title: Differential regulation of cyclooxygenase 2 expression by small GTPases Ras, Rac1, and RhoA.
abstract: Cyclooxygenase 2 (COX-2) is an immediate early gene induced by a variety of stimuli and its expression is stimulated by individual activation of Ras or Rho GTPases. Here we investigate the role of coordinate activation of Ras and Rho GTPases in the induction of COX-2. Individual expression of constitutively active Ras, RhoA, or Rac1 was capable of stimulating COX-2 expression in NIH3T3 cells, but co-expression of constitutively active RhoA with either constitutively active Ras or Rac1 was required for full stimulation of COX-2 expression. Serum growth factors differentially activated Ras, RhoA, and Rac1, which correlated with the activation of Raf-1, ERK, and c-Jun as well as with induction of COX-2. Inhibition of Ras significantly blocked the activation of Raf-1, ERK, and c-Jun and the stimulation of COX-2 expression in response to serum. In contrast, inhibition of Rho family GTPases partially blocked serum induction of ERK activation but had little effects on COX-2 expression. Both inhibitors of MEK (PD098059) and JNK (SP600125) inhibited serum induction of COX-2. PD98059 only inhibited constitutively active Ras-induced COX-2 expression, while SP600125 significantly inhibited both constitutively active Ras- and RhoA-induced COX-2 expression. Together, our data suggest that constitutively active oncogenic Ras and Rho coordinately stimulate COX-2 expression whereas transient activation of Ras but not RhoA or Rac1 mediates the induction of COX-2 in response to serum. Furthermore, ERK and JNK activation are both required for serum- and oncogenic Ras-mediated COX-2 expression whereas only JNK activation is required for oncogenic RhoA-mediated stimulation of COX-2 expression.
authors.affiliation: Department of Biochemistry, Kansas City University of Medicine and Biosciences, 1750 Independence Avenue, Kansas City, Missouri 64106, USA. echang@kcumb.edu
authors.forename: Yu-Wen E
authors.initials: YW
authors.lastname: Chang
authors.forename: Kevin
authors.initials: K
authors.lastname: Putzer
authors.forename: Ling
authors.initials: L
authors.lastname: Ren
authors.forename: Barbara
authors.initials: B
authors.lastname: Kaboord
authors.forename: Terry W
authors.initials: TW
authors.lastname: Chance
authors.forename: M Walid
authors.initials: MW
authors.lastname: Qoronfleh
authors.forename: Rolf
authors.initials: R
authors.lastname: Jakobi
mesh_terms: D016475:3T3 Cells; D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D006133:Growth Substances / Q000097:blood / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D009154:Mutation / Q000235:genetics; D015398:Signal Transduction; D020830:rac1 GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018631:ras Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D006133:Growth Substances; D048049:Extracellular Signal-Regulated MAP Kinases; D020830:rac1 GTP-Binding Protein; D018631:ras Proteins; D020742:rhoA GTP-Binding Protein