Molecular characterization of prostaglandin F receptor (FP) and E receptor subtype 3 (EP3) in chickens.

Prostaglandin E and F regulate diverse physiological functions including gastrointestinal motility, fever induction and reproduction. This multitude of biological effects is mediated via their four E receptor subtypes (EP(1), EP(2), EP(3) and EP(4)) and F receptor (FP), respectively. Majority of these studies was performed in mammalian species, while investigations on their roles were impeded by inadequate information on their receptors in avian species. In present study, full-length cDNAs of chicken EP(3) (cEP(3)) and two isoforms of FP - cFPa and cFPb - were cloned from adult hen ovary. The putative cEP(3) and cFPa share high amino acid sequence identity with their respective orthologs, while the predicted cFPb is a novel middle-truncated splice variant which lacks 107 amino acids between transmembrane domains 4 and 6. RT-PCR showed that cEP(3), cFPa and cFPb are widely expressed in adult tissues examined, including ovary and oviduct. Using a pGL3-CRE luciferase reporter system, cEP(3)-expressing DF1 cells inhibited forskolin-induced luciferase activity (EC(50): <1.9 pM) upon PGE(2) treatment, suggesting that cEP(3) may functionally couple to Gi protein. Upon PGF(2α) addition, cFPa was shown to potentially couple to intracellular Ca(2+)-signaling pathway by pGL3-NFAT-RE reporter assay (EC(50): 2.9 nM), while cFPb showed no response. Using a pGL4-SRE reporter system, both cEP(3) and cFPa exhibited potential MAPK activation by PGE(2) and PGF(2α) at EC(50) 0.34 and 13 nM, respectively. Molecular characterization of these receptors paved the road to the better understanding of PGE(2) and PGF(2α) roles in avian physiology and comparative endocrinology studies.