HTS-compatible FRET-based conformational sensors clarify membrane receptor activation

Optimizing the signal-to-noise ratio in time-resolved FRET through generation of agonist-responsive cell-surface receptor biosensors, including GABA B receptors and EGFR, which are useful for monitoring conformational changes associated with receptor activation. Cell surface receptors represent a vast majority of drug targets. Efforts have been conducted to develop biosensors reporting their conformational changes in live cells for pharmacological and functional studies. Although Förster resonance energy transfer (FRET) appears to be an ideal approach, its use is limited by the low signal-to-noise ratio. Here we report a toolbox composed of a combination of labeling technologies, specific fluorophores compatible with time-resolved FRET and a novel method to quantify signals. This approach enables the development of receptor biosensors with a large signal-to-noise ratio. We illustrate the usefulness of this toolbox through the development of biosensors for various G-protein-coupled receptors and receptor tyrosine kinases. These receptors include mGlu, GABA B , LH, PTH, EGF and insulin receptors among others. These biosensors can be used for high-throughput studies and also revealed new information on the activation process of these receptors in their cellular environment.