Homodimerization of CB2cannabinoid receptor triggered by a bivalent ligand enhances cellular signaling

ABSTRACT G protein-coupled receptors (GPCRs) exist within a landscape of interconvertible conformational states and in dynamic equilibrium between monomers and higher-order oligomers, both influenced by ligand binding. Here, we have shown that a homobivalent ligand formed by equal chromenopyrazole moieties as pharmacophores, connected by 14 methylene units, can modulate the dynamics of the cannabinoid CB2 receptor (CB2R) homodimerization by simultaneously binding both protomers of the CB2R-CB2R homodimer. Computational and pharmacological experimentals showed that one of the ligand pharmacophores binds to the orthosteric site of one protomer, and the other pharmacophore to a membrane-oriented pocket between transmembranes 1 and 7 of the partner protomer. This provides unique pharmacological properties, such as increased potency in Gi binding and increased recruitment of β-arrestin. Thus, by modulating dimerization dynamics, it may be possible to fine-tune CB2R activity with potentially improved therapeutic outcomes. HIGHLIGHTS A homobivalent ligand of CB2R (PM369) modulates the dynamics of receptor homodimerization PM369 binds to the orthosteric site of one protomer and to a complementary, membrane-facing, site of the other protomer PM369 triggers CB2R homodimerization via the TM 1/7 interface that provides unique pharmacological properties PM369 potentiates signaling, increased potency in Gi binding and increased recruitment of β-arrestin These results highlight new approaches to control GPCR signaling Competing Interest Statement The authors have declared no competing interest. ABBREVIATIONS - CB1R - cannabinoid receptors type 1 (CB1R) - CB2R - cannabinoid receptors type 2 - GPCR - G protein-coupled receptor - cAMP - cyclic adenosine monophosphate - TM - transmembrane helix - MD - molecular dynamics - BRET - bioluminescence resonance energy transfer - Rluc - Renilla luciferase - PLA - proximity ligation assay - GFP - green fluorescent protein - Rmsd - root-mean square deviation - BiFC - bimolecular fluorescence complementation - YFP - yellow fluorescent protein