscopy, two proteins may appear co-localized without necessarily interacting. With BiFC, fluorescence is only observed when the two proteins of interest interact. FRET is another excellent method for studying protein:protein interactions, but can be technically challenging. FRET experiments require the donor and acceptor to be of similar brightness and stoichiometry in the cell. In addition, one must account for bleed through of the donor into the acceptor channel and vice versa. Unlike FRET, BiFC has little background fluorescence, little post processing of image data, does not require high overexpression, and can detect weak or transient interactions. Bioluminescence resonance energy transfer (BRET) is a method similar to FRET except the donor is an enzyme (e.g. luciferase) that catalyzes a substrate to become bioluminescent thereby exciting an acceptor. BRET lacks the technical problems of bleed through and high background fluorescence but lacks the ability to provide spatial information due to the lack of substrate localization to specific compartments8. Overall, BiFC is an excellent method for visualizing subcellular localization of protein complexes to gain insight into compartmentalized signaling.

The subcellular localization of proteins is important in determining the spatio-temporal regulation of cell signaling. Here, we describe bimolecular fluorescence complementation (BiFC) as a straightforward method for monitoring the spatial interactions of proteins in the cell.

Fluorescencia de Complementación bimolecular

Defining the subcellular distribution of signaling complexes is imperative to understanding the output from that complex. Conventional methods such as ...

Detection of Protein Interactions in Plant using a Gateway Compatible Bimolecular Fluorescence Complementation (BiFC) System

We have developed a BiFC technique to test the interaction between two proteins in vivo. This is accomplished by splitting a yellow fluorescent protein (YFP) into two non-overlapping fragments. Each fragment is cloned in-frame to a gene of interest. These constructs can then be co-transformed into Nicotiana benthamiana via Agrobacterium mediated transformation, allowing the transit expression of fusion proteins. The reconstitution of YFP signal only occurs when the inquest proteins interact 1-7. To test and validate the protein-protein interactions, BiFC can be used together with yeast two hybrid (Y2H) assay. This may detect indirect interactions which can be overlooked in the Y2H. Gateway technology is a universal platform that enables researchers to shuttle the gene of interest (GOI) into as many expression and functional analysis systems as possible8,9. Both the orientation and reading frame can be maintained without using restriction enzymes or ligation to make expression-ready clones. As a result, one can eliminate all the re-sequencing steps to ensure consistent results throughout the experiments. We have created a series of Gateway compatible BiFC and Y2H vectors which provide researchers with easy-to-use tools to perform both BiFC and Y2H assays10. Here, we demonstrate the ease of using our BiFC system to test protein-protein interactions in N. benthamiana plants.

Detection of Protein Interactions in Plant using a Gateway Compatible Bimolecular Fluorescence Complementation BiFC System

We have developed a technique to test protein-protein interactions in plant. A yellow fluorescent protein (YFP) is split into two non-overlapping fragments. Each fragment is cloned in-frame to a gene of interest via Gateway system, enabling expression of fusion proteins. Reconstitution of YFP signal only occurs when the inquest proteins interact.

Detección de interacciones de proteínas en la planta mediante un Gateway Compatible Complementación fluorescencia bimoleculares (BiFC) del sistema

We have developed a BiFC technique to test the interaction between two proteins in vivo. This is accomplished by splitting a yellow fluorescent protein ...

A Liquid Phase Affinity Capture Assay Using Magnetic Beads to Study Protein-Protein Interaction: The Poliovirus-Nanobody Example

In this article, a simple, quantitative, liquid phase affinity capture assay is presented. Provided that one protein can be tagged and another protein labeled, this method can be implemented for the investigation of protein-protein interactions. It is based on one hand on the recognition of the tagged protein by cobalt coated magnetic beads and on the other hand on the interaction between the tagged protein and a second specific protein that is labeled. First, the labeled and tagged proteins are mixed and incubated at room temperature. The magnetic beads, that recognize the tag, are added and the bound fraction of labeled protein is separated from the unbound fraction using magnets. The amount of labeled protein that is captured can be determined in an indirect way by measuring the signal of the labeled protein remained in the unbound fraction. The described liquid phase affinity assay is extremely useful when conformational conversion sensitive proteins are assayed. The development and application of the assay is demonstrated for the interaction between poliovirus and poliovirus recognizing nanobodies1. Since poliovirus is sensitive to conformational conversion2 when attached to a solid surface (unpublished results), the use of ELISA is limited and a liquid phase based system should therefore be preferred. An example of a liquid phase based system often used in polioresearch3,4 is the micro protein A-immunoprecipitation test5. Even though this test has proven its applicability, it requires an Fc-structure, which is absent in the nanobodies6,7. However, as another opportunity, these interesting and stable single-domain antibodies8 can be easily engineered with different tags. The widely used (His)6-tag shows affinity for bivalent ions such as nickel or cobalt, which can on their turn be easily coated on magnetic beads. We therefore developed this simple quantitative affinity capture assay based on cobalt coated magnetic beads. Poliovirus was labeled with 35S to enable unhindered interaction with the nanobodies and to make a quantitative detection feasible. The method is easy to perform and can be established with a low cost, which is further supported by the possibility of effectively regenerating the magnetic beads.

