title: Molecular and pharmacological characterization of zebrafish 'relaxant' prostanoid receptors.
abstract: Prostanoids comprising prostaglandins (PGs) and thromboxanes have been shown to play physiological and pathological roles in zebrafish. However, the molecular basis of zebrafish prostanoid receptors has not been characterized to date. Here, we demonstrate that there exist at least six 'relaxant' (Gs-coupled) prostanoid receptors in zebrafish; one PGI2 receptor IP and five PGE2 receptors comprising two EP2 (EP2a and EP2b), and three EP4 receptors (EP4a, EP4b and EP4c). In contrast, we failed to find a zebrafish PGD2 receptor with any structure and/or character similarities to the mammalian DP1 receptor. [(3)H]iloprost, a stable IP radioligand, specifically bound to the membrane of cells expressing zebrafish IP with a Kd of 42nM, and [(3)H]PGE2 specifically bound to the membranes of cells expressing zebrafish EP2a, EP2b, EP4a, EP4b and EP4c with a Kd of 6.9, 6.0, 1.4, 3.3 and 1.2nM, respectively. Upon agonist stimulation, the 'relaxant' prostanoid receptors showed intracellular cAMP accumulation. The responsiveness of these zebrafish receptors to subtype-specific agonists correlated with their structural conservation to the corresponding receptor in mammals. RT-PCR analysis revealed that the six zebrafish prostanoid receptors show unique tissue distribution patterns; each receptor gene may hence be under unique transcriptional regulation. This work provides further insights into the diverse functions of prostanoids in zebrafish.
authors.affiliation: Department of Pharmaceutical Biochemistry, Graduate School of Pharmaceutical Sciences, Kumamoto University, Chuo-ku, Kumamoto 862-0973, Japan.
authors.forename: Kyoshiro
authors.initials: K
authors.lastname: Tsuge
authors.forename: Ryo
authors.initials: R
authors.lastname: Iwasaki
authors.forename: Kazushi
authors.initials: K
authors.lastname: Morimoto
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Inazumi
authors.forename: Osamu
authors.initials: O
authors.lastname: Kawahara
authors.forename: Atsuo
authors.initials: A
authors.lastname: Kawahara
authors.forename: Soken
authors.initials: S
authors.lastname: Tsuchiya
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Sugimoto
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D020869:Gene Expression Profiling; D008024:Ligands; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D011982:Receptors, Prostaglandin / Q000378:metabolism*; D015398:Signal Transduction; D015027:Zebrafish
chemical_list: D008024:Ligands; D011982:Receptors, Prostaglandin
keywords: GPCR; Pharmacology; Prostacyclin; Prostaglandins; Signal transduction; Tissue distribution