Insights into cannabinoid receptor 2 (CB2) anterograde trafficking and pharmacological chaperoning.

Cannabinoid Receptor 2 (CB(2)) is a promising therapeutic target for modulating inflammation. Canonical signalling responses to receptor ligands are critically dependent on cell surface receptor expression. However, it is also now appreciated that intracellular G protein-coupled receptors can contribute to signalling responses and influence functional outcomes. Therefore, understanding how the subcellular distribution of receptors is controlled is also highly pertinent. CB(2) is observed to be expressed at the cell surface as well as having a considerable proportion expressed intracellularly. Despite this distribution being well established, little is known about the regulation of CB(2) anterograde trafficking and subcellular distribution. We report that sustained treatment with a range of CB(2) agonists and inverse agonists stimulates a distinct population of CB(2) to be delivered to the cell surface, at various expression levels and despite agonists concurrently internalising cell surface CB(2). We present evidence that this ligand-stimulated anterograde trafficking is a result of CB(2) agonists, as well as inverse agonists, acting as pharmacological chaperones. We also report that a di-lysine (KK) motif in the CB(2) C-terminal tail is required for basal delivery to the cell surface. Corroborating the hypothesis that CB(2) ligands can act as pharmacological chaperones, sustained CB(2) ligand stimulation induces cell surface expression of the mutated receptor and alters maturation states as measured by western blotting. Our finding that prolonged exposure to CB(2) ligands can induce CB(2) cell surface delivery via pharmacological chaperoning may well have important implications for optimal design of CB(2)-targeted therapeutics.