Molecular mechanisms of inverse agonism via κ-opioid receptor-G protein complexes

Aaliyah S Tyson; Saif Khan; Zenia Motiwala; Gye Won Han; Zixin Zhang; Mohsen Ranjbar; Daniel Styrpejko; Nokomis Ramos-Gonzalez; Stone Woo; Kelly Villers; Delainey Landaker; Terry Kenakin; Ryan Shenvi; Susruta Majumdar; Cornelius Gati

doi:10.1038/s41589-024-01812-0

Molecular mechanisms of inverse agonism via κ-opioid receptor-G protein complexes

Nat Chem Biol. 2025 Jul;21(7):1046-1057. doi: 10.1038/s41589-024-01812-0. Epub 2025 Jan 7.

Authors

Aaliyah S Tyson^{1

2}, Saif Khan^{1

3}, Zenia Motiwala^{1

3

4}, Gye Won Han¹, Zixin Zhang^{1

5}, Mohsen Ranjbar^{1

2}, Daniel Styrpejko^{1

3}, Nokomis Ramos-Gonzalez⁶, Stone Woo⁷, Kelly Villers¹, Delainey Landaker¹, Terry Kenakin⁸, Ryan Shenvi⁷, Susruta Majumdar⁶, Cornelius Gati^{9

10

11}

Affiliations

¹ The Bridge Institute, Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA.
² Department of Chemistry, University of Southern California, Los Angeles, CA, USA.
³ Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.
⁴ Amgen Inc., Thousand Oaks, CA, USA.
⁵ Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
⁶ Center for Clinical Pharmacology, University of Health Sciences and Pharmacy at St. Louis and Washington University School of Medicine, St. Louis, MO, USA.
⁷ Department of Chemistry, Scripps Research, La Jolla, CA, USA.
⁸ Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA.
⁹ The Bridge Institute, Michelson Center for Convergent Biosciences, University of Southern California, Los Angeles, CA, USA. gati@usc.edu.
¹⁰ Department of Chemistry, University of Southern California, Los Angeles, CA, USA. gati@usc.edu.
¹¹ Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA. gati@usc.edu.

Abstract

Opioid receptors, a subfamily of G protein-coupled receptors (GPCRs), are key therapeutic targets. In the canonical GPCR activation model, agonist binding is required for receptor-G protein complex formation, while antagonists prevent G protein coupling. However, many GPCRs exhibit basal activity, allowing G protein association without an agonist. The pharmacological impact of agonist-free receptor-G protein complexes is poorly understood. Here we present biochemical evidence that certain κ-opioid receptor (KOR) inverse agonists can act via KOR-G_i protein complexes. To investigate this phenomenon, we determined cryo-EM structures of KOR-G_i protein complexes with three inverse agonists: JDTic, norBNI and GB18, corresponding to structures of inverse agonist-bound GPCR-G protein complexes. Remarkably, the orthosteric binding pocket resembles the G protein-free 'inactive' receptor conformation, while the receptor remains coupled to the G protein. In summary, our work challenges the canonical model of receptor antagonism and offers crucial insights into GPCR pharmacology.

MeSH terms

Cryoelectron Microscopy
Drug Inverse Agonism*
GTP-Binding Proteins* / chemistry
GTP-Binding Proteins* / metabolism
HEK293 Cells
Humans
Models, Molecular
Naltrexone / analogs & derivatives
Naltrexone / chemistry
Naltrexone / pharmacology
Protein Binding
Receptors, G-Protein-Coupled / metabolism
Receptors, Opioid, kappa* / agonists
Receptors, Opioid, kappa* / antagonists & inhibitors
Receptors, Opioid, kappa* / chemistry
Receptors, Opioid, kappa* / metabolism

Substances

Receptors, Opioid, kappa
GTP-Binding Proteins
Receptors, G-Protein-Coupled
Naltrexone

Abstract

MeSH terms

Substances

Grants and funding