title: Glucocorticoid inhibits growth factor-induced differentiation of hippocampal progenitor HiB5 cells.
abstract: In the present study, we investigated the effect of glucocorticoid on neuronal differentiation of hippocampal progenitor HiB5 cells. Dexamethasone (DEX), a synthetic glucocorticoid, inhibited platelet-derived growth factor (PDGF)-induced differentiation of HiB5 cells. The inhibitory effect of DEX was antagonized by RU486, a glucocorticoid receptor (GR) antagonist, indicating the GR-mediated processes. Nestin mRNA level was decreased and midsize neurofilament (NF-M) mRNA level was increased as a function of neuronal differentiation. DEX significantly blocked PDGF-induced down-regulation of nestin mRNA level, and up-regulation of NF-M mRNA level, which were similar to those of undifferentiated cells. DEX inhibited PDGF-induced activation of cyclic AMP-responsive element binding protein (CREB) and AP-1, suggesting that glucocorticoid interfered with signal transduction cascades linking the PDGF receptor and downstream transcription factors. Indeed, DEX reduced PDGF-induced phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2). Tyrosine phosphatase inhibitor reversed the effect of DEX on ERK1/2. In accordance with this finding, blockage of ERK1/2 signaling pathway with PD098059, a potent inhibitor for Ras/ERK pathway, mimicked the inhibitory effect of DEX on differentiation processes. Taken together, these results indicate that glucocorticoid inhibits PDGF-induced differentiation of hippocampal progenitor HiB5 cells by inhibiting the ERK1/2 signaling cascade via a tyrosine phosphatase-dependent mechanism.
authors.affiliation: Development and Neuroendocrine Research Laboratory, School of Biological Sciences, Seoul National University, Seoul, Korea.
authors.forename: G H
authors.initials: GH
authors.lastname: Son
authors.forename: D
authors.initials: D
authors.lastname: Geum
authors.forename: H
authors.initials: H
authors.lastname: Jung
authors.forename: K
authors.initials: K
authors.lastname: Kim
mesh_terms: D015139:Blotting, Southern; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology; D005938:Glucocorticoids / Q000494:pharmacology*; D006133:Growth Substances / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology* / Q000187:drug effects; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D016501:Neurites / Q000187:drug effects; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000096:biosynthesis / Q000187:drug effects; D018161:Receptors, Mineralocorticoid / Q000096:biosynthesis / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013234:Stem Cells / Q000187:drug effects*; D014162:Transfection
chemical_list: D005938:Glucocorticoids; D006133:Growth Substances; D010982:Platelet-Derived Growth Factor; D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D003907:Dexamethasone; D008156:Luciferases; D017027:Protein Tyrosine Phosphatases