In this article, a simple, quantitative, liquid phase affinity capture assay is presented. It is a reliable technique based on the interaction between magnetic beads and tagged proteins (e.g. nanobodies) on one hand and the affinity between the tagged protein and a second, labeled protein (e.g. poliovirus) on the other.

Una afinidad líquido fase de captura de ensayo utilizando partículas magnéticas para estudiar la interacción proteína-proteína: el ejemplo de poliomyelits-Nanobodies

In this article, a simple, quantitative, liquid phase affinity capture assay is presented. Provided that one protein can be tagged and another protein ...

Quantitative Analysis of Autophagy using Advanced 3D Fluorescence Microscopy

Prostate cancer is the leading form of malignancies among men in the U.S. While surgery carries a significant risk of impotence and incontinence, traditional chemotherapeutic approaches have been largely unsuccessful. Hormone therapy is effective at early stage, but often fails with the eventual development of hormone-refractory tumors. We have been interested in developing therapeutics targeting specific metabolic deficiency of tumor cells. We recently showed that prostate tumor cells specifically lack an enzyme (argininosuccinate synthase, or ASS) involved in the synthesis of the amino acid arginine1. This condition causes the tumor cells to become dependent on exogenous arginine, and they undergo metabolic stress when free arginine is depleted by arginine deiminase (ADI)1,10. Indeed, we have shown that human prostate cancer cells CWR22Rv1 are effectively killed by ADI with caspase-independent apoptosis and aggressive autophagy (or macroautophagy)1,2,3. Autophagy is an evolutionarily-conserved process that allows cells to metabolize unwanted proteins by lysosomal breakdown during nutritional starvation4,5. Although the essential components of this pathway are well-characterized6,7,8,9, many aspects of the molecular mechanism are still unclear - in particular, what is the role of autophagy in the death-response of prostate cancer cells after ADI treatment? In order to address this question, we required an experimental method to measure the level and extent of autophagic response in cells - and since there are no known molecular markers that can accurately track this process, we chose to develop an imaging-based approach, using quantitative 3D fluorescence microscopy11,12.
Using CWR22Rv1 cells specifically-labeled with fluorescent probes for autophagosomes and lysosomes, we show that 3D image stacks acquired with either widefield deconvolution microscopy (and later, with super-resolution, structured-illumination microscopy) can clearly capture the early stages of autophagy induction. With commercially available digital image analysis applications, we can readily obtain statistical information about autophagosome and lysosome number, size, distribution, and degree of colocalization from any imaged cell. This information allows us to precisely track the progress of autophagy in living cells and enables our continued investigation into the role of autophagy in cancer chemotherapy.

Autophagy is a ubiquitous process that enables cells to degrade and recycle proteins and organelles. We apply advanced fluorescence microscopy to visualize and quantify the small, but essential, physical changes associated with the induction of autophagy, including the formation and distribution of autophagosomes and lysosomes, and their fusion into autolysosomes.

Análisis cuantitativo de la autofagia mediante microscopía de fluorescencia avanzada 3D

Prostate cancer is the leading form of malignancies among men in the U.S. While surgery carries a significant risk of impotence and incontinence, ...

A High Throughput MHC II Binding Assay for Quantitative Analysis of Peptide Epitopes

Biochemical assays with recombinant human MHC II molecules can provide rapid, quantitative insights into immunogenic epitope identification, deletion, or design1,2. Here, a peptide-MHC II binding assay is scaled to 384-well format. The scaled down protocol reduces reagent costs by 75% and is higher throughput than previously described 96-well protocols1,3-5. Specifically, the experimental design permits robust and reproducible analysis of up to 15 peptides against one MHC II allele per 384-well ELISA plate. Using a single liquid handling robot, this method allows one researcher to analyze approximately ninety test peptides in triplicate over a range of eight concentrations and four MHC II allele types in less than 48 hr. Others working in the fields of protein deimmunization or vaccine design and development may find the protocol to be useful in facilitating their own work. In particular, the step-by-step instructions and the visual format of JoVE should allow other users to quickly and easily establish this methodology in their own labs.

