Prostaglandin E Receptor EP1 Forms a Complex with Dopamine D1 Receptor and Directs D1-Induced cAMP Production to Adenylyl Cyclase 7 through Mobilizing Gbg Subunits in Human Embryonic Kidney 293T Cells

The mechanism underlying the crosstalk between multiple G protein–coupled receptors remains poorly understood. We previously reported that prostaglandin E receptor EP1 facilitates dopamine D1 receptor signaling in striatal slices and promotes behavioral responses induced by D1 receptor agonists. Here, using human embryonic kidney (HEK)-293T cells expressing D1 and EP1, we have analyzed the mechanism underlying EP1mediated facilitation of D1 receptor signaling. Fluorescent immunostaining showed that EP1 and D1 receptors are partly colocalized in the cells, and coprecipitation experiments revealed a molecular complex of EP1 and D1 receptors. Treatment of the cells with 17S,17,20-dimethyl-2,5-ethano-6-oxo-PGE1 (ONODI-004), an EP1-selective agonist, enhanced cAMP production induced by D1 agonists (6)-6-chloro-2,3,4,5-tetrahydro-1phenyl-1H-3-benzazepine hydrobromide (SKF-81297) and 6-chloro-2,3,4,5-tetrahydro-1-(3-methylphenyl)-3-(2-propenyl)-1H3-benzazepine-7,8-diol hydrobromide (SKF-83822). Although this facilitative effect of EP1 stimulation was not affected by pharmacologic blockade of EP1-induced Ca increase, it was blocked by overexpressionofGtaasaGbg scavenger.Consistently,depletionof adenylyl cyclase (AC) 7, a Gbg-sensitive AC isoform, abolished the facilitative action of EP1 onD1-induced cAMPproduction. Notably, neither Gta overexpression nor AC7 depletion affected cAMP production induced byD1 stimulation alone. In contrast, depletion ofAC6,anotherAC isoform, reducedcAMPproduction inducedby D1 stimulation alone, but spared its facilitation by EP1 stimulation. Collectively, these data suggest that, through complex formation with D1, EP1 signaling directs the D1 receptor through Gbg to be coupled to AC7, an AC isoform distinct from those used by the D1 receptor alone, in HEK-293T cells.