Phosphorylation and hetero‐oligomerization regulate the dopamine D3 receptor/adenylyl cyclase type 5 signaling complex

Abstract

The dopamine D3 receptor (D3R) is a seven‐transmembrane‐spanning protein mediating its intracellular effects through the activation of heterotrimeric Gi/o proteins. The D3R‐mediated Gi/o protein activation culminates in an isoform‐specific inhibition of adenylyl cyclase type 5 (AC5) as previously demonstrated using a co‐transfection approach. In the present study, we explore the role of phosphorylation and hetero‐oligomerization in regulating the functional interplay between D3R and AC5 in co‐transfected human embryonic kidney 293 (HEK293) cells using immunoprecipitation, whole cell phosphorylation and cAMP assays. Whole cell phosphorylation experiments show that D3R exhibits basal and dopamine‐induced phosphorylation in cells not expressing AC5. Interestingly, our preliminary studies demonstrate that D3R is dephosphorylated in AC5‐expressing HEK293 cells following dopamine exposure. Moreover, our co‐immunoprecipitation studies imply that D3R and AC5 form hetero‐oligomers under basal conditions. However, dopamine stimulation curtails the D3R‐AC5 hetero‐oligomerization. Overall, our work suggests a novel paradigm in 7TMR‐mediated signaling whereby the phosphorylation of a 7TMR under steady‐state conditions and following agonist stimulation differentially regulate the hetero‐oligomerization process between the receptor and its effector. Supported by CIHR (MOP‐84442; MT).