title: Hyperosmotic stress strongly potentiates serum response factor (SRF)-dependent transcriptional activity in Ehrlich Lettré Ascites cells through a mechanism involving p38 mitogen-activated protein kinase.
abstract: Long-term osmotic stress results in altered gene transcription, however, with the exception of the TonE/TonEBP system, the underlying mechanisms are poorly understood. We previously showed that upon osmotic shrinkage of Ehrlich Lettré Ascites (ELA) fibroblasts, the MEK1-ERK1/2 pathway is transiently inhibited while p38 MAPK is activated, in turn impacting on cell survival (Pedersen et al., 2007, Cell Physiol Biochem 20: 735-750). Here, we show that downstream of these kinases, two transcription factors with major roles in control of cell proliferation and death, serum response factor (SRF) and cAMP response element-binding protein (CREB) are differentially regulated in ELA cells. SRF Ser(103) phosphorylation and SRF-dependent transcriptional activity were strongly augmented 5-30 min and 24 h, respectively, after hyperosmotic stress (50% increase in extracellular ionic strength), in a p38 MAPK-dependent manner. In contrast, CREB Ser(133) was transiently dephosphorylated upon osmotic shrinkage. The ERK1/2 effector ribosomal S kinase (RSK) and the ERK1/2- and p38 MAPK effector mitogen- stress-activated protein kinase 1 (MSK1) both phosphorylate CREB at Ser(133) . RSK and MSK1 were dephosphorylated within 5 min of shrinkage. MSK1 phosphorylation recovered within 30 min in a p38-MAPK-dependent manner. CREB was transiently dephosphorylated after shrinkage in a manner exacerbated by p38 MAPK inhibition or MSK1 knockdown, but unaffected by inhibition of RSK. In conclusion, in ELA cells, hyperosmotic stress activates SRF in a p38 MAPK-dependent manner and transiently inactivates CREB, likely due to MSK1 inactivation. We suggest that these events contribute to shrinkage-induced changes in gene transcription and death/survival balance.
authors.affiliation: Department of Biology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Andrej
authors.initials: A
authors.lastname: Gorbatenko
authors.forename: Maria
authors.initials: M
authors.lastname: Wiwel
authors.forename: Henrik
authors.initials: H
authors.lastname: Klingberg
authors.forename: Anni Bech
authors.initials: AB
authors.lastname: Nielsen
authors.forename: András
authors.initials: A
authors.lastname: Kapus
authors.forename: Stine Falsig
authors.initials: SF
authors.lastname: Pedersen
mesh_terms: D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009997:Osmotic Pressure / Q000502:physiology; D010766:Phosphorylation; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D026362:Serum Response Factor / Q000378:metabolism*; D013312:Stress, Physiological / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D026362:Serum Response Factor; D012694:Serine; D019893:Ribosomal Protein S6 Kinases; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases