Ligand-Induced Regulation and Localization of Cannabinoid CB₁ and Dopamine D_2L Receptor Heterodimers

Abstract

The cannabinoid CB 1 (CB 1 ) and dopamine D 2 (D 2 ) receptors are coexpressed in the basal ganglia, an area of the brain involved in such processes as cognition, motor function, and emotional control. Several lines of evidence suggest that CB 1 and D 2 receptors may oligomerize, providing a unique pharmacology in vitro and in vivo. However, limited information exists on the regulation of CB 1 and D 2 receptor dimers. We used a novel technique, multicolor bimolecular fluorescence complementation (MBiFC) Increasing evidence suggests that G protein-coupled receptors (GPCRs) may function in receptor dimeric or higher order oligomeric complexes (for review, see Milligan, 2008). One set of receptors that has received significant attention relevant to oligomerization is the CB 1 cannabinoid (CB 1 ) receptor and dopamine D 2 (D 2 ) receptor (for review, see Fuxe et al., 2008). It is thought that the cannabinoid system negatively modulates dopamine circuits as activation of the CB 1 receptor leads to an attenuation of dopamine signaling (Laviolette and Grace, 2006). The CB 1 receptor is widely expressed in the central nervous system, with great abundance in the basal ganglia (Herkenham et al., 1991). CB 1 receptors are located on striatal GABAergic neurons (Herkenham et al., 1991), and they are also found on dendrites in both the dorsal striatum and the nucleus accumbens (Pickel et al., 2006). The D 2 receptor exists as two splice variants, D 2S (short) and D 2L (long). The D 2S variant is highly expressed on presynaptic dopaminergic neurons, whereas the D 2L variant is found postsynaptically on dopaminergic neurons throughout the striatum

Heteromultimerization of Cannabinoid CB1 Receptor and Orexin OX1 Receptor Generates a Unique Complex in Which Both Protomers Are Regulated by Orexin A

“…For example, interactions with the angiotensin AT 1 receptor (54) results in CB 1 blockers limiting mitogenic signaling by the AT 1 receptor, and although not observed in all studies (40), interactions of the CB 1 receptor with the -opioid receptor (56,57) have also been reported to modulate function. Further interactions with the dopamine D 2 receptor (58,59) and with the ␤ 2 -adrenoreceptor (60) have also been reported to have functional sequelae. By contrast, there is little information on other heteromers that incorporate the OX 1 receptor.…”

Type 1 Cannabinoid Receptor Ligands Display Functional Selectivity in a Cell Culture Model of Striatal Medium Spiny Projection Neurons

“…AEA, 2-AG, THC, WIN, and CP promoted G␣ q -dependent transient PLC␤3 activation. cells express dopamine D 2 receptors and CB 1 -D 2 dimerization may contribute to the actions of CP in these cells (59).…”

Development of a High-Throughput Screening Paradigm for the Discovery of Small-Molecule Modulators of Adenylyl Cyclase: Identification of an Adenylyl Cyclase 2 Inhibitor

“…The AC stimulation was carried out at room temperature for 1 hour, and the reaction was stopped by the addition of cold (4°C) TCA to provide a final TCA concentration of 3%. The cAMP in the lysate was then quantified using a [ 3 H]cAMP competition assay as previously described (Przybyla and Watts, 2010). C2C12 cell cAMP experiments were performed similarly, with the exceptions that the assay was performed in 96-well format on continuously propagated cells before differentiation into myotubes, and compounds were delivered by multichannel pipette for both pretreatment and stimulation steps.…”