Cloning and expression of prostaglandin E2 receptor subtype 1 (ep 1 ) in Bostrichthys sinensis

Our previous studies suggested that prostaglandin E-2 (PGE(2)) is a putative sex pheromone in Chinese black sleeper Bostrichthys sinensis, a fish species that inhabits intertidal zones and mates and spawns inside a muddy burrow. We found immunoreactivities of PGE(2) receptor subtypes (Ep(1-3)) expressed in the olfactory sac, but only Ep(1) presented higher density of immunoreactivity in mature fish than that in immature fish in both sexes. To gain a better understanding of the underlying molecular mechanism for the detection of PGE(2) in the olfactory system, we cloned an ep (1) cDNA from the adult olfactory sac. The open-reading frame of the ep (1) consisted of 1,134-bp nucleotides that encoded a 378-amino acid-long protein with a seven-transmembrane domain, typical for the G protein-coupled receptors superfamily. Expression of ep (1) mRNA was observed in all tissues examined, with higher levels obtained in the olfactory sacs and testes. The expression of ep (1) mRNA in the olfactory sacs and gonads was significantly higher in both sexes of mature fish than in those of immature ones. Taken together, our results suggested that Ep(1), which is highly expressed in the olfactory sacs and gonads of mature fish, is important for the control of reproduction and may be involved in PGE(2)-initiated spawning behavior in B. sinensis.