Molecular characterization of prostaglandin F receptor (FP) and E receptor subtype 1 (EP 1) in zebrafish

Abstract

Prostaglandins E (PGE) and F (PGF) mediate diverse physiological functions via their cell surface receptors - prostaglandin E receptor (EP) subtypes 1, 2, 3 and 4 (EP 1; EP 2; EP 3; EP 4) and F receptor (FP). In teleost fishes, PGE was implicated in gill epithelium ion transport, while both PGE and PGF were involved in oocyte maturation, follicular rupture and coordination of reproductive behaviors. However, little is known about the mechanisms behind their actions. In present study, we first identified the full-length ORF cDNA clones of three zebrafish prostaglandin E receptor subtype 1 (zEP 1) isoforms - zEP 1a, zEP 1b and zEP 1c - and FP (zFP) from adult ovary. RT-PCR showed that zEP 1a, zEP 1b and zFP are widely expressed in adult tissues, while zEP 1c mRNA expression is mainly confined in brain and kidney. Using a pGL3-NFAT-RE luciferase reporter system, both zEP 1a and zEP 1b expressed in DF-1 cells were shown to be activated by PGE 2 potently while zEP 1c and zFP were activated by PGF 2a effectively, suggesting that the four receptors are functionally coupled to intracellular Ca 2+-signaling pathway. Furthermore, EP1a and EP1b, but not EP1c were suggested to couple to cAMP-PKA signaling pathway using a pGL3-CRE luciferase reporter assay. Although zEP 1c might originate as a paralog to zEP 1a and zEP 1b, its functional coupling to PGF 2α instead of PGE 2 suggested that zEP 1 isoforms might have sub-functionalized in their ligand binding and G protein coupling specificity, in addition to differential tissue distribution. Characterization of these receptors undoubtedly furthered our understanding on the diverse yet highly target-specific responses of prostaglandins in teleosts. © 2012 Elsevier Inc.