Name: purification of the membrane compartment for endoplasmic reticulum-associated degradation of exogenous antigens in cross-presentation
Uploaded: 2017-08-21T14:00:00.000+00:00
Duration: 12 min 48 s
Description: Watch this Scientific Journal Video about Purification of the Membrane Compartment for Endoplasmic Reticulum-associated Degradation of Exogenous Antigens in Cross-presentation at JoVE.com

Este trabajo es apoyado por la Universidad de Takasaki de la salud y el bienestar.

1. cultivo de células y la adición de antígenos exógenos bOVA <ol><li>preparar utilizando un etiquetado de biotina-proteína kit siguiendo el fabricante &#39; Protocolo s. 
	Nota: Normalmente, bOVA contiene biotina de 2 M por 1 M huevos en promedio.</li>
	<li>DC2.4 crecer las células en RPMI-1640 suplementado con 2 mM L-glutamina, piruvato de sodio 1 mM, 0.1 mM aminoácidos no esenciales, 100 U/mL de penicilina-estreptomicina, 2-Mercaptoetanol de 55 mM, 10 mM HEPES (pH 7,5) y suero de ternera fetal 10% (en lo sucesivo RPMI) a 37 ° C en 5 % CO 2 en una incubadora humidificada (en lo sucesivo sin mención, las células se incuban en esta condición). También es posible utilizar DMEM suplementado con 10% de suero fetal de becerro, 3,7 g/L de NaHCO 3 (en adelante DMEM) en lugar del RPMI.</li>
	<li>Un día antes de la purificación, dividir las células en RPMI a 1 x 10 5 células/mL en una placa de cultivo de tejidos. Evitar mantener las células en un estado confluente. Las células DC2.4 pueden altamente incorporar antígenos exógenos hasta un estado semi-confluente, pero pierde rápidamente la capacidad después de alcanzar un estado de excesiva confluentes.</li>
	<li>Antes la DC2.4 las células son parcialmente confluentes, Añadir 250 μg/mL de bOVA para 1 x 10 6 células/mL e incube durante 2-4 h. 
	Nota: Durante los experimentos posteriores, todos los buffers y reactivos se mantienen a 4 ° C a menos que se indique lo contrario.</li>
</ol> 2. Preparación de los microsomas <ol><li>las células DC2.4 de la cosecha mediante pipeteo suave de la placa de tejido en un tubo cónico de 50 mL nuevo.</li>
	<li>Centrifugar a 1.000 x g durante 5 min, 4 ° C y retirar cuidadosamente el medio con bOVA por la aspiración de.</li>
	<li>Lavar las DC2.4 las células dos veces con 40 mL de tampón PBS (1,37 mM NaCl, 8,1 mM Na 2 HPO 4, 2,68 mM KCl, 1,47 mM KH 2 PO 4) por centrifugación a 1.000 x g durante 5 min, 4 ° C y descarte el sobrenadante cada vez por la aspiración de.</li>
	Células <li>Resuspender el precipitado en el paso 2.3 en 1-2 mL (1/20-1/10 volumen de medio de cultivo) de homogeneización medio (0.25 M sacarosa, 1 mM EDTA, 10 mM HEPES-NaOH [pH 7.4]) con el volumen de 1/1.000 de cócteles inhibidores de proteasa y transferencia DC2.4 resuspendidos en un helada homogeneizadores Dounce.</li>
	<li>Romper las células DC2.4 resuspendidas suavemente por 10-20 movimientos con la helada homogeneizadores Dounce. 
	Nota: Durante la etapa de interrupción, los homogeneizadores Dounce es enfriado en hielo.</li>
	<li>La suspensión celular interrumpió la transferencia a un nuevo tubo cónico de 15 mL.</li>
	<li>Medio de homogeneización de 8-9 mL total 10 mL y centrifugar el tubo cónico 10 min a 2.000 x g y 4 ° C.</li>
	<li>Transferir el sobrenadante a un nuevo tubo cónico de 15 mL para eliminar las células intactas y núcleos y centrifugar el tubo cónico nuevamente durante 10 minutos a 2.000 x g y 4 ° C.</li>
	<li>Transferir el sobrenadante a un tubo nuevo de ultracentrifugación y centrifugar durante 45 min a 100.000 x g y 4 ° C.</li>
	<li>Aspirar el sobrenadante y resuspender el precipitado cuidadosamente en 1-2 mL de medio de homogeneización con volumen de 1/1.000 de cócteles inhibidores de proteasa por pipetear la solución arriba y abajo varias veces para hacer una fracción del microsoma para experimentos posteriores.</li>
	<li>Transferencia de la fracción del microsoma en un nuevo tubo de fondo redondo 5 mL. 
	Nota: Después de este paso, es posible enriquecer los microsomas objetivo de iodixanol centrifugación gradiente de densidad según el fabricante &#39; protocolo de s, para quitar los microsomas no específicos. Las fracciones de pico para los antígenos exógenos son recogidas y luego sometidas al siguiente paso de purificación (paso 3).</li>
</ol> 3. Purificación de los microsomas con bOVA que ERAD <ol><li>Agregar de 1/100 volumen de frescos granos SA-magnéticos para la fracción del microsoma de paso 2.11 en 5 mL redondo tubo inferior. 
	Nota: Antes de este paso, es posible borrar previamente la fracción del microsoma por perlas de control magnético para reducir la contaminación de los microsomas no específico.</li>
	<li>Mezclar bien suavemente y gire el tubo de fondo redondo despacio durante 30 minutos a 4 ° C.</li>
	<li>Añadir 2-3 mL de medio de homogeneización total 4 ml en el tubo de fondo redondo y suavemente mezclar bien.</li>
	<li>Coloque el tubo de fondo redondo sobre un soporte magnético e incubar 10 min a 4 ° C. Puesto que los granos a las vesículas son atraídos por el imán, micro-beads marrón poco a poco se acumularán a la pared del tubo más cercana al imán.</li>
