title: Dexamethasone induces rapid serine-phosphorylation and membrane translocation of annexin 1 in a human folliculostellate cell line via a novel nongenomic mechanism involving the glucocorticoid receptor, protein kinase C, phosphatidylinositol 3-kinase, and mitogen-activated protein kinase.
abstract: Our recent studies on rat pituitary tissue suggest that the annexin 1 (ANXA1)-dependent inhibitory actions of glucocorticoids on ACTH secretion are effected via a paracrine mechanism that involves protein kinase C (PKC)-dependent translocation of a serine-phosphorylated species of ANXA1 (Ser-P-ANXA1) to the plasma membrane of the nonsecretory folliculostellate cells. In the present study, we have used a human folliculostellate cell line (PDFS) to explore the signaling mechanisms that cause the translocation of Ser-P-ANXA1 to the membrane together with Western blot analysis and flow cytometry to detect the phosphorylated protein. Exposure of PDFS cells to dexamethasone caused time-dependent increases in the expression of ANXA1 mRNA and protein, which were first detected within 2 h of steroid contact. This genomic response was preceded by the appearance within 30 min of substantially increased amounts of Ser-P-ANXA1 and by translocation of the phosphorylated protein to the cell surface. The prompt membrane translocation of Ser-P-ANXA1 provoked by dexamethasone was inhibited by the glucocorticoid receptor, antagonist, mifepristone, but not by actinomycin D or cycloheximide, which effectively inhibit mRNA and protein synthesis respectively in our preparation. It was also inhibited by a nonselective PKC inhibitor (PKC(9-31)), by a selective inhibitor of Ca(2+)-dependent PKCs (Go 6976) and by annexin 5 (which sequesters PKC in other systems). In addition, blockade of phosphatidylinositiol 3-kinase (wortmannin) or MAPK pathways with PD 98059 or UO 126 (selective for MAPK kinse 1 and 2) prevented the steroid-induced translocation of Ser-P-ANXA1 to the cell surface. These results suggest that glucocorticoids induce rapid serine phosphorylation and membrane translocation of ANXA1 via a novel nongenomic, glucocorticoid receptor-dependent mechanism that requires MAPK, phosphatidylinositiol 3-kinase, and Ca(2+)-dependent PKC pathways.
authors.affiliation: Department of Neuroendocrinology, Division of Neuroscience and Psychological Medicine, Faculty of Medicine, Imperial College London, Hammersmith Hospital Campus, London W12 ONN, United Kingdom. e.solito@imperial.ac.uk
authors.forename: Egle
authors.initials: E
authors.lastname: Solito
authors.forename: Abeda
authors.initials: A
authors.lastname: Mulla
authors.forename: John F
authors.initials: JF
authors.lastname: Morris
authors.forename: Helen C
authors.initials: HC
authors.lastname: Christian
authors.forename: Roderick J
authors.initials: RJ
authors.lastname: Flower
authors.forename: Julia C
authors.initials: JC
authors.lastname: Buckingham
mesh_terms: D018263:Adenocarcinoma, Follicular; D000818:Animals; D017305:Annexin A1 / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D010911:Pituitary Neoplasms; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011817:Rabbits; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D017305:Annexin A1; D003907:Dexamethasone; D004791:Enzyme Inhibitors; D005938:Glucocorticoids; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D011965:Receptors, Glucocorticoid; D012694:Serine