Structural and Dynamic Insights into the Biased Signaling Mechanism of the Human Kappa Opioid Receptor

Abstract

ABSTRACTThe κ-opioid receptor (KOR) is a member of the G protein-coupled receptor (GPCR) family, responsible for modulating cellular responses through transducers such as G proteins and arrestins. G protein-biased KOR agonists hold promise due to their potential to mitigate side effects such as drug aversion and sedation while preserving analgesic and antipruritic effects. Here, we shed light on the structural dynamics of the human KOR-Gisignaling complex bound with either nalfurafine (a G-protein-biased agonist) or U-50,488H (a balanced agonist) using cryo-electron microscopy (cryo-EM). Cryo-EM structures of the KOR-Gisignaling complexes identify the ligand binding mode in the activated state. Vibrational spectroscopy analysis reveals changes in the ligand-binding pocket upon binding to these ligands. Cell-based mutant experiments pinpoint four amino acids (K2275.40, C2866.47, H2916.52, and Y3127.34; Ballesteros–Weinstein numbering is shown in superscript) that play crucial roles in arrestin recruitment. Among these four amino acids, H2916.52and Y3127.34are also implicated in G-protein coupling. Our findings pave the way for targeting specific residues in the KOR ligand-binding pocket to enhance KOR-mediated therapeutic effects while mitigating unwanted side effects.