Esta investigación ha sido financiada por el fondo de puesta en marcha de la Universidad Simon Fraser.

1. Cosecha Membranas <ol><li> Añadir tampón hipotónico (Tris-HCl 10 mM, KCl 10, 1,5 mM de MgCl 2, pH 8,0) con un cóctel inhibidor de la proteasa en un sedimento de células (~ 10 8 células) y se incuba durante 15-30 min en hielo. Lisar las células haciendo pasar la muestra a través de agujas de jeringa (5-10 pasadas) o la homogeneización de la muestra por un homogeneizador Dounce (15-30 golpes). Utilice un hemocitómetro y tinción con azul de tripano para comprobar la eficiencia de la lisis. </li><li> Obtener la fracción microsomal por una centrifugación diferencial del lisado a 3.000 gx 15 min y después a 100 000 gx 2 h. La primera centrifugación obtiene un gránulo que es la fracción nuclear, y la posterior centrifugación del sobrenadante genera un segundo gránulo, que es la fracción microsomal que contiene la membrana plasmática, así como orgánulos unidos a la membrana 8. El sobrenadante final es la fracción citosólica. Guarde las fracciones microsomales de -80 ° C congelador durante más Analyses como se indica a continuación. </li></ol> 2. Disolver, Desnaturalizar, y digerir proteínas de membrana <ol><li> Disolver la fracción microsomal en el tampón de desnaturalización (40 mM de Tris, EDTA 10 mM, TCEP 10, 0,5% Rapigest, pH 8) y a continuación se incuba la solución a 100 ° C durante 10 min. </li><li> Enfriar la solución se calentó a temperatura ambiente, añadir ultra-alta pureza en polvo urea en la solución a 8 M concentración final y se incuba la muestra a 37 ° C durante 30 min. </li><li> Añadir solución de yodoacetamida a la muestra a 15 mM de concentración final, y se incuba la solución en la oscuridad durante 30 min a temperatura ambiente para alquilar los tioles libres en la muestra. Añadir solución de DTT a la muestra a una concentración final de 10 mM y se incuba la solución durante otros 10 minutos a temperatura ambiente para enfriar rápidamente la yodoacetamida excesiva. </li><li> Diluir 10 veces la solución obtenida con 40 mM de tampón Tris a pH 8, y, posteriormente, añadir tripsina a la muestra en una proporción 01:20 de trypsin de la proteína total. Mantener la reacción de digestión en un 37 ° C horno durante la noche para asegurar que se complete la reacción. </li><li> Terminar la digestión por la acidificación de la solución de la muestra a pH 1 con HCl, una condición que también rompe el detergente, es decir, Rapigest. Degradar el Rapigest a 37 ° C durante 1 hora, y retire la precipitación desarrollado por centrifugación. </li><li> Limpiar el sobrenadante que contiene péptidos de la muestra por un cartucho C-18 de extracción en fase sólida (SPE) y secar la muestra obtenida por SpeedVac. </li><li> Realizar un análisis de SDS-PAGE de muestras antes y después de la digestión con tripsina para confirmar la eficacia de la digestión. </li></ol> 3. Captura glucopéptidos <ol><li> Disolver los péptidos limpiado en el tampón de acoplamiento (acetato de sodio 100 mM, pH 5,5). Añadir peryodato de sodio en la solución de péptido a una concentración final 10 mM durante 30 minutos en la oscuridad, a temperatura ambiente. Esto se oxida los grupos cis-diol en los glicanos a aldehídos, Que permiten que los glicanos para acoplar a la resina a través de la química hidrazida. Se detiene la peryodato excesiva por sulfito de sodio a una concentración final de 20 mM y pH 5 durante 10 min a temperatura ambiente. </li><li> Introducir resina hidrazida derivatizado en la solución de péptido en una proporción de 01:04 (resina de solución) a par de glicopéptidos a la resina. Se incuba la reacción a 37 ° C durante 1-2 días con rotación de extremo a extremo para el acoplamiento completo. </li><li> Retirar los péptidos no unidos por lavado de la resina dos veces con 1 ml de cada uno de los siguientes: agua DI, 1,5 M NaCl, metanol y 80% de acetonitrilo. Finalmente, lavar la resina con 3 x 1 ml de 100 mM NH 4 HCO 3 a pH 8 para intercambiar el tampón del sistema a 100 mM NH 4 HCO 3. <ol><li> Recoger el sobrenadante y los lavados para el análisis de péptidos no unidos (opcional). </li></ol></li><li> Soltar los N-glicopéptidos de la resina por PNGasa F en una incubación durante la noche a 37 ° C con unan de extremo a extremo de rotación. Recoge los péptidos liberados por centrifugación y un lavado con acetonitrilo al 80%. Se seca la solución obtenida en el SpeedVac para el análisis LC-MS. </li></ol> 4. Fraccionamiento adicional (opcional) Para simplificar aún más la complejidad de la muestra, fraccionar los N-glicopéptidos obtenidos. Por ejemplo, volver a disolver los péptidos secos en 10 mM de formiato de amonio, pH 3 con 20% de acetonitrilo y el uso de intercambio catiónico fuerte (SCX) cromatografía para fraccionar los péptidos. Seque el eluyente obtenido, y luego analizar las fracciones de péptidos obtenidos por fase inversa LC-MS 8,17,18. 5. Limpieza de los N-glicopéptidos Liberadas (Opcional) Si se elevan las preocupaciones por la contaminación potencial de los péptidos, redisolver los péptidos secos en ácido fórmico al 0,1% y el uso de una columna de SPE MCX para limpiar aún más los péptidos antes de análisis por LC-MS de fase inversa. <strong&gt; Nota: Los parámetros de búsqueda de base de datos. Durante la escisión selectiva de N-glicopéptidos de la resina, PNGasa F convierte la asparagina vinculado-N glicano a un ácido aspártico. Por lo tanto, hay un 0,9840 Da desplazamiento de masa de los liberados N-glicopéptidos. Para identificar con precisión estos péptidos, se necesita añadir a los parámetros de búsqueda, junto con modificaciones comunes tales como la carbamidometilación de la cisteína y la oxidación de la metionina de esta modificación.

