Hybridization of β-adrenergic agonists and antagonists confers G protein bias.

Starting from the beta-adrenoceptor agonist isoprenaline and beta-blocker carvedilol, we designed and synthesized three different chemotypes of agonist/antagonist hybrids. Investigations of ligand-mediated receptor activation using bioluminescence resonance energy transfer biosensors revealed a predominant effect of the aromatic head group on the intrinsic activity of our ligands, as ligands with a carvedilol head group were devoid of agonistic activity. Ligands composed of a catechol head group and an antagonist-like oxypropylene spacer possess significant intrinsic activity for the activation of Gas, while they only show weak or even no beta-arrestin-2 recruitment at both beta(1)- and beta(2)-AR Molecular dynamics simulations suggest that the difference in G protein efficacy and beta-arrestin recruitment of the hybrid (S)-22, the full agonist epinephrine, and the beta(2)-selective, G protein-biased partial agonist salmeterol depends on specific hydrogen bonding between Ser(5.46) and Asn(6.55), and the aromatic head group of the ligands.