9pa6
Ligand-free kappa-opioid receptor in complex with Gi1
Structural highlights
FunctionOPRK_HUMAN G-protein coupled opioid receptor that functions as receptor for endogenous alpha-neoendorphins and dynorphins, but has low affinity for beta-endorphins. Also functions as receptor for various synthetic opioids and for the psychoactive diterpene salvinorin A. Ligand binding causes a conformation change that triggers signaling via guanine nucleotide-binding proteins (G proteins) and modulates the activity of down-stream effectors, such as adenylate cyclase. Signaling leads to the inhibition of adenylate cyclase activity. Inhibits neurotransmitter release by reducing calcium ion currents and increasing potassium ion conductance. Plays a role in the perception of pain. Plays a role in mediating reduced physical activity upon treatment with synthetic opioids. Plays a role in the regulation of salivation in response to synthetic opioids. May play a role in arousal and regulation of autonomic and neuroendocrine functions.[1] [2] [3] [4] Publication Abstract from PubMedKetamine offers rapid relief for treatment-resistant depression and severe pain in the clinic, providing immediate benefits that traditional medications often fail to deliver. While its antagonistic action at the N-methyl-D-aspartate receptor (NMDAR) is a key mechanism, ketamine's dual nature as both a promising treatment and a drug with abuse potential suggests its therapeutic effects extend beyond NMDAR inhibition. Here we provide structural evidence of human opioid receptors bound to ketamine and its parent analog phencyclidine (PCP), supporting that both ligands can directly bind and activate opioid receptors. The structures, together with site-directed mutagenesis and structure-activity relationship studies, identify key motifs involved in ketamine and PCP recognition and efficacy modulation. Furthermore, we determine the structure of the ligand-free state of human kappa opioid receptor, revealing molecular details before ligand engagement. Compared to PCP, ketamine displays more notable binding dynamics in the orthosteric site that may contribute to its unique pharmacology at opioid receptors. Our findings highlight the importance of including opioid receptors to fully understand ketamine's versatility in clinical settings. Structural basis of opioid receptor activation by PCP and ketamine.,Jiang Q, Han J, Fine EJ, Ramos-Gonzalez N, Rangari VA, Ruiz MV, Critz ML, Suomivuori CM, Wang J, Albert TL, Whiddon K, Li K, Robertson MJ, Huang XP, Land BB, Majumdar S, Fay JF, Dror RO, Che T Nat Struct Mol Biol. 2026 Jun 22. doi: 10.1038/s41594-026-01839-y. PMID:42332075[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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