Protein-Protein Interaction Based Functional Screening Cell Lines
The LinkLight™ technology is a Protein-Protein Interaction-based functional screening cell line for biological activity. It detects compounds that not only bind to the target protein, but also activate a specific pathway.
The target protein covers cell surface receptor including G-Protein Coupled Receptors (GPCR), Nuclear Hormone Receptors (NHR), and Receptor Tyrosine Kinases (RTK). The most common pathways for target receptors include β-arrestin and 14-3-3, and all readouts use a standard luciferase assay as the detection method.
The principle underlying LinkLight™ technology is based on the protein-protein interaction between target protein and its signal adaptor upon activation. The design consists of two components:
The Target Protein (Protein A) is fused to the protease TEV.
The Pathway Protein (Protein B) is fused with an inactive, permuted luciferase containing a Tobacco Etch Virus (TEV) protease cleavage sequence.
Upon activation of Protein A, Protein B is recruited to its site and the two proteins can now interact. Interaction in such close proximity leads to the TEV cleavage of the inactive permuted luciferase, and thus active luciferase is reconstituted. These active luciferase signals should be specific and sensitive for a specified protein.
Interaction of Proteins A and B:
G-protein coupled receptors (GPCRs) are the largest and most diverse classes of membrane receptors in eukaryotes. GPCRs play a vast range of biological function and become important therapeutic targets. Approximately 30% of all modern medicinal drugs target GPCRs.
ß-arrestins are ubiquitously expressed and have become an important factor in identifying functionally selective or biased ligands for G-protein-coupled receptors.
14-3-3 proteins are ~ 30 kDa proteins that are ubiquitously expressed in eukaryotic cells and most highly expressed in the brain. Several GPCRs signal through 14-3-3, and GPCR antagonists can specifically block agonist-induced 14-3-3 signaling.
Linking GPCR signaling to the vast 14-3-3 protein interaction networks provides the potential for understanding GPCR signaling at a more complex level, as well as for the development of new approaches that target specific protein–protein interactions that may aid GPCR drug discovery.
Kinase functions depend on their intrinsic enzymatic activity as well as extrinsic protein interaction networks. In a cell, kinases constitutively and transiently interact with other proteins. The interactions modulate the kinase’s conformation, stability, subcellular location, signaling transduction, and/or intrinsic enzymatic activity. LinkLight™ kinase assays are based on kinase and kinase signal adaptor protein interactions, and utilize protein-protein interactions as cellular function readouts.
Cell-based kinase LinkLight™ assays offer opportunities for identifying non-traditional kinase inhibitors. Compounds modulating kinase functions by targeting non-ATP binding domains could be identified.
Nuclear Hormone Receptor Pathways
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