Cell lines that express FAP tagged GPCRs can be used to measure drug selectivity. Selectivity assays can be run on agonists, antagonist or compounds that recycle the receptor back to the cell surface (re-sensitization).
An example of the agonist selectivity for 3 adrenergic receptors is shown below. The increase in red signal is a result of internalized receptor.
ADRA2A, ADRB1, and ADRB2 all show similar response to epinephrine. Isoproterenol is a strong agonist to ADRB2, moderate to ADRB1 and very weak to ADRA2A. Finally nor-epinephrine is a stong agonist to both ADRA2A and ADRB1, but very weak to ADRB2. These data are all in good agreement with the expected response for these compounds. SpectraGenetics has tagged more than 150 GPCRs and validated more than 30 cell lines.