Cloning, functional expression, and characterization of the human prostaglandin E2 receptor EP2 subtype.

A cDNA clone encoding the human prostaglandin (PG) E2 receptor EP2 subtype has been isolated from a human lung cDNA library. The 1.9-kilobase pair cDNA, hEP2, encodes for a 488-amino acid protein with a predicted molecular mass of 53,115 and has the seven putative transmembrane domains characteristic of G protein-coupled receptors. The specific binding of [3H]PGE2 to COS cell membranes transfected with the hEP2 cDNA was of high affinity with an equilibrium dissociation constant (Kd) of 1 nM and the rank order of potency for prostaglandins in competition for [3H]PGE2 specific binding was PGE1 = PGE2 >> iloprost > PGF2 alpha > PGD2. In competition studies using more selective prostanoid-receptor agonist and antagonists, the [3H]PGE2 specific binding was competed by MB28767, an EP3 agonist, but not by the EP1-preferring antagonists AH6809 and SC19220, or by the EP2 agonist butaprost. Electrophysiological studies of Xenopus oocytes co-injected with hEP2 and cystic fibrosis transmembrane conductance regulator (cAMP-activated Cl- channel) cDNAs detected PGE2-specific inward Cl- currents, demonstrating that the hEP2 cDNA encoded a functional receptor which produced an increase in cAMP levels. Thus, we have cloned the human EP2 receptor subtype which is functionally coupled to increase in cAMP. Northern blot analysis showed that hEP2 is expressed as a 3.8-kilobase mRNA in a number of human tissues with the highest expression levels present in the small intestine.