Cannabinoid and opioid receptor activities can be modulated by a variety of post-translational mechanisms including the formation of interacting complexes. This study examines the involvement of endogenous and exogenous chaperones in modulating the abundance and activity of cannabinoid CB1 receptor (CB1R), δ opioid receptor (DOR), and CB1R-DOR interacting complexes. Focusing on endogenous protein chaperones, namely receptor transporter proteins (RTPs), we examined relative mRNA expression in the mouse spinal cord and found RTP4 to be expressed at higher levels compared with other RTPs. Next, we assessed the effect of RTP4 on receptor abundance by manipulating RTP4 expression in cell lines. Overexpression of RTP4 causes an increase and knock-down causes a decrease in the levels of CB1R, DOR, and CB1R-DOR interacting complexes; this is accompanied by parallel changes in signaling. The ability of small molecule lipophilic ligands to function as exogenous chaperones was examined using receptor-selective antagonists. Long-term treatment leads to increases in receptor abundance and activity with no changes in mRNA supporting a role as pharmacological chaperones. Finally, the effect of cannabidiol (CBD), a small molecule ligand and a major active component of cannabis, on receptor abundance and activity in mice was examined. We find that CBD administration leads to increases in receptor abundance and activity in mouse spinal cord. Together, these results highlight a role for chaperones (proteins and small molecules) in modulating levels and activity of CB1R, DOR, and their interacting complexes potentially through mechanisms including receptor maturation and trafficking.

SIGNIFICANCE STATEMENT This study highlights a role for chaperones (endogenous and small membrane-permeable molecules) in modulating levels of cannabinoid CB1 receptor, delta opioid receptor, and their interacting complexes. These chaperones could be developed as therapeutics for pathologies involving these receptors.

This work was supported in part by grants from National Institutes of Health National Institute of Drug Abuse [Grants DA008863 and DA058681], the National Center for Advancing Translational Sciences [Grant R03 TR002940] (to L.A.D.), a NARSAD Young Investigator award [Grant 31297] (to A.O.), and Japan Society for the Promotion of Science KAKENHI [Grant 21K07275] (to W.F.).

↵1 Current affiliation: Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan and Faculty of Pharmacy, Juntendo University, Urayasu, Chiba, Japan.

No author has an actual or perceived conflict of interest with the contents of this article.

dx.doi.org/10.1124/jpet.124.002187.

↵This article has supplemental material available at jpet.aspetjournals.org.