title: Epidermal growth factor receptor is an obligatory intermediate for oxytocin-induced cyclooxygenase 2 expression and prostaglandin F2 alpha production in bovine endometrial epithelial cells.
abstract: Oxytocin (OT) triggers the luteolytic pulses of prostaglandin F(2 alpha) (PGF(2 alpha)) from the endometrial epithelial cells in ruminants. We have proposed that the embryonic signal interferon-tau exerts its antiluteolytic effect by disrupting the OT signaling axis. Accordingly, we have attempted to define the signaling pathway of OT-induced PGF(2 alpha) production in the bovine endometrium using our newly characterized epithelial cell line (bEEL). OT receptor was coupled to the classical G alpha(q) pathway as evidenced by calcium release and activation of phospholipase C. Similarly, OT-induced PGF(2 alpha) production was mediated through the canonical ERK1/2 pathway. Because of the importance of receptor and nonreceptor tyrosine kinases in G protein-coupled receptor signaling, we studied the role of epidermal growth factor receptor (EGFR), c-Src, and phosphoinositide 3-kinase (PI3K) on OT-induced PGF(2 alpha) production in association with cyclooxygenase 2 (COX2) expression and ERK1/2 and Akt phosphorylation. The EGFR inhibitor AG1478 (10 microm) nearly abolished basal and OT-induced PGF(2 alpha) production and down-regulated COX2 expression and ERK1/2 phosphorylation. Because the transactivated EGFR can serve as a ligand for the signaling proteins with Src homology 2 (SH2) domain, we hypothesized a role for c-Src and PI3K in OT-induced PGF(2 alpha) production. Inhibitors of c-Src (PP2, 10 microm) and PI3K (LY294002, 25 microm) produced a significant decrease in OT-induced PGF(2 alpha) production and reduced COX2 expression. Also, PP2, but not LY294002, decreased OT-induced ERK1/2 phosphorylation. Because LY294002 did not affect ERK1/2 phosphorylation, but inhibited PGF(2 alpha) production and down-regulated COX2 expression, it is likely that the Akt pathway is also involved in PGF(2 alpha) production. Thus, EGFR may simultaneously activate c-Src and PI3K to amplify the OT signaling to increase the output of PGF(2 alpha) in bEEL cells.
authors.affiliation: Unité d'Ontogénie et Reproduction, Centre Hospitalier Universitaire de Québec, Centre Hospitalier de l'Université Laval, Université Laval, Québec QC G1V 4G2 Canada.
authors.forename: Narayanan
authors.initials: N
authors.lastname: Krishnaswamy
authors.forename: Nicolas
authors.initials: N
authors.lastname: Lacroix-Pepin
authors.forename: Pierre
authors.initials: P
authors.lastname: Chapdelaine
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Taniguchi
authors.forename: Gilles
authors.initials: G
authors.lastname: Kauffenstein
authors.forename: Arpita
authors.initials: A
authors.lastname: Chakravarti
authors.forename: Ghislain
authors.initials: G
authors.lastname: Danyod
authors.forename: Michel A
authors.initials: MA
authors.lastname: Fortier
mesh_terms: D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D015237:Dinoprost / Q000378:metabolism*; D004717:Endometrium / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D007424:Intracellular Fluid / Q000378:metabolism; D010121:Oxytocin / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D018045:Receptors, Oxytocin / Q000378:metabolism; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism; D019061:src-Family Kinases
chemical_list: D000081247:CSK Tyrosine-Protein Kinase; D002118:Calcium; D051546:Cyclooxygenase 2; D015237:Dinoprost; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D010121:Oxytocin; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D051057:Proto-Oncogene Proteins c-akt; D018045:Receptors, Oxytocin; D010738:Type C Phospholipases; D019061:src-Family Kinases