Design, Synthesis, and In Vitro Characterization of a Tryptamine-Based Visible-Light Photoswitchable 5-HT2AR Ligand Showing Efficacy Preference for β-Arrestin over Mini-Gq.

A photoswitchable ligand for the serotonin 2A receptor (5-HT2AR) was designed to independently study G protein- and β-arrestin2-dependent signaling pathways. The cis-photoisomer binds the receptor with greater affinity than the trans-isomer, at nanomolar concentrations. In functional assays, this ligand showed a preference for recruiting β-arrestin2 over mini-Gαq relative to LSD, offering a tool to investigate β-arrestin2's role in 5-HT2AR signaling and its potential involvement in psychedelic effects.

Study at a glance

Abstract

The serotonin 2A receptor (5-HT2AR) modulates various neurotransmitter systems and is implicated in psychiatric disorders, including depression and schizophrenia. Despite progress, the detailed mechanisms of signaling at the 5-HT2AR 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-HT2AR ligand. In radioligand binding studies, the cis-photoisomer has a greater affinity than the trans-isomer at the 5-HT2AR and binds at nanomolar concentrations. In two highly analogous functional assays, the photoswitchable ligand showed a preference for β-arrestin2 recruitment over mini-Gαq recruitment relative to LSD, providing a compelling tool for investigating the role of β-arrestin2 recruitment in 5-HT2AR signaling and elucidating its potential role in psychedelic effects.