This work was supported by FIRB-Merit grants RBNE08YFN3_005 and RBNE08HWLZ_012, and the Italian Ministry of Economy and Finance to the CNR for the Project &#8220;FaReBio di Qualit&#224;&#8221;.

1. Preparar soluciones siRNA <ol><li> Resuspender 5 nmol de revueltos (Ctrl) y 5 nmol de BRCA2 siRNA gránulos secos en 100 l de RNasa libre de agua (concentración final de siRNA: 50 m). Este es el stock siRNA y debe ser almacenado a -20 ° C en 10 alícuotas. </li><li> Tomar una alícuota de 10 l de la población de siRNA y añadir 40 l de RNasa libre de agua para obtener la solución de trabajo de 10 M siRNA. Esta dilución debe ser almacenado a -20 ° C hasta su uso. NOTA: La solución de trabajo siRNA no debe someterse a la congelación / descongelación de más de 3 veces. </li></ol> 2. Siembra del epiteliales humanas Líneas Celulares <ol><li> Retire el medio de crecimiento de las líneas celulares epiteliales humanas que crecen como monocapas de células en placas de cultivo de tejidos en un incubador humidificado a 37 ° C, 5% de CO 2. </li><li> Lavar las células en la placa una vez con PBS (RT 10 ml de PBS para una placa de 100 mm). </li><li> Para separar las células de la placa,añadir 2 ml de 0,25% de tripsina / EDTA 0,53 mM solución e incubar 3-5 min dependiendo del tipo de célula. </li><li> Antes de recolectar las células desprendidas, neutralizar la tripsina mediante la adición de 2 ml de medio de crecimiento completo que contenía suero bovino fetal al 10%. </li><li> Transferir las células a un tubo de 15 ml. </li><li> Centrifugar las células a 320-330 xg durante 3 min a 4 ° C en un rotor de cubeta oscilante. </li><li> Resuspender los sedimentos celulares en 5 ml de medio de antibióticos libres. </li><li> Contar las células bajo el microscopio en una cámara de Burker o mediante el uso de un sistema de conteo automatizado de acuerdo con las instrucciones del fabricante. </li><li> Semilla las células en placas de 6 pocillos a ser alrededor del 80% de confluencia después de 24 horas (0,5 a 1 x 10 6 células en 2 ml de medio para cada pocillo). El número de células óptimas que se sembró pueden variar dependiendo de las líneas celulares específicos y la tasa de crecimiento. NOTA: No agregue los antibióticos en el medio en este punto porque los antibióticos interfieren negativamente con la eficiencia de transfección. Es muy importante que las células están en pases de cultivo bajo (&lt;10) para lograr una alta eficiencia de transfección de ARNsi BRCA2. </li></ol> 3. transfectar células con siRNA <ol><li> Veinticuatro horas después de la siembra de las células, proceder con la primera ronda de la transfección. <ol><li> Diluir 6 l de 10 siRNA transfección reactivo específico basado en lípidos en 130 l de medio de suero reducido. </li><li> Diluir 3 l de 10 mM siRNA (30 pmol) en 130 l de medio de suero reducido. </li><li> Combine el siRNA diluida con el reactivo de transfección se diluye y se incuba durante 5-10 minutos a temperatura ambiente. </li><li> Durante la incubación, retirar el medio de las células y añadir 2 ml de medio fresco pre-calentado a 37 ° C (sin antibióticos). </li><li> Añadir 250 l de los complejos de reactivo de transfección siRNA-a las células (esta cantidad es para un solo pocillo de una placa de 6 pocillos). </li><li> Se incuban las células en un incubador humidificado a 3776; C con 5% de CO 2. </li></ol></li><li> Después de 24 horas, proceder a la segunda ronda de transfección repitiendo los pasos 3.1.1-3.1.5 con la siguiente modificación para el paso 3.1.2: diluir 5 l de 10 mM siRNA (50 pmol) en 130 l de medio de suero reducido. <ol><li> Se incuban las células durante 1-2 días a 37 ° C antes del análisis. NOTA: Dos rondas de transfecciones y uso de una relación de reactivos de alta siRNA / transfección en la segunda ronda son esenciales para conseguir una alta eficiencia de silenciamiento BRCA2. </li></ol></li></ol> 4. lisar células para el análisis de inmunotransferencia <ol><li> Preparar tampón de lisis fresco con PBS (pH 7,4) que contiene 1% de la no iónico, no desnaturalizante octilfenoxipolietoxietanol detergente, pirofosfato de sodio 5 mM, ortovanadato de sodio 1 mM, fluoruro de sodio 10 mM, fluoruro de fenilmetilsulfonilo 2 mM, 10 mg / ml de leupeptina, 10 g / ml de aprotinina. Guárdelo en hielo. </li><li> Retire el medio de las células y wcenizas ellos una vez con PBS frío (2 ml / pocillo) en la placa. Para evitar cualquier arrastre PBS, retire completamente de la placa. </li><li> Añadir 200 l de tampón de lisis a cada pocillo. NOTA: Si las células tienen que ser utilizados también para otros ensayos, trypsinize las células como se describe en el paso 2.1 a 2.6 y resuspender las células en tampón apropiado / medio de acuerdo a la aplicación a utilizar. </li><li> Girar suavemente la placa para distribuir uniformemente el tampón de lisis y se incuba durante 15 min a 4 ° C en un rotador. </li><li> Recoger el lisado celular en un tubo de microcentrífuga en hielo utilizando un rascador de células. </li><li> Centrifugar a 17900 xg durante 25 min a 4 ° C y recoger el sobrenadante en un tubo nuevo. </li><li> Medir la concentración de proteína usando un ensayo de proteína disponible comercialmente de acuerdo con las instrucciones del fabricante. </li></ol> Análisis de inmunotransferencia 5. BRCA2 <ol><li> Preparar el tampón de desarrollo diluyendo 50 ml de 20x Tris-Acetato SDS corriendo bUffer (Tricina 50 mM, 50 mM Tris Base, 0,1% SDS, pH 8,24) con 950 ml de agua destilada. </li><li> Preparar la muestra como sigue: añadir 15 g de lisado celular total, 5 l de tampón de muestra 4x que contienen dodecil sulfato de litio a pH 8,4, 2 l de 10x muestra de agente reductor (0.5 M DTT), y tampón de lisis hasta un volumen final de 20 l. NOTA: Este protocolo permite la detección de BRCA2 en líneas de células normales también cuando se utiliza una menor cantidad de proteínas totales (hasta 5 g). </li><li> Desnaturalizar las muestras a 55 ° C durante 10 min. NOTA: Es fundamental utilizar 55 ° C. Dado que la proteína BRCA2 es termosensible 11, las temperaturas de desnaturalización más altos dan lugar a la pérdida constante de larga duración intacta (390 kDa) proteína BRCA2. </li><li> Configurar la cámara electroforética de acuerdo con las instrucciones del fabricante. </li><li> Cargar las muestras y 10 l de alto peso molecular pre-manchado estándar de la proteína en un gel prefabricado (Tris-acetato 3-8%) y funcionar a 120 V para abcabo de 2 h 12. Detener la ejecución de electroforesis antes del 55 kDa marcador azul deja el gel prefabricado. </li><li> Preparar el tampón de transferencia con 50 ml de tampón de transferencia de 20x, 100 ml de 100% de metanol y 850 ml de agua. </li><li> Activar membrana de PVDF (0,45 micras de tamaño de poro) por inmersión en metanol al 100% durante 5 minutos, enjuague con agua destilada y se equilibre en tampón de transferencia al menos durante 5 minutos. Remojar las esponjas del aparato de transferencia en tampón de transferencia a 4 ° C hasta su uso. </li><li> Cuando la corrida electroforética es más, armar el sándwich en la pila de la transferencia en el siguiente orden (de abajo arriba): tres esponjas saturadas en tampón de transferencia, una hoja de papel de grado 3MM saturado en tampón de transferencia, el gel, membrana de PVDF se activa, uno 3MM hoja de papel de grado saturado en tampón de transferencia, tres esponjas saturado en tampón de transferencia 13,14. Coloque la pila en las proteínas de aparatos y de transferencia a 350 mA durante 4 horas a 4 ° C oa 180 mA durante la noche a 4 ° C. NOTA: Ser BRCA2 una proteína muy grande, es crucial para extender el tiempo de transferencia de 1 hr (como se sugiere por el fabricante y la mayoría de los protocolos de transferencia) a 4 hr o durante la noche para asegurar la transferencia completa de proteínas de alto peso molecular. Además, debido al tiempo de transferencia de largo, es esencial para realizar la transferencia en una habitación fría a 4 ° C para minimizar el sobrecalentamiento y facilitar el desmontaje sandwich. Sistemas de transferencia semi-secos no son buenas para la transferencia de las proteínas de gran tamaño. </li><li> Después de la transferencia, lavar la membrana con TBS, bloquearlo durante 1 hora a RT en TBS-Tween 0,25% (TBS-T) que contiene leche en polvo desnatada al 5% y la sonda durante la noche a 4 ° C con anticuerpo policlonal de conejo anti-l 30 BRCA2 ( 200 g / ml), se diluyó en 9 ml de TBS-T + 5% leche en polvo desnatada [1: 300 (v / v) de dilución]. </li><li> Se lava la membrana tres veces (10 min cada una) con TBS-T, entonces incubar el filtro durante 1 hora con 1 l de rábano picante conjugada con peroxidasa anti-conejo anticuerpo secundario diluido en 10 ml de TBS-T + 5% leche en polvo desnatada. A partir de entonces, lavar la membrana tres veces (10 min cada uno) con TBS-T. </li><li> Realizar inmunodetección por ECL para revelar proteína BRCA2 mediante un aumento de quimioluminiscencia (ECL) Western Blot reactivo de detección, siguiendo las instrucciones del fabricante. Visualizar bandas immunochemiluminescent en alta resolución de películas ECL. </li><li> Realizar la inmunodetección con un anticuerpo para un gen de mantenimiento, como β-tubulina (55 kDa), en el mismo filtro como control de carga mediante el uso de un anticuerpo monoclonal para β-tubulina diluido a 1: 1000 (10 l de anticuerpo anti-tubulina en 10 ml TBS-T + 5% de leche seca no grasa) durante 1 hora a RT. Lavar y se incuba el anticuerpo secundario como se describe para BRCA2 (5.10 a 5.11), excepto para el uso de rábano picante conjugado con peroxidasa anti-ratón en lugar de anti-anticuerpo secundario de conejo. </li><li> Adquirir una imagen digital de las películas impresionadas con bandas immunochemiluminescent y analizar la intensidad de la banda de imagen dedicada software de análisis (por ejemplo,., ImageJ). </li></ol>

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The authors have nothing to disclose.

