title: Cyclic AMP-dependent down regulation of ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) in rat C6 glioma.
abstract: In this communication, we demonstrate that an increase in intracellular cAMP by 1) addition of dibutyrylic cAMP (dbcAMP), a membrane-permeable cAMP-analogue, or 2) activation of the β-adrenoceptor with (-)-isoproterenol, down regulates the levels of ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) mRNA, NPP1 protein and ecto-NPPase activity in rat C6 glioma cells. DbcAMP and (-)-isoproterenol inhibit NPP1 expression in a time and dose-dependent manner. After 48h of stimulation, 1mM dbcAMP or 5μM (-)-isoproterenol decreases the amount of NPP1 protein by 75±3% and 81±1% respectively. Contrary to down regulation of NPP1, we observe an up regulation of glial fibrillary acidic protein (GFAP), a differentiation marker for astrocytic cells. Using specific inhibitors and activators, we have shown that Ca(2+), PKA, PI 3-K/PKB/GSK-3, Epac/Rap1/PP2A and MAP kinase modules are not involved in the inhibition of NPP1 gene expression. The transcription factor c-jun is significantly reduced while c-fