G protein-coupled receptors display a drug target as they sense extracellular hormones or growth factors and translate their presence into intracellular signals. In course of the activation cascade of the Gq type receptor, Inositol 1 phosphate (IP1) is generated that is detected by Cisbios IP-One assay to report receptor activation.
The assay uses an IP1-specific antibody that is coupled to a donor fluorophore with high lifetime. It binds to IP1 that is linked to the acceptor fluorophore. Upon excitation the proximity of antibody and IP1 and hence, of donor and acceptor fluorophore, leads to energy transfer of the donor-emission light to the acceptor and a high TR-FRET signal. IP1 that is produced by cells and not fluorescent displaces the acceptor IP1 and decreases the TR-FRET signal.
The cellular IP-one assay proved a reliable and fast method to screen a large number of samples using the PHERAstar® microplate reader.