	<li>Con el tubo restante en el soporte magnético, descartar cuidadosamente el sobrenadante por aspiración para eliminar las vesículas.</li>
	<li>Lavado los granos magnéticos enlazados a las vesículas dos veces con 5 mL de medio de homogeneización por el magnético reposar 10 min a 4 ° C y descarte el sobrenadante cada vez por aspiración cuidadosamente. 
	Nota: Sin el soporte magnético, purificación por centrifugados a 2.000 x g durante 10 min, 4 ° C está también disponible.</li>
	<li>Resuspender las bolas magnéticas vinculadas a las vesículas con cuidado en 100 μl de medio de homogeneización por pipetear la solución arriba y abajo varias veces.</li>
	<li>Transferir las vesículas resuspendidas en un microtubo nuevo como del microsoma purificado para experimentos posteriores. 
	Nota: Típicamente, 50 fracción del microsoma de μl que contiene 1 x 10 7 células de 5-20 μg proteínas puede ser aislado.</li>
</ol> 4. Análisis de los microsomas purificada perlas <ol><li>Resuspender el magnético a las vesículas de paso 3.8 por 100-200 μL de tampón de TNE (pH de 20 mM Tris-HCl 7.4, 150 mM NaCl, 0.5 M de EDTA, de 1% Nonidet P-40) con volumen de 1/1.000 de cócteles inhibidores de proteasa en lugar del medio de homogeneización.</li>
	<li>Transferir el lisado de paso 4.1 a un nuevo microtubo de 1.5ml.</li>
	<li>Determinar la concentración de proteína de paso 4.2 usando un kit de ensayo BCA por el fabricante &#39; Protocolo s. 
	Nota: Normalmente, 5-10 μl lisado de paso 4.2 es suficiente para determinar la concentración de proteína.</li>
	<li>Transferir el lisado de paso 4.2 (2 μg de proteína para la tinción de plata y 10 μg de proteína para el borrar occidental) en microtubos nuevo.</li>
	<li>Colocar los microtubos en un bloque de calor las proteínas 95 ° C y hervir en 1 x de tampón de carga de gel SDS (100 mM Tris-HCl de pH 6.8, azul de bromofenol 200 mM Ditiotreitol, 4% SDS, de 0,2%, 20% de glicerol) por 5 min</li>
	<li>Centrifugar microtubos 10 min a 21.500 x g y 4 º C. recoger el sobrenadante en nuevos microtubos para quitar las fracciones insolubles.</li>
	<li>Analizar las proteínas resueltas en el paso 4.6 (2 μg) por página de SD standard.</li>
	<li>Visualiza las bandas de proteínas por la tinción utilizando la tinción de plata de plata kit siguiendo el fabricante &#39; Protocolo s.</li>
	<li>Analizar las proteínas resueltas en el paso 4.6 (10 μg) por estándar SD-PAGE y Western-blotting. Utilizar el reactivo (SA-HRP) por el fabricante &#39; s protocolo y visualizar por fluorografía.</li>
</ol> 5. In Vitro Reconstitución de ubiquitinación ERAD de bOVA usando microsomas de purificada <ol><li>transferencia la purificada microsomas (5-10 μg de proteína) de paso 3.8 con un volumen de 50% de reticulocitos lisado (RL), en 1 x buffer de reacción (50 mM Tris, pH 7.4, 3 mM ATP, 0,5 mM MgCl 2) y 12:02 bandera etiqueta ubiquitina en un microtubo nuevo. El volumen final de este experimento es 20-40 μl.</li>
	<li>Incubar los microtubos por 2 h a 37 ° C. 
	Nota: Si la cantidad de ubiquitinated bOVA en paso 5.12 es demasiado pequeña para detección por Western blotting, agregue 10 μm de MG132 o 2 μm de lactacystin para inhibir el procesamiento de la bOVA ubiquitinated por proteasomas.</li>
	<li>Detener la reacción mediante la colocación de los microtubos en hielo.</li>
	<li>Resolver los microsomas por agregar 500 μl de tampón de TNE con volumen de 1/1.000 de cócteles inhibidores de proteasa.</li>
	<li>Centrifugar microtubos 10 min a 21,500 x g y 4 º C. recoger el sobrenadante a un nuevo microtubo para quitar las fracciones insolubles, que contienen ubiquitinated bOVA en DC2.4 antes del ensayo de ubiquitinación en vitro.</li>
	<li>Transferir el sobrenadante a un microtubo nuevo y añadir volumen 1/100 de nuevos granos SA-magnético (generalmente 5 μL para 500 μl del sobrenadante).</li>
	<li>Mezclar bien suavemente y gire el microtubo lentamente durante 30 minutos a 4 ° C.</li>
	<li>Centrifugar microtubos 10 min a 21.500 x g y 4 ° C. desechar el sobrenadante por aspiración a recuperar la bOVA y bOVA ubiquitinated atado con las bolas magnéticas SA.</li>
	<li>Lavar dos veces los granos SA-magnético recogidos con 1 mL de tampón de la TNE por centrifugación 10 min a 21.500 x g y 4 ° C. descarte el sobrenadante cada vez por la aspiración de.</li>
	<li>Hervir los granos SA-magnético en 1 x gel SDS cargando buffer por 5 min a 95 ° C en un bloque de calor para resolver las proteínas purificadas por las bolas magnéticas SA.</li>
	<li>Centrifugar microtubos 10 min a 21.500 x g y 4 º C. recoger el sobrenadante a un nuevo microtubo para quitar las fracciones insolubles.</li>
	<li>Analizar los granos SA-magnético enlazados a las proteínas por estándar SD-PAGE y Western-blotting. Es el uso de anticuerpos (Anti-Flag, anti-multi-Ub y anti-mouse IgG-HRP) y el reactivo (SA-HRP) por el fabricante &#39; Protocolo s y visualizados por fluorografía.</li>
</ol>

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L., Kyritsis, C., Tamp&#233;, R., Cresswell, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early+phagosomes+in+dendritic+cells+form+a+cellular+compartment+sufficient+for+cross+presentation+of+exogenous+antigens.">Early phagosomes in dendritic cells form a cellular compartment sufficient for cross presentation of exogenous antigens.</a> Proc Natl Acad Sci U S A. 100 (22), 12889-12894 (2003).</li><li>Saveanu, L., 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=IRAP+identifies+an+endosomal+compartment+required+for+MHC+class+I+cross-presentation.">IRAP identifies an endosomal compartment required for MHC class I cross-presentation.</a> Science. 325 (5937), 213-217 (2009).</li><li>Zehner, M., 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=The+translocon+protein+Sec61+mediates+antigen+transport+from+endosomes+in+the+cytosol+for+cross-presentation+to+CD8(+)+T+cells.">The translocon protein Sec61 mediates antigen transport from endosomes in the cytosol for cross-presentation to CD8(+) T cells.</a> Immunity. 42 (5), 850-863 (2015).</li></ol>

Los autores no tienen nada que revelar.

En estudios previos de CP, los antígenos exógenos incorporados acumulan en el área restricta del último endosome o ER por microscopía inmunofluorescente16,30,31,32. Se estima que ERAD-como transporte y procesamiento de antígenos exógenos se llevan a cabo en estas áreas especializadas de la ER o último endosome, el compartimento celular fue identificado por sacarosa o iodixanol centrifu...

El MHC las moléculas se expresan en la superficie de todas las células nucleadas, con cortos péptidos antigénicos derivados de antígenos endógenos, que son procesados por el sistema ubiquitina-proteasoma en el citosol1. Después de procesar, se transportan péptidos antigénicos en el lumen del retículo endoplásmico (ER) por el transportador de péptidos TAP. En el lumen del re, una serie de chaperonas específicas ayudan a la carga del péptido y el plegamiento correcto del MHC I complejo. Esta serie de moléculas se llama el complejo de carga (PLC), que indica que el ER es un compartimiento central para péptido cargando al MHC y2. Después de la carga, de péptidos del MHC las moléculas son transportadas a la superficie de la célula y juega un papel clave en el sistema inmune adaptativo auto marcadores, como permite el CD8+ los linfocitos T citotóxicos (CTLs) para detectar células cancerosas o agentes infecciosos por antigénica péptidos de las proteínas del mismo3.
En el antígeno que presenta las células (APC), péptidos antigénicos de los antígenos exógenos son también presentados en MHC4,5,6,7,8 a través de CP, que es fundamentalmente por DCs9,10,11. CP es esencial tanto para la activación de ingenuo CD8+ T memoria CD8 y células+ T células antiinfecciosas y anti-tumoral CTLs12,13y en el mantenimiento de la tolerancia inmune mediante la inactivación de autoactuante ingenuo T células14,15. El CP juega un papel importante muchos en el sistema inmune adaptativo, sin embargo, los mecanismos moleculares de CP tienen todavía ser descrito en detalle. Estudios previos de CP revelaron que antígenos exógenos fueron localizados en el retículo endoplasmático y el endosome y fueron procesados por ERAD, lo que sugiere que los antígenos exógenos son transportados desde el endosome a ER para ERAD-como proceso y péptido carga16 . Sin embargo, evidencia acumulada indica que la carga de péptido de CP se realiza no en la sala de emergencia sino en compartimentos endocíticos no clásica, que también tienen características distintivas de la ER (figura 1)17,18 ,19,20,21. Para evitar la degradación de los precursores del péptido antigénico por la alta actividad de aminopeptidasa22 en el citosol, el procesamiento y el péptido carga en CP se produce en la zona proximal de estos compartimentos endocíticos no clásica (figura 1). Aunque las caracterizaciones de estos compartimentos endocíticos son polémicas, hay no hay moléculas específicas existentes distintos antígenos exógenos en este compartimiento.
ERAD es una vía celular, que elimina específicamente proteínas mal plegadas de la ER. En el camino ERAD, proteínas mal plegadas retrogradely son transportadas a través de la membrana del ER al citoplasma y procesadas por el sistema de ubiquitina-proteasoma23,24,25. Cuando las moléculas grandes, como las proteínas, son transportadas a través de la bicapa lipídica, estas moléculas pasan a través de un aparato molecular llamado un translocon, tales como el complejo Sec61 y Derlin complejo en el ER26y el complejo de Tom y Tim complejo en la las mitocondrias27. Cuando exógeno agregado antígenos son transportados a través de la membrana del ER, que deben penetrar la bicapa lipídica en complejo con translocons, como el complejo Sec61. El método descrito aquí purificada la vesícula específica mediante la utilización de estas moléculas de penetración de la membrana como marcadores para los compartimentos endocíticos.
El método descrito aquí es un nuevo protocolo de purificación de vesícula usando el celular de DC como línea DC2.428 y biotinilado ovoalbúmina (bOVA) como un antígeno exógeno. Los compartimentos endocíticos se purificaron por estreptavidina (SA)-granos magnéticos mediante la penetración de la membrana bOVA como fabricante. En esta purificado microsoma, algunos añaden exógenamente bOVA se conservan en fracciones de membrana pero se transporta al exterior del microsoma y entonces ubiquitinated, procesaron en vitro29. Este microsome purificada contiene proteínas específicas del compartimiento endocíticas, sino también proteínas ER residente para ERAD y el péptido carga compleja; lo que sugiere que el compartimiento celular el compartimiento endocítico prospectivo para CP29. Este protocolo no es dependiente en el tipo de antígenos exógenos y también es aplicable para otros subconjuntos de DC y otros tipos de células, como macrófagos, células B y las células endoteliales, para aclarar el mecanismo molecular exacto de DCs para perito CP.

