A proteome-scale map of the human interactome network.

Just as reference genome sequences revolutionized human genetics, reference maps of interactome networks will be critical to fully understand genotype-phenotype relationships. Here, we describe a systematic map of ?14,000 high-quality human binary protein-protein interactions. At equal quality, this map is ?30% larger than what is available from small-scale studies published in the literature in the last few decades. While currently available information is highly biased and only covers a relatively small portion of the proteome, our systematic map appears strikingly more homogeneous, revealing a "broader" human interactome network than currently appreciated. The map also uncovers significant interconnectivity between known and candidate cancer gene products, providing unbiased evidence for an expanded functional cancer landscape, while demonstrating how high-quality interactome models will help "connect the dots" of the genomic revolution.

Automated antibody dispensing to improve high-parameter flow cytometry throughput and analysis.

Over the past decade, the flow cytometry field has witnessed significant advancements in the number of fluorochromes that can be detected. This enables researchers to analyze more than 40 markers simultaneously on thousands of cells per second. However, with this increased complexity and multiplicity of markers, the manual dispensing of antibodies for flow cytometry experiments has become laborious, time-consuming, and prone to errors. An automated antibody dispensing system could provide a potential solution by enhancing the efficiency, and by improving data quality by faithfully dispensing the fluorochrome-conjugated antibodies and by enabling the easy addition of extra controls. In this study, a comprehensive comparison of different liquid handlers for dispensing fluorochrome-labeled antibodies was conducted for the preparation of flow cytometry stainings. The evaluation focused on key criteria including dispensing time, dead volume, and reliability of dispensing. After benchmarking, the I.DOT, a non-contact liquid handler, was selected and optimized in more detail. In the end, the I.DOT was able to prepare a 25-marker panel in 20 min, including the full stain, all FMOs and all single stain controls for cells and beads. Having all these controls improved the validation of the panel, visualization, and analysis of the data. Thus, automated antibody dispensing by dispensers such as the I.DOT reduces time and errors, enhances data quality, and can be easily integrated in an automated workflow to prepare samples for flow cytometry.

Kinase Substrate Sensor (KISS), a mammalian in situ protein interaction sensor.

Probably every cellular process is governed by protein-protein interaction (PPIs), which are often highly dynamic in nature being modulated by in- or external stimuli. Here we present KISS, for KInase Substrate Sensor, a mammalian two-hybrid approach designed to map intracellular PPIs and some of the dynamic features they exhibit. Benchmarking experiments indicate that in terms of sensitivity and specificity KISS is on par with other binary protein interaction technologies while being complementary with regard to the subset of PPIs it is able to detect. We used KISS to evaluate interactions between different types of proteins, including transmembrane proteins, expressed at their native subcellular location. In situ analysis of endoplasmic reticulum stress-induced clustering of the endoplasmic reticulum stress sensor ERN1 and ligand-dependent ß-arrestin recruitment to GPCRs illustrated the method's potential to study functional PPI modulation in complex cellular processes. Exploring its use as a tool for in cell evaluation of pharmacological interference with PPIs, we showed that reported effects of known GPCR antagonists and PPI inhibitors are properly recapitulated. In a three-hybrid setup, KISS was able to map interactions between small molecules and proteins. Taken together, we established KISS as a sensitive approach for in situ analysis of protein interactions and their modulation in a changing cellular context or in response to pharmacological challenges.

Reconstructing the TIR Side of the Myddosome: a Paradigm for TIR-TIR Interactions.

Members of the Toll-like receptor and interleukin-1 (IL-1) receptor families all signal via Toll/IL-1R (TIR) domain-driven assemblies with adaptors such as MyD88. We here combine the mammalian two-hybrid system MAPPIT and saturation mutagenesis to complement and extend crystallographic and nuclear magnetic resonance data, and reveal how TIR domains interact. We fully delineate the interaction sites on the MyD88 TIR domain for homo-oligomerization and for interaction with Mal and TLR4. Interactions between three sites drive MyD88 homo-oligomerization. The BB-loop interacts with the αE-helix, explaining how BB-loop mimetics inhibit MyD88 signaling. The αC'-helix interacts symmetrically. The MyD88 TIR domains thus assemble into a left-handed helix, compatible with the Myddosome death domain crystal structure. This assembly explains activation of MyD88 by Mal and by an oncogenic mutation, and regulation by phosphorylation. These findings provide a paradigm for the interaction of mammalian TIR domains.