Cross‐talk between dopamine D1 and corticotropin releasing factor type 2 receptors leads to occlusion of their ERK1/2 signaling

One manner in which G protein–coupled receptors potentiate, increase, and change their functionality is through the formation of heteromers in a specific cellular context. Previously, we have shown that dopamine D1 receptor (D1R) and the corticotropin releasing factor receptor type‐2α (CRF2α) heteromerize in HEK293T cells, enabling D1R to mobilize intracellular calcium in response to D1R agonists. In this study, we further investigated the pharmacological properties of the CRF2α‐D1R heteromer and the consequences of the heteromerization in their signaling and subcellular localization when both receptors are co‐expressed in HEK293T cells. Using immunoprecipitation assays, we observed that the addition of 10 μM dopamine in the incubation medium significantly decreased the amount of CRF2α on the cell surface of cells expressing both receptors. The presence of agonists of both receptors increased the interaction between CRF2α and D1R as assessed by co‐immunoprecipitation. However, the presence of agonists of both receptors resulted in a lesser efficient activation of the mitogen‐activated protein kinase/extracellular signal‐regulated kinase. Using a synaptosomal preparation of rat prefrontal cortex devoid of post‐synaptic elements, we found that CRF2α and D1R co‐localize in synaptic terminals of the rat medial prefrontal cortex and that the simultaneous activation of both receptors also occluded phosphorylation of extracellular signal‐regulated kinase. These results strengthen the idea that the heteromer CRF2a‐D1R is an entity functionally different from each receptor that composes it and suggests that its formation is enhanced by CRF and dopamine co‐transmission, as occurs in stress and addiction. We are studying the mechanisms determining the strong interaction between stress and addiction. Thus we studied the signaling of corticotropin‐releasing factor receptor type‐2α (CRF2α) and dopamine D1 receptor (D1R) receptors that colocalize in synaptic terminals of the rat medial prefrontal cortex (PFC) originated in the basolateral amygdala (BLA). We observed that the activation of either CRF2α or D1R induces an increase in ERK phosphorylation. However, the coactivation of both receptors occludes the phosphorylation of ERK. This new evidence strengthens the idea that the CRF2a‐D1R heteromer is a functional entity that differs from each receptor alone. Further studies should address the contribution of CRF2a‐D1R heteromer to the strong interaction between stress an