Agradecemos Laurie Destroismaisons e Sarah Peyrard para excelente suporte técnico e Dr.Alexandre Prat para o acesso ao citômetro de fluxo. Gostaríamos também de agradecer o Dr. Timothy Miller, por sua contribuição em relação à remoção da mielina dos preparativos. Este trabalho foi financiado pelos Institutos Canadenses de Pesquisa (CIHR) Neuromuscular Parceria de Pesquisa em Saúde, Fundação Canadense para Inovação, Sociedade ALS do Canadá, a Fundação para a Pesquisa Frick ALS, Fundação CHUM e Fonds de la Recherche en Santé du Québec (CVV). Ambos CVV e NA são estudiosos de Pesquisa do Fonds de la Recherche en Santé du Québec e CIHR novos pesquisadores. SP é apoiado pela Tim Noël Studentship da Sociedade ALS do Canadá.

Os animais utilizados neste estudo foram tratados em estrita conformidade com um protocolo (N08001CVsr), aprovado pelo du Centre Hospitalier de l&#39;Université de Montréal (CRCHUM) Comitê Institucional Centre de Recherche para a Protecção dos Animais, que segue padrões nacionais indicados pela Canadian Conselho on Animal Care (CCAC). Prepare todos os reagentes necessários para realizar esse protocolo (Tabela 1). Todos os outros detalhes sobre equipamentos, suprimentos e fornecedores podem ser encontrados na lista de materiais. <img alt="Tabela 1" fo:content-width="5in" src="/files/ftp_upload/51887/51887table1.jpg" width="500" /> Tabela 1 Composições de buffer. 1 Coleção de Rat Medula Espinhal <ol><li> Profundamente anestesiar o rato (Sprague Dawley) com 4% isoflorane. Verifique anaesthetization pela falta de reflexo sobre beliscar of the pata dianteira. Eutanásia do rato por decapitação com uma guilhotina. Este método é o preferido da eutanásia sobre os outros, o que poderia distorcer a medula espinhal. </li><li> Cortar a pele do para trás para expor a coluna vertebral. Corte a coluna vertebral com tesoura osso logo acima do osso pélvico. Visualize a abertura da coluna vertebral. </li><li> Inserir uma seringa de 10 ml, com uma ponta de pipeta de 200 uL (ligado através de fusão ligeiramente mais de chama), cheio com salina tamponada com fosfato (PBS), para a coluna vertebral. </li><li> Lave a espinal medula por meio da aplicação de uma quantidade de pressão para o êmbolo. </li><li> Se houver sangue na medula espinhal, lavar com PBS, antes de prosseguir para o próximo passo. NOTA: Este método também foi validado para o cérebro e fígado. Se estes tecidos incluindo, recolher metade do cérebro do rato sacrificados e um pedaço de fígado, em igual peso para a medula espinhal. Todas as outras medidas idênticas. </li></ol> 2 Isolamento de Medula Espinhal Mitochondria (Adaptado de Vande Velde et al. 4) <ol><li> Recolhe toda a medula espinhal e lugar intacto em 5 ml homogeneizador de vidro com 5 volumes (~ 3,25 mL) Tampão de homogeneização (HB). Para a recuperação ideal de mitocôndrias isoladas, realizar todas as etapas no gelo ou em câmara fria. Homogeneizar o tecido com a mão até que não haja grandes pedaços de tecido permanecem, cerca de oito cursos. Coloque homogeneizado em duas (2 ml) ou três (1,7 ml) tubos de microcentrífuga. Centrífuga 1300 xg durante 10 min a 4 ° C numa microcentrífuga de bancada. </li><li> Recuperar sobrenadante e colocar em um tubo de ultracentrífuga 5 ml. Adicionar 750 mL (~ 0,5 volumes) HB ao tubo de microcentrífuga contendo sedimento e ressuspender cuidadosamente o sedimento. Repita os passos de centrifugação e ressuspensão mais duas vezes. Piscina todos os sobrenadantes (S1a e s1b) para o mesmo tubo de 5 mL ultracentrífuga acima. Este passo serve para remover pequenos fragmentos. </li><li> Centrífuga reunidas S1 usando uma ultracentrífuga equipado com uma podridão balde oscilanteou e centrifugar a 17000 xg durante 15 min a 4 ° C. </li><li> Manter o sobrenadante (S2) para posterior processamento, se a fracção citosólica é de interesse (por exemplo, por análise de Western blot). Ressuspender o sedimento (P2), a fracção mitocondrial em bruto, em 4 ml de HB + 50 mM de KCl. Centrífuga 17.000 xg durante 15 min a 4 ° C num rotor de balde oscilante. Descartar o sobrenadante e ressuspender o pellet gentilmente (P3) em 800 mL HB. NOTA: As mitocôndrias são lavadas com KCl HB + 50 mM para remover quaisquer contaminantes mitocôndrias-associados não-específicos. </li><li> Em um novo tubo de 5 ml de ultracentrífuga, adicionar exactamente 800 ul do sedimento ressuspenso (P3). </li><li> A este tubo adicionar, 200 ul de iodixanol (meio de gradiente de densidade), criando deste modo uma concentração final de 12% de iodixanol. Misture o conteúdo do tubo com cuidado, mas completamente via pipeta com um P1000. A adição de iodixanol primeiro, e em seguida sedimento ressuspenso (P3) pode ser preferível para facilitar a mistura completa. Centrifugar em um ultracentrifuge equipado com um rotor basculante a 17.000 xg durante 15 min a 4 ° C. </li><li> NOTA: O fígado não contêm mielina e, portanto, este passo não é necessário se somente o fígado está sendo processado. No entanto, se o fígado está a ser processado em simultâneo com a mitocôndria do SNC, é recomendado para o tratamento de todos os tecidos de forma igual. </li><li> Aspirar a camada de mielina na parte superior do tubo e cuidadosamente remover e descartar o sobrenadante. Pellet pode estar solto. Ressuspender o sedimento em 4 ml de HB. Centrifugar novamente a 17000 xg durante 10 min a 4 ° C. Descartar o sobrenadante e ressuspender o sedimento em 4 ml HB. Voltar a centrifugar e remover o sobrenadante. </li><li> Ressuspender o sedimento final (P7) em 100-200 ul HB e transferir para um tubo de microcentrífuga de 1,7 ml. Este exemplo contém mitocôndrias isoladas. </li><li> Vá para a quantificação de proteínas. Diluir as amostras da curva padrão e em 2% de dodecilsulfato de sódio (SDS) para assegurar a solubilização adequada das mitocôndrias during quantificação da proteína. </li></ol> 3. imunomarcação de mitocôndrias isoladas de Citometria de Fluxo <ol><li> Para cada mistura de coloração para ser testado, pipeta 25 ug de mitocôndrias isoladas para um tubo de microcentrífuga de 1,7 ml. Incluir uma amostra unstained em cada experimento; e para cada anticorpo, não se esqueça de incluir uma amostra para o controlo apropriado do isotipo. </li><li> Centrifuga-se a 17000 xg durante 2 min a 4 ° C numa microcentrífuga de bancada. </li><li> Remover o sobrenadante e ressuspender mitocôndrias isoladas em 50 uL Tampão de mitocôndrias (M Tampão) suplementado com 10% de ácido gordo livre de BSA durante 15 min a 4 ° C (passo de bloqueio). NOTA: Durante a rotulagem, realizar incubações em uma geladeira a 4 ° C. </li><li> Adicionar o anticorpo primário (anti-coelho MFN2, 20 ug por ml) para o tubo e incubar durante 30 min a 4 ° C. NOTA: Determinar a concentração ideal de cada anticorpo empiricamente por titulação. Devido à variabilidade da concentração e / ou purity, diferentes lotes do mesmo anticorpo do mesmo fabricante pode levar a resultados diferentes; Por conseguinte, a titulação é necessária para cada novo lote de anticorpo. </li><li> Lavar o anticorpo primário não ligado: Centrifugar a 17.000 xg durante 2 min a 4 ° C. Remover o sobrenadante e ressuspender cuidadosamente o sedimento em 200 ul M Tampão. Centrifuga-se a 17000 xg durante 2 min a 4 ° C. Remover o sobrenadante e ressuspender o sedimento em 50 mL M Tampão. </li><li> Adicionar anticorpo secundário (de burro anti-IgG de coelho de ficoeritrina (PE), 0,5 mg por ml) para o tubo e incubar as amostras durante 30 min a 4 ° C, protegidos da luz. </li><li> Lavar o anticorpo secundário não ligado: Centrifugar a 17.000 xg durante 2 min a 4 ° C. Remover o sobrenadante e ressuspender o sedimento em 200 ul M Tampão. Centrifuga-se a 17000 xg durante 2 min a 4 ° C. Remover o sobrenadante e ressuspender o sedimento em 500 ul M Tampão. </li><li> Para garantir os eventos são de fato mitocôndria, mancha mitocôndrias isoladas com umacorante fluorescente específico para mitocôndrias 15 min à temperatura ambiente, protegida da luz. Se a coloração de outros parâmetros funcionais (potencial transmembrana mitocondrial ou a produção de superóxido) é desejada, vá para a etapa 4 Se não, vá para a etapa 5 para aquisição. NOTA: É importante verificar que o espectro de emissão do anticorpo secundário é compatível com aquela dos corantes funcionais. Por exemplo, se a verificação de pureza mitocondrial com um corante comercial com propriedades espectrais semelhantes à potencial transmembrana com FITC e éster metílico de tetrametilrodamina (TMRM), um anticorpo secundário seria viável aloficocianina (APC: Ex 650 nm / Em 660 nm). Adicionar controlos compensações, por exemplo, uma amostra immunolabeled ou coradas com uma única fluoroforo, quando aplicável. </li><li> Transferir para um tubo de fluxo adequado para o carregamento citómetro. (Para facilitar o pequeno tamanho da amostra, um tubo de microtitulação é colocado dentro de 3 ml citômetro de fluxo tubo.) Manter as amostras em gelo e proceder imediatamente àcitometria de fluxo para a aquisição. </li></ol> 4. Assaying mitocondrial potencial transmembrana mitocondrial e Superoxide Produção por citometria de fluxo <ol><li> Verificar que as mitocôndrias isoladas têm um potencial transmembrana intacta por coloração com 100 nM TMRM (Ex 548 nm / Em 574 nm) 5, no passo 3.8, durante 15 min à temperatura ambiente, protegida da luz. Para comparação do potencial transmembranar entre as amostras e as populações, a utilização de concentrações inferior / não-extinção de TMRM (1 a 30 nM), pode ser mais adequado 6. <ol><li> Como controlo para a coloração TMRM, mancha mitocôndrias isoladas com 100 nM TMRM na presença de 100 ^ M de cianeto de carbonilo m-cloro-fenil hidrazina (CCCP), um desacoplador mitocondrial que despolarizará mitocôndrias. A concentração de CCCP necessária para despolarizar a mitocôndria pode ser menor se as concentrações mais baixas de corante são utilizados. </li></ol></li><li> Verifique se mitocôndrias isoladas produzir superóxido mitocondrial por Sãoaining com um indicador de superóxido mitocondrial 7 apropriado, também na etapa 3.8, durante 15 min à temperatura ambiente, protegida da luz. <ol><li> Como um controlo para a produção de superóxido mitocondrial, mancha mitocôndrias isoladas com o corante na presença de 10 uM antimicina A, um inibidor do complexo III da cadeia respiratória, que irá aumentar a produção de superóxido mitocondrial. </li></ol></li></ol> 5. Aquisição e Análise de immunolabeled mitocôndrias isoladas por citometria de fluxo <ol><li> Instrumento criado: tensões mudar de linear para o modo de log para facilitar a análise das mitocôndrias isoladas e definidas tensões (FSC: 450; SSC: 250). Certifique-se de que os eventos são recolhidos em modo de FSC-A (área) bem como FSC-W (largura) e FSC-H (altura), para ser capaz de excluir dupletos (isto é, dois eventos, que passam pelo detector, ao mesmo tempo ) na análise de recolha de pós-dados. Defina o número de eventos a serem coletados para 100.000. Adquirir controles de compensação, Se aplicável. </li><li> Aquisição de dados: Antes de aquisição de dados, evitar vórtex amostras. Em vez disso, misture batendo suavemente tubo. Inicialmente coletar eventos a uma pressão baixa, durante gating. Portão em população total. Ajustar tensões de histogramas em conformidade, normalmente o pico da amostra não corada irá corresponder à segunda década (10 2). Uma vez que portas estão estabelecidas, e as amostras estão sendo processados, a pressão pode ser ligado à alta. </li><li> Análise: Visualize doublets traçando FSC-W contra FSC. Identificar singlets e doublet. Portão em singlets. Selecione a população mitocondrial pela passagem em eventos que são marcadas positivamente com um corante mitocondrial seletivo. </li><li> Determine rotulagem fundo do controle isotipo. Utilizando o exemplo de controlo de isotipo, determinar a percentagem da população rotulagem mitocondrial positivo para anticorpo MFN2. </li></ol>