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Los autores declaran que no tienen intereses financieros en competencia.

Aquí presentamos una estrategia glucopéptidos captura para perfilar las proteínas de la superficie celular. El método se puede aplicar para estudiar las proteínas secretadas, tales como los de la sangre, así como en otros fluidos corporales o en medios de cultivo celular. El éxito del método se basa en la digestión completa de las muestras; por lo tanto, una caracterización de SDS-PAGE de la eficiencia de la digestión es necesario, especialmente para el análisis por primera vez d...

Proteínas de superficie celular interactúan con el medio ambiente extracelular y transmiten señales desde el exterior al interior de una célula. Por lo tanto, estas proteínas, incluyendo las proteínas de la matriz extracelular, desempeñan papeles críticos en todos los aspectos de la biología celular y la fisiología que van desde la proliferación, el crecimiento, la migración, la diferenciación al envejecimiento y así sucesivamente. Proteínas de superficie funcionan mediante la interacción con otras células, proteínas y moléculas pequeñas 1-3. La caracterización molecular de las proteínas de la superficie celular es de gran interés no sólo para los biólogos sino también para las empresas farmacéuticas, ya que más del 60% de los medicamentos están dirigidos a las proteínas de la superficie celular 4. Espectrometría de masas tándem (MS), con su sensibilidad superior, exactitud, y el rendimiento para la identificación de proteínas y péptidos, ha sido una herramienta poderosa para los estudios proteómicos globales 5,6. Sin embargo, las proteínas de superficie plantean importantes desafíos a la proteómica basadas en MS, comoexisten la mayoría de las proteínas de la superficie en cantidades bajas y con modificaciones pesados. Las regiones que abarcan la membrana de las proteínas de la superficie hacerlos hidrófobo; esto es especialmente el caso para las proteínas transmembrana multipaso. Es por lo tanto difícil de disolver proteínas de membrana en soluciones acuosas sin la ayuda de un detergente; sin embargo, el uso de detergentes generalmente suprime el rendimiento de HPLC y MS 1,7,8 en la identificación de proteínas. Por lo tanto, las proteínas de membrana han sido mal caracterizada proteómica directas basadas LC-MS. La glicosilación es una de las modificaciones post-traduccionales más importantes y abundantes que tienen lugar en las proteínas de la superficie celular 9. La enorme complejidad y heterogeneidad de los glicanos obstaculizan MS señal de péptidos &quot;10. Sin embargo, varios métodos proteómicos han utilizado esta modificación única para enriquecer las proteínas de superficie y para eliminar los restos de azúcar a partir de proteínas antes del análisis LC-MS. Estos métodos incluyen a base de la lectina de afinidad de captura 11 y captura química a base de ácido bórico o basado-hidrazida 12, así como las separaciones de cromatografía hidrófilos 8,13. La eliminación de los glicanos transforma proteínas de la membrana a las proteínas regulares y simplifica drásticamente la caracterización MS. Debido a que la glicosilación tiene lugar también en las proteínas secretadas que tienen alta solubilidad en contraste con proteínas de la membrana, muchos métodos glycoproteomic están optimizados para proteínas solubles, y tienden a tener menor selectividad glicopéptido y la sensibilidad cuando se realiza el despliegue proteínas de membrana 8,14. Otros métodos también existen para enriquecer, en particular, las proteínas de la superficie celular, tales como los que utilizan ultracentrifugación 15 y estrategias de etiquetado 16. Una comparación detallada entre nuestro método y otros métodos existentes para la caracterización de proteínas de la membrana se llevó a cabo recientemente 17, y los resultados indicaron que nuestro método puede llevar a cabo igualmente bien, si no semejor, que todos los métodos de proteómica membrana en comparación, pero con una mayor simplicidad. Para ayudar a los investigadores utilizan este método, detallamos aquí un protocolo general. Este método integra varias ventajas de las estrategias de glycoproteomics existentes y se diseñó específicamente para glicoproteínas de membrana, sin embargo, el método funciona igual de bien para las proteínas secretadas. Las características de este método incluyen: 1) una completa solubilización de proteínas de membrana, 2) un enriquecimiento de glicopéptidos en lugar de glicoproteínas para eliminar el impedimento estérico potencial cuando se utiliza un sustrato sólido de captura, 3) el uso de la química hidrazida para formar enlaces covalentes entre glicopéptidos y el sustrato de captura, de tal manera que los glicopéptidos unidos pueden tolerar lavados rigurosos para alta glycoselectivity, y 4) la capacidad para llevar a cabo todo el procedimiento de captura en un tubo para reducir la pérdida de muestra y se acorta la duración del procedimiento. Después de la aplicación de este método para el estudio de una variabledad de muestras biológicas incluyendo las células y los tejidos, se observó una alta selectividad (&gt; 90%) a las glicoproteínas 8,17,18.