Debido a que las mutaciones en la línea germinal del gen BRCA2 plomo a un mayor riesgo de varios tipos de cáncer, incluyendo el cáncer femenino y masculino de mama, cáncer de ovario, cáncer de próstata, cáncer de páncreas, y el melanoma 3,4, una serie de estudios se han realizado para entender la función biológica de la proteína BRCA2. La mayoría de estos estudios son principalmente basados ​​en genética debido a dificultades técnicas en el análisis de una proteína gigante como BR...

El gen BRCA2 (cáncer de mama susceptibilidad gen-2) codifica para una proteína supresora de tumores que juega un papel crucial en la reparación de ADN de doble filamento se rompe mediante la regulación de la función de la enzima recombinasa Rad51 1. BRCA2 también ha sido implicado en la modulación de la transcripción y en el control del ciclo celular 2. Mutaciones de la línea germinal en el gen BRCA2 inducen una susceptibilidad autosómica dominante a cáncer de mama y de ovario en mujeres y el cáncer de próstata en hombres, así como predisposición a otros tipos de cáncer 3,4. Sin embargo, a pesar del aumento en el riesgo de desarrollar cáncer, mutaciones BRCA2 que suprimen o reducen la función BRCA2 pueden hacer que las células cancerosas sean más vulnerables a los agentes quimioterapéuticos que causan daño en el ADN de 5-7. Cánceres esporádicos presentan una baja tasa de mutaciones BRCA2 (&lt;3%) a pesar de los niveles reducidos de la proteína BRCA2 han sido detectados en algunos tipos de cáncer, lo que sugiere que la proteína BRCA2se puede perder durante la tumorigénesis en cánceres esporádicos a través de mecanismos no mutacional dependientes 7,8. Por lo tanto, es importante para entender completamente las funciones de BRCA2 en el contexto de la biología del cáncer, así como en otros entornos biológicos. Una poderosa herramienta utilizada para identificar nuevas funciones de un gen en células de mamífero es silenciar su expresión. Como un ejemplo, silenciamiento de la expresión de BRCA2 en una variedad de células epiteliales normales ha conducido recientemente a la identificación de una nueva función de BRCA2 como regulador de la resistencia a la anoikis, un paso importante durante la adquisición de la capacidad invasiva de células de cáncer metastásico y 9. El silenciamiento génico puede conseguirse mediante la introducción en las células ya sea de interferencia (SI) de ARN pequeño o corto horquilla (sh) moléculas de ARN dirigidas a la gen específico. La alta potencia de siRNA y su facilidad de uso lo convierten en la herramienta preferente para silenciar a los experimentos encaminados a la obtención de nuevos conocimientos sobre los procesos biológicos críticos unnd para identificar nuevas dianas terapéuticas. Sin embargo, desmontables eficiente de la expresión génica puede no ser fácilmente alcanzable para todos los genes y puede ser muy variable dependiendo del tipo de célula. Debido a una disminución en los niveles de proteína intracelular es el fenotipo más relevante bajo investigación, es crucial para cuantificar el silenciamiento de genes por análisis de inmunotransferencia del producto del gen. Con este sentido, la proteína BRCA2 presenta otro desafío: ser una proteína grande (aproximadamente 390 kDa), existen dificultades técnicas para el análisis bioquímico convencional, incluyendo inmunotransferencia. Presentamos aquí un protocolo optimizado para silenciamiento eficiente de BRCA2 en líneas de células epiteliales humanas y para la detección rápida y exitosa de la proteína BRCA2 desmontables por inmunotransferencia análisis.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>BRCA2 siRNA</td>
			<td>Dharmacon</td>
			<td>L-003462-00</td>
			<td>SMARTpool: ON-TARGETplus BRCA2 siRNA</td>
		</tr>
		<tr>
			<td>Ctrl siRNA</td>
			<td>Dharmacon</td>
			<td>&#160;D-001810-10-05</td>
			<td>ON-TARGETplus Non-targeting Pool</td>
		</tr>
		<tr>
			<td>Lipofectamine RNAiMAX Reagent&#160;</td>
			<td>Life Technologies</td>
			<td><a href="http://www.lifetechnologies.com/order/catalog/product/13778075">13778075</a></td>
			<td>Transfection Reagent</td>
		</tr>
		<tr>
			<td>OPTI-MEM I Reduced Serum Medium</td>
			<td>Life Technologies</td>
			<td>31985-070</td>
			<td>Medium for transfection procedure</td>
		</tr>
		<tr>
			<td>NuPAGE Tris-Acetate 3-8% 1,5 mm Gel precast</td>
			<td>Life Technologies</td>
			<td>EA0378</td>
			<td>Gel for protein electrophoresis</td>
		</tr>
		<tr>
			<td>NuPAGE LDS Sample buffer&#160;</td>
			<td>Life Technologies</td>
			<td>NP0007</td>
			<td>Reagent for protein electrophoresis</td>
		</tr>
		<tr>
			<td>NuPAGE Sample Reducing agent (10x)</td>
			<td>Life Technologies</td>
			<td>NP0004</td>
			<td>Reagent for protein electrophoresis</td>
		</tr>
		<tr>
			<td>NuPAGE Antioxidant</td>
			<td>Life Technologies</td>
			<td>NP0005</td>
			<td>Reagent for protein electrophoresis</td>
		</tr>
		<tr>
			<td>HiMark Pre-stained protein standard</td>
			<td>Life Technologies</td>
			<td>LC5699</td>
			<td>Prestained marker for gel electrophoresis</td>
		</tr>
		<tr>
			<td>XCell SureLoc Mini-Cell&#160; System</td>
			<td>Life Technologies</td>
			<td>EI0002</td>
			<td>Equipment for protein electrophoresis/transfer</td>
		</tr>
		<tr>
			<td>NuPAGE Tris-Acetate SDS Running Buffer</td>
			<td>Life Technologies</td>
			<td>LA0041</td>
			<td>Reagent for Western blotting</td>
		</tr>
		<tr>
			<td>PVDF membrane</td>
			<td>Millipore</td>
			<td>IPVH00010</td>
			<td>Reagent for Western blotting</td>
		</tr>
		<tr>
			<td>NuPAGE Transfer Buffer</td>
			<td>Life Technologies</td>
			<td>NP0006-1</td>
			<td>Reagent for Western blotting</td>
		</tr>
		<tr>
			<td>BRCA2 H-300 rabbit polyclonal antibody</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-8326</td>
			<td>1:300 dilution</td>
		</tr>
		<tr>
			<td>Beta-tubulin monoclonal antibody</td>
			<td>Sigma Aldrich</td>
			<td>T4026-100UL</td>
			<td>1:1000 dilution</td>
		</tr>
		<tr>
			<td>Skim Milk powder</td>
			<td>Sigma Aldrich</td>
			<td>70166</td>
			<td>Reagent for Western blotting</td>
		</tr>
		<tr>
			<td>Tween-20</td>
			<td>Sigma Aldrich</td>
			<td>P1379</td>
			<td>Reagent for Western blotting</td>
		</tr>
		<tr>
			<td>SuperSignal West Pico/Femto Chemiluminescent Substrate</td>
			<td>Pierce Thermo Scientific</td>
			<td>34080/34096</td>
			<td>Chemiluminescence system</td>
		</tr>
		<tr>
			<td>PNT1A cells</td>
			<td>SIGMA Aldrich (for ECACC)</td>
			<td>95012614</td>
			<td>PNT1A human, normal prostate epithelium immortalized with SV40</td>
		</tr>
		<tr>
			<td>Nthy cells</td>
			<td>SIGMA Aldrich (for ECACC)</td>
			<td>90011609</td>
			<td>Nthy-ori 3-1 Cell Line human, thyroid follicular epithelial cells</td>
		</tr>
		<tr>
			<td>Cell Proliferation Kit I (MTT)</td>
			<td>Roche</td>
			<td>11465007001</td>
			<td>Kit for cell proliferation assays</td>
		</tr>
	</tbody>
</table>