<table><tbody><tr><td>RPMI 1640</td><td>gibco by life technologies</td><td>11875-093</td><td></td></tr><tr><td>Fetal bovine serum</td><td>Equitech bio</td><td>SFB30</td><td></td></tr><tr><td>Sodium pyruvate</td><td>gibco by life technologies</td><td>11360-070</td><td></td></tr><tr><td>MEM non-essential amino acids</td><td>gibco by life technologies</td><td>11140-050</td><td></td></tr><tr><td>HEPES</td><td>gibco by life technologies</td><td>15630-080</td><td></td></tr><tr><td>2-mercaptoethanol</td><td>gibco by life technologies</td><td>21985-023</td><td></td></tr><tr><td>L-glutamine</td><td>gibco by life technologies</td><td>25030-164</td><td></td></tr><tr><td>Penisicillin-Sreptomycin</td><td>gibco by life technologies</td><td>15140-122</td><td></td></tr><tr><td>DMEM</td><td>gibco by life technologies</td><td>12100-46</td><td></td></tr><tr><td>OVA</td><td>SIGMA</td><td>A5503</td><td></td></tr><tr><td>Biotin-protein labelling kit</td><td>Thermo Fisher Scientific</td><td>F6347</td><td></td></tr><tr><td>MG-132</td><td>Santa Cruz Biotechnology</td><td>201270</td><td></td></tr><tr><td>lactacystin</td><td>SIGMA</td><td>L6785</td><td></td></tr><tr><td>Dounce homogenizer</td><td>IUCHI</td><td>131703</td><td></td></tr><tr><td>protease inhibitor cocktails</td><td>SIGMA</td><td>P8340</td><td></td></tr><tr><td>iodixanol</td><td>Cosmo bio</td><td>1114542</td><td></td></tr><tr><td>SA-magnetic beads</td><td>New England Biolabs</td><td>201270</td><td></td></tr><tr><td>control magnetic beads</td><td>Chemagen</td><td>M-PVA012</td><td></td></tr><tr><td>magnetic stand</td><td>BD Biosciences</td><td>552311</td><td></td></tr><tr><td>BCA protein assay kit</td><td>Thermo Fisher Scientific</td><td>23225</td><td></td></tr><tr><td>silver staining kits</td><td>Cosmo bio</td><td>423413</td><td></td></tr><tr><td>Reticulocyte Lysate</td><td>Promega</td><td>1730714</td><td></td></tr><tr><td>Flag-tagged ubiquitin</td><td>SIGMA</td><td>U5382</td><td></td></tr><tr><td>anti-ovalbumin (OVA,mouse)</td><td>Antibody Shop</td><td>HYB 094-06</td><td></td></tr><tr><td>ant-multi-ubiquitin (mouse)</td><td>MBL</td><td>D058&amp;minus;3</td><td></td></tr><tr><td>anti-Flag (mouse)</td><td>SIGMA</td><td>F3165</td><td></td></tr><tr><td>trypsin</td><td>SIGMA</td><td>85450C</td><td></td></tr></tbody></table>

purification of the membrane compartment for endoplasmic reticulum-associated degradation of exogenous antigens in cross-presentation

Las células dendríticas (DCs) son altamente capaces de procesar y presentar antígenos exógenos internalizados a clase principal de histocompatibilidad (MHC) las moléculas también conocido como Cruz-presentación (CP). CP desempeña un papel importante no sólo en la estimulación de la ingenua CD8+ T memoria CD8 y células+ T las células infecciosas e inmunidad del tumor sino también en la inactivación de automática ingenuo T células por anergia de células T o células T de supresión. Aunque el mecanismo molecular crítico de CP queda por ser aclarada, acumulando indicios que antígenos exógenos se procesan a través del retículo endoplasmático asociado degradación (ERAD) después de su exportación de no clásicas endocíticas compartimientos. Hasta hace poco, las caracterizaciones de estos compartimentos endocíticos fueron limitadas porque no había marcadores moleculares específicos distintos antígenos exógenos. El método descrito aquí es un nuevo protocolo de aislamiento de la vesícula, que permite la purificación de estos compartimentos endocíticos. Usando esta purificado microsoma, hemos reconstituido la ERAD-como transporte, ubiquitinación y procesamiento de los antígenos exógenos en vitro, sugiriendo que el sistema ubiquitina-proteasoma procesado el antígeno exógeno después de la exportación de este compartimiento celular. Este protocolo se puede aplicar más a otros tipos de células para aclarar el mecanismo molecular de CP.