<table border="0" cellpadding="0" cellspacing="0" width="701">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">DTT</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:119px;">646563</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">TCEP</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:119px;">646547</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Iodoacetamide</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:119px;">A3221</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Rapigest SF</td>
			<td style="width:199px;">Waters</td>
			<td style="width:119px;">186001860</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium periodate</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:119px;">311448</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">PNGase F</td>
			<td style="width:199px;">New England Biolabs</td>
			<td style="width:119px;">P0704S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Affi-Gel Hz Hydrazide gel</td>
			<td style="width:199px;">Bio-Rad</td>
			<td style="width:119px;">153-6047</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Trypsin</td>
			<td style="width:199px;">Worthington Biomedical</td>
			<td style="width:119px;">LS02115</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sep-Pak C-18 cartridge</td>
			<td style="width:199px;">Waters</td>
			<td style="width:119px;">WAT054955</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Oasis MCX cartridge</td>
			<td style="width:199px;">Waters</td>
			<td style="width:119px;">186000252</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Protease inhibitor coctail</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:119px;">P8340</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Urea</td>
			<td style="width:199px;">Amersco</td>
			<td style="width:119px;">568</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sodium sulphite</td>
			<td style="width:199px;">Caledon</td>
			<td style="width:119px;">8360-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Invertase</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:119px;">I0408</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Alpha-1 trypsin</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:119px;">F2006</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ribonulease B</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:119px;">R7884</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Avidin</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:119px;">A9275</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ovalbumin</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:119px;">A5503</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Conalbumin</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:119px;">C0755</td>
			<td></td>
		</tr>
	</tbody>
</table>

glycopeptide capture for cell surface proteomics

Proteínas de superficie celular, incluyendo las proteínas de la matriz extracelular, participan en todos los principales procesos y funciones celulares, tales como el crecimiento, la diferenciación y la proliferación. Una caracterización completa de estas proteínas proporciona una rica información para el descubrimiento de biomarcadores, la identificación del tipo de célula, y la selección de medicamentos-objetivo, así como ayudar a avanzar en nuestra comprensión de la biología celular y fisiología. Proteínas de superficie, sin embargo, plantean desafíos analíticos significativos, debido a su inherente baja abundancia, alta hidrofobicidad, y las modificaciones posteriores a la traducción pesados. Tomando ventaja de la glicosilación prevalente en proteínas de la superficie, se introduce aquí un enfoque glicopéptido de captura de alto rendimiento que integra las ventajas de varios medios N-glycoproteomics existentes. Nuestro método puede enriquecer los glicopéptidos derivados de proteínas de la superficie y retire sus glicanos para proteómica fáciles utilizando LC-MS. La N-glicoproteoma resuelto comprende la información de la identidad y la cantidad de proteínas, así como sus sitios de glicosilación. Este método se ha aplicado a una serie de estudios en áreas que incluyen el cáncer, las células madre, y la toxicidad del fármaco. La limitación del método radica en la baja abundancia de proteínas de la membrana de superficie, de tal manera que se requiere una cantidad relativamente grande de muestras para este análisis en comparación con estudios centrados en las proteínas citosólicas.

Un diagrama de flujo representativo del procedimiento experimental se resume en la figura 1. El etiquetado y otras etapas de fraccionamiento son opcionales y detalles se describen en una publicación reciente 18. Otra opción es analizar los péptidos no modificados, que no reaccionan con la resina. Las ventajas de análisis de los péptidos no modificados incluyen el potencial de identificación de péptidos y proteínas no glicosiladas, tales como claudinas en uniones estrechas; Una ventaja...

Watch this Scientific Journal Video about Glycopeptide Capture for Cell Surface Proteomics at JoVE.com

Glycopeptide Capture for Cell Surface Proteomics

Proteínas de la superficie celular son biológicamente importantes y ampliamente glicosilada. Presentamos aquí un enfoque glucopéptidos captura para solubilizar, enriquecer y deglycosylate estas proteínas para análisis proteómicos fáciles LC-MS basados.

Captura Glicopéptido Proteómica Superficie Celular

Cell surface proteins, including extracellular matrix proteins, participate in all major cellular processes and functions, such as growth, ...

glycopeptide-capture-for-cell-surface-proteomics

Research

JoVE Journal

Biology

11.2K vistas.  Simon Fraser University.  Proteínas de la superficie celular son biológicamente importantes y ampliamente glicosilada. Presentamos aquí un enfoque glucopéptidos captura para solubilizar, enriquecer y deglycosylate estas proteínas para análisis proteómicos fáciles LC-MS basados. 

