Esta pesquisa foi financiada pelo fundo de arranque de Simon Fraser University.

1. Colheita Membranas <ol><li> Adicionar tampão hipotónico (10 mM Tris-HCl, 10 mM de KCl, 1,5 mM MgCl 2, pH 8,0) com o cocktail inibidor de protease para um agregado de células (~ 10 8 células) e incuba-se durante 15-30 minutos em gelo. Lyse as células por fazer passar a amostra através de agulhas de seringas (5-10 passagens) ou homogeneizar a amostra por um homogeneizador Dounce (15-30 AVC). Use um hemocitômetro e coloração azul de tripan para verificar a eficiência da lise. </li><li> Obter a fracção microssomal por uma centrifugação diferencial do ligado em 3000 gx 15 min e em seguida a 100.000 gx 2 hr. A primeira centrifugação obtém uma pelete que é a fracção nuclear, e a subsequente centrifugação do sobrenadante gera um segundo sedimento, que é a fracção microssomal que contém a membrana plasmática, bem como organelos ligados à membrana 8. O sobrenadante final é a fracção citosólica. Guarde as frações microssomais em freezer -80 ° C para mais analysé como se indica a seguir. </li></ol> 2. Dissolve, desnaturação e Digest Proteínas da Membrana <ol><li> Dissolve-se a fracção microssomal no tampão de desnaturação (Tris 40 mM, EDTA 10 mM, 10 mM de TCEP, 0,5% Rapigest, pH 8) e depois incubar a solução a 100 ° C durante 10 min. </li><li> Arrefece-se a solução aquecida até à temperatura ambiente, adicionar ultra-alta pureza ureia em pó a uma solução de 8 M de concentração final e incubar a amostra a 37 ° C durante 30 min. </li><li> Adicionar solução de estoque de iodoacetamida à amostra de 15 mM de concentração final, e incubar a solução no escuro durante 30 min à temperatura ambiente para alquilar os tióis livres na amostra. Adicionar solução de estoque de DTT para a amostra a uma concentração final de 10 mM e incuba-se a solução durante mais 10 min à temperatura ambiente para extinguir o excesso de iodoacetamida. </li><li> Dilui-se a solução obtida com 10x tampão de Tris 40 mM a pH 8, e, subsequentemente, adicionar tripsina à amostra a uma razão de 01:20 trypsin para a proteína total. Manter a reacção de digestão durante a noite num forno de 37 ° C para assegurar o fim da reacção. </li><li> Terminar a digestão por acidificação da solução de amostra para pH 1 com HCl, uma condição que também divide o detergente, ou seja Rapigest. Degradar o Rapigest a 37 ° C durante 1 hora, e remover a precipitação desenvolvido por centrifugação. </li><li> Limpar o sobrenadante que contém péptidos de amostra por um cartucho C-18 de extracção em fase sólida (SPE) e secar a amostra obtida por speedvac. </li><li> Realizar uma análise de SDS-PAGE de amostras antes e depois de digestão com tripsina para confirmar a eficiência da digestão. </li></ol> 3. Captura glicopéptido <ol><li> Dissolve-se os péptidos limpas no tampão (acetato de sódio 100 mM, pH 5,5) de acoplamento. Adicionar periodato de sódio na solução de péptido com uma concentração final de 10 mM durante 30 min no escuro, à temperatura ambiente. Isto irá oxidar os grupos cis-diol em glicanos de aldeídos, Que permitem que os glicanos a par com a resina através de química hidrazida. Extingue-se o excesso de periodato de sulfito de sódio a uma concentração final de 20 mM e pH 5 durante 10 minutos à temperatura ambiente. </li><li> Introduzir resina derivatizada com hidrazida para a solução de péptido com uma razão de 1:4 (resina de solução) para acoplar glicopéptidos à resina. Incubar a reacção a 37 ° C durante 1-2 dias com a rotação de ponta a ponta para o acoplamento completo. </li><li> Remover os péptidos não ligados por lavagem da resina duas vezes com 1 ml de cada um dos seguintes: água DI, 1,5 M de NaCl, 80% de metanol e acetonitrilo. Finalmente, lava-se a resina 3x com 1 ml de NH 4 HCO 3 a 100 mM, pH 8 para trocar o tampão do sistema de NH 4 HCO 3 a 100 mM. <ol><li> Recolhe-se o sobrenadante e as lavagens para a análise de péptidos não ligados (opcional). </li></ol></li><li> Soltar os N-glicopéptidos a partir da resina por PNGase F numa incubação durante a noite a 37 ° C com umn fim-de-final da rotação. Recolha os peptídeos liberados por centrifugação e lavagem acetonitrila 80%. Seca-se a solução obtida no Speedvac para análise por LC-MS. </li></ol> 4. Fraccionamento adicional (opcional) Para simplificar ainda mais a complexidade da amostra, fracionar as N-glicopeptídeos obtidos. Por exemplo, dissolver-se os péptidos secos em 10 mM de formato de amónia, pH = 3 com 20% de acetonitrilo e utilizar de permuta catiónica forte (SCX) de cromatografia para fraccionar os péptidos. Seca-se o eluente obtido, e, em seguida, analisar as fracções de péptido obtidas por inversão de fases LC-MS 8,17,18. 5. Limpeza de N-glicopeptídeos Lançado (Opcional) Se levantar preocupações para o potencial de contaminação dos péptidos, redissolver os péptidos secos em ácido fórmico a 0,1% e usar uma coluna SPE MCX para limpar ainda mais os péptidos antes de fase reversa A análise por LC-MS. <strong&gt; Nota: Os parâmetros de busca de banco de dados. Durante a clivagem selectiva de N-glicopéptidos fora da resina, PNGase F converte a asparagina ligada de N-glicanos de um ácido aspártico. Portanto, existe um deslocamento de massa de 0,9840 Da dos libertadas N-glicopéptidos. Para identificar com precisão estes péptidos, esta modificação pode ser adicionada para os parâmetros de pesquisa juntamente com modificações comuns, tais como o carbamidomethylation de cisteína e à oxidação do que a metionina.

<ol>
	<li>Cho, W., Stahelin, R. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Membrane-protein+interactions+in+cell+signaling+and+membrane+trafficking.">Membrane-protein interactions in cell signaling and membrane trafficking.</a> Annual review of biophysics and biomolecular structure. 34, 119-151 (2005).</li><li>Tadevosyan, A., Vaniotis, G., Allen, B. G., Hebert, T. E., Nattel, S. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=protein-coupled+receptor+signalling+in+the+cardiac+nuclear+membrane:+evidence+and+possible+roles+in+physiological+and+pathophysiological+function.">protein-coupled receptor signalling in the cardiac nuclear membrane: evidence and possible roles in physiological and pathophysiological function.</a> The Journal of physiology. 590, 1313-1330 (2012).</li><li>White, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biophysical+dissection+of+membrane+proteins.">Biophysical dissection of membrane proteins.</a> Nature. 459, 344-346 (2009).</li><li>Heijne, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Membrane-protein+topology.+.">Membrane-protein topology. .</a> Nature reviews Molecular cell biology. 7, 909-918 (2006).</li><li>Cox, J., Mann, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+high-resolution+proteomics+for+data-driven+systems+biology.">Quantitative high-resolution proteomics for data-driven systems biology.</a> Annual review of biochemistry. 80, 273-299 (2011).</li><li>Lamond, A. I., 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=Advancing+cell+biology+through+proteomics+in+space+and+time+(PROSPECTS).">Advancing cell biology through proteomics in space and time (PROSPECTS).</a> Mol Cell Proteomics. 11, (2012).</li><li>Savas, J. N., Stein, B. D., Wu, C. C., Yates 3rd, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mass+spectrometry+accelerates+membrane+protein+analysis.">Mass spectrometry accelerates membrane protein analysis.</a> Trends in biochemical sciences. 36, 388-396 (2011).</li><li>Sun, B., 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=Shotgun+glycopeptide+capture+approach+coupled+with+mass+spectrometry+for+comprehensive+glycoproteomics.">Shotgun glycopeptide capture approach coupled with mass spectrometry for comprehensive glycoproteomics.</a> Mol Cell Proteomics. 6, 141-149 (2007).</li><li>Lowe, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glycosylation,+immunity,+and+autoimmunity.">Glycosylation, immunity, and autoimmunity.</a> Cell. 104, 809-812 (2001).</li><li>Dodds, E. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gas-phase+dissociation+of+glycosylated+peptide+ions.">Gas-phase dissociation of glycosylated peptide ions.</a> Mass spectrometry reviews. 31, 666-682 (2012).</li><li>Kaji, H., 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=Lectin+affinity+capture,+isotope-coded+tagging+and+mass+spectrometry+to+identify+N-linked+glycoproteins.">Lectin affinity capture, isotope-coded tagging and mass spectrometry to identify N-linked glycoproteins.</a> Nat Biotechnol. 21, 667-672 (2003).</li><li>Zhang, H., Li, X. J., Martin, D. B., Aebersold, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+quantification+of+N-linked+glycoproteins+using+hydrazide+chemistry,+stable+isotope+labeling+and+mass+spectrometry.">Identification and quantification of N-linked glycoproteins using hydrazide chemistry, stable isotope labeling and mass spectrometry.</a> Nat Biotechnol. 21, 660-666 (2003).</li><li>Hagglund, P., Bunkenborg, J., Elortza, F., Jensen, O. N., Roepstorff, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+strategy+for+identification+of+N-glycosylated+proteins+and+unambiguous+assignment+of+their+glycosylation+sites+using+HILIC+enrichment+and+partial+deglycosylation.">A new strategy for identification of N-glycosylated proteins and unambiguous assignment of their glycosylation sites using HILIC enrichment and partial deglycosylation.</a> J Proteome Res. 3, 556-566 (2004).</li><li>Bond, M. R., Kohler, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+methods+for+glycoprotein+discovery.">Chemical methods for glycoprotein discovery.</a> Current opinion in chemical biology. 11, 52-58 (2007).</li><li>Pasini, E. 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=In-depth+analysis+of+the+membrane+and+cytosolic+proteome+of+red+blood+cells.">In-depth analysis of the membrane and cytosolic proteome of red blood cells.</a> Blood. 108, 791-801 (2006).</li><li>Wollscheid, B., 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=Mass-spectrometric+identification+and+relative+quantification+of+N-linked+cell+surface+glycoproteins.">Mass-spectrometric identification and relative quantification of N-linked cell surface glycoproteins.</a> Nat Biotechnol. 27, 378-386 (2009).</li><li>Sun, B., 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=N-Glycoproteome+of+E14.Tg2a+mouse+embryonic+stem+cells.">N-Glycoproteome of E14.Tg2a mouse embryonic stem cells.</a> PLoS ONE. 8, (2013).</li><li>Sun, B., 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=Glycocapture-assisted+global+quantitative+proteomics+(gagQP)+reveals+multiorgan+responses+in+serum+toxicoproteome.">Glycocapture-assisted global quantitative proteomics (gagQP) reveals multiorgan responses in serum toxicoproteome.</a> J Proteome Res. 12, 2034-2044 (2013).</li></ol>

Os autores declaram que não têm interesses financeiros concorrentes.

Aqui apresentamos uma estratégia de captura de glycopeptide para perfilar as proteínas da superfície celular. O método pode ser aplicado para estudar as proteínas segregadas, tal como aqueles em sangue, assim como em outros fluidos corporais, ou em meios de cultura de células. O sucesso do método que se baseia na digestão completa de amostras; por conseguinte, uma caracterização de SDS-PAGE da eficiência da digestão é necessário, especialmente para a análise pela primeira vez ...

Proteínas da superfície da célula interagir com o ambiente extracelular e transmitir sinais a partir do exterior para o interior de uma célula. Assim, estas proteínas, incluindo proteínas de matriz extracelular, desempenham papéis críticos em todos os aspectos da biologia celular e fisiologia variando de proliferação, o crescimento, a migração, a diferenciação de envelhecimento e assim por diante. Proteínas de superfície de funcionar interagindo com outras células, proteínas e pequenas moléculas 1-3. Caracterização molecular de proteínas da superfície celular, é de grande interesse, não só para os biólogos, mas também para as empresas farmacêuticas, mais do que 60% ​​da droga são dirigidos a proteínas da superfície da célula 4. Espectrometria de massa em tandem (MS), com a sua sensibilidade superior, precisão e rendimento para a identificação de proteínas e peptídeos, tem sido uma ferramenta poderosa para estudos de proteômica globais 5,6. No entanto, as proteínas de superfície representam desafios significativos para proteômica baseada em MS, comoa maioria das proteínas de superfície existe em baixas quantidades, e com modificações pesados. As regiões que atravessam a membrana das proteínas de superfície de torná-los hidrófobos; este é especialmente o caso de proteínas transmembrana multipass. É, portanto, difícil de dissolver as proteínas de membrana em soluções aquosas, sem a ajuda de um detergente; no entanto, o uso de detergentes geralmente suprime o desempenho de HPLC e MS 1,7,8 na identificação de proteínas. Portanto, as proteínas da membrana foram mal caracterizado em proteômica baseada LC-MS diretos. A glicosilação é uma das modificações pós-tradução mais importantes e abundantes que ocorrem em proteínas da superfície das células 9. A enorme complexidade e heterogeneidade dos glicanos dificultar sinal de 10 MS &#39;peptídeos. No entanto, vários métodos proteomic usaram esta modificação única para enriquecer as proteínas de superfície e para remover as porções de açúcar a partir de proteínas antes da análise por LC-MS. Estes métodos incluem baseada em lectina de captura por afinidade e 11 à base de ácido de captura 12 ou químico bórico à base de hidrazida, bem como separações cromatográficas hidrofílicos 8,13. A remoção dos glicanos transforma as proteínas da membrana de proteínas e regulares drasticamente simplifica a caracterização MS. Porque glicosilação também ocorre em proteínas secretadas que têm alta solubilidade em contraste com a membrana proteínas, muitos métodos glycoproteomic são otimizados para proteínas solúveis, e tendem a ter menor seletividade glycopeptide e sensibilidade ao ser implantado para a membrana proteínas 8,14. Outros métodos também existe para o enriquecimento, em particular, as proteínas da superfície celular, tais como aqueles utilizando ultracentrifugação 15 e estratégias de rotulagem 16. Uma comparação detalhada entre o nosso método e outros métodos existentes para a caracterização de proteínas de membrana foi realizada recentemente 17, e os resultados indicaram que o método pode executar igualmente bem, se nãomelhor, do que todos os métodos de comparação proteómica membrana, mas com maior simplicidade. Para ajudar os pesquisadores a utilizar este método, detalhamos aqui um protocolo geral. Este método integra várias vantagens de estratégias glycoproteomics existentes e é concebido especificamente para glicoproteínas de membrana, no entanto, o método funciona igualmente bem para as proteínas secretadas. As características deste método incluem: 1) uma solubilização completa de proteínas de membrana, 2) um enriquecimento de glicopéptidos em vez de glicoproteínas para eliminar o potencial impedimento espacial quando se utiliza um substrato de captura de sólidos, 3) a utilização da química de hidrazida para formar ligações covalentes entre glicopéptidos e o substrato de captura, de modo a que os glicopéptidos ligados tolera lavagens rigorosas para alta glycoselectivity, e 4) a capacidade de realizar o processo de captura de todo em um tubo para a perda de amostra reduzida ea duração do procedimento encurtado. Depois de implementar este método para estudar uma variáveledade de amostras biológicas, incluindo células e tecidos, observou-se uma selectividade elevada (&gt; 90%) às glicoproteínas 8,17,18.

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

glycopeptide capture for cell surface proteomics

Proteínas de superfície celular, incluindo as proteínas da matriz extracelular, participam em todos os principais processos e funções celulares, tais como o crescimento, a diferenciação e proliferação. A caracterização detalhada destas proteínas fornece informações ricas para a descoberta de biomarcadores, a identificação do tipo de célula, e seleção-alvo da droga, bem como ajudando a avançar a nossa compreensão da biologia celular e fisiologia. Proteínas de superfície, no entanto, colocam desafios analíticos significativos, devido à sua inerente baixa abundância, alta hidrofobicidade, e pesadas modificações pós-traducionais. Aproveitando a glicosilação em proteínas de superfície predominante, apresentamos aqui uma abordagem de captura de glicopéptido de alto rendimento, que integra as vantagens de vários meios N-glycoproteomics existentes. Nosso método pode enriquecer os glicopeptídeos derivados de proteínas de superfície e remover seus glicanos para proteômica fáceis utilizando LC-MS. A N-glycoproteome resolvido compreende a informação de identidade e quantidade de proteína, bem como os seus locais de glicosilação. Este método foi aplicado a uma série de estudos em diversas áreas, incluindo o cancro, as células estaminais, e a toxicidade da droga. A limitação do método reside na fraca abundância de proteínas de membrana de superfície, de tal modo que uma quantidade relativamente grande de amostras é necessária para esta análise em comparação com estudos centrados em proteínas citosólicas.

Uma carta do procedimento experimental fluxo representativo é resumido na Figura 1. A rotulagem e as novas medidas de fracionamento são opcionais e os detalhes estão descritos em uma publicação recente 18. Uma outra opção é para analisar os péptidos não modificados, que não reagem com a resina. As vantagens da análise dos péptidos não modificados incluem a identificação potencial de peptídeos e proteínas não glicosiladas, tais como claudinas nas junções apertadas; uma van...

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

Glycopeptide Capture for Cell Surface Proteomics

As proteínas de superfície são biologicamente importantes e amplamente glicosilada. Apresentamos aqui uma abordagem de captura de glycopeptide para solubilizar, enriquecer e deglycosylate estas proteínas para análise proteômica baseada LC-MS fáceis.

Captura de glicopeptídeos de Superfície Celular Proteômica

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

glycopeptide-capture-for-cell-surface-proteomics

Research

JoVE Journal

Biology

11.2K visualizações.  Simon Fraser University.  As proteínas de superfície são biologicamente importantes e amplamente glicosilada. Apresentamos aqui uma abordagem de captura de glycopeptide para solubilizar, enriquecer e deglycosylate estas proteínas para análise proteômica baseada LC-MS fáceis. 

Vídeo: Glycopeptide Capture for Cell Surface Proteomics

Cell Capture Using a Microfluidic Device

Captura de célula usando um dispositivo micro

Biologia

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

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

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

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

Avidez baseado Triagem Interação Extracelular (AVEXIS) para a detecção escalável de baixa afinidade Extracelular receptor-ligante Interações

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

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

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

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

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

Metabólica Labeling e Membrana Fracionamento para Comparative Analysis proteômica de<em&gt; Arabidopsis thaliana</em&gt; Culturas suspensão de células

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

Proteomic Sample Preparation from Formalin Fixed and Paraffin Embedded Tissue

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

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

Preparação de Amostras de proteômica fixados em formalina e embebidos em parafina Tissue

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

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

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

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

Captura de Espectrometria de Massa Compound - uma ferramenta poderosa para identificar novos c-di-GMP efetoras Proteínas

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

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

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

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

Não enzimática, Soro livre de Cultura de Tecidos de lesões mamárias pré-invasivas para a geração espontânea de Mammospheres

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

Selected Reaction Monitoring Mass Spectrometry for Absolute Protein Quantification

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

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

Reação selecionada Monitoramento Espectrometria de Massa para Absolute Quantificação de Proteína

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

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

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

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

Enriquecimento de Proteínas da Matriz Extracelular a partir de tecidos e digestão em péptidos para Análise de Espectrometria de Massa

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

Surface Spreading and Immunostaining of Yeast Chromosomes

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

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

Espalhando superfície e Immunostaining de cromossomas da levedura

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

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

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

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

Analisando celular superfície de adesão remodelação em resposta à tensão mecânica usando pérolas magnéticas

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

Methods Article

Captura de glicopeptídeos de Superfície Celular Proteômica