silencing of brca2 to identify novel brca2-regulated biological functions in cultured human cells

El silenciamiento de la proteína BRCA2 supresor de tumores y su detección por análisis bioquímicos convencionales representan un gran desafío técnico debido al gran tamaño de la proteína BRCA2 humano (aproximadamente 390 kDa). Se presenta modificaciones de transfección y inmunotransferencia protocolos estándar siRNA para silenciar BRCA2 humano y detectar la proteína BRCA2 endógeno, respectivamente, en las líneas de células epiteliales humanas. Los pasos clave incluyen una alta proporción de reactivo de transfección siRNA ay dos rondas posteriores de siRNA transfección dentro del mismo experimento. El uso de estas y otras modificaciones en el protocolo estándar logramos consistentemente más de 70% silenciamiento del gen BRCA2 humano a juzgar por el análisis de inmunotransferencia con anticuerpos anti-BRCA2. Además, la desnaturalización de los lisados ​​de células a 55 ° C en lugar de la convencional 70-100 ° C y otras optimizaciones técnicas del procedimiento de inmunotransferencia permite la detección de la proteína BRCA2 intacta incluso when muy bajas cantidades de material de partida están disponibles o cuando los niveles de expresión de proteínas BRCA2 son muy bajos. Silenciamiento eficiente de BRCA2 en las células humanas ofrece una valiosa estrategia para interrumpir la función de BRCA2 en células con BRCA2 intacto, incluyendo las células tumorales, para examinar nuevas vías moleculares y las funciones celulares que pueden ser afectados por mutaciones BRCA2 patógenos en los tumores. La adaptación de este protocolo para el silenciamiento y el análisis de otros &quot;grandes&quot; como proteínas BRCA2 eficiente debe ser fácilmente alcanzable.

Antes de proceder con un ensayo biológico / bioquímica para examinar el efecto de silenciamiento BRCA2 en las funciones celulares, el primer paso es para confirmar la especificidad de la silenciamiento mediante el uso de un siRNA revueltos (no la orientación siRNA) lado a lado con BRCA2 siRNA (Figura 1A ). Es importante llevar a cabo una segunda ronda de siRNA transfección con una alta relación de siRNA / transfección para conseguir una alta eficiencia del silenciamiento BRCA2. D...

Watch this Scientific Journal Video about Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells at JoVE.com

Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells

Gene silencing by siRNA represents a convenient experimental strategy to analyze BRCA2-dependent biological functions with immediate implications to better understand cancer biology. A method to efficiently silence BRCA2, along with the experimental procedure to detect and quantify changes in BRCA2 protein expression by immunoblotting in human cell lines, is presented.

Silencios de<em&gt; BRCA2</em&gt; Para identificar las funciones biológicas novedosas BRCA2 reguladas en células humanas cultivadas

Silencing of the tumor suppressor protein BRCA2 and its detection by conventional biochemical analyses represent a great technical challenge owing to the ...

silencing-brca2-to-identify-novel-brca2-regulated-biological

Research

JoVE Journal

Biology

Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells

9.0K vistas.  National Research Council. Gene silencing by siRNA represents a convenient experimental strategy to analyze BRCA2-dependent biological functions with immediate implications to better understand cancer biology. A method to efficiently silence BRCA2, along with the experimental procedure to detect and quantify changes in BRCA2 protein expression by immunoblotting in human cell lines, is presented. 

Video: Silencing of BRCA2 to Identify Novel BRCA2-regulated Biological Functions in Cultured Human Cells

Live Imaging of Dense-core Vesicles in Primary Cultured Hippocampal Neurons

Observing and characterizing dynamic cellular processes can yield important information about cellular activity that cannot be gained from static images.  Vital fluorescent probes, particularly green fluorescent protein (GFP) have revolutionized cell biology stemming from the ability to label specific intracellular compartments and cellular structures. For example, the live imaging of GFP (and its spectral variants) chimeras have allowed for a dynamic 
analysis of the cytoskeleton, organelle transport, and membrane dynamics in a multitude of organisms and cell types [1-3].  Although live imaging has become prevalent, this approach still poses many technical challenges, particularly in primary cultured neurons.  One challenge is the expression of GFP-tagged proteins in post-mitotic neurons; the other is the ability to capture fluorescent images while minimizing phototoxicity, photobleaching, 
and maintaining general cell health.  Here we provide a protocol that describes a lipid-based transfection method that yields a relatively low transfection rate (~0.5%), however is ideal for the imaging of fully polarized neurons.  A low transfection rate is essential so that single axons and dendrites can be characterized as to their orientation to the cell body to confirm directionality of transport, i.e., anterograde v. retrograde.  Our approach to imaging 
GFP expressing neurons relies on a standard wide-field fluorescent microscope outfitted with a CCD camera, image capture software, and a heated imaging chamber. We have imaged a wide variety of organelles or structures, for example, dense-core vesicles, mitochondria, growth cones, and actin without any special optics or excitation requirements other than a fluorescent light source. Additionally, spectrally-distinct, fluorescently 
labeled proteins, e.g., GFP and dsRed-tagged proteins, can be visualized near simultaneously to characterize co-transport or other coordinated cellular events.  The imaging approach described here is flexible for a variety of imaging applications and can be adopted by a laboratory for relatively little cost provided a microscope is available.

Live cell imaging is of particular utility when studying the dynamics of organelle trafficking. Here we describe a protocol for live imaging of dense-core vesicles in cultured neurons using wide-field fluorescence microscopy. This protocol is flexible and can be adapted to image other organelles such as mitochondria, endosomes, and peroxisomes.

Imágenes en vivo del denso núcleo de vesículas en la Primaria neuronas del hipocampo cultivadas

Observing and characterizing dynamic cellular processes can yield important information about cellular activity that cannot be gained from static images.  ...

Investigación

Biología

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the messagefor review see 1. However, it's now widely accepted that synonymous codon usage is the primary cause of non-uniform translational elongation rates1. Synonymous codons are not used with identical frequency. A bias exists in the use of synonymous codons with some codons used more frequently than others2. Codon bias is organism as well as tissue specific2,3. Moreover, frequency of codon usage is directly proportional to the concentrations of cognate tRNAs4. Thus, a frequently used codon will have higher multitude of corresponding tRNAs, which further implies that a frequent codon will be translated faster than an infrequent one. Thus, regions on mRNA enriched in rare codons (potential pause sites) will as a rule slow down ribosome movement on the message and cause accumulation of nascent peptides of the respective sizes5-8. These pause sites can have functional impact on the protein expression, mRNA stability and protein foldingfor review see 9. Indeed, it was shown that alleviation of such pause sites can alter ribosome movement on mRNA and subsequently may affect the efficiency of co-translational (in vivo) protein folding1,7,10,11. To understand the process of protein folding in vivo, in the cell, that is ultimately coupled to the process of protein synthesis it is essential to gain comprehensive insights into the impact of codon usage/tRNA content on the movement of ribosomes along mRNA during translational elongation.
Here we describe a simple technique that can be used to locate major translation pause sites for a given mRNA translated in various cell-free systems6-8. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA. The rationale is that at low-frequency codons, the increase in the residence time of the ribosomes results in increased amounts of nascent peptides of the corresponding sizes. In vitro transcribed mRNA is used for in vitro translational reactions in the presence of radioactively labeled amino acids to allow the detection of the nascent chains. In order to isolate ribosome bound nascent polypeptide complexes the translation reaction is layered on top of 30% glycerol solution followed by centrifugation. Nascent polypeptides in polysomal pellet are further treated with ribonuclease A and resolved by SDS PAGE. This technique can be potentially used for any protein and allows analysis of ribosome movement along mRNA and the detection of the major pause sites. Additionally, this protocol can be adapted to study factors and conditions that can alter ribosome movement and thus potentially can also alter the function/conformation of the protein.

Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA

A technique to identify translational pause sites on mRNA is described. This procedure is based on isolation of nascent polypeptides accumulating on ribosomes during in vitro translation of a target mRNA, followed by the size analysis of the nascent chains using a denaturing gel electrophoresis.

El aislamiento de los ribosomas polipéptidos nacientes Bound<em&gt; In vitro</em&gt; Para la identificación de sitios de traslación pausa a lo largo del ARNm

The rate of translational elongation is non-uniform. mRNA secondary structure, codon usage and mRNA associated proteins may alter ribosome movement on the ...

A Quantitative Assay to Study Protein:DNA Interactions, Discover Transcriptional Regulators of Gene Expression, and Identify Novel Anti-tumor Agents

Many DNA-binding assays such as electrophoretic mobility shift assays (EMSA), chemiluminescent assays, chromatin immunoprecipitation (ChIP)-based assays, and multiwell-based assays are used to measure transcription factor activity. However, these assays are nonquantitative, lack specificity, may involve the use of radiolabeled oligonucleotides, and may not be adaptable for the screening of inhibitors of DNA binding. On the other hand, using a quantitative DNA-binding enzyme-linked immunosorbent assay (D-ELISA) assay, we demonstrate nuclear protein interactions with DNA using the RUNX2 transcription factor that depend on specific association with consensus DNA-binding sequences present on biotin-labeled oligonucleotides. Preparation of cells, extraction of nuclear protein, and design of double stranded oligonucleotides are described. Avidin-coated 96-well plates are fixed with alkaline buffer and incubated with nuclear proteins in nucleotide blocking buffer. Following extensive washing of the plates, specific primary antibody and secondary antibody incubations are followed by the addition of horseradish peroxidase substrate and development of the colorimetric reaction. Stop reaction mode or continuous kinetic monitoring were used to quantitatively measure protein interaction with DNA. We discuss appropriate specificity controls, including treatment with non-specific IgG or without protein or primary antibody. Applications of the assay are described including its utility in drug screening and representative positive and negative results are discussed.

We developed a quantitative DNA-binding, ELISA-based assay to measure transcription factor interactions with DNA. High specificity for the RUNX2 protein was achieved with a consensus DNA-recognition oligonucleotide and specific monoclonal antibody. Colorimetric detection with an enzyme-coupled antibody substrate reaction was monitored in real time.

Un ensayo cuantitativo para estudiar proteínas: DNA Interacciones, reguladores Descubra transcripcional de la expresión génica, e identificar agentes antitumoral

Many DNA-binding assays such as electrophoretic mobility shift assays (EMSA), chemiluminescent assays, chromatin immunoprecipitation (ChIP)-based assays, ...

Visualization of Endoplasmic Reticulum Subdomains in Cultured Cells

The lipids and proteins in eukaryotic cells are continuously exchanged between cell compartments, although these retain their distinctive composition and functions despite the intense interorganelle molecular traffic. The techniques described in this paper are powerful means of studying protein and lipid mobility and trafficking in vivo and in their physiological environment. Fluorescence recovery after photobleaching (FRAP) and fluorescence loss in photobleaching (FLIP) are widely used live-cell imaging techniques for studying intracellular trafficking through the exo-endocytic pathway, the continuity between organelles or subcompartments, the formation of protein complexes, and protein localization in lipid microdomains, all of which can be observed under physiological and pathological conditions. The limitations of these approaches are mainly due to the use of fluorescent fusion proteins, and their potential drawbacks include artifactual over-expression in cells and the possibility of differences in the folding and localization of tagged and native proteins. Finally, as the limit of resolution of optical microscopy (about 200 nm) does not allow investigation of the fine structure of the ER or the specific subcompartments that can originate in cells under stress (i.e. hypoxia, drug administration, the over-expression of transmembrane ER resident proteins) or under pathological conditions, we combine live-cell imaging of cultured transfected cells with ultrastructural analyses based on transmission electron microscopy.

We describe the imaging approaches we use to investigate the distribution and mobility of the transfected fluorescent proteins resident in the endoplasmic reticulum (ER) by means of the confocal imaging of living cells. We also ultrastructurally analyze the effect of their expression on the architecture of this subcellular compartment.

Visualización del retículo endoplasmático subdominios en células cultivadas

The lipids and proteins in eukaryotic cells are continuously exchanged between cell compartments, although these retain their distinctive composition and ...

