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P2062
LipoSignal  A Homogeneous, Cell-Free Assay for Screening for Modulators of GPCR Activation
Presenter David Sieg, Integral Molecular Inc., USA
Additional Authors: Bridget Puffer, Megan Bower, Sharon Willis, Antony Wanless, Justin Schilling, Benjamin J. Doranz
Current methodologies to screen for compounds targeting G protein-coupled receptors (GPCRs) typically involve detecting downstream signals (e.g. Ca2+, cAMP, or IP3) in live cells, or radioactive labeling of signaling intermediates (e.g. 35S-GTPgS) in membrane preparations. These approaches have proven utility, but also have major limitations due to the variability of live cells, impurity of membrane preparations, hazards of radioactivity, and difficulty in expressing some GPCRs.  LipoSignal is a cell-free GPCR-based drug discovery platform utilizing Integral Molecular’s proprietary Lipoparticle technology.  Lipoparticles are cell-free, nanoscale (150 nm diameter) virus-like particles derived directly from cellular plasma membranes, and are engineered to incorporate high concentrations of GPCRs.  LipoSignal exploits a combination of exceptionally pure and homogeneous Lipoparticles containing GPCRs, G proteins, and an analog of GTP that becomes highly fluorescent upon binding an activated G protein.  Agonist-stimulated activation of the GPCR results in increased fluorescence that can be readily detected in standard fluorescent plate readers.  A variety of GPCRs, G protein subtypes, and agonists have been validated for function within the LipoSignal assay, with the ability to discriminate between full, partial, weak, and strong agonists as well as detecting a wide range of GPCR inhibitors. LipoSignal is extremely sensitive, thus enabling detection of very weak to extremely potent compounds within the same assay configuration.