Para dilucidar el mecanismo molecular de la CP, es necesario identificar los compartimentos celulares donde someterse a antígenos exógenos ERAD-como transporte y procesamiento. Mientras que observaciones por microscopía de inmunofluorescencia o microscopia electrónica identificaron el compartimento celular donde antígenos exógenos acumularon16,17,18,1<sup ...

Watch this Scientific Journal Video about Purification of the Membrane Compartment for Endoplasmic Reticulum-associated Degradation of Exogenous Antigens in Cross-presentation at JoVE.com

Purification of the Membrane Compartment for Endoplasmic Reticulum-associated Degradation of Exogenous Antigens in Cross-presentation

El método descrito aquí es un nuevo protocolo de aislamiento de la vesícula, que permite la purificación de los compartimentos celulares donde se procesan los antígenos exógenos por degradación retículo endoplasmático asociado en presentación cruzada.

Purificación del compartimento de la membrana de retículo endoplasmático asociado degradación de antígenos exógenos en presentación cruzada

Dendritic cells (DCs) are highly capable of processing and presenting internalized exogenous antigens upon major histocompatibility class (MHC) I ...

purification-membrane-compartment-for-endoplasmic-reticulum

Universidad de Cartagena UDEC

Research

JoVE Journal

Immunology and Infection

8.2K vistas.  Takasaki University of Health and Welfare. El método descrito aquí es un nuevo protocolo de aislamiento de la vesícula, que permite la purificación de los compartimentos celulares donde se procesan los antígenos exógenos por degradación retículo endoplasmático asociado en presentación cruzada.

Video: Purification of the Membrane Compartment for Endoplasmic Reticulum-associated Degradation of Exogenous Antigens in Cross-presentation

Large-Scale Purification of Porcine or Bovine Photoreceptor Outer Segments for Phagocytosis Assays on Retinal Pigment Epithelial Cells

Analysis of one of the vital functions of retinal pigment epithelial (RPE) cells, the phagocytosis of spent aged distal fragments of photoreceptor outer segments (POS) can be performed in vitro. Photoreceptor outer segments with stacks of membranous discs containing the phototransduction machinery are continuously renewed in the retina. Spent POS are eliminated daily by RPE cells. Rodent, porcine/bovine and human RPE cells recognize POS from various species in a similar manner. To facilitate performing large series of experiments with little variability, a large stock of POS can be isolated from porcine eyes and stored frozen in aliquots. This protocol takes advantage of the characteristic of photopigments that display an orange color when kept in the dark. Under dim red light, retinae are collected in a buffer from opened eyecups cut in halves. The retinal cell suspension is homogenized, filtered and loaded onto a continuous sucrose gradient. After centrifugation, POS are located in a discrete band in the upper part of the gradient that has a characteristic orange color. POS are then collected, spun, resuspended sequentially in wash buffers, counted and aliquoted. POS obtained this way can be used for phagocytosis assays and analysis of protein activation, localization or interaction at various times after POS challenge. Alternatively, POS can be labeled with fluorophores, e.g., FITC, before aliquoting for subsequent fluorescence quantification of POS binding or engulfment. Other possible applications include the use of modified POS or POS challenge combined with stress conditions to study the effect of oxidative stress or aging on RPE cells.

This article describes the protocol for the purification of photoreceptor outer segment fragments (POS) via ultracentrifugation from porcine/bovine retinae using homogenization and sucrose gradient centrifugation. This protocol allows the preparation of large stocks of POS aliquots, labeled or unlabeled, that can then be stored at -80 &#176;C.

A gran escala de purificación de porcino o bovino fotorreceptor Outer Segmentos para Fagocitosis ensayos sobre células pigmento retiniano epitelial

Analysis of one of the vital functions of retinal pigment epithelial (RPE) cells, the phagocytosis of spent aged distal fragments of photoreceptor outer ...

Investigación

Inmunología e Infección

Reconstitution of Msp1 Extraction Activity with Fully Purified Components

As the center for oxidative phosphorylation and apoptotic regulation, mitochondria play a vital role in human health. Proper mitochondrial function depends on a robust quality control system to maintain protein homeostasis (proteostasis). Declines in mitochondrial proteostasis have been linked to cancer, aging, neurodegeneration, and many other diseases. Msp1 is a AAA+ ATPase anchored in the outer mitochondrial membrane that maintains proteostasis by removing mislocalized tail-anchored proteins. Using purified components reconstituted into proteoliposomes, we have shown that Msp1 is necessary and sufficient to extract a model tail-anchored protein from a lipid bilayer. Our simplified reconstituted system overcomes several of the technical barriers that have hindered detailed study of membrane protein extraction. Here, we provide detailed methods for the generation of liposomes, membrane protein reconstitution, and the Msp1 extraction assay.

