CLONING OF A NOVEL HUMAN PROSTAGLANDIN RECEPTOR WITH CHARACTERISTICS OF THE PHARMACOLOGICALLY DEFINED EP(2) SUBTYPE

A cDNA that when expressed has the binding and functional characterist ics of the pharmacologically defined EP(2) prostaglandin (PG) receptor [Cardiovasc. Drug Rev. 11:165-179 (1993)] has been cloned from a huma n placenta library. This clone, known as Hup-4, encodes a protein of 3 58 amino acids that has only similar to 30% overall identity with othe r PG receptors, including mouse and human clones that have been design ated as EP(2) receptors [J. Biol. Chem. 268:7759-7762 (1993); Biochem. Biophys. Res. Commun. 197:263-270(1993)]. In COS-7 cells transfected with Hup-4, PGE(2) stimulated the formation of cAMP with an EC(50) of similar to 50 nM The EP(2)-selective agonists AH13205 and butaprost we re also active, with EC(50) values in the range of 2-6 mu M. The order of potency of PGs for competition with binding of [H-3]PGE(2) to memb ranes prepared from COS-7 cells transfected with Hup-4 was PGE(2) grea ter than or equal to PGE(1) > 16,16-dimethyl-PGE(2) greater than or eq ual to 11-deoxy-PGE(1) > butaprost > AH13205 > 19(R)-OH-PGE(2). Natura l PGs and analogues that are selective for the FP (PGF(2 alpha)), DP ( PGD(2)), EP(1) (sulprostone), EP(3) (MB 28767), and EP(4) (1-OH-PGE(1) ) receptors were inactive or competed poorly with the binding of [H-3] PGE(2) (<50% displacement of specific binding at 10 mu M). Northern bl ot analysis showed the presence of a Hup-4 message of similar to 3.1 k ilobases in mRNA from human lung and placenta. Reverse transcription-p olymerase chain reaction studies also indicated that Hup-4 is probably expressed in human uterus and in HL-60 (human promyelocytic leukemia) cells. Our findings suggest that Hup-4 encodes the pharmacologically defined EP(2) receptor, whereas the mouse and human cDNAs previously c lassified as EP(2) may represent another EP receptor subtype or the re cently defined EP(4) subtype [Prostaglandins 47:151-168 (1994)].