Soo Jung Oh, Ruiru Guo, Christopher Lucaj, Neshira Gutierrez, Kh Tanvir Ahmed, Alexander H Williams, Chang-Guo Zhan, Gregory B Dudley, Hideaki Yano
Synthetic cannabinoid receptor agonists (SCRAs) exhibit higher efficacy and potency at CB1 and CB2 cannabinoid receptors compared to Δ9-tetrahydrocannabinol, contributing to adverse effects associated with their growing prevalence as novel psychoactive substances. The indole-based SCRAs GBD-002 and GBD-003, incorporating 2,2-dimethylindane, differ by a single substituent position yet display markedly different receptor binding profiles. We evaluated both the GBD-002/GBD-003 pair and an analogous structural isomer pair JWH-018/JWH-018 2'-naphthyl using bioluminescence resonance energy transfer (BRET) assays to assess key CB1 and CB2 transducer pathways, including Gαi1 engagement, β-arrestin 2 recruitment, and cAMP inhibition. Site-directed mutagenesis characterized contributions of nonconserved residues between CB1 and CB2 as well as aromatic residues on CB1 transmembrane helix 2 (TM2). This study provided insights into the molecular determinants of cannabinoid receptor selectivity and efficacy.