Here, we present a detailed protocol for reconstitution of Msp1 extraction activity with fully purified components in defined proteoliposomes.

Reconstitución de la actividad de extracción de Msp1 con componentes totalmente purificados

As the center for oxidative phosphorylation and apoptotic regulation, mitochondria play a vital role in human health. Proper mitochondrial function ...

Bioquímica

An Efficient and High Yield Method for Isolation of Mouse Dendritic Cell Subsets

Dendritic cells (DCs) are professional antigen-presenting cells primarily responsible for acquiring, processing and presenting antigens on antigen presenting molecules to initiate T-cell-mediated immunity. Dendritic cells can be separated into several phenotypically and functionally heterogeneous subsets. Three important subsets of splenic dendritic cells are plasmacytoid, CD8&#945;Pos and CD8&#945;Neg cells. The plasmacytoid DCs are natural producers of type I interferon and are important for anti-viral T cell immunity. The CD8&#945;Neg DC subset is specialized for MHC class II antigen presentation and is centrally involved in priming CD4 T cells. The CD8&#945;Pos DCs are primarily responsible for cross-presentation of exogenous antigens and CD8 T cell priming. The CD8&#945;Pos DCs have been demonstrated to be most efficient at the presentation of glycolipid antigens by CD1d molecules to a specialized T cell population known as invariant natural killer T (iNKT) cells. Administration of Flt-3 ligand increases the frequency of migration of dendritic cell progenitors from bone marrow, ultimately resulting in expansion of dendritic cells in peripheral lymphoid organs in murine models. We have adapted this model to purify large numbers of functional dendritic cells for use in cell transfer experiments to compare in vivo proficiency of different DC subsets.

Distinct dendritic cell subsets exist as rare populations in lymphoid organs, and therefore are challenging to isolate in sufficient numbers and purity for immunological experiments. Here we describe a high efficiency, high yield method for isolation of all of the currently known major subsets of mouse splenic dendritic cells.

Un método de rendimiento eficiente y de alta para el aislamiento de ratón subconjuntos de células dendríticas

Dendritic cells (DCs) are professional antigen-presenting cells primarily responsible for acquiring, processing and presenting antigens on antigen ...

Isolation of Salmonella typhimurium-containing Phagosomes from Macrophages

Salmonella typhimurium is a facultative intracellular bacterium that causes gastroenteritis in humans. After invasion of the lamina propria, S. typhimurium bacteria are quickly detected and phagocytized by macrophages, and contained in vesicles known as phagosomes in order to be degraded. Isolation of S. typhimurium-containing phagosomes have been widely used to study how S. typhimurium infection alters the process of phagosome maturation to prevent bacterial degradation. Classically, the isolation of bacteria-containing phagosomes has been performed by sucrose gradient centrifugation. However, this process is time-consuming, and requires specialized equipment and a certain degree of dexterity. Described here is a simple and quick method for the isolation of S. typhimurium-containing phagosomes from macrophages by coating the bacteria with biotin-streptavidin-conjugated magnetic beads. Phagosomes obtained by this method can be suspended in any buffer of choice, allowing the utilization of isolated phagosomes for a broad range of assays, such as protein, metabolite, and lipid analysis. In summary, this method for the isolation of S. typhimurium-containing phagosomes is specific, efficient, rapid, requires minimum equipment, and is more versatile than the classical method of isolation by sucrose gradient-ultracentrifugation.

Isolation of Salmonella typhimurium-containing Phagosomes from Macrophages

We describe here a simple and quick method for the isolation of Salmonella typhimurium-containing phagosomes from macrophages by coating the bacteria with biotin and streptavidin.

Aislamiento de Salmonella typhimurium-que contienen fagosomas de los macrófagos

Salmonella typhimurium is a facultative intracellular bacterium that causes gastroenteritis in humans. After invasion of the lamina propria, S. ...

Studying Organelle Dynamics in B Cells During Immune Synapse Formation

Recognition of surface-tethered antigens&#160;by the B cell receptor (BCR)&#160;triggers the formation of an immune synapse (IS), where both signaling&#160;and antigen uptake are coordinated. IS formation involves dynamic actin remodeling accompanied by the polarized recruitment to the synaptic membrane of the centrosome and associated intracellular organelles such as lysosomes and the Golgi apparatus. Initial stages of actin remodeling allow B cells to increase their cell surface and maximize the quantity of antigen-BCR complexes gathered at the synapse. Under certain conditions, when B cells recognize antigens associated to rigid surfaces, this process is coupled to the local recruitment and secretion of lysosomes, which can facilitate antigen extraction. Uptaken antigens&#160;are internalized into specialized endo-lysosome compartments for processing into peptides, which are loaded onto major histocompatibility complex II (MHC-II) molecules for further presentation to T helper cells. Therefore, studying organelle dynamics associated with the formation of an IS is crucial to understanding how B cells are activated. In the present article we will discuss both imaging and a biochemical technique used to study changes in intracellular organelle positioning and cytoskeleton rearrangements that are associated with the formation of an IS in B cells.

