This work was supported in part by funding from the Institut Pasteur and by grants from the Ligue nationale contre le Cancer (grants R05/75-129 and RS07/75-75), the Association pour la Recherche sur le Cancer (grants ARC A09/1/5031 and 4867), and the Agence Nationale de la Recherche (ANR07 MIME 009 02 and ANR09 MIEN 026 01). M.M was a recipient of a M.E.N.R.T fellowship.

1. Yeast Two-hybrid Screenings
<ol>
	<li>Make the following required solutions
	<ol>
		<li>Complete Synthetic Drop Out (SD): dissolve 26.7 g of minimal SD base with glucose in 1 L of water. Add 2 g of amino acid mixture prepared as follows: 2 g Adenine hemisulfate, 2 g Arginine HCl, 2 g Histidine HCl, 2 g Isoleucine, 4 g Leucine, 2 g Lysine HCl, 2 g Methionine, 3 g Phenylalanine, 2 g L-Serine, 2 g L-Threonine, 3 g Tryptophan, 2 g Tyrosine, 1.2 g Uracil, 9 g Valine.</li...

<ol>
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Independently, yeast-two hybrid and mammalian interaction assays, such as GST pull-down, LUMIER or MAPPIT, have proven to be effective tools to detect protein-protein interactions, but are limited by the high rate of false-positive and false-negative interactions associated with these techniques 15. Moreover, evidence is growing that combining orthogonal methods increases the reliability of the obtained interaction dataset 7. The recent development of the HT-GPCA technique described here has not onl...

The increasing amount of data collected to generate protein-protein interaction maps opens perspectives to further understand pathogen infections. As global understanding of pathogen infections begins to emerge, it provides access to the range of perturbations induced by pathogens proteins when connecting the human proteome 1. It thereby offers a way to comprehend how pathogens manipulate the host cell machinery. In particular, the mapping of several viral-host interaction networks revealed that viral proteins preferentially target host proteins that are highly connected in the cellular network (hubs), or that are central to many paths in a network (bottlenecks proteins) 2-4. These interactions allow viruses to manipulate important cellular processes, which is instrumental to replicate and produce infectious progeny. Comparative interactions mapping were recently conducted on related viruses with the goal to extract information relative to pathogenesis 4. Furthermore, studies of the host-pathogens interactions landscape have been extended to many pathogens 5. The targeted cell factors identification provides insights into the strategies used by pathogens to infect cells and allows detection of potential pathogenic markers.
The yeast two-hybrid system is the most popular method to identify binary interactions since genetic screening is an efficient and sensitive tool for high-throughput mapping of protein-protein interactions. The approach proposed here further improves individual Y2H screenings by assessing a protein of multiple pathogens strain variants, thus providing access to a comparative overview of pathogen-host protein-protein interactions. Moreover, a major limitation of yeast two-hybrid screening lies in a high false-negative rate, since it recovers about 20% of total interactions 6. This implies that interactions detected with only a subset of pathogens variants might have escaped detection with the others. Therefore, individual partners emerging from all the two-hybrid screenings are further challenged for interaction with the complete range of strains studied, providing comparative interaction datasets. Since it was demonstrated that combining different methodologies strongly increases the robustness of protein-protein interaction datasets 7, this validation is performed in mammalian cells by a newly developed protein-fragment complementation assay called HT-GPCA 8. This cell-based system allows the detection of protein interactions by complementation of the Gaussia princeps split luciferase and has been designed to be compatible with a high-throughput format. Thanks to its luminescence-based technology and its low background noise compared with other fluorescence-based assay, HT-GPCA shows a strikingly high sensitivity.
Overall, this approach constitutes an efficient tool to generate a comprehensive mapping of host-pathogen interplays, which represents the first step toward a global understanding of the host cell hijacking.

<table border="1">
	<tbody>
		<tr>
			<td>Name of Reagent/Material</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Yeast strains</td>
			<td>Clontech</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Minimal SD base</td>
			<td>US biological</td>
			<td>D9500</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Amino acids</td>
			<td>Sigma</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>3-amino-1,2,4-Triazole (3-AT)</td>
			<td>Acros organics</td>
			<td>264571000</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Zymolase</td>
			<td>Seikagaku</td>
			<td>120491</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Gibco-Life Technologies</td>
			<td>31966</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>BioWest</td>
			<td>S1810</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Phosphate buffer Saline (PBS)</td>
			<td>Gibco-Life Technologies</td>
			<td>14190</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>Gibco-Life Technologies</td>
			<td>15140</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Trypsin-EDTA</td>
			<td>Gibco-Life Technologies</td>
			<td>25300</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Renilla luciferase assay</td>
			<td>Promega</td>
			<td>E2820</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>White culture plate</td>
			<td>Greiner Bio-One</td>
			<td>655083</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>96-wellPCR plates</td>
			<td>4titude</td>
			<td>4t-i0730/C</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Incubator (30 &deg;C)</td>
			<td>Memmert</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Incubator (37 &deg;C)</td>
			<td>Heraeus</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Luminometer</td>
			<td>Berthold</td>
			<td>Centro XS-LB 960</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

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.

A major strength of HT-GPCA lies in its high sensitivity, as illustrated by the assessment of false positive and false negative rates for the HPV E2 protein in Figure 2 (adapted from reference 13). To determine the false negative rate, known interactions of E2 from HPV16 were assessed by HT-GPCA (Figure 2A). Four out of 18 interactions were not recovered (corresponding to a 22% false negative rate). The false positive interactions were measured to be 5.8% using 12 HPV E2 proteins against...

Watch this Scientific Journal Video about A Comparative Approach to Characterize the Landscape of Host-Pathogen Protein-Protein Interactions at JoVE.com

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

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.

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

a-comparative-approach-to-characterize-landscape-host-pathogen

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Immunology and Infection

11.1K vistas.  Institut Pasteur. Este artículo se centra en la identificación de la interacción de datos de alta confianza entre anfitrión y proteínas de patógenos utilizando una combinación de los dos métodos ortogonales: levadura de dos híbridos seguido de un ensayo de interacción de alto rendimiento en células de mamífero llamado HT-GPCA.