Biochemical assays with recombinant human MHC II molecules can provide rapid, quantitative insights into immunogenic epitope identification, deletion, or design. &#160;Here, a peptide-MHC II binding assay scaled to 384-well plates is described. This cost effective format should prove useful in the fields of protein deimmunization and vaccine design and development.

Un ensayo de unión de alto rendimiento MHC II para el análisis cuantitativo del péptido epítopos

Biochemical assays with recombinant human MHC II molecules can provide rapid, quantitative insights into immunogenic epitope identification, deletion, or ...

Protein-protein Interactions Visualized by Bimolecular Fluorescence Complementation in Tobacco Protoplasts and Leaves

Many proteins interact transiently with other proteins or are integrated into multi-protein complexes to perform their biological function. Bimolecular fluorescence complementation (BiFC) is an in vivo method to monitor such interactions in plant cells. In the presented protocol the investigated candidate proteins are fused to complementary halves of fluorescent proteins and the respective constructs are introduced into plant cells via agrobacterium-mediated transformation. Subsequently, the proteins are transiently expressed in tobacco leaves and the restored fluorescent signals can be detected with a confocal laser scanning microscope in the intact cells. This allows not only visualization of the interaction itself, but also the subcellular localization of the protein complexes can be determined. For this purpose, marker genes containing a fluorescent tag can be coexpressed along with the BiFC constructs, thus visualizing cellular structures such as the endoplasmic reticulum, mitochondria, the Golgi apparatus or the plasma membrane. The fluorescent signal can be monitored either directly in epidermal leaf cells or in single protoplasts, which can be easily isolated from the transformed tobacco leaves. BiFC is ideally suited to study protein-protein interactions in their natural surroundings within the living cell. However, it has to be considered that the expression has to be driven by strong promoters and that the interaction partners are modified due to fusion of the relatively large fluorescence tags, which might interfere with the interaction mechanism. Nevertheless, BiFC is an excellent complementary approach to other commonly applied methods investigating protein-protein interactions, such as coimmunoprecipitation, in vitro pull-down assays or yeast-two-hybrid experiments.

Formation of protein complexes in vivo can be visualized by bimolecular fluorescence complementation. Interaction partners are fused to complementary parts of fluorescent tags and transiently expressed in tobacco leaves, resulting in a reconstituted fluorescent signal upon close proximity of the two proteins.

Interacciones proteína-proteína se visualizó por fluorescencia Bimolecular Complementación en protoplastos de tabaco y hojas

Many proteins interact transiently with other proteins or are integrated into multi-protein complexes to perform their biological function. Bimolecular ...

High-throughput Image Analysis of Tumor Spheroids: A User-friendly Software Application to Measure the Size of Spheroids Automatically and Accurately

The increasing number of applications of three-dimensional (3D) tumor spheroids as an in vitro model for drug discovery requires their adaptation to large-scale screening formats in every step of a drug screen, including large-scale image analysis. Currently there is no ready-to-use and free image analysis software to meet this large-scale format. Most existing methods involve manually drawing the length and width of the imaged 3D spheroids, which is a tedious and time-consuming process. This study presents a high-throughput image analysis software application &#8211; SpheroidSizer, which measures the major and minor axial length of the imaged 3D tumor spheroids automatically and accurately; calculates the volume of each individual 3D tumor spheroid; then outputs the results in two different forms in spreadsheets for easy manipulations in the subsequent data analysis. The main advantage of this software is its powerful image analysis application that is adapted for large numbers of images. It provides high-throughput computation and quality-control workflow. The estimated time to process 1,000 images is about 15 min&#160;on a minimally configured laptop, or around 1 min&#160;on a multi-core performance workstation. The graphical user interface (GUI) is also designed for easy quality control, and users can manually override the computer results. The key method used in this software is adapted from the active contour algorithm, also known as Snakes, which is especially suitable for images with uneven illumination and noisy background that often plagues automated imaging processing in high-throughput screens. The complimentary &#8220;Manual Initialize&#8221; and &#8220;Hand Draw&#8221; tools provide the flexibility to SpheroidSizer in dealing with various types of spheroids and diverse quality images. This high-throughput image analysis software remarkably reduces labor and speeds up the analysis process. Implementing this software is beneficial for 3D tumor spheroids to become a routine in vitro model for drug screens in industry and academia.

We present a high-throughput image analysis software application to measure the size of three-dimensional tumor spheroids imaged with bright-field microscopy. This application provides a fast and effective way to examine the effects of therapeutic drugs on spheroids, which is beneficial for researchers who wish to use spheroids in drug screens.

De alto rendimiento de imagen Análisis de esferoides tumorales: una aplicación de software fácil de usar para medir el tamaño de esferoides forma automática y precisa

The increasing number of applications of three-dimensional (3D) tumor spheroids as an in vitro model for drug discovery requires their adaptation to ...