Video: Glycopeptide Capture for Cell Surface Proteomics

Cell Capture Using a Microfluidic Device

Captura de células utilizando un dispositivo de microfluidos

Investigación

Biología

Avidity-based Extracellular Interaction Screening (AVEXIS) for the Scalable Detection of Low-affinity Extracellular Receptor-Ligand Interactions

Extracellular protein:protein interactions between secreted or membrane-tethered proteins are critical for both initiating intercellular communication and ensuring cohesion within multicellular organisms. Proteins predicted to form extracellular interactions are encoded by approximately a quarter of human genes1, but despite their importance and abundance, the majority of these proteins have no documented binding partner. Primarily, this is due to their biochemical intractability: membrane-embedded proteins are difficult to solubilise in their native conformation and contain structurally-important posttranslational modifications. Also, the interaction affinities between receptor proteins are often characterised by extremely low interaction strengths (half-lives &lt; 1 second) precluding their detection with many commonly-used high throughput methods2. 
Here, we describe an assay, AVEXIS (AVidity-based EXtracellular Interaction Screen) that overcomes these technical challenges enabling the detection of very weak protein interactions (t1/2 &le; 0.1 sec) with a low false positive rate3. The assay is usually implemented in a high throughput format to enable the systematic screening of many thousands of interactions in a convenient microtitre plate format (Fig. 1). It relies on the production of soluble recombinant protein libraries that contain the ectodomain fragments of cell surface receptors or secreted proteins within which to screen for interactions; therefore, this approach is suitable for type I, type II, GPI-linked cell surface receptors and secreted proteins but not for multipass membrane proteins such as ion channels or transporters.
The recombinant protein libraries are produced using a convenient and high-level mammalian expression system4, to ensure that important posttranslational modifications such as glycosylation and disulphide bonds are added. Expressed recombinant proteins are secreted into the medium and produced in two forms: a biotinylated bait which can be captured on a streptavidin-coated solid phase suitable for screening, and a pentamerised enzyme-tagged (&beta;-lactamase) prey. The bait and prey proteins are presented to each other in a binary fashion to detect direct interactions between them, similar to a conventional ELISA (Fig. 1). The pentamerisation of the proteins in the prey is achieved through a peptide sequence from the cartilage oligomeric matrix protein (COMP) and increases the local concentration of the ectodomains thereby providing significant avidity gains to enable even very transient interactions to be detected. By normalising the activities of both the bait and prey to predetermined levels prior to screening, we have shown that interactions having monomeric half-lives of 0.1 sec can be detected with low false positive rates3.

Avidity-based Extracellular Interaction Screening AVEXIS for the Scalable Detection of Low-affinity Extracellular Receptor-Ligand Interactions

AVEXIS is a high throughput protein interaction assay developed to systematically screen for novel extracellular receptor-ligand pairs involved in cellular recognition processes. It is specifically designed to detect transient protein interactions that are difficult to identify using other high throughput approaches.

Avidez detección basada en la interacción extracelular (AVEXIS) para la detección escalable de extracelular de baja afinidad interacciones ligando-receptor

Extracellular protein:protein interactions between secreted or membrane-tethered proteins are critical for both initiating intercellular communication and ...

Metabolic Labeling and Membrane Fractionation for Comparative Proteomic Analysis of Arabidopsis thaliana Suspension Cell Cultures

Plasma membrane microdomains are features based on the physical properties of the lipid and sterol environment and have particular roles in signaling processes. Extracting sterol-enriched membrane microdomains from plant cells for proteomic analysis is a difficult task mainly due to multiple preparation steps and sources for contaminations from other cellular compartments. The plasma membrane constitutes only about 5-20% of all the membranes in a plant cell, and therefore isolation of highly purified plasma membrane fraction is challenging. A frequently used method involves aqueous two-phase partitioning in polyethylene glycol and dextran, which yields plasma membrane vesicles with a purity of 95% 1. Sterol-rich membrane microdomains within the plasma membrane are insoluble upon treatment with cold nonionic detergents at alkaline pH. This detergent-resistant membrane fraction can be separated from the bulk plasma membrane by ultracentrifugation in a sucrose gradient 2. Subsequently, proteins can be extracted from the low density band of the sucrose gradient by methanol/chloroform precipitation. Extracted protein will then be trypsin digested, desalted and finally analyzed by LC-MS/MS. Our extraction protocol for sterol-rich microdomains is optimized for the preparation of clean detergent-resistant membrane fractions from Arabidopsis thaliana cell cultures.
We use full metabolic labeling of Arabidopsis thaliana suspension cell cultures with K15NO3 as the only nitrogen source for quantitative comparative proteomic studies following biological treatment of interest 3. By mixing equal ratios of labeled and unlabeled cell cultures for joint protein extraction the influence of preparation steps on final quantitative result is kept at a minimum. Also loss of material during extraction will affect both control and treatment samples in the same way, and therefore the ratio of light and heave peptide will remain constant. In the proposed method either labeled or unlabeled cell culture undergoes a biological treatment, while the other serves as control 4.

Metabolic Labeling and Membrane Fractionation for Comparative Proteomic Analysis of Arabidopsis thaliana Suspension Cell Cultures

Here we describe a robust method for the fractionation of plant plasma membranes into detergent resistant and detergent soluble membranes based on a mixture of unlabeled and in vivo fully 15N labeled Arabidopsis thaliana cell cultures. The procedure is applied for comparative proteomic studies to understand signaling processes.

Metabólicas etiquetado y de membrana de fraccionamiento para Comparativo Proteómica Análisis de<em&gt; Arabidopsis thaliana</em&gt; Culturas suspensión celular

Plasma membrane microdomains are features based on the physical properties of the lipid and sterol environment and have particular roles in signaling ...

Proteomic Sample Preparation from Formalin Fixed and Paraffin Embedded Tissue

Preserved clinical material is a unique source for proteomic investigation of human disorders. Here we describe an optimized protocol allowing large scale quantitative analysis of formalin fixed and paraffin embedded (FFPE) tissue. The procedure comprises four distinct steps. The first one is the preparation of sections from the FFPE material and microdissection of cells of interest. In the second step the isolated cells are lysed and processed using 'filter aided sample preparation' (FASP) technique. In this step, proteins are depleted from reagents used for the sample lysis and are digested in two-steps using endoproteinase LysC and trypsin. 
After each digestion, the peptides are collected in separate fractions and their content is determined using a highly sensitive fluorescence measurement. Finally, the peptides are fractionated on 'pipette-tip' microcolumns. The LysC-peptides are separated into 4 fractions whereas the tryptic peptides are separated into 2 fractions. In this way prepared samples allow analysis of proteomes from minute amounts of material to a depth of 10,000 proteins. Thus, the described workflow is a powerful technique for studying diseases in a system-wide-fashion as well as for identification of potential biomarkers and drug targets.

Archival formalin fixed and paraffin embedded (FFPE) clinical samples are valuable material for investigation of diseases. Here we demonstrate a sample preparation workflow allowing in-depth proteomic analysis of microdissected FFPE tissue.

Proteómica Preparación de muestras de formol fija y embebidos en parafina de tejidos

Preserved clinical material is a unique source for proteomic investigation of human disorders. Here we describe an optimized protocol allowing large scale ...

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 ...

Non-enzymatic, Serum-free Tissue Culture of Pre-invasive Breast Lesions for Spontaneous Generation of Mammospheres

Breast ductal carcinoma in situ (DCIS), by definition, is proliferation of neoplastic epithelial cells within the confines of the breast duct, without breaching the collagenous basement membrane. While DCIS is a non-obligate precursor to invasive breast cancers, the molecular mechanisms and cell populations that permit progression to invasive cancer are not fully known. To determine if progenitor cells capable of invasion existed within the DCIS cell population, we developed a methodology for collecting and culturing sterile human breast tissue at the time of surgery, without enzymatic disruption of tissue.
Sterile breast tissue containing ductal segments is harvested from surgically excised breast tissue following routine pathological examination. Tissue containing DCIS is placed in nutrient rich, antibiotic-containing, serum free medium, and transported to the tissue culture laboratory. The breast tissue is further dissected to isolate the calcified areas. Multiple breast tissue pieces (organoids) are placed in a minimal volume of serum free medium in a flask with a removable lid and cultured in a humidified CO2 incubator. Epithelial and fibroblast cell populations emerge from the organoid after 10 - 14 days. Mammospheres spontaneously form on and around the epithelial cell monolayer. Specific cell populations can be harvested directly from the flask without disrupting neighboring cells. Our non-enzymatic tissue culture system reliably reveals cytogenetically abnormal, invasive progenitor cells from fresh human DCIS lesions.

Primary cell culture using intact tissue organoids provides a model system that mimics the multi-cellular in vivo microenvironment. We developed a serum-free primary breast epithelium tissue culture model that perpetuates mixed cell culture lineages and exhibits differentiated morphology, without enzymatic tissue disruption. Breast organoids remain viable for &#62;6 months.

No enzimática, libre de suero Cultivo de Tejidos de lesiones de mama pre-invasivas para la generación espontánea de mammospheres

Breast ductal carcinoma in situ (DCIS), by definition, is proliferation of neoplastic epithelial cells within the confines of the breast duct, without ...

Selected Reaction Monitoring Mass Spectrometry for Absolute Protein Quantification

Absolute quantification of target proteins within complex biological samples is critical to a wide range of research and clinical applications. This protocol provides step-by-step instructions for the development and application of quantitative assays using selected reaction monitoring (SRM) mass spectrometry (MS). First, likely quantotypic target peptides are identified based on numerous criteria. This includes identifying proteotypic peptides, avoiding sites of posttranslational modification, and analyzing the uniqueness of the target peptide to the target protein. Next, crude external peptide standards are synthesized and used to develop SRM assays, and the resulting assays are used to perform qualitative analyses of the biological samples. Finally, purified, quantified, heavy isotope labeled internal peptide standards are prepared and used to perform isotope dilution series SRM assays. Analysis of all of the resulting MS data is presented. This protocol was used to accurately assay the absolute abundance of proteins of the chemotaxis signaling pathway within RAW 264.7 cells (a mouse monocyte/macrophage cell line). The quantification of Gi2 (a heterotrimeric G-protein &#945;-subunit) is described in detail.

This protocol describes how to perform absolute quantification assays of target proteins within complex biological samples using selected reaction monitoring. It was used to accurately quantify proteins of the mouse macrophage chemotaxis signaling pathway. Target peptide selection, assay development, and qualitative and quantitative assays are described in detail.

Reacción seleccionada Monitoreo espectrometría de masas para Absolute Proteína cuantificación

Absolute quantification of target proteins within complex biological samples is critical to a wide range of research and clinical applications. This ...

Enrichment of Extracellular Matrix Proteins from Tissues and Digestion into Peptides for Mass Spectrometry Analysis

The extracellular matrix (ECM) is a complex meshwork of cross-linked proteins that provides biophysical and biochemical cues that are major regulators of cell proliferation, survival, migration, etc. The ECM plays important roles in development and in diverse pathologies including cardio-vascular and musculo-skeletal diseases, fibrosis, and cancer. Thus, characterizing the composition of ECMs of normal and diseased tissues could lead to the identification of novel prognostic and diagnostic biomarkers and potential novel therapeutic targets. However, the very nature of ECM proteins (large in size, cross-linked and covalently bound, heavily glycosylated) has rendered biochemical analyses of ECMs challenging. To overcome this challenge, we developed a method to enrich ECMs from fresh or frozen tissues and tumors that takes advantage of the insolubility of ECM proteins. We describe here in detail the decellularization procedure that consists of sequential incubations in buffers of different pH and salt and detergent concentrations and that results in 1) the extraction of intracellular (cytosolic, nuclear, membrane and cytoskeletal) proteins and 2) the enrichment of ECM proteins. We then describe how to deglycosylate and digest ECM-enriched protein preparations into peptides for subsequent analysis by mass spectrometry.

This protocol describes a procedure for enriching ECM proteins from tissues or tumors and deglycosylating and digesting the ECM-enriched preparations into peptides to analyze their protein composition by mass spectrometry.

Enriquecimiento de la Matriz Extracelular Las proteínas de los tejidos y la digestión en péptidos para el análisis de espectrometría de masas

The extracellular matrix (ECM) is a complex meshwork of cross-linked proteins that provides biophysical and biochemical cues that are major regulators of ...

Surface Spreading and Immunostaining of Yeast Chromosomes

The small size of nuclei of the budding yeast Saccharomyces cerevisiae limits the utility of light microscopy for analysis of the subnuclear distribution of chromatin-bound proteins. Surface spreading of yeast nuclei results in expansion of chromatin without loss of bound proteins. A method for surface spreading balances fixation of DNA bound proteins with detergent treatment. The method demonstrated is slightly modified from that described by Josef Loidl and Franz Klein1,2. The method has been used to characterize the localization of many chromatin-bound proteins at various stages of the mitotic cell cycle, but is especially useful for the study of meiotic chromosome structures such as meiotic recombinosomes and the synaptonemal complex. We also describe a modification that does not require use of Lipsol, a proprietary detergent, which was called for in the original procedure, but no longer commercially available. An immunostaining protocol that is compatible with the chromosome spreading method is also described.

A method for surface-spreading chromosomes from budding yeast is presented. This method is derived from a method previously described by Loidl and Klein. In addition, we demonstrate a procedure for immunostaining of spread chromosomes.

Difusión de superficies y inmunotinción de cromosomas de la levadura

The small size of nuclei of the budding yeast Saccharomyces cerevisiae limits the utility of light microscopy for analysis of the subnuclear distribution ...

Analyzing Cell Surface Adhesion Remodeling in Response to Mechanical Tension Using Magnetic Beads

Mechanosensitive cell surface adhesion complexes allow cells to sense the mechanical properties of their surroundings. Recent studies have identified both force-sensing molecules at adhesion sites, and force-dependent transcription factors that regulate lineage-specific gene expression and drive phenotypic outputs. However, the signaling networks converting mechanical tension into biochemical pathways have remained elusive. To explore the signaling pathways engaged upon mechanical tension applied to cell surface receptor, superparamagnetic microbeads can be used. Here we present a protocol for using magnetic beads to apply forces to cell surface adhesion proteins. Using this approach, it is possible to investigate not only force-dependent cytoplasmic signaling pathways by various biochemical approaches, but also adhesion remodeling by magnetic isolation of adhesion complexes attached to the ligand-coated beads. This protocol includes the preparation of ligand-coated superparamagnetic beads, and the application of define tensile forces followed by biochemical analyses. Additionally, we provide a representative sample of data demonstrating that tension applied to integrin-based adhesion triggers adhesion remodeling and alters protein tyrosine phosphorylation.

Cell surface adhesions are central in mechanotransduction, as they transmit mechanical tension and initiate the signaling pathways involved in tissue homeostasis and development. Here, we present a protocol for dissecting the biochemical pathways that are activated in response to tension, using ligand-coated magnetic microbeads and force application to adhesion receptors.

El análisis de la superficie celular Adhesión Remodeling en respuesta a la tensión mecánica usando perlas magnéticas

Mechanosensitive cell surface adhesion complexes allow cells to sense the mechanical properties of their surroundings. Recent studies have identified both ...