Alternative splicing generates multiple isoforms of a rabbit prostaglandin E2 receptor.

Four cDNA clones homologous with a murine prostaglandin E2 receptor have been isolated from a rabbit kidney cortex cDNA library. These cDNAs encode related proteins that differ only in their COOH-terminal sequences. Southern blot analysis of rabbit genomic DNA indicates that these receptor cDNAs represent alternatively spliced variants derived from a single gene. This was confirmed by isolation and sequence analysis of genomic clones containing common region exons and unique 3'-coding exons, which contained intron/exon boundaries at the predicted splice junctions. Transient expression of a novel full-length cDNA in COS1 cells confirmed the ligand binding profile typical of an EP3 receptor subtype. Ribonuclease protection assays indicate that the gene encoding these receptors is most highly expressed in kidney, adrenal, and stomach with lower but significant expression in uterus, lung, heart, ileum, spleen, and brain. Moreover, each of the cloned isoforms is expressed in the kidney. In situ hybridization analyses of rabbit kidney demonstrated that the level of expression is highest in the outer medulla with lesser expression in the cortex and no detectable expression in the inner medulla. The ligand binding profile and tissue distribution of these receptors is consistent with a functional role for this family of EP3 receptors in mediating the renal actions of prostaglandins as well as the effects of prostaglandins on gastric acid secretion and adrenal function.