Lysergic acid diethylamide (LSD) acts through serotonin 5-HT2-family receptors, primarily 5-HT2A, but the closely related 5-HT2B receptor serves as a model due to its high expression. Cryo-electron microscopy structures of LSD-bound 5-HT2B in three states—transducer-free, coupled with Gq protein, and coupled with β-arrestin-1—reveal distinct signaling snapshots from a partially active to fully active states. These findings provide comprehensive molecular insights into LSD's signaling mechanisms and may accelerate the discovery of novel psychedelic drugs.
Ketamine, used for treatment-resistant depression and severe pain, acts primarily by blocking the N-methyl-D-aspartate receptor, but its therapeutic and abuse-related effects may involve additional targets. Structural evidence shows that ketamine and its analog phencyclidine (PCP) can directly bind to and activate human opioid receptors. The study identifies key molecular motifs involved in this binding and efficacy modulation, and also reveals the structure of the ligand-free state of the κ opioid receptor. Ketamine exhibits more dynamic binding than PCP at the orthosteric site, which may explain its distinct pharmacology. These findings indicate that opioid receptors are important for understanding ketamine's clinical versatility.