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Os autores não têm nada a revelar.

É cada vez mais evidente que as mitocôndrias são jogadores-chave na fisiologia normal e na doença. Enquanto imunotransferência pode determinar quais as proteínas são encontradas dentro da mitocôndria ou na superfície mitocondrial em uma determinada condição, este método relatórios sobre a média da totalidade da população. Este método não pode dar informações sobre abundância relativa de subpopulações mitocondriais ou subconjuntos. Embora tenha sido previamente assumido que todas as mitocôndrias s...

As mitocôndrias são organelas altamente dinâmicos que passam por vários ciclos de fissão e fusão, são transportados para locais de alta demanda energética e responder rapidamente a estímulos fisiológicos 1. Uma vez que é cada vez mais reconhecido que as mitocôndrias dentro de tecidos diferentes, mesmo diferentes compartimentos celulares, têm perfis funcionais distintos, são necessários novos métodos para identificar esses subconjuntos mitocondriais distintas. Microscopia fornece um meio pelo qual as mitocôndrias individuais pode ser visualizada e a presença de uma proteína com ou em mitocôndrias pode ser determinada por imunofluorescência 2. No entanto, a análise quantitativa por este método é de trabalho intensivo e é mais adequado para as experiências utilizando linhas de células imortalizadas ou primárias. O estudo das mitocôndrias indivíduo derivado de tecido é significativamente mais difícil, e a maioria dos métodos de não permitir a fácil identificação de subconjuntos mitocondriais concorrentemente com a avação da função mitocondrial 3. A fim de resolver este obstáculo, um novo método para immunolabel mitocôndrias isoladas a partir de tecidos de roedores e, subsequentemente, analisadas por citometria de fluxo foi desenvolvido. Isto permite a rápida detecção e quantificação de proteínas localizadas na membrana mitocondrial externa, o que em comparação com a análise por microscopia, é muito menos trabalho intensivo e permite a análise de milhares de mitocôndrias em uma única amostra. Este ensaio pode ser aplicado para monitorizar o destino e a quantidade relativa de proteínas de membrana exterior mitocondrial que se pensa estar constitutivamente presente na mitocôndria, o recrutamento de proteínas à superfície mitocondrial, ou a detecção de proteínas mislocalized para a mitocôndria em condições patológicas. Além disso, a incorporação de corantes indicadores fluorescentes convencionais permite a avaliação simultânea de certos aspectos da função mitocondrial em mitocondrial distintasubpopulações.

<table border="0" cellpadding="0" cellspacing="0" width="1276">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Name of Material/ Equipment</td>
			<td style="width:349px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:543px;">Comments/Description</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:267px;">Rats</td>
			<td style="width:349px;">Charles River</td>
			<td style="width:119px;">Strain code 400</td>
			<td style="width:543px;">Adult (9 weeks to 18 weeks) male or female rats can be used for the isolation protocol. Weight of rats is dependent on gender and age (males between 300 to 500 g and females between 200 to 350 g) are typically used.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Dounce homogenizer</td>
			<td style="width:349px;">Kontes Glass Co.&#160;</td>
			<td style="width:119px;">885450-0022</td>
			<td>Duall 22</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Microcentrifuge</td>
			<td style="width:349px;">Thermo Scientific</td>
			<td style="width:119px;"></td>
			<td>Sorvall Legend Micro 17 R</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Ulara-Clear Ultracentrifuge tubes</td>
			<td style="width:349px;">Beckman Coultier</td>
			<td style="width:119px;">344057</td>
			<td>Transparent, thin walled&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Sorvall Ultracentrifuge</td>
			<td style="width:349px;">Thermo Scientific</td>
			<td style="width:119px;"></td>
			<td>Sorvall WX UltraSeries</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">AH-650 rotor and buckets&#160;&#160;</td>
			<td style="width:349px;">Thermo Scientific</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:267px;">Opti-prep</td>
			<td style="width:349px;">Axis-Shield</td>
			<td style="width:119px;">1114542</td>
			<td>Iodixanol, density gradient medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Fatty acid free Bovine Serum Albumin</td>
			<td style="width:349px;">Sigma</td>
			<td style="width:119px;">A8806</td>
			<td>Must be fatty acid free for mitochondria</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Sodium succinate dibasic hexahydrate&#160;&#160;</td>
			<td style="width:349px;">Sigma</td>
			<td style="width:119px;">S9637</td>
			<td></td>
		</tr>
		<tr height="18">
			<td height="18" style="height:18px;width:267px;">Rabbit anti-Mitofusin2 antibody</td>
			<td style="width:349px;">Sigma</td>
			<td style="width:119px;">M6319</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:267px;">Rabbit IgG</td>
			<td style="width:349px;">Jackson Immuno Research&#160;</td>
			<td style="width:119px;">011-000-003</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Anti-Rabbit IgG PE</td>
			<td style="width:349px;">eBioscience</td>
			<td style="width:119px;">12-4739-81</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Micro titer tube</td>
			<td style="width:349px;">Bio-Rad</td>
			<td style="width:119px;">223-9391</td>
			<td>For sample acquisition by flow cytometry&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">MitoTrackerGreen (MTG)</td>
			<td style="width:349px;">Invitrogen</td>
			<td style="width:119px;">M7514</td>
			<td>100 nM: Ex490 nm/Em516 nm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">TMRM</td>
			<td style="width:349px;">Invitrogen</td>
			<td style="width:119px;">T668</td>
			<td>100 nM: Ex548 nm/Em574 nm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">CCCP</td>
			<td style="width:349px;">Sigma</td>
			<td style="width:119px;">C2759</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">MitoSOX Red</td>
			<td style="width:349px;">Invitrogen</td>
			<td style="width:119px;">M36008</td>
			<td>5 &#181;M: Ex540 nm/Em600 nm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">Antimycin A</td>
			<td style="width:349px;">Sigma</td>
			<td style="width:119px;">A8874</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">LSR II flow cytometer</td>
			<td style="width:349px;">BD</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">BS FACSDiva Software</td>
			<td style="width:349px;">BD</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:267px;">FlowJo</td>
			<td style="width:349px;">TreeStar Inc.&#160;</td>
			<td style="width:119px;"></td>
			<td>Software used for analysis</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:267px;">BCA protein assay kit&#160;&#160;</td>
			<td style="width:349px;">Pierce/Thermo Scientific</td>
			<td style="width:119px;">23225</td>
			<td style="width:543px;">Bradford assay is not recomended as it is not compatible with high concentrations of SDS</td>
		</tr>
	</tbody>
</table>

immunodetection of outer membrane proteins by flow cytometry of isolated mitochondria

Métodos para detectar e monitorar os componentes proteína da membrana externa mitocondrial nos tecidos animais são vitais para estudar a fisiologia mitocondrial e fisiopatologia. Este protocolo descreve uma técnica em que as mitocôndrias isoladas de tecidos de roedores são immunolabeled e analisadas por citometria de fluxo. As mitocôndrias são isoladas a partir de medulas espinhais de roedores e submetido a um passo de enriquecimento rápido, de modo a remover a mielina, um contaminante de fracções mitocondriais preparadas a partir de tecido nervoso. Mitocôndrias isoladas são então marcadas com um anticorpo de escolha e um anticorpo secundário conjugado com fluorescência. Análise por citometria de fluxo, verifica a pureza relativa das preparações mitocondriais por coloração com um corante específico mitocondrial, seguido por detecção e quantificação de proteínas immunolabeled. Esta técnica é rápida, quantificável e de elevado rendimento, que permite a análise de centenas de milhares de mitocôndrias por amostra. É aplicável para avaliar novela proteins na superfície mitocondrial sob condições fisiológicas normais, bem como as proteínas que se podem tornar mislocalized para este organelo durante a patologia. Importante, este método pode ser acoplado a corantes indicadores fluorescentes para informar sobre certas actividades das subpopulações mitocondriais e é possível para as mitocôndrias do sistema nervoso central (cérebro e medula espinal), bem como o fígado.

As mitocôndrias derivadas de medulas espinais de rato pode ser immunolabeled com um anticorpo direcionado para Mitofusin2 (MFN2), uma proteína implicada na fusão da membrana externa da mitocôndria 8. A seguir ao isolamento e marcação com um anticorpo específico MFN2 e um anticorpo secundário conjugado com fluorescência, as mitocôndrias são processadas por citometria de fluxo (Figura 1). Após a aquisição de dados, as amostras são analisadas utilizando o software de análise de c...

Watch this Scientific Journal Video about Immunodetection of Outer Membrane Proteins by Flow Cytometry of Isolated Mitochondria at JoVE.com

Immunodetection of Outer Membrane Proteins by Flow Cytometry of Isolated Mitochondria

Aqui descrito é um método para detectar e quantificar as proteínas da membrana exterior mitocondrial por imunomarcação das mitocôndrias isoladas a partir de tecidos de roedores e de análise por citometria de fluxo. Este método pode ser estendido para avaliar os aspectos funcionais de subpopulações mitocondriais.

Imunodetecção de membrana externa proteínas por citometria de fluxo de mitocôndrias isoladas

Methods to detect and monitor mitochondrial outer membrane protein components in animal tissues are vital to study mitochondrial physiology and ...

immunodetection-outer-membrane-proteins-flow-cytometry-isolated

Research

JoVE Journal

Biology

15.4K visualizações.  Université de Montréal, CRCHUM.  Aqui descrito é um método para detectar e quantificar as proteínas da membrana exterior mitocondrial por imunomarcação das mitocôndrias isoladas a partir de tecidos de roedores e de análise por citometria de fluxo. Este método pode ser estendido para avaliar os aspectos funcionais de subpopulações mitocondriais. 

Vídeo: Immunodetection of Outer Membrane Proteins by Flow Cytometry of Isolated Mitochondria

IP-FCM:  Immunoprecipitation Detected by Flow Cytometry

Immunoprecipitation detected by flow cytometry (IP-FCM) is an efficient method for detecting and quantifying protein-protein interactions. The basic principle extends that of sandwich ELISA, wherein the captured primary analyte can be detected together with other molecules physically associated within multiprotein complexes. The procedure involves covalent coupling of polystyrene latex microbeads with immunoprecipitating monoclonal antibodies (mAb) specific for a protein of interest, incubating these beads with cell lysates, probing captured protein complexes with fluorochrome-conjugated probes, and analyzing bead-associated fluorescence by flow cytometry. IP-FCM is extremely sensitive, allows analysis of proteins in their native (non-denatured) state, and is amenable to either semi-quantitative or quantitative analysis. As additional advantages, IP-FCM requires no genetic engineering or specialized equipment, other than a flow cytometer, and it can be readily adapted for high-throughput applications.

The IP-FCM method is presented, which allows a sensitive, robust, biochemical assessment of native protein-protein interactions, without requiring genetic engineering or large sample sizes.

FCM-IP: Imunoprecipitação Detectado por citometria de fluxo

Immunoprecipitation detected by flow cytometry (IP-FCM) is an efficient method for detecting and quantifying protein-protein interactions. The basic ...

Biologia

Quantitative Measurement of GLUT4 Translocation to the Plasma Membrane by Flow Cytometry

Glucose is the main source of energy for the body, requiring constant regulation of its blood concentration. Insulin release by the pancreas induces glucose uptake by insulin-sensitive tissues, most notably the brain, skeletal muscle, and adipocytes. Patients suffering from type-2 diabetes and/or obesity often develop insulin resistance and are unable to control their glucose homeostasis. New insights into the mechanisms of insulin resistance may provide new treatment strategies for type-2 diabetes.
The GLUT family of glucose transporters consists of thirteen members distributed on different tissues throughout the body1. Glucose transporter type 4 (GLUT4) is the major transporter that mediates glucose uptake by insulin sensitive tissues, such as the skeletal muscle. Upon binding of insulin to its receptor, vesicles containing GLUT4 translocate from the cytoplasm to the plasma membrane, inducing glucose uptake. Reduced GLUT4 translocation is one of the causes of insulin resistance in type-2 diabetes2,3.
The translocation of GLUT4 from the cytoplasm to the plasma membrane can be visualized by immunocytochemistry, using fluorophore-conjugated GLUT4-specific antibodies.
Here, we describe a technique to quantify total amounts of GLUT4 translocation to the plasma membrane of cells during a chosen duration, using flow cytometry. This protocol is rapid (less than 4 hours, including incubation with insulin) and allows the analysis of as few as 3,000 cells or as many as 1 million cells per condition in a single experiment. It relies on anti-GLUT4 antibodies directed to an external epitope of the transporter that bind to it as soon as it is exposed to the extracellular medium after translocation to the plasma membrane.

This protocol describes a rapid technique to quantify the translocation of GLUT4 from the cytoplasm to the plasma membrane of cells by flow cytometry.

Medição quantitativa do GLUT4 translocação para a membrana plasmática por citometria de fluxo

Glucose is the main source of energy for the body, requiring constant regulation of its blood concentration. Insulin release by the pancreas induces ...

Flow Cytometry Purification of Mouse Meiotic Cells

The heterogeneous nature of cell types in the testis and the absence of meiotic cell culture models have been significant hurdles to the study of the unique differentiation programs that are manifest during meiosis. Two principal methods have been developed to purify, to varying degrees, various meiotic fractions from both adult and immature animals: elutriation or Staput (sedimentation) using BSA and/or percoll gradients. Both of these methods rely on cell size and density to separate meiotic cells1-5. Overall, except for few cell populations6, these protocols fail to yield sufficient purity of the numerous meiotic cell populations that are necessary for detailed molecular analyses. Moreover, with such methods usually one type of meiotic cells can be purified at a given time, which adds an extra level of complexity regarding the reproducibility and homogeneity when comparing meiotic cell samples.
Here, we describe a refined method that allows one to easily visualize, identify, and purify meiotic cells, from germ cells to round spermatids, using FACS combined with Hoechst 33342 staining7,8. This method provides an overall snapshot of the entire meiotic process and allows one to highly purify viable cells from most stage of meiosis. These purified cells can then be analyzed in detail for molecular changes that accompany progression through meiosis, for example changes in gene expression9,10and the dynamics of nucleosome occupancy at hotspots of meiotic recombination11.

An efficient method to obtain highly purified viable meiotic fractions from mouse testis is described, which combines a refined cell dissociation protocol with fluorescent activated cell sorting (FACS). This method takes advantage of differences in the DNA content and nuclear density of discrete meiotic fractions.

