This work was supported by a grant from the NIH. The assays shown in Figure 1 was performed by Dr. Joseph Fasolo. We thank Dr. Rui Chen for helpful comments.

1. Preparação Probe <ol><li> Cultura e purificar as sondas V5-quinase de fusão usados ​​para examinar as interacções com outras proteínas, como segue: <ol><li> Use recém-riscado estirpe Y258 levedura (MATa pep4-3, his4-580, ura3-53, leu2-3,112) contendo proteína V5-fusão (expressa a partir pYES-DEST52 vetor gateway). Use a proteína isolada como sonda sobre os microarrays. A chapa completa de levedura-uracilo sintético (Sc-Ura) / 2% de dextrose / Agar e crescer a 30 ° C durante 3 dias de cultura congelada (-80 ° C em glicerol). </li><li> Inocular culturas de arranque (5-20 ml) a partir de uma única colônia e crescer durante a noite em Sc-Ura / 2% de dextrose em plataforma de agitação (220-250 rpm) ou roda a 30 ° C. </li><li> Na manhã seguinte, inocular 400 ml de SC-ura / 2% de rafinose cultura com cultura fermento suficiente para um OD 600 de 0,1 definitiva. </li><li> Cresça os inóculos para DO600 de 0,6, seguido pela indução de galactose do fu V5-cinasesion construção de expressão por adição de uma solução de extracto de levedura 3x / Peptona (YEP) suplementado com 6% de galactose, através da adição de suficiente para diluir o meio de indução por um factor de 3 de modo a que a concentração final de 2% de galactose é. </li><li> Induzir as células a 30 ° C durante 6 horas na mesa vibratória. Usar um balão de Erlenmeyer de 2 L para garantir arejamento adequado. </li><li> Células colheita utilizando um JA-10 (ou equivalente) do rotor de fiação de 400 ml de suspensão de células a 1000 xg durante 5 min a 4 ° C. </li><li> Lavar as células uma vez com 50 ml de tampão gelado PBS e transferir para um tubo de 50 ml. Lave o pellet novamente em tampão PBS frio gelo (sem detergentes ou outros aditivos) utilizados para a lise e transferência de 2 ml snap-cap tubos para a lise. </li><li> Rodar as células a 20.000 xg durante 1 min a 4 ° C, a uma pelete e a pipeta de distância tampão. </li><li> Coloque os tubos em gelo e continue com a etapa de lise. </li><li> Lisar as células (pelete de 250-350 uL) com 00,5 milímetros esferas de zircónia em um 1: 1: 1 de volume de sedimento celular, os grânulos, e solução salina tamponada com fosfato (PBS) de tampão de lise e vórtice a mistura utilizando uma plataforma de agitação 3 vezes em intervalos de 2 min a 4 ° C. </li><li> Centrifugar o lisado a 20.000 x g numa microcentrífuga mesa durante 10 min a 4 ° C. </li><li> Pipeta sobrenadante para um tubo de centrífuga de policarbonato de alta velocidade e por esclarecer ulracentrufugation durante 30 minutos a 150.000 x g a 4 ° C. </li><li> Transferir o lisado clarificado para um tubo contendo resina de afinidade de Ni 2+ pré-lavada (~ 100 mL) e incuba-se em um nutator durante 2 horas a 4 ° C para capturar Histidina (His) 6X com etiquetas V5-proteína de fusão. </li><li> Lavou-se a resina três vezes durante 10 min a 4 ° C com tampão de lavagem. Pellet da resina utilizando uma centrífuga de topo de mesa durante 5 min a 1000 xg, a 4 ° C e aspirar o sobrenadante. Adicionar tampão de lavagem fresca para cada lavagem e devolver o tubo do nutator para a agitação durante a lavagem. </li><li> Após a lavagem steps estão completos, aplicar a resina é lavada para uma nova coluna G-25 para a eluição. </li><li> Aplicar 25 ul de tampão de eluição de uma forma passo a passo começando com imidazole 100 mM a 500 mM de imidazole em incrementos de 50 mm, para um total de 9 fracções. </li><li> Ensaio das fracções recolhidas utilizando gel de dodecilsulfato de sódio poliacrilamida (SDS-PAGE) e coloração com Coomassie para identificar a fracção (s) mais altamente enriquecida para utilização no ensaio e adicionar glicerol a 30% e armazenar a -80 ° C até serem usadas no ensaio. </li></ol></li></ol> 2. Sondagem os Arrays NOTA: Por favor consulte o passo 2.6 desta seção para preparar a solução de anticorpos antes de iniciar o ensaio. <ol><li> Para detectar interacções, dilui-se o conjugado anticorpo-V5 fluoróforo (isto é AlexaFluor 647) a 260 ng / ml em tampão de sonda e homogeneizar por agitação. NOTA: Preparar esta solução de anticorpo 30 minutos antes da utilização e colocar o tubo sobre um nutatou ou roda para assegurar a mistura completa e uma suspensão homogénea de anticorpo. </li><li> Dilui-se a sonda de proteína V5-fusão numa gama de concentrações de 5-500 ug / ml. NOTA: optimizada para cada ensaio de interacção proteína-proteína, usando tampão de sonda. Optimization envolve a adição de mais sondas para sondar buffer. Tipicamente, 10 ug / ml é utilizada como ponto de partida e ajustado em conformidade com base na intensidade do sinal. </li><li> Remover os microarrays da proteína a partir do congelador (-20 ° C) e trazer a 4 ° C no frigorífico imediatamente antes da utilização. </li><li> Adicionar tampão de bloqueio directamente para o porta-lâminas contendo as proteínas micorarrays e cobrir o topo com parafilme para evitar fugas. Bloquear as matrizes em tampão de bloqueio durante 1 hora, agitando a 50 rpm em uma fase, a 4 ° C. </li><li> Após o bloqueio, as matrizes de transferência para uma câmara humidif içada arrefecida a 4 ° C, e adicionar 90 ul de sonda diluída directamente para a superfície da matriz. Overlay o arrays com um deslizamento levantador levantada e incubar estático (sem agitação) na câmara humidificada a 4 ° C durante 1,5 h. </li><li> Lavam-se as matrizes de três vezes durante 1 min cada em tampão de sonda em três tubos de 50 mL cónicos. Adicionar o slide para tubos cônicos contendo tampão sonda pré-refrigerados suficiente para envolver completamente o slide. Permitir que o deslizamento levantador para deslizar suavemente fora do microarray proteína (não forçá-lo, pois isso pode resultar em danos à superfície da matriz). </li><li> Aplique a solução de anticorpo diretamente a matriz imediatamente após a conclusão da lavagem (passo 2.5) e sobreposição com um deslizamento levantador criado como antes. Incubar as matrizes durante 30 min a 4 ° C na câmara humidificada. </li><li> Execute o mesmo passo de lavagem como anteriormente (3 vezes 1 min em tampão de sonda), e centrifugação num tubo de 50 ml a 800 xg numa centrifugadora de mesa, durante 5 min à temperatura ambiente. Secar as matrizes em um suporte de slides no escuro por 30 minutos antes de a digitalização da matriz em 647 nm. </li></ol>

