title: Role of PI4K and PI3K-AKT in ERK1/2 activation by GnRH in the pituitary gonadotropes.
abstract: The role of PI4K and PI3K-AKT in ERK1/2 activation by GnRH was examined. A relatively long preincubation (60 min) with wortmannin (10 nM and 10 μM), and LY294002 (10 μM and 100 μM) (doses known to inhibit PI3K and PI4K, respectively), were required to inhibit GnRH-and PMA-stimulated ERK1/2 activity in αT3-1 and LβT2 gonadotrope cells. A similar preincubation protocol was required to demonstrate inhibition of IGF-1-stimulated AKT activation lending support for the need of prolonged incubation (60 min) with wortmannin in contrast to other cellular systems. To rule out that the inhibitors acted upon PI(4,5)P2 levels, we followed the [Ca(2+)]i response to GnRH and found that wortmannin has no significant effect on GnRH-induced [Ca(2+)]i responses. Surprisingly, GnRH and PMA reduced, while IGF-1 increased AKT phosphorylation. We suggest that PI3K inhibits GnRH-stimulated αGSU activity, has no effect upon GnRH-stimulated LHβ activity and enhanced the GnRH-stimulated FSHβ transcription. Hence, PI4K and PI3K-AKT play a role in GnRH to ERK1/2 signaling, while PI3K may regulate also GnRH-induced gonadotropin gene expression.
authors.affiliation: Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat Aviv 69978, Israel.
authors.forename: Tali H
authors.initials: TH
authors.lastname: Bar-Lev
authors.affiliation: Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat Aviv 69978, Israel.
authors.forename: Dagan
authors.initials: D
authors.lastname: Harris
authors.affiliation: National Institute of Child Health and Human Development, National Institute of Health, Bethesda, MD 20892-4510, USA.
authors.forename: Melanija
authors.initials: M
authors.lastname: Tomić
authors.affiliation: National Institute of Child Health and Human Development, National Institute of Health, Bethesda, MD 20892-4510, USA.
authors.forename: Stanko
authors.initials: S
authors.lastname: Stojilkovic
authors.affiliation: Reproductive Endocrinology, OB/GYN, Rambam Health Care Campus, Technion-Faculty of Medicine, Haifa 31096, Israel.
authors.forename: Zeev
authors.initials: Z
authors.lastname: Blumenfeld
authors.affiliation: Medical Research Council (MRC) Centre of Reproductive Health, University of Edinburgh, The Queen's Medical Research Institute, Edinburgh, Scotland EH16 4TJ, United Kingdom.
authors.forename: Pamela
authors.initials: P
authors.lastname: Brown
authors.affiliation: Department of Biological Regulation, the Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Rony
authors.initials: R
authors.lastname: Seger
authors.affiliation: Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat Aviv 69978, Israel. Electronic address: ZviN@tauex.tau.ac.il.
authors.forename: Zvi
authors.initials: Z
authors.lastname: Naor
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase / Q000378:metabolism*; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology; D052681:Gonadotrophs / Q000187:drug effects / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D006062:Gonadotropins / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D002867:Chromones; D006062:Gonadotropins; D009025:Morpholines; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D007987:Gonadotropin-Releasing Hormone; D058539:Phosphatidylinositol 3-Kinase; D019870:1-Phosphatidylinositol 4-Kinase; D051057:Proto-Oncogene Proteins c-akt; D000077191:Wortmannin
keywords: ERK1/2; GnRH; Gonadotropes; LβT2 cells; MAPK; PI3K; PI4K; PKC; αT3-1 cells