Purificação de Citometria de Fluxo de células de camundongo meiótica

The heterogeneous nature of cell types in the testis and the absence of meiotic cell culture models have been significant hurdles to the study of the ...

Use of a Robot for High-throughput Crystallization of Membrane Proteins in Lipidic Mesophases

Structure-function studies of membrane proteins greatly benefit from having available high-resolution 3-D structures of the type provided through macromolecular X-ray crystallography (MX). An essential ingredient of MX is a steady supply of ideally diffraction-quality crystals. The in meso or lipidic cubic phase (LCP) method for crystallizing membrane proteins is one of several methods available for crystallizing membrane proteins. It makes use of a bicontinuous mesophase in which to grow crystals. As a method, it has had some spectacular successes of late and has attracted much attention with many research groups now interested in using it. One of the challenges associated with the method is that the hosting mesophase is extremely viscous and sticky, reminiscent of a thick toothpaste. Thus, dispensing it manually in a reproducible manner in small volumes into crystallization wells requires skill, patience and a steady hand. A protocol for doing just that was developed in the Membrane Structural &amp; Functional Biology (MS&amp;FB) Group1-3. JoVE video articles describing the method are available1,4. 
The manual approach for setting up in meso trials has distinct advantages with specialty applications, such as crystal optimization and derivatization. It does however suffer from being a low throughput method. Here, we demonstrate a protocol for performing in meso crystallization trials robotically. A robot offers the advantages of speed, accuracy, precision, miniaturization and being able to work continuously for extended periods under what could be regarded as hostile conditions such as in the dark, in a reducing atmosphere or at low or high temperatures. An in meso robot, when used properly, can greatly improve the productivity of membrane protein structure and function research by facilitating crystallization which is one of the slow steps in the overall structure determination pipeline. 
In this video article, we demonstrate the use of three commercially available robots that can dispense the viscous and sticky mesophase integral to in meso crystallogenesis. The first robot was developed in the MS&amp;FB Group5,6. The other two have recently become available and are included here for completeness.	
An overview of the protocol covered in this article is presented in Figure 1. All manipulations were performed at room temperature (~20 &deg;C) under ambient conditions.

Herein is described a robotic approach to high-throughput crystallization of membrane proteins in lipidic mesophases for use in structure determination using macromolecular X-ray crystallography. Three robots capable of handling the viscous and sticky protein-laden mesophase integral to the method are introduced.

A utilização de um robô para alta capacidade de cristalização de proteínas de membrana em mesofases lipídicas

Structure-function studies of membrane proteins greatly benefit from having available high-resolution 3-D structures of the type provided through ...

Harvesting and Cryo-cooling Crystals of Membrane Proteins Grown in Lipidic Mesophases for Structure Determination by Macromolecular Crystallography

An important route to understanding how proteins function at a mechanistic level is to have the structure of the target protein available, ideally at atomic resolution. Presently, there is only one way to capture such information as applied to integral membrane proteins (Figure 1), and the complexes they form, and that method is macromolecular X-ray crystallography (MX). To do MX diffraction quality crystals are needed which, in the case of membrane proteins, do not form readily. A method for crystallizing membrane proteins that involves the use of lipidic mesophases, specifically the cubic and sponge phases1-5, has gained considerable attention of late due to the successes it has had in the G protein-coupled receptor field6-21 (<a href="http://www.mpdb.tcd.ie" target="_blank">www.mpdb.tcd.ie</a>). However, the method, henceforth referred to as the in meso or lipidic cubic phase method, comes with its own technical challenges. These arise, in part, due to the generally viscous and sticky nature of the lipidic mesophase in which the crystals, which are often micro-crystals, grow. Manipulating crystals becomes difficult as a result and particularly so during harvesting22,23. Problems arise too at the step that precedes harvesting which requires that the glass sandwich plates in which the crystals grow (Figure 2)24,25 are opened to expose the mesophase bolus, and the crystals therein, for harvesting, cryo-cooling and eventual X-ray diffraction data collection.
The cubic and sponge mesophase variants (Figure 3) from which crystals must be harvested have profoundly different rheologies4,26. The cubic phase is viscous and sticky akin to a thick toothpaste. By contrast, the sponge phase is more fluid with a distinct tendency to flow. Accordingly, different approaches for opening crystallization wells containing crystals growing in the cubic and the sponge phase are called for as indeed different methods are required for harvesting crystals from the two mesophase types. Protocols for doing just that have been refined and implemented in the Membrane Structural and Functional Biology (MS&amp;FB) Group, and are described in detail in this JoVE article (Figure 4). Examples are given of situations where crystals are successfully harvested and cryo-cooled. We also provide examples of cases where problems arise that lead to the irretrievable loss of crystals and describe how these problems can be avoided. In this article the Viewer is provided with step-by-step instructions for opening glass sandwich crystallization wells, for harvesting and for cryo-cooling crystals of membrane proteins growing in cubic and in sponge phases.

Herein is described procedures implemented in the Caffrey Membrane Structural and Functional Biology Group to harvest and cryo-cool membrane protein crystals grown in lipidic cubic and sponge phases for use in structure determination using macromolecular X-ray crystallography.

Colheita e Cryo-resfriamento cristais de proteínas de membrana crescida no mesofases lipídicas para a determinação da estrutura de Cristalografia Macromolecular

An important route to understanding how proteins function at a mechanistic level is to have the structure of the target protein available, ideally at ...