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<li>Popescu, S. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Differential+binding+of+calmodulin-related+proteins+to+their+targets+revealed+through+high-density+Arabidopsis+protein+microarrays%5BTitle%5D)+AND+%22Proceedings+of+the+National+Academy+of+Sciences+of+the+United+States+of+America%22%5BJournal%5D)">Differential binding of calmodulin-related proteins to their targets revealed through high-density Arabidopsis protein microarrays.</a> Proceedings of the National Academy of Sciences of the United States of America. 104, 4730-4735 (2007).</li>
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<li>Ptacek, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Global+analysis+of+protein+phosphorylation+in+yeast%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Global analysis of protein phosphorylation in yeast.</a> Nature. 438, 679-684 (2005).</li>
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The authors declare that they have no competing financial interests.

O protocolo apresentado foi inicialmente realizada usando 85 proteínas de fusão de cinase-V5 únicas proteínas de levedura para comparar a actividade de ligação entre as famílias distintas e relacionadas de proteína-quinases de levedura, resultando na identificação de novas redes de interacção quinase in vivo 1. Como uma tecnologia de criação de perfil proteômica emergentes, o desenvolvimento de Alto Rendimento (HTP) rastreio de proteomas usando microarrays da proteína contavam com bib...

A necessidade de se realizar análises globais de bioquímica de proteínas e actividade in vivo de ligação resultou no desenvolvimento de novos métodos para perfilar as interacções proteína-proteína (IBP) e as modificações pós-traducionais de proteomas inteiros 1,3-8. Microarrays da proteína são fabricados como microarrays funcionais de proteínas utilizando proteínas funcionais full-length 4-6,8,9, ou microarrays da proteína analíticas contendo anticorpos 10,11. Eles foram concebidos para conter uma elevada densidade de proteínas dispostas em lâminas de microscópio com uma variedade de químicas de superfície para facilitar uma variedade de condições experimentais necessários para a realização de uma ampla análises bioquímicas 12. Nitrocelulose e de superfície aldeído químicas para fixação química através de métodos de lisina ou de fixação de afinidade, tais como lâminas de quelatos de níquel para a fixação de proteínas His-tag e glutationa para fixação afinidade entre outros 13. </p&gt; A utilização de microarranjos de proteínas funcionais para detectar interacções proteína-proteína requer acesso a uma biblioteca de proteínas de alta qualidade funcional 14. S. cerevisiae é favorável à produção de uma tal biblioteca através do emparelhamento de afinidade de elevada cópia etiquetados com construções de proteínas de alto rendimento técnicas de purificação cromatográfica. A grande maioria do genoma da levedura foi sequenciado e quase todo o proteoma pode ser expresso a partir de um plasmídeo de elevado número de cópias para a purificação e análises bioquímicas 12. Uma vez que as proteínas são obtidas e dispostos em formato de 384 poços, eles são impressas em uma lâmina de microscópio permitindo a análise bioquímica rápida paralelo multi-paramétricos e interrogatório bioinformática 8,14-16. Protein microarrays foram utilizadas para ensaios enzimáticos e interacções com proteínas, lípidos, moléculas pequenas, e ácidos nucleicos, entre muitas outras aplicações. A acessibilidade de proteínas na superfície de proteomamatrizes de torná-los passíveis de diferentes tipos de detecção analítica, incluindo imuno-afinidade, Surface Plasmon Resonance, fluorescência e muitas outras técnicas. Além disso, permite o controle preciso da condição experimental, onde ele pode ser difícil de fazer in vivo. O objectivo deste protocolo é para demonstrar o uso apropriado de microarrays de proteína funcionais para detectar interacções proteína-proteína. Esta aplicação permite a análise bioquímica paralela de alta taxa de transferência de actividades de ligação de proteínas utilizando uma substância altamente purificado (proteína) de interesse. Um C-terminal (C-terminal) com a etiqueta de proteína isco V5-fusão de interesse é produzida a partir de um plasmídeo de elevado número de cópias numa estirpe de levedura optimizado para a purificação de proteínas. Marcação de C-terminal assegura que a proteína de comprimento completo foi traduzido. A proteína utilizada no presente estudo é Tda1-V5 proteína de fusão de cinase, que é purificado utilizando resina de afinidade de níquel através de uma marcação His6X. A construç fusão Tda1-V5t é purificado através de eluição em série, utilizando um gradiente de imidazole para eluir a fracção mais altamente enriquecida para uso no ensaio.