Herein we describe two approaches to characterize cell polarization events in B lymphocytes during the formation of an IS. The first, involves quantification of organelle recruitment and cytoskeleton rearrangements at the synaptic membrane. The second is a biochemical approach, to characterize changes in composition of the centrosome, which undergoes polarization to the immune synapse.

Estudio de la dinámica de los organelos en células B durante la formación de la sinapsis inmune

Recognition of surface-tethered antigens&#160;by the B cell receptor (BCR)&#160;triggers the formation of an immune synapse (IS), where both ...

Isolation And Dendritic Cell-Uptake of Small Extracellular Vesicles from Echinococcus granulosus

The secretion of extracellular vesicles by cestodes is crucial for enabling cellular communication not only among parasites but also with host tissues. In particular, small extracellular vesicles (sEVs) act as nano-carriers transferring natural antigens, which are critical in host immunomodulation and parasite survival. This article presents a step-by-step protocol to isolate sEVs from larval stage cultures of Echinococcus granulosus and analyzes their uptake by dendritic cells obtained from murine bone marrow, which acquire adhesion and antigen presentation capacity during their maturation after one week of in vitro culture. This article provides comprehensive information for generating, purifying, and quantifying sEVs using ultracentrifugation alongside parallel analyses of dynamic light scattering and transmission electron microscopy. Additionally, a detailed experimental protocol is outlined for isolating and cultivating mouse bone marrow cells and driving their differentiation into dendritic cells using Flt3L. These dendritic cells can present antigens to na&#239;ve T cells, thereby modulating the type of immune response in vivo. Thus, alternative protocols, including confocal microscopy and flow cytometry analysis, are proposed to check the acquired maturational phenotype of dendritic cells previously exposed to parasitic sEVs. Finally, it is worth noting that the described protocol can be applied as a whole or in individual parts to carry out parasite in vitro culture, isolate extracellular vesicles, generate bone marrow-derived dendritic cell cultures, and perform uptake assays with these cells.

Here, we describe in vitro culture conditions, isolation, and increased generation of extracellular vesicles (EVs) from Echinococcus granulosus. The small EVs were characterized by dynamic light scattering and transmission electron microscopy. The uptake by bone marrow-derived dendritic cells and their phenotypic modulation were studied using confocal microscopy and flow cytometry.

Aislamiento y absorción de células dendríticas de pequeñas vesículas extracelulares de Echinococcus granulosus

The secretion of extracellular vesicles by cestodes is crucial for enabling cellular communication not only among parasites but also with host tissues. In ...

Intralumenal Vesicles and Multivesicular Bodies

Intraluminal vesicles (ILVs) are small vesicles 50-80 nm in diameter formed during the maturation of early endosomes. A specialized endosome containing numerous ILVs is called a multivesicular body (MVB). ILVs contain internalized molecules such as antigens, nucleic acids, proteins, and metabolites. Some of these molecules are released from the MVBs inside exosomes and are transported to other cells. Other MVBs contain molecules that are retained in the ILVs and are later degraded within the cell.
MVBs were first observed in neuronal cells in 1955 using electron microscopy. MVBs have a diameter of 400-500 nm, are spherical, and were initially thought to be a form of the late endosome; however, recent studies have shown that MVBs are an intermediate form of these organelles between the early and the late endosomes.
ILV formation takes place when a ubiquitin-tagged protein enters the cell in an endocytic vesicle and fuses with the early endosome. As the early endosome matures, the endosomal membrane bends inwards to form ILVs. An ESCRT protein complex mediates ILV formation. Phosphatidylinositol 3-phosphate (PtdIns3P) is also required for ILV formation. PtdIns3P acts as a docking site for ESCRTs for the bending of the endosomal membrane.
The ESCRT complex and the ATPase, Vps4, required for ILV formation can be hijacked by enveloped retroviruses that infect host cells. Normally, ILVs are formed inside maturing endosomes with the help of ESCRTs within the cell, and the ubiquitin-tagged proteins are recognized and sorted into ILVs. In contrast, retroviruses use the ESCRTs to be released outside the cell. For example, the human immunodeficiency virus (HIV) codes for proteins, such as Gag, NC-p2, and Tat, that require ubiquitination for export. This ubiquitination is essential because ESCRTs and Vps4 recognize and sort only ubiquitin-tagged proteins into viral buds. Once the viral particles bud off from an infected cell, they are released into the extracellular space to infect other host cells.

Vesículas intraluminales y cuerpos multivesiculares

Intraluminal vesicles (ILVs) are small vesicles 50-80 nm in diameter formed during the maturation of early endosomes. A specialized endosome containing ...

Educación

JoVE Core

Biología Celular

Unit 1

Endocitosis y exocitosis

TÉRMINOS Y CONCEPTOS CLAVES

Receptor Downregulation in MVBs

Multivesicular bodies (MVBs) are mature endosomes that sort ubiquitinated proteins and then fuse with lysosomes to degrade the sorted proteins. Epidermal growth factor (EGF) and its receptor (EGFR) form a complex that can be internalized through endocytosis, sorted into an MVB, and later degraded.
The EGFR can initiate signaling pathways that&#160; lead to cell proliferation, migration, and differentiation. Overexpression of EGFR&#160; stimulates cells to proliferate. Excessive&#160; EGFR activation may result in cancer; therefore, EGFR expression must be tightly regulated. The degradation of the EGF-EGFR complex through the endocytic pathway is a means of downregulating EGFR and preventing its overexpression.
EGF binding to EGFR induces EGFR dimerization. EGFR is ubiquitinated by a ubiquitin ligase. Ubiquitination triggers the endocytosis of the dimerized EGF-EGFR complex. Once inside the cell, the complex is first sorted into the early endosome. As the early endosome matures, ESCRT proteins, or endosomal sorting complexes required for transport, translocate&#160; the EGFR-EGF complex into intraluminal vesicles (ILVs). Several ILVs are formed inside the maturing endosome, eventually becoming multivesicular bodies (MVBs). MVBs containing the EGF-EGFR complex then fuses with a lysosome for degradation of the EGFR-EGF complex.
Similar to EGFR, cytokine receptors are also internalized and downregulated by MVBs. Ubiquitinated receptor-cytokine complexes are endocytosed and later delivered to MVBs for degradation. The degradation weakens the cytokine signaling. In the case of pro-inflammatory cytokines, such as tumor necrosis factor alpha (TNF&#593;) or interleukin-1 (IL-1), any defect in ubiquitination, endocytosis, or degradation of the receptor-cytokine complex through MVB can cause enhanced or sustained signaling. This may lead to inflammatory diseases like Crohn&#39;s disease or rheumatoid arthritis.

Regulación negativa de receptores en MVBs

Multivesicular bodies (MVBs) are mature endosomes that sort ubiquitinated proteins and then fuse with lysosomes to degrade the sorted proteins. Epidermal ...

Export of Misfolded Proteins out of the ER

After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for transport to their final destination, while misfolded proteins are held back in the ER lumen. The ER chaperones attempt to unfold and refold the misfolded proteins but sometimes fail to achieve the correct native conformation. Such terminally misfolded proteins are then exported to the cytosol by ER-associated degradation or ERAD pathway for degradation.
Different modes of ERAD pathways
Hrd1 is a ubiquitin ligase and a retro-translocation channel for misfolded polypeptides. It complexes with another membrane protein, Hrd3, to form the core ERAD machinery. The other players associated with these core proteins depend upon the topology of the misfolded protein. The retrotranslocation complex depends on the luminal lectin chaperones to identify misfolded proteins. Studies in the yeast system suggest the presence of ERAD-C, ERAD-L, and ERAD-M pathways to export misfolded proteins from various parts of the ER. The target proteins of the ERAD-L and ERAD-M pathways use the Hrd1 channel to exit the ER lumen and membrane, respectively, while the ERAD-C pathway utilizes the Doa10p ubiquitin ligase complex to degrade the cytoplasmic domains of the ER membrane proteins. Sometimes, these pathways can overlap as some misfolded proteins need translocation machinery from two different ERAD pathways to exit the ER. The mammalian ERAD machinery is more complex than yeast and has multiple proteins that export and mark proteins for proteasomal degradation. Eventually, all ERAD pathways converge due to their dependence on a cytoplasmic AAA-ATPase to provide the mechanical force to extract proteins through the membrane.
Degradation of non-glycosylated proteins
The ER has another lectin-independent system that monitors and clears the non-glycosylated proteins from ER. It consists of the resident ER chaperone, BiP protein, and the ER-localized DnaJ family members (ERdjs). ER stress induces the production of HERP, a ubiquitin-like membrane protein, which assembles with other ERAD proteins like the Hrd1 and AAA-ATPase, forming a complex. BiP uses some ERdj proteins as cofactors to recruit non-glycosylated misfolded proteins to the HERP complex for retrotranslocation and ubiquitination of the misfolded protein. HERP is associated with the proteasome on the cytosolic side, where it delivers the misfolded proteins for degradation.

Exportación de proteínas mal plegadas fuera del RER

After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for ...

Transporte transmembrana en el retículo endoplasmático y peroxisomas

Antigen Presenting Cells

The immune system is a complex network of cells and molecules that protects the body from foreign invaders. T cells, a type of white blood cell, play a crucial role in this process. They recognize and attack foreign substances, such as pathogens, that enter the body.
T cells require the help of antigen-presenting cells (APCs), which process foreign antigens into smaller fragments that can be recognized by T cells. These APCs are highly specialized cells that efficiently internalize antigens through phagocytosis or receptor-mediated endocytosis.
Dendritic cells, a type of professional APC, are particularly efficient at antigen processing and presentation. They are highly mobile and can be found in tissues first exposed to foreign antigens, such as the skin, mucosal surfaces, and lymphoid organs.
Macrophages may also function as APCs, and are found in all tissues. They can engulf and process foreign antigens and release cytokines, which activate T cells and other immune cells, thereby coordinating the immune response.
B cells are another type of APC that can present antigens to T cells. When an antigen is presented to a B cell, it activates the B cell to produce antibodies against the antigen. This activation process involves the binding of the antigen to the B cell receptor, followed by a series of molecular signaling events that produce antibodies.
When an APC engulfs an antigen, it breaks into smaller fragments and combines them with major histocompatibility complex (MHC) molecules. The antigen-MHC complex is then transported to the APC&#39;s plasma membrane, where it is presented to a T cell.
The appropriate T cell receptor recognizes the processed antigen complex, triggering an immune response against the foreign invader. This process is crucial for protecting the body from infection and disease.

Células presentadoras de antígenos

Antigen-presenting cells, also known as APCs, process foreign antigens, such as fragments from pathogens, for recognition by T cells.
When an APC engulfs ...