Capture Compound Mass Spectrometry - A Powerful Tool to Identify Novel c-di-GMP Effector Proteins

Considerable progress has been made during the last decade towards the identification and characterization of enzymes involved in the synthesis (diguanylate cyclases) and degradation (phosphodiesterases) of the second messenger c-di-GMP. In contrast, little information is available regarding the molecular mechanisms and cellular components through which this signaling molecule regulates a diverse range of cellular processes. Most of the known effector proteins belong to the PilZ family or are degenerated diguanylate cyclases or phosphodiesterases that have given up on catalysis and have adopted effector function. Thus, to better define the cellular c-di-GMP network in a wide range of bacteria experimental methods are required to identify and validate novel effectors for which reliable in silico predictions fail.
We have recently developed a novel Capture Compound Mass Spectrometry (CCMS) based technology as a powerful tool to biochemically identify and characterize c-di-GMP binding proteins. This technique has previously been reported to be applicable to a wide range of organisms1. Here we give a detailed description of the protocol that we utilize to probe such signaling components. As an example, we use Pseudomonas aeruginosa, an opportunistic pathogen in which c-di-GMP plays a critical role in virulence and biofilm control. CCMS identified 74% (38/51) of the known or predicted components of the c-di-GMP network. This study explains the CCMS procedure in detail, and establishes it as a powerful and versatile tool to identify novel components involved in small molecule signaling.

The ubiquitous second messenger c-di-GMP controls growth and behavior of many bacteria. We have developed a novel Capture Compound Mass Spectrometry based technology to biochemically identify and characterize c-di-GMP binding proteins in virtually any bacterial species.

Captura compuesto Espectrometría de Masas - Una herramienta de gran alcance para identificar nuevos c-di-GMP efectoras Proteínas

Considerable progress has been made during the last decade towards the identification and characterization of enzymes involved in the synthesis ...

siRNA Screening to Identify Ubiquitin and Ubiquitin-like System Regulators of Biological Pathways in Cultured Mammalian Cells

Post-translational modification of proteins with ubiquitin and ubiquitin-like molecules (UBLs) is emerging as a dynamic cellular signaling network that regulates diverse biological pathways including the hypoxia response, proteostasis, the DNA damage response and transcription.&#160; To better understand how UBLs regulate pathways relevant to human disease, we have compiled a human siRNA &#8220;ubiquitome&#8221; library consisting of 1,186 siRNA duplex pools targeting all known and predicted components of UBL system pathways. This library can be screened against a range of cell lines expressing reporters of diverse biological pathways to determine which UBL components act as positive or negative regulators of the pathway in question.&#160; Here, we describe a protocol utilizing this library to identify ubiquitome-regulators of the HIF1A-mediated cellular response to hypoxia using a transcription-based luciferase reporter.&#160; An initial assay development stage is performed to establish suitable screening parameters of the cell line before performing the screen in three stages: primary, secondary and tertiary/deconvolution screening. &#160;The use of targeted over whole genome siRNA libraries is becoming increasingly popular as it offers the advantage of reporting only on members of the pathway with which the investigators are most interested.&#160; Despite inherent limitations of siRNA screening, in particular false-positives caused by siRNA off-target effects, the identification of genuine novel regulators of the pathways in question outweigh these shortcomings, which can be overcome by performing a series of carefully undertaken control experiments.

Here, we describe a methodology to perform a targeted siRNA &#8220;ubiquitome&#8221; screen to identify novel ubiquitin and ubiquitin-like regulators of the HIF1A-mediated cellular response to hypoxia.&#160; This can be adapted to any biological pathway where a robust read out of reporter activity is available.

Screening siRNA para identificar ubiquitina y reguladores del sistema ubiquitina-como de las vías biológicas en células de mamífero en cultivo

Post-translational modification of proteins with ubiquitin and ubiquitin-like molecules (UBLs) is emerging as a dynamic cellular signaling network that ...

Nephrotoxin Microinjection in Zebrafish to Model Acute Kidney Injury

The kidneys are susceptible to harm from exposure to chemicals they filter from the bloodstream. This can lead to organ injury associated with a rapid decline in renal function and development of the clinical syndrome known as acute kidney injury (AKI). Pharmacological agents used to treat medical circumstances ranging from bacterial infection to cancer, when administered individually or in combination with other drugs, can initiate AKI. Zebrafish are a useful animal model to study the chemical effects on renal function in vivo, as they form an embryonic kidney comprised of nephron functional units that are conserved with higher vertebrates, including humans. Further, zebrafish can be utilized to perform genetic and chemical screens, which provide opportunities to elucidate the cellular and molecular facets of AKI and develop therapeutic strategies such as the identification of nephroprotective molecules. Here, we demonstrate how microinjection into the zebrafish embryo can be utilized as a paradigm for nephrotoxin studies.

Renal injuries incurred from nephrotoxins, which include drugs ranging from antibiotics to chemotherapeutics, can result in complex disorders whose pathogenesis remains incompletely understood. This protocol demonstrates how zebrafish can be used for disease modeling of these conditions, which can be applied to the identification of renoprotective measures.

Nefrotoxina Microinyección en pez cebra para modelar la lesión renal aguda

The kidneys are susceptible to harm from exposure to chemicals they filter from the bloodstream. This can lead to organ injury associated with a rapid ...

