title: Differential G protein coupling preference of mammalian and nonmammalian gonadotropin-releasing hormone receptors.
abstract: Recently, we have identified three distinct types of gonadotropin-releasing hormone receptor (GnRHR) in the bullfrog (designated bfGnRHR-1, bfGnRHR-2, and bfGnRHR-3). In the present study, we compared G protein coupling preference of mammalian and nonmammalian GnRHRs. In a transient expression system, stimulation of either bfGnRHRs or rat GnRHR by GnRH significantly increased both inositol phosphates (IP) and cAMP productions, but ratios of IP to cAMP induction levels were quite different among the receptors, indicating differential G protein coupling preference. Using cAMP-dependent protein kinase A (PKA)-specific (CRE-luc) or protein kinase C (PKC)-specific reporter (c-fos-luc) systems, we further examined G(s) and G(q/11) coupling preference of these GnRHRs. Since activities of CRE-luc and c-fos-luc were highly dependent on cell types, GnRH-induced CRE-luc or c-fos-luc activity was normalized by forskolin-induced CRE-luc or 12-O-tetradecanoylphenol-13-acetate (TPA)-induced c-fos-luc activity, respectively. This normalized result indicated that bfGnRHR-2 couples to G(s) more actively than G(q/11), while bfGnRHR-1 and -3 couple to G(s) and G(q/11) with similar strength. However, the rat GnRHR appeared to couple to G(q/11) more efficiently than G(s). This study was further confirmed by an experiment in which GnRH augmented CRE-driven luciferase activity in alphaT3-1 cells when CRE-luc was cotransfected with bfGnRHRs but not with vehicle or rat GnRHR. Collectively, these results indicate that mammalian and nonmammalian GnRHRs may induce diverse cellular and physiological responses through differential activation of PKA and PKC signaling pathways.
authors.affiliation: Hormone Research Center, Chonnam National University, 500-757 Gwangju, South Korea.
authors.forename: Da Young
authors.initials: DY
authors.lastname: Oh
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Ryun Sup
authors.initials: RS
authors.lastname: Ahn
authors.forename: Jae Yong
authors.initials: JY
authors.lastname: Park
authors.forename: Jae Young
authors.initials: JY
authors.lastname: Seong
authors.forename: Hyuk Bang
authors.initials: HB
authors.lastname: Kwon
mesh_terms: D000818:Animals; D002645:Chickens; D000242:Cyclic AMP / Q000032:analysis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D017930:Genes, Reporter; D016762:Genes, fos; D006367:HeLa Cells; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007295:Inositol Phosphates / Q000737:chemistry; D008156:Luciferases / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D011892:Rana catesbeiana; D051381:Rats; D011966:Receptors, LHRH / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors; D014158:Transcription, Genetic
chemical_list: D007295:Inositol Phosphates; D011966:Receptors, LHRH; D000242:Cyclic AMP; D008156:Luciferases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins