title: Prostaglandin G/H synthase isoenzyme 2 expression in fibroblasts: regulation by dexamethasone, mitogens, and oncogenes.
abstract: Mitogens increase prostaglandin synthesis in fibroblasts. In the present studies, transcriptional activation of the prostaglandin G/H synthase isoenzyme 2 (PGHS-2) gene is shown to be responsible for this induction. Transcription of the PGHS-2 gene maximally increased within 15 min of stimulation, and elevated cellular PGHS-2 mRNA, protein, and prostaglandin synthase activity were detected shortly thereafter. Pulse-chase experiments showed induced isoenzyme 2 is short lived, with a half-life of 22 min in chicken embryo fibroblasts. Neoplastic transformation of fibroblasts by a variety of oncogenes induced either or both PGHS-1 and PGHS-2 mRNAs in immortalized murine NIH3T3 cells. Some preference of oncogenes such as v-src to induce PGHS-2 mRNA has been previously observed. However, in this study exceptions in which v-src did not induce PGHS-2 mRNA were noted. Analysis of independent cell lines transformed by v-fes showed this oncogene induced both PGHS-1 and PGHS-2. Dexamethasone, a synthetic glucocorticoid, selectively decreased both basal and induced levels of PGHS-2 mRNA. Simultaneous addition of the steroid with mitogen reduced mitogen-induced PGHS-2 mRNA levels by 80%. However, nuclear run-on experiments failed to detect any decrease in PGHS-2 mRNA transcription. This suggested dexamethasone rapidly caused PGHS-2 mRNA destabilization. Cycloheximide blocked PGHS-2 mRNA decrease. A fibroblast cell line, RS2, was identified that contained only isoenzyme 2 and possessed PGHS activity that was more highly mitogen-inducible than in any other cell line yet described. Mitogen-inducible activity in RS2 cells was inhibited by aspirin, indicating that PGHS-2, like PGHS-1, can be inactivated by this drug.
authors.affiliation: Department of Chemistry, Brigham Young University, Provo, Utah 84602.
authors.forename: G E
authors.initials: GE
authors.lastname: Evett
authors.forename: W
authors.initials: W
authors.lastname: Xie
authors.forename: J G
authors.initials: JG
authors.lastname: Chipman
authors.forename: D L
authors.initials: DL
authors.lastname: Robertson
authors.forename: D L
authors.initials: DL
authors.lastname: Simmons
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001358:Avian Sarcoma Viruses / Q000235:genetics; D002461:Cell Line, Transformed; D002642:Chick Embryo; D003513:Cycloheximide / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D016762:Genes, fos; D016391:Genes, src; D007527:Isoenzymes / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008934:Mitogens / Q000494:pharmacology*; D009857:Oncogenes; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D014176:Protein Biosynthesis; D014158:Transcription, Genetic
chemical_list: D007527:Isoenzymes; D008934:Mitogens; D003907:Dexamethasone; D003513:Cycloheximide; D011451:Prostaglandin-Endoperoxide Synthases