High-resolution Time-lapse Imaging and Automated Analysis of Microtubule Dynamics in Living Human Umbilical Vein Endothelial Cells

The physiological process by which new vasculature forms from existing vasculature requires specific signaling events that trigger morphological changes within individual endothelial cells (ECs). These processes are critical for homeostatic maintenance such as wound healing, and are also crucial in promoting tumor growth and metastasis. EC morphology is defined by the organization of the cytoskeleton, a tightly regulated system of actin and microtubule (MT) dynamics that is known to control EC branching, polarity and directional migration, essential components of angiogenesis. To study MT dynamics, we used high-resolution fluorescence microscopy coupled with computational image analysis of fluorescently-labeled MT plus-ends to investigate MT growth dynamics and the regulation of EC branching morphology and directional migration. Time-lapse imaging of living Human Umbilical Vein Endothelial Cells (HUVECs) was performed following transfection with fluorescently-labeled MT End Binding protein 3 (EB3) and Mitotic Centromere Associated Kinesin (MCAK)-specific cDNA constructs to evaluate effects on MT dynamics. PlusTipTracker software was used to track EB3-labeled MT plus ends in order to measure MT growth speeds and MT growth lifetimes in time-lapse images. This methodology allows for the study of MT dynamics and the identification of how localized regulation of MT dynamics within sub-cellular regions contributes to the angiogenic processes of EC branching and migration.

Protocols for Human Umbilical Vein Endothelial Cell (HUVEC) culture, transient transfection of fluorescently-labeled markers of microtubule growth, live-cell imaging and automated analysis of interphase microtubule growth dynamics are detailed.

-Alta resolución de imagen de lapso de tiempo y análisis automatizado de los microtúbulos en la dinámica de estar umbilical humana Las células endoteliales de vena

The physiological process by which new vasculature forms from existing vasculature requires specific signaling events that trigger morphological changes ...

A Graphical User Interface for Software-assisted Tracking of Protein Concentration in Dynamic Cellular Protrusions

Filopodia are dynamic, finger-like cellular protrusions associated with migration and cell-cell communication. In order to better understand the complex signaling mechanisms underlying filopodial initiation, elongation and subsequent stabilization or retraction, it is crucial to determine the spatio-temporal protein activity in these dynamic structures. To analyze protein function in filopodia, we recently developed a semi-automated tracking algorithm that adapts to filopodial shape-changes, thus allowing parallel analysis of protrusion dynamics and relative protein concentration along the whole filopodial length. Here, we present a detailed step-by-step protocol for optimized cell handling, image acquisition and software analysis. We further provide instructions for the use of optional features during image analysis and data representation, as well as troubleshooting guidelines for all critical steps along the way. Finally, we also include a comparison of the described image analysis software with other programs available for filopodia quantification. Together, the presented protocol provides a framework for accurate analysis of protein dynamics in filopodial protrusions using image analysis software.

We present a software solution for semi-automated tracking of relative protein concentration along the length of dynamic cellular protrusions.

Una interfaz gráfica de usuario para el seguimiento asistido por software de la concentración de proteínas en protones dinámicos celulares

Filopodia are dynamic, finger-like cellular protrusions associated with migration and cell-cell communication. In order to better understand the complex ...

Glucose Uptake Measurement and Response to Insulin Stimulation in In Vitro Cultured Human Primary Myotubes

Skeletal muscle is the largest glucose deposit in mammals and largely contributes to glucose homeostasis. Assessment of insulin sensitivity of muscle cells is of major relevance for all studies dedicated to exploring muscle glucose metabolism and characterizing metabolic alterations. In muscle cells, glucose transporter type 4 (GLUT4) proteins translocate to the plasma membrane in response to insulin, thus allowing massive entry of glucose into the cell. The ability of muscle cells to respond to insulin by increasing the rate of glucose uptake is one of the standard readouts to quantify muscle cell sensitivity to insulin. Human primary myotubes are a suitable in vitro model, as the cells maintain many features of the donor phenotype, including insulin sensitivity. This in vitro model is also suitable for the test of any compounds that could impact insulin responsiveness. Measurements of the glucose uptake rate in differentiated myotubes reflect insulin sensitivity.
In this method, human primary muscle cells are cultured in vitro to obtain differentiated myotubes, and glucose uptake rates with and without insulin stimulation are measured. We provide a detailed protocol to quantify passive and active glucose transport rates using radiolabeled [3H] 2-deoxy-D-Glucose ([3H]2dG). Calculation methods are provided to quantify active basal and insulin-stimulated rates, as well as stimulation fold.

Glucose Uptake Measurement and Response to Insulin Stimulation in In Vitro Cultured Human Primary Myotubes

In this method, human primary muscle cells are cultured in vitro to obtain differentiated myotubes and glucose uptake rates are measured. We provide a detailed protocol to quantify rates in basal and insulin-stimulated states using radiolabeled [3H] 2-deoxy-D-Glucose.

Medición de la Absorción de Glucosa y Respuesta a la Estimulación de la Insulina en<em&gt; In Vitro</em&gt; Myotubes primario humano cultivado

Skeletal muscle is the largest glucose deposit in mammals and largely contributes to glucose homeostasis. Assessment of insulin sensitivity of muscle ...