Multi-parameter Measurement of the Permeability Transition Pore Opening in Isolated Mouse Heart Mitochondria

The mitochondrial permeability transition pore (mtPTP) is a non specific channel that forms in the inner mitochondrial membrane to transport solutes with a molecular mass smaller than 1.5 kDa. Although the definitive molecular identity of the pore is still under debate, proteins such as cyclophilin D, VDAC and ANT contribute to mtPTP formation. While the involvement of mtPTP opening in cell death is well established1, accumulating evidence indicates that the mtPTP serves a physiologic role during mitochondrial Ca2+ homeostasis2, bioenergetics and redox signaling 3.
mtPTP opening is triggered by matrix Ca2+ but its activity can be modulated by several other factors such as oxidative stress, adenine nucleotide depletion, high concentrations of Pi, mitochondrial membrane depolarization or uncoupling, and long chain fatty acids4. In vitro, mtPTP opening can be achieved by increasing Ca2+ concentration inside the mitochondrial matrix through exogenous additions of Ca2+ (calcium retention capacity). When Ca2+ levels inside mitochondria reach a certain threshold, the mtPTP opens and facilitates Ca2+ release, dissipation of the proton motive force, membrane potential collapse and an increase in mitochondrial matrix volume (swelling) that ultimately leads to the rupture of the outer mitochondrial membrane and irreversible loss of organelle function.
Here we describe a fluorometric assay that allows for a comprehensive characterization of mtPTP opening in isolated mouse heart mitochondria. The assay involves the simultaneous measurement of 3 mitochondrial parameters that are altered when mtPTP opening occurs: mitochondrial Ca2+ handling (uptake and release, as measured by Ca2+ concentration in the assay medium), mitochondrial membrane potential, and mitochondrial volume. The dyes employed for Ca2+ measurement in the assay medium and mitochondrial membrane potential are Fura FF, a membrane impermeant, ratiometric indicator which undergoes a shift in the excitation wavelength in the presence of Ca2+, and JC-1, a cationic, ratiometric indicator which forms green monomers or red aggregates at low and high membrane potential, respectively. Changes in mitochondrial volume are measured by recording light scattering by the mitochondrial suspension. Since high-quality, functional mitochondria are required for the mtPTP opening assay, we also describe the steps necessary to obtain intact, highly coupled and functional isolated heart mitochondria.

A spectrofluorometric protocol for the measurement of the mitochondrial permeability transition pore opening in isolated mouse heart mitochondria is presented here. The assay involves the simultaneous measurement of mitochondria Ca2+ handling, mitochondrial membrane potential and mitochondrial volume. The procedure for obtaining high-quality and functional heart mitochondria is also described.

Parâmetro Multi-Medição da abertura dos poros transição de permeabilidade em mitocôndrias isoladas de coração Rato

The mitochondrial permeability transition pore (mtPTP) is a non specific channel that forms in the inner mitochondrial membrane to transport solutes with ...

Optimized Staining and Proliferation Modeling Methods for Cell Division Monitoring using Cell Tracking Dyes

Fluorescent cell tracking dyes, in combination with flow and image cytometry, are powerful tools with which to study the interactions and fates of different cell types in vitro and in vivo.1-5 Although there are literally thousands of publications using such dyes, some of the most commonly encountered cell tracking applications include monitoring of:
<ol>
	<li>stem and progenitor cell quiescence, proliferation and/or differentiation6-8</li>
	<li>antigen-driven membrane transfer9 and/or precursor cell proliferation3,4,10-18 and</li>
	<li>immune regulatory and effector cell function1,18-21.</li>
</ol>
Commercially available cell tracking dyes vary widely in their chemistries and fluorescence properties but the great majority fall into one of two classes based on their mechanism of cell labeling. "Membrane dyes", typified by PKH26, are highly lipophilic dyes that partition stably but non-covalently into cell membranes1,2,11. "Protein dyes", typified by CFSE, are amino-reactive dyes that form stable covalent bonds with cell proteins4,16,18. Each class has its own advantages and limitations. The key to their successful use, particularly in multicolor studies where multiple dyes are used to track different cell types, is therefore to understand the critical issues enabling optimal use of each class2-4,16,18,24.
The protocols included here highlight three common causes of poor or variable results when using cell-tracking dyes. These are:
<ol>
	<li>Failure to achieve bright, uniform, reproducible labeling. This is a necessary starting point for any cell tracking study but requires attention to different variables when using membrane dyes than when using protein dyes or equilibrium binding reagents such as antibodies.</li>
	<li>Suboptimal fluorochrome combinations and/or failure to include critical compensation controls. Tracking dye fluorescence is typically 102 - 103 times brighter than antibody fluorescence. It is therefore essential to verify that the presence of tracking dye does not compromise the ability to detect other probes being used.</li>
	<li>Failure to obtain a good fit with peak modeling software. Such software allows quantitative comparison of proliferative responses across different populations or stimuli based on precursor frequency or other metrics. Obtaining a good fit, however, requires exclusion of dead/dying cells that can distort dye dilution profiles and matching of the assumptions underlying the model with characteristics of the observed dye dilution profile.</li>
</ol>
Examples given here illustrate how these variables can affect results when using membrane and/or protein dyes to monitor cell proliferation.

Successful use of cell tracking dyes to monitor immune cell function and proliferation involves several critical steps. We describe methods for: 1) obtaining bright, uniform, reproducible label-ing with membrane dyes; 2) selecting fluorochromes and data acquisition conditions; and 3) choosing a model to quantify cell proliferation based on dye dilution.

Optimizado coloração e Proliferação Métodos de Modelagem para Monitoramento Divisão Celular usando Corantes Rastreamento celulares

Fluorescent cell tracking dyes, in combination with flow and image cytometry, are powerful tools with which to study the interactions and fates of ...

Cytosolic Calcium Measurements in Renal Epithelial Cells by Flow Cytometry

A variety of cellular processes, both physiological and pathophysiological, require or are governed by calcium, including exocytosis, mitochondrial function, cell death, cell metabolism and cell migration to name but a few. Cytosolic calcium is normally maintained at low nanomolar concentrations; rather it is found in high micromolar to millimolar concentrations in the endoplasmic reticulum, mitochondrial matrix and the extracellular compartment. Upon stimulation, a transient increase in cytosolic calcium serves to signal downstream events. Detecting changes in cytosolic calcium is normally performed using a live cell imaging set up with calcium binding dyes that exhibit either an increase in fluorescence intensity or a shift in the emission wavelength upon calcium binding. However, a live cell imaging set up is not freely accessible to all researchers. Alternative detection methods have been optimized for immunological cells with flow cytometry and for non-immunological adherent cells with a fluorescence microplate reader. Here, we describe an optimized, simple method for detecting changes in epithelial cells with flow cytometry using a single wavelength calcium binding dye. Adherent renal proximal tubule epithelial cells, which are normally difficult to load with dyes, were loaded with a fluorescent cell permeable calcium binding dye in the presence of probenecid, brought into suspension and calcium signals were monitored before and after addition of thapsigargin, tunicamycin and ionomycin.

Calcium is involved in numerous physiological and pathophysiological signaling pathways. Live cell imaging requires specialized equipment and can be time consuming. A quick, simple method using a flow cytometer to determine relative changes in cytosolic calcium in adherent epithelial cells brought into suspension was optimized.

Medidas cálcio citosólico em células epiteliais renais por citometria de fluxo

A variety of cellular processes, both physiological and pathophysiological, require or are governed by calcium, including exocytosis, mitochondrial ...

Analysis of Cell Suspensions Isolated from Solid Tissues by Spectral Flow Cytometry

Flow cytometry has been used for the past 40 years to define and analyze the phenotype of lymphoid and other hematopoietic cells. Initially restricted to the analysis of a few fluorochromes, currently there are dozens of different fluorescent dyes, and up to 14-18 different dyes can be combined at a time. However, several limitations still impair the analytical capabilities. Because of the multiplicity of fluorescent probes, data analysis has become increasingly complex due to the need of large, multi-parametric compensation matrices. Moreover, mutant mouse models carrying fluorescent proteins to detect and trace specific cell types in different tissues have become available, so the analysis (by flow cytometry) of auto-fluorescent cell suspensions obtained from solid organs is required. Spectral flow cytometry, which distinguishes the shapes of emission spectra along a wide range of continuous wavelengths, addresses some of these problems. The data is analyzed with an algorithm that replaces compensation matrices and treats auto-fluorescence as an independent parameter. Thus, spectral flow cytometry should be capable of discriminating fluorochromes with similar emission peaks and can provide a multi-parametric analysis without compensation requirements.
This protocol describes the spectral flow cytometry analysis, allowing for a 21-parameter (19 fluorescent probes) characterization and the management of an auto-fluorescent signal, providing high resolution in minor population detection. The results presented here show that spectral flow cytometry presents advantages in the analysis of cell populations from tissues difficult to characterize in conventional flow cytometry, such as the heart and the intestine. Spectral flow cytometry thus demonstrates the multi-parametric analytical capacity of high-performing conventional flow cytometry without the requirement for compensation and enables auto-fluorescence management.

This article describes spectral cytometry, a new approach in flow cytometry that uses the shapes of emission spectra to distinguish fluorochromes. An algorithm replaces compensations and can treat auto-fluorescence as an independent parameter. This new approach allows for the proper analysis of cells isolated from solid organs.

Análise de suspensões celulares isoladas de tecidos sólidos por citometria de fluxo espectral

Flow cytometry has been used for the past 40 years to define and analyze the phenotype of lymphoid and other hematopoietic cells. Initially restricted to ...

Measuring Endoreduplication by Flow Cytometry of Isolated Tuber Protoplasts

Endoreduplication, the replication of a cell's nuclear genome without subsequent cytokinesis, yields cells with increased DNA content and is associated with specialization, development and increase in cellular size. In plants, endoreduplication seems to facilitate the growth and expansion of certain tissues and organs. Among them is the tuber of potato (Solanum tuberosum), which undergoes considerable cellular expansion in fulfilling its function of carbohydrate storage. Thus, endoreduplication may play an important role in how tubers are able to accommodate this abundance of carbon. However, the cellular debris resulting from crude nuclear isolation methods of tubers, methods that can be used effectively with leaves, precludes the estimation of the tuber endoreduplication index (EI). This article presents a technique for assessing tuber endoreduplication through the isolation of protoplasts while demonstrating representative results obtained from different genotypes and compartmentalized tuber tissues. The major limitations of the protocol are the time and reagent costs required for sample preparation as well as relatively short lifespan of samples after lysis of protoplasts. While the protocol is sensitive to technical variation, it represents an improvement over traditional methods of nuclear isolation from these large specialized cells. Possibilities for improvements to the protocol such as recycling enzyme, the use of fixatives, and other alterations are proposed.

The protocol described herein is a method for measuring endoreduplication within tubers of potato (Solanum tuberosum). It includes plasmolysis and protoplast extraction steps to decrease the noise and debris in downstream flow cytometric analysis.

Endoreduplicação por citometria de fluxo de protoplastas de tubérculos isolados de medição

Endoreduplication, the replication of a cell's nuclear genome without subsequent cytokinesis, yields cells with increased DNA content and is associated ...