Recruitment of ß-arrestin 1 and 2 to the ß2-adrenoceptor: analysis of 65 ligands.

UNLABELLED: Beyond canonical signaling via Gαs and cAMP, the concept of functional selectivity at ß2-adrenoceptors (ß2ARs) describes the ability of adrenergic drugs to stabilize ligand-specific receptor conformations to initiate further signaling cascades comprising additional G-protein classes or ß-arrestins (ßarr). A set of 65 adrenergic ligands including 40 agonists and 25 antagonists in either racemic or enantiopure forms was used for ßarr recruitment experiments based on a split-luciferase assay in a cellular system expressing ß2AR. Many agonists showed only (weak) partial agonism regarding ßarr recruitment. Potencies and/or efficacies increased depending on the number of chirality centers in (R) configuration; no (S)-configured distomer was more effective at inducing ßarr recruitment other than the eutomer. ßarr2 was recruited more effectively than ßarr1. The analysis of antagonists revealed no significant effects on ßarr recruitment. Several agonists showed preference for activation of Gαs GTPase relative to ßarr recruitment, and no ßarr-biased ligand was identified. IN CONCLUSION: 1) agonists show strong bias for Gαs activation relative to ßarr recruitment; 2) agonists recruit ßarr1 and ßarr2 with subtle differences; and 3) there is no evidence for ßarr recruitment by antagonists.