MOLECULAR-CLONING AND CHARACTERIZATION OF THE HUMAN PROSTANOID DP RECEPTOR

A cDNA encoding a functional human prostanoid DP (hDP) receptor has been constructed from a genomic clone and a fragment cloned by 3'-rapid amplification of cDNA ends-polymerase chain reaction. The hDP receptor consists of 359 amino acid residues with a predicted molecular mass of 40,276 and has the putative heptahelical transmembrane domains characteristic of G-protein-coupled receptors. The deduced amino acid sequence of the hDP receptor, when compared with ail other members of the prostanoid receptor family, shows the highest degree of identity with the hIP and hEP(2) receptors, followed by the hEP(4) receptor. Radioreceptor binding studies using membranes prepared from mammalian COS-M6 cells transiently transfected with an expression vector containing the DP receptor cDNA showed that the rank order of affinities for prostaglandins and prostaglandin analogs, in competition for [H-3]prostaglandin D-2 (PGD(2)) specific binding sites, was as predicted for the DP receptor, with PGD(2) >> PGE(2) > PGF(2 alpha) = iloprost > U46619. The signal transduction pathway of the cloned hDP receptor was studied by transfecting the hDP expression vector into HEK 293(EBNA) cells, Activation of the hDP receptor with PGD(2) resulted in an elevation of intracellular cAMP and in mobilization of Ca2+, but did not lead to generation of inositol 1,4,5-trisphosphate. Northern blot analysis of human tissues showed that the hDP receptor has a very discrete tissue distribution and was detectable only in retina and small intestine. In summary, we have cloned and expressed a functional cDNA for the hDP receptor.