Abstract
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 EP1-mediated 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 (ONO-DI-004), an EP1-selective agonist, enhanced cAMP production induced by D1 agonists (±)-6-chloro-2,3,4,5-tetrahydro-1-phenyl-1H-3-benzazepine hydrobromide (SKF-81297) and 6-chloro-2,3,4,5-tetrahydro-1-(3-methylphenyl)-3-(2-propenyl)-1H-3-benzazepine-7,8-diol hydrobromide (SKF-83822). Although this facilitative effect of EP1 stimulation was not affected by pharmacologic blockade of EP1-induced Ca2+ increase, it was blocked by overexpression of Gtα as a Gβγ scavenger. Consistently, depletion of adenylyl cyclase (AC) 7, a Gβγ-sensitive AC isoform, abolished the facilitative action of EP1 on D1-induced cAMP production. Notably, neither Gtα overexpression nor AC7 depletion affected cAMP production induced by D1 stimulation alone. In contrast, depletion of AC6, another AC isoform, reduced cAMP production induced by 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 Gβγ to be coupled to AC7, an AC isoform distinct from those used by the D1 receptor alone, in HEK-293T cells.
Footnotes
- Received May 10, 2013.
- Accepted July 10, 2013.
This work was supported in part by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan; and by a Core Research for Evolutionary Science and Technology grant from Japan Science and Technology Agency.
↵This article has supplemental material available at http://molpharm.aspetjournals.org.
- Copyright © 2013 by The American Society for Pharmacology and Experimental Therapeutics
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