Abstract
The serotonin 2A receptor (5-HT(2A)R) modulates various neurotransmitter systems and is implicated in psychiatric disorders, including depression and schizophrenia. Despite progress, the detailed mechanisms of signaling at the 5-HT(2A)R and its therapeutic implications remain unclear, warranting further exploration. Overcoming the limitations of conventional pharmacology, photopharmacology addresses issues such as spatial selectivity and spatiotemporal resolution by incorporating light as an additional external control element. To study the roles of G protein- and β-arrestin2-dependent signaling pathways independently, we designed a photoswitchable, pathway-selective 5-HT(2A)R ligand. In radioligand binding studies, the cis-photoisomer has a greater affinity than the trans-isomer at the 5-HT(2A)R and binds at nanomolar concentrations. In two highly analogous functional assays, the photoswitchable ligand showed a preference for β-arrestin2 recruitment over mini-Gα(q) recruitment relative to LSD, providing a compelling tool for investigating the role of β-arrestin2 recruitment in 5-HT(2A)R signaling and elucidating its potential role in psychedelic effects.