Optical control of the β(2)-adrenergic receptor with opto-prop-2: A cis-active azobenzene analog of propranolol

In this study, we synthesized and evaluated new photoswitchable ligands for the beta-adrenergic receptors β(1)-AR and β(2)-AR, applying an azologization strategy to the first-generation beta-blocker propranolol. The resulting compounds (Opto-prop-1, -2, -3) have good photochemical properties with high levels of light-induced trans-cis isomerization (>94%) and good thermal stability (t(1/2) > 10 days) of the resulting cis-isomer in an aqueous buffer. Upon illumination with 360-nm light to PSS(cis), large differences in binding affinities were observed for photoswitchable compounds at β(1)-AR as well as β(2)-AR. Notably, Opto-prop-2 (VUF17062) showed one of the largest optical shifts in binding affinities at the β(2)-AR (587-fold, cis-active), as recorded so far for photoswitches of G protein-coupled receptors. We finally show the broad utility of Opto-prop-2 as a light-dependent competitive antagonist of the β(2)-AR as shown with a conformational β(2)-AR sensor, by the recruitment of downstream effector proteins and functional modulation of isolated adult rat cardiomyocytes.