<table><tbody><tr><td>Petri Dishes</td><td>VWR</td><td>NC-10747</td><td>or comparable</td></tr><tr><td>Bacto yeast extract</td><td>Difco</td><td>0217-17</td><td></td></tr><tr><td>Bacto peptone</td><td>Difco</td><td>0118-17</td><td></td></tr><tr><td>Bacto agar</td><td>Difco</td><td>0140-01</td><td></td></tr><tr><td>Dextrose</td><td>Sigma</td><td>D9434</td><td></td></tr><tr><td>Raffinose</td><td>Sigma</td><td>R0514</td><td></td></tr><tr><td>Galactose</td><td>Sigma</td><td>G0750</td><td></td></tr><tr><td>Sc-Ura drop out media</td><td>MP Bio</td><td>114410622</td><td></td></tr><tr><td>Small Culture tubes</td><td>VWR/Fisher</td><td></td><td></td></tr><tr><td>Large Erlenmeyer Flask</td><td>VWR/Fisher</td><td></td><td></td></tr><tr><td>Centrifuge JA-10 rotor</td><td></td><td></td><td></td></tr><tr><td>Centrifuge tubes (500 ml)</td><td></td><td></td><td></td></tr><tr><td>Falcon tube (50 ml)</td><td>VWR/Fisher</td><td>21008-951</td><td></td></tr><tr><td>PBS Tablets</td><td>Sigma</td><td>P4417</td><td></td></tr><tr><td>FastPrep Tubes (2 ml screw cap tube)</td><td></td><td></td><td></td></tr><tr><td>FastPrep Machine</td><td>MP Biomedicals</td><td>116004500</td><td></td></tr><tr><td>Zircon Beads</td><td>BioSpec</td><td>11079105</td><td></td></tr><tr><td>Triton X100</td><td>Sigma</td><td>P4417</td><td></td></tr><tr><td>DTT</td><td>Sigma</td><td>D9779</td><td></td></tr><tr><td>MgCl&lt;sub&gt;2&lt;/sub&gt;</td><td>Sigma</td><td>M8266&amp;nbsp;</td><td></td></tr><tr><td>NaCl</td><td>Sigma</td><td>S3014&amp;nbsp;</td><td></td></tr><tr><td>Imidazole (pH = 7.4)</td><td>Sigma</td><td>I5513&amp;nbsp;</td><td></td></tr><tr><td>PMSF</td><td>Sigma</td><td>93482</td><td></td></tr><tr><td>Complete Inhibitor Cocktail (EDTA Free)</td><td>Roche</td><td>11873580001</td><td></td></tr><tr><td>Phosphatase inhibitor cocktail 1</td><td>sigma</td><td>P2850</td><td></td></tr><tr><td>BSA</td><td>Sigma</td><td>A2153&amp;nbsp;</td><td></td></tr><tr><td>Tween-20</td><td>Sigma</td><td>P1379&amp;nbsp;</td><td></td></tr><tr><td>ATP</td><td>Sigma</td><td>A1852&amp;nbsp;</td><td></td></tr><tr><td>Shaking Incubator (30 &amp;deg;C)</td><td></td><td></td><td></td></tr><tr><td>Nickel Affinity Resin</td><td>Life Technologies</td><td>R901-01</td><td></td></tr><tr><td>G25 column</td><td>GE life sciences</td><td>27-5325-01&amp;nbsp;</td><td></td></tr><tr><td>Nutator</td><td>VWR/Fisher</td><td></td><td></td></tr><tr><td>SDS-PAGE Gel (NuPage)</td><td>Life Technologies</td><td></td><td></td></tr><tr><td>Coomassie Blue Stain</td><td>Life Technologies</td><td></td><td></td></tr><tr><td>Monoclonal V5 Antibody</td><td>Life Technologies</td><td>R960-25</td><td></td></tr><tr><td>Alexa647 Tagged monoclonal V5 Antibody</td><td>Life Technologies</td><td>451098</td><td></td></tr><tr><td>Protein Microarrays Kit</td><td>Life Technologies</td><td>PAH0525013</td><td></td></tr><tr><td>Genepix Scanner</td><td>Molecular Devices</td><td></td><td></td></tr><tr><td>Lifter Slips</td><td>Thomas Scientific</td><td></td><td>http://www.thomassci.com/Supplies/Microscope-Cover-Glass/_/LIFTER-SLIPS/</td></tr><tr><td>Lysis Buffer: 0.1% Triton X-100, 0.5 mM DTT,&lt;br/&gt; 2 mM MgCl&lt;sub&gt;2&lt;/sub&gt;, 500 mM NaCl, 50 mM imidazole (pH 7.4), Complete protease inhibitor cocktail &amp;ndash; EDTA-free, Phosphatase inhibitor Cocktail 1, 1 mM PMSF&amp;nbsp; (add just prior to use)</td><td></td><td></td><td>Add the reagents to 1x PBS (0.01 M phosphate buffer, 0.0027 M potassium chloride, 0.137 M sodium chloride; pH 7.4) to obtain the desired volume of lysis solution</td></tr><tr><td>Blocking Buffer: 1% bovine serum albumin (BSA), 0.1% Tween-20</td><td></td><td></td><td>Add the reagents to 1x PBS to obtain the desired volume of blocking buffer</td></tr><tr><td>Probe Buffer: 2 mM MgCl&lt;sub&gt;2&lt;/sub&gt;, 0.5 mM DTT, 0.05% Triton X-100, 50 mM NaCl, 500 &amp;mu;M ATP (for kinases), 1% BSA</td><td></td><td></td><td>Add the reagent to 1x PBS to obtain desired volume of probe buffer</td></tr><tr><td>Wash Buffer: 0.1% Triton X-100, 500 mM NaCl, 0.5 mM DTT, 50 mM imidazole (pH 7.4),2 mM MgCl&lt;sub&gt;2&lt;/sub&gt;</td><td></td><td></td><td>Add the reagent to 1x PBS to obtain desired volume of probe buffer</td></tr><tr><td>Elution Buffer: 0.1% Triton X-100, 0.5 mM DTT, 2 mM MgCl&lt;sub&gt;2&lt;/sub&gt;, 500 mM NaCl, 50 &amp;ndash; 500 mM imidazole (pH 7.4), Complete protease inhibitor cocktail &amp;ndash; EDTA-free, Phosphatase inhibitor Cocktail 1, 1 mM PMSF (add just prior to use)</td><td></td><td></td><td>Before you begin, it is important to note the concentration gradient of imidazole (50 &amp;ndash; 500 mM) and to create separate tubes for each concentration (it is advisable to create the interval using 50 mM increments). Add the reagent to 1x PBS to obtain desired volume of probe buffer</td></tr><tr><td>3x YEP +6% galactose: Dissolve 30 g of yeast extract and&amp;nbsp; 60 g of peptone in 700 ml of H2O, and autoclave. Add 300 ml of filter sterilized 20% galactose (wt/vol)</td><td></td><td></td><td>&amp;nbsp;Galactose should not be autoclaved</td></tr></tbody></table>

probing high-density functional protein microarrays to detect protein-protein interactions

Microarrays proteicos funcionais de alta densidade contendo ~ 4200 proteínas de levedura recombinantes são examinados para interacções proteína-proteína-quinase, utilizando uma proteína de fusão purificada por afinidade, de levedura de quinase contendo uma etiqueta de epitopo-V5 para read-out. Quinase purificada é obtida através da cultura de uma estirpe de levedura optimizado para a produção de proteínas de cópias elevado contendo um plasmídeo contendo uma fusão de quinase-V5 construir sob um promotor GAL indutível. A levedura é cultivada em meios restritiva com uma fonte de carbono neutro durante 6 horas, seguido por indução com galactose a 2%. Em seguida, a cultura é colhida e quinase é purificado usando técnicas cromatográficas padrão de afinidade para se obter uma proteína-quinase de elevada pureza para utilização no ensaio. A quinase purificada é diluída com tampão de quinase de um conjunto adequado para o ensaio e os microarrays da proteína estão bloqueados antes da hibridação com o microarray da proteína. Após a hibridação, as matrizes são sondados com V5 monoclonal ANTIBody para identificar proteínas ligadas pela proteína cinase-V5. Finalmente, as matrizes são digitalizados utilizando um scanner de microarray padrão, e os dados são extraídos para a análise informática jusante 1,2 para determinar uma confiança elevada conjunto de interacções de proteínas a jusante para validação in vivo.

A actividade de interacção proteína-proteína foi observada usando um leitor de chip padrão para avaliar a Tda1-V5 proteína quinase construção de fusão como uma proteína de isco contra um microarray proteico funcional levedura contendo aproximadamente 4200 único S. proteínas de fusão com GST cerevisiae. Além disso interrogatório com o software GenePix revelou uma infinidade de eventos de diferentes intensidades de ligação. A afinidade foi medida a partir da intensidade do sinal graduada...

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Probing High-density Functional Protein Microarrays to Detect Protein-protein Interactions

Utilizando microarrays de proteína que contêm quase toda a S. cerevisiae proteoma é sondado para um rápido interrogatório imparcial de milhares de interações proteína-proteína em paralelo. Este método pode ser utilizado para a molécula de proteína-pequena, a modificação pós-traducional, e outros ensaios in high-throughput.

Sondagem de alta densidade microarrays proteína funcional para detectar interacções proteína-proteína

High-density functional protein microarrays containing ~4,200 recombinant yeast proteins are examined for kinase protein-protein interactions using an ...

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Research

JoVE Journal

Biology

8.0K visualizações.  Stanford University.  Utilizando microarrays de proteína que contêm quase toda a S. cerevisiae proteoma é sondado para um rápido interrogatório imparcial de milhares de interações proteína-proteína em paralelo. Este método pode ser utilizado para a molécula de proteína-pequena, a modificação pós-traducional, e outros ensaios in high-throughput. 

Vídeo: Probing High-density Functional Protein Microarrays to Detect Protein-protein Interactions

Resolving Affinity Purified Protein Complexes by Blue Native PAGE and Protein Correlation Profiling

Most proteins act in association with others; hence, it is crucial to characterize these functional units in order to fully understand biological processes. Affinity purification coupled to mass spectrometry (AP-MS) has become the method of choice for identifying protein-protein interactions. However, conventional AP-MS studies provide information on protein interactions, but the organizational information is lost. To address this issue, we developed a strategy to unravel the distinct functional assemblies a protein might be involved in, by resolving affinity-purified protein complexes prior to their characterization by mass spectrometry. Protein complexes isolated through affinity purification of a bait protein using an epitope tag and competitive elution are separated through blue native electrophoresis. Comparison of protein migration profiles through correlation profiling using quantitative mass spectrometry allows assignment of interacting proteins to distinct molecular entities. This method is able to resolve protein complexes of close molecular weights that might not be resolved by traditional chromatographic techniques such as gel filtration. With little more work than conventional AP-geLC-MS/MS, we demonstrate this strategy may in many cases be adequate for obtaining protein complex topological information concomitantly to identifying protein interactions.

Here we present protocols for affinity purification of protein complexes and their separation by blue native PAGE, followed by protein correlation profiling using label free quantitative mass spectrometry. This method is useful to resolve interactomes into distinct protein complexes.

Resolver purificada por afinidade complexos de proteínas por Azul Native PAGE e Proteína Correlação Profiling

Most proteins act in association with others; hence, it is crucial to characterize these functional units in order to fully understand biological ...

Bioquímica

Extracellular Protein Microarray Technology for High Throughput Detection of Low Affinity Receptor-Ligand Interactions

Secreted factors, membrane-tethered receptors, and their interacting partners are main regulators of cellular communication and initiation of signaling cascades during homeostasis and disease, and as such represent prime therapeutic targets. Despite their relevance, these interaction networks remain significantly underrepresented in current databases; therefore, most extracellular proteins have no documented binding partner. This discrepancy is primarily due to the challenges associated with the study of the extracellular proteins, including expression of functional proteins, and the weak, low affinity, protein interactions often established between cell surface receptors. The purpose of this method is to describe the printing of a library of extracellular proteins in a microarray format for screening of protein-protein interactions. To enable detection of weak interactions, a method based on multimerization of the query protein under study is described. Coupled to this microbead-based multimerization approach for increased multivalency, the protein microarray allows robust detection of transient protein-protein interactions in high throughput. This method offers a rapid and low sample consuming-approach for identification of new interactions applicable to any extracellular protein. Protein microarray printing and screening protocol are described. This technology will be useful for investigators seeking a robust method for discovery of protein interactions in the extracellular space.

Here, we present a protocol to screen extracellular protein microarrays for identification of novel receptor-ligand interactions in high throughput. We also describe a method to enhance detection of transient protein-protein interactions by using protein-microbead complexes.

Tecnologia de Microarray da proteína extracelular para a deteção de alta taxa de transferência de interações ligante-Receptor de baixa afinidade

Secreted factors, membrane-tethered receptors, and their interacting partners are main regulators of cellular communication and initiation of signaling ...

A Comparative Approach to Characterize the Landscape of Host-Pathogen Protein-Protein Interactions

Significant efforts were gathered to generate large-scale comprehensive protein-protein interaction network maps. This is instrumental to understand the pathogen-host relationships and was essentially performed by genetic screenings in yeast two-hybrid systems. The recent improvement of protein-protein interaction detection by a Gaussia luciferase-based fragment complementation assay now offers the opportunity to develop integrative comparative interactomic approaches necessary to rigorously compare interaction profiles of proteins from different pathogen strain variants against a common set of cellular factors.
This paper specifically focuses on the utility of combining two orthogonal methods to generate protein-protein interaction datasets: yeast two-hybrid (Y2H) and a new assay, high-throughput Gaussia princeps protein complementation assay (HT-GPCA) performed in mammalian cells.
A large-scale identification of cellular partners of a pathogen protein is performed by mating-based yeast two-hybrid screenings of cDNA libraries using multiple pathogen strain variants. A subset of interacting partners selected on a high-confidence statistical scoring is further validated in mammalian cells for pair-wise interactions with the whole set of pathogen variants proteins using HT-GPCA. This combination of two complementary methods improves the robustness of the interaction dataset, and allows the performance of a stringent comparative interaction analysis. Such comparative interactomics constitute a reliable and powerful strategy to decipher any pathogen-host interplays.

This article focuses on the identification of high-confident interaction datasets between host and pathogen proteins using a combination of two orthogonal methods: yeast two-hybrid followed by a high-throughput interaction assay in mammalian cells called HT-GPCA.

Uma abordagem comparativa para caracterizar a paisagem de Patógeno-Hospedeiro interações proteína-proteína

Significant efforts were gathered to generate  large-scale comprehensive protein-protein interaction network maps. This is  instrumental to understand the ...

Imunologia e Infecção

Quantification of Protein Interaction Network Dynamics using Multiplexed Co-Immunoprecipitation

Dynamic protein-protein interactions control cellular behavior, from motility to DNA replication to signal transduction. However, monitoring dynamic interactions among multiple proteins in a protein interaction network is technically difficult. Here, we present a protocol for Quantitative Multiplex Immunoprecipitation (QMI), which allows quantitative assessment of fold changes in protein interactions based on relative fluorescence measurements of Proteins in Shared Complexes detected by Exposed Surface epitopes (PiSCES). In QMI, protein complexes from cell lysates are immunoprecipitated onto microspheres, and then probed with a labeled antibody for a different protein in order to quantify the abundance of PiSCES. Immunoprecipitation antibodies are conjugated to different MagBead spectral regions, which allows a flow cytometer to differentiate multiple parallel immunoprecipitations and simultaneously quantify the amount of probe antibody associated with each. QMI does not require genetic tagging and can be performed using minimal biomaterial compared to other immunoprecipitation methods. QMI can be adapted for any defined group of interacting proteins, and has thus far been used to characterize signaling networks in T cells and neuronal glutamate synapses. Results have led to new hypothesis generation with potential diagnostic and therapeutic applications. This protocol includes instructions to perform QMI, from the initial antibody panel selection through to running assays and analyzing data. The initial assembly of a QMI assay involves screening antibodies to generate a panel, and empirically determining an appropriate lysis buffer. The subsequent reagent preparation includes covalently coupling immunoprecipitation antibodies to MagBeads, and biotinylating probe antibodies so they can be labeled by a streptavidin-conjugated fluorophore. To run the assay, lysate is mixed with MagBeads overnight, and then beads are divided and incubated with different probe antibodies, and then a fluorophore label, and read by flow cytometry. Two statistical tests are performed to identify PiSCES that differ significantly between experimental conditions, and results are visualized using heatmaps or node-edge diagrams.

Quantitative Multiplex Immunoprecipitation (QMI) uses flow cytometry for sensitive detection of differences in the abundance of targeted protein-protein interactions between two samples. QMI can be performed using a small amount of biomaterial, does not require genetically engineered tags, and can be adapted for any previously defined protein interaction network.

Quantificação da dinâmica da rede de interação de proteínas usando co-imunoprecipitação multiplexada

Dynamic protein-protein interactions control cellular behavior, from motility to DNA replication to signal transduction. However, monitoring dynamic ...

In-vivo Detection of Protein-protein Interactions on Micro-patterned Surfaces

Unraveling the interaction network of molecules in-vivo is key to understanding the mechanisms that regulate cell function and metabolism. A multitude of methodological options for addressing molecular interactions in cells have been developed, but most of these methods suffer from being rather indirect and therefore hardly quantitative. On the contrary, a few high-end quantitative approaches were introduced, which however are difficult to extend to high throughput. To combine high throughput capabilities with the possibility to extract quantitative information, we recently developed a new concept for identifying protein-protein interactions (Schwarzenbacher et al., 2008). Here, we describe a detailed protocol for the design and the construction of this system which allows for analyzing interactions between a fluorophore-labeled protein ("prey") and a membrane protein ("bait") in-vivo. Cells are plated on micropatterned surfaces functionalized with antibodies against the bait exoplasmic domain. Bait-prey interactions are assayed via the redistribution of the fluorescent prey. The method is characterized by high sensitivity down to the level of single molecules, the capability to detect weak interactions, and high throughput capability, making it applicable as screening tool.

In-vivo Detection of Protein-protein Interactions on Micro-patterned Surfaces

This video shows experiments with subsequent analysis of protein-protein interactions by the use of micro-patterned surfaces. The approach offers the possibility to detect protein interactions in living cells and combines high throughput capabilities with the possibility to extract quantitative information.

In vivo Detecção de interações proteína-proteína em Micro-padrão Superfícies

Unraveling the interaction network of molecules in-vivo is key to understanding the mechanisms that regulate cell function and metabolism. A multitude of ...

Biologia

Chemically-blocked Antibody Microarray for Multiplexed High-throughput Profiling of Specific Protein Glycosylation in Complex Samples

In this study, we describe an effective protocol for use in a multiplexed high-throughput antibody microarray with glycan binding protein detection that allows for the glycosylation profiling of specific proteins. Glycosylation of proteins is the most prevalent post-translational modification found on proteins, and leads diversified modifications of the physical, chemical, and biological properties of proteins. Because the glycosylation machinery is particularly susceptible to disease progression and malignant transformation, aberrant glycosylation has been recognized as early detection biomarkers for cancer and other diseases. However, current methods to study protein glycosylation typically are too complicated or expensive for use in most normal laboratory or clinical settings and a more practical method to study protein glycosylation is needed. The new protocol described in this study makes use of a chemically blocked antibody microarray with glycan-binding protein (GBP) detection and significantly reduces the time, cost, and lab equipment requirements needed to study protein glycosylation. In this method, multiple immobilized glycoprotein-specific antibodies are printed directly onto the microarray slides and the N-glycans on the antibodies are blocked. The blocked, immobilized glycoprotein-specific antibodies are able to capture and isolate glycoproteins from a complex sample that is applied directly onto the microarray slides. Glycan detection then can be performed by the application of biotinylated lectins and other GBPs to the microarray slide, while binding levels can be determined using Dylight 549-Streptavidin. Through the use of an antibody panel and probing with multiple biotinylated lectins, this method allows for an effective glycosylation profile of the different proteins found in a given human or animal sample to be developed.
Introduction
Glycosylation of protein, which is the most ubiquitous post-translational modification on proteins, modifies the physical, chemical, and biological properties of a protein, and plays a fundamental role in various biological processes1-6. Because the glycosylation machinery is particularly susceptible to disease progression and malignant transformation, aberrant glycosylation has been recognized as early detection biomarkers for cancer and other diseases 7-12. In fact, most current cancer biomarkers, such as the L3 fraction of &alpha;-1 fetoprotein (AFP) for hepatocellular carcinoma 13-15, and CA199 for pancreatic cancer 16, 17 are all aberrant glycan moieties on glycoproteins. However, methods to study protein glycosylation have been complicated, and not suitable for routine laboratory and clinical settings. Chen et al. has recently invented a chemically blocked antibody microarray with a glycan-binding protein (GBP) detection method for high-throughput and multiplexed profile glycosylation of native glycoproteins in a complex sample 18. In this affinity based microarray method, multiple immobilized glycoprotein-specific antibodies capture and isolate glycoproteins from the complex mixture directly on the microarray slide, and the glycans on each individual captured protein are measured by GBPs. Because all normal antibodies contain N-glycans which could be recognized by most GBPs, the critical step of this method is to chemically block the glycans on the antibodies from binding to GBP. In the procedure, the cis-diol groups of the glycans on the antibodies were first oxidized to aldehyde groups by using NaIO4 in sodium acetate buffer avoiding light. The aldehyde groups were then conjugated to the hydrazide group of a cross-linker, 4-(4-N-MaleimidoPhenyl)butyric acid Hydrazide HCl (MPBH), followed by the conjugation of a dipeptide, Cys-Gly, to the maleimide group of the MPBH. Thus, the cis-diol groups on glycans of antibodies were converted into bulky none hydroxyl groups, which hindered the lectins and other GBPs bindings to the capture antibodies. This blocking procedure makes the GBPs and lectins bind only to the glycans of captured proteins. After this chemically blocking, serum samples were incubated with the antibody microarray, followed by the glycans detection by using different biotinylated lectins and GBPs, and visualized with Cy3-streptavidin. The parallel use of an antibody panel and multiple lectin probing provides discrete glycosylation profiles of multiple proteins in a given sample 18-20. This method has been used successfully in multiple different labs 1, 7, 13, 19-31. However, stability of MPBH and Cys-Gly, complicated and extended procedure in this method affect the reproducibility, effectiveness and efficiency of the method. In this new protocol, we replaced both MPBH and Cys-Gly with one much more stable reagent glutamic acid hydrazide (Glu-hydrazide), which significantly improved the reproducibility of the method, simplified and shorten the whole procedure so that the it can be completed within one working day. In this new protocol, we describe the detailed procedure of the protocol which can be readily adopted by normal labs for routine protein glycosylation study and techniques which are necessary to obtain reproducible and repeatable results.

In this study, we describe an improved protocol for a multiplexed high-throughput antibody microarray with lectin detection method that can be used in glycosylation profiling of specific proteins. This protocol features new reliable reagents and significantly reduces the time, cost, and lab equipment requirements as compared to the previous procedure.

Microarray de anticorpos quimicamente bloqueada para Multiplexed perfil de alta capacidade de glicosilação proteína específica em amostras complexas

 In this study, we describe an effective protocol for use in a multiplexed high-throughput antibody microarray with glycan binding protein detection that ...

Identification of Protein Interaction Partners in Mammalian Cells Using SILAC-immunoprecipitation Quantitative Proteomics

Quantitative proteomics combined with immuno-affinity purification, SILAC immunoprecipitation, represent a powerful means for the discovery of novel protein:protein interactions. By allowing the accurate relative quantification of protein abundance in both control and test samples, true interactions may be easily distinguished from experimental contaminants. Low affinity interactions can be preserved through the use of less-stringent buffer conditions and remain readily identifiable. This protocol discusses the labeling of tissue culture cells with stable isotope labeled amino acids, transfection and immunoprecipitation of an affinity tagged protein of interest, followed by the preparation for submission to a mass spectrometry facility. This protocol then discusses how to analyze and interpret the data returned from the mass spectrometer in order to identify cellular partners interacting with a protein of interest. As an example this technique is applied to identify proteins binding to the eukaryotic translation initiation factors: eIF4AI and eIF4AII.

SILAC immunoprecipitation experiments represent a powerful means for discovering novel protein:protein interactions. By allowing the accurate relative quantification of protein abundance in both control and test samples, true interactions may be easily distinguished from experimental contaminants, and low affinity interactions preserved through use of less-stringent buffer conditions.

Identificação de parceiros de interação de proteínas em células de mamíferos utilizando SILAC-imunoprecipitação quantitativos Proteômica

Quantitative proteomics combined with immuno-affinity purification, SILAC immunoprecipitation, represent a powerful means for the discovery of novel ...

Identifying Protein-protein Interaction Sites Using Peptide Arrays

Protein-protein interactions mediate most of the processes in the living cell and control homeostasis of the organism. Impaired protein interactions may result in disease, making protein interactions important drug targets. It is thus highly important to understand these interactions at the molecular level. Protein interactions are studied using a variety of techniques ranging from cellular and biochemical assays to quantitative biophysical assays, and these may be performed either with full-length proteins, with protein domains or with peptides. Peptides serve as excellent tools to study protein interactions since peptides can be easily synthesized and allow the focusing on specific interaction sites. Peptide arrays enable the identification of the interaction sites between two proteins as well as screening for peptides that bind the target protein for therapeutic purposes. They also allow high throughput SAR studies. For identification of binding sites, a typical peptide array usually contains partly overlapping 10-20 residues peptides derived from the full sequences of one or more partner proteins of the desired target protein. Screening the array for binding the target protein reveals the binding peptides, corresponding to the binding sites in the partner proteins, in an easy and fast method using only small amount of protein.
In this article we describe a protocol for screening peptide arrays for mapping the interaction sites between a target protein and its partners. The peptide array is designed based on the sequences of the partner proteins taking into account their secondary structures. The arrays used in this protocol were Celluspots arrays prepared by INTAVIS Bioanalytical Instruments. The array is blocked to prevent unspecific binding and then incubated with the studied protein. Detection using an antibody reveals the binding peptides corresponding to the specific interaction sites between the proteins.

Peptide array screening is a high throughput assay for identifying protein-protein interaction sites. This allows mapping multiple interactions of a target protein and can serve as a method for identifying sites for inhibitors that target a protein. Here we describe a protocol for screening and analyzing peptide arrays.

A identificação da proteína-proteína Locais de interacção Usando Peptide Arrays

Protein-protein interactions mediate most of the processes in the living cell and control homeostasis of the organism. Impaired protein interactions may ...

Genome-wide Protein-protein Interaction Screening by Protein-fragment Complementation Assay (PCA) in Living Cells

Proteins are the building blocks, effectors and signal mediators of cellular processes. A protein&#8217;s function, regulation and localization often depend on its interactions with other proteins. Here, we describe a protocol for the yeast protein-fragment complementation assay (PCA), a powerful method to detect direct and proximal associations between proteins in living cells. The interaction between two proteins, each fused to a dihydrofolate reductase (DHFR) protein fragment, translates into growth of yeast strains in presence of the drug methotrexate (MTX). Differential fitness, resulting from different amounts of reconstituted DHFR enzyme, can be quantified on high-density colony arrays, allowing to differentiate interacting from non-interacting bait-prey pairs. The high-throughput protocol presented here is performed using a robotic platform that parallelizes mating of bait and prey strains carrying complementary DHFR-fragment fusion proteins and the survival assay on MTX. This protocol allows to systematically test for thousands of protein-protein interactions (PPIs) involving bait proteins of interest and offers several advantages over other PPI detection assays, including the study of proteins expressed from their endogenous promoters without the need for modifying protein localization and for the assembly of complex reporter constructs.

Genome-wide Protein-protein Interaction Screening by Protein-fragment Complementation Assay PCA in Living Cells

Proteins interact with each other and these interactions determine in a large part their functions. Protein interaction partners can be identified at high-throughput in vivo using a yeast fitness assay based on the dihydrofolate reductase protein-fragment complementation assay (DHFR-PCA).

Genome-wide proteína-proteína Interaction Triagem por proteína-fragmento de Complementação Assay (PCA) em células vivas

Proteins are the building blocks, effectors and signal mediators of cellular processes. A protein&#8217;s function, regulation and localization often ...

Protein-protein Interfaces

Many proteins form complexes to carry out their functions, making protein-protein interactions (PPIs) essential for an organism&#39;s survival. Most PPIs are stabilized by numerous weak noncovalent chemical forces. The physical shape of the interfaces determines the way two proteins interact. Many globular proteins have closely-matching shapes on their surfaces, which form a large number of weak bonds. Additionally, many PPIs occur between two helices or between a surface cleft and a polypeptide chain or string.
Various computational and biochemical methods are used to study protein interfaces. Laboratory methods, such as affinity purification, mass spectrometry, and protein microarrays, can be used to identify new interactions. Co-immunoprecipitation of proteins and yeast two-hybrid screening are widely used to provide evidence on whether two proteins interact in vitro.&#160; Computer programs can predict PPIs based on similar interactions found in other proteins by comparing protein sequences and three-dimensional structures. Other computational approaches, such as phylogenetic profiling, predict PPIs based on the coevolution of binding partners. Additionally, gene fusion analysis is used to predict interaction partners by finding protein pairs that are fused in the genome of other organisms.&#160;
Proteins typically interact with multiple partners either at the same or different times, and they may contain more than one interaction interface.&#160; Many proteins form large complexes that perform specific functions that can only be carried out by the complete complex. In some cases, these protein interactions are regulated; that is, a protein may interact with different partners based on cellular needs. Further computational and statistical analyses sort such interactions into networks, which are curated in online interactome databases. These searchable databases enable users to study specific protein interactions, as well as design drugs that can enhance or disrupt interactions at the interface.

Protein Complexes and Protein-Protein Interactions

Interfaces Proteína-Proteína

Many proteins form complexes to carry out their functions, making protein-protein interactions (PPIs) essential for an organism&#39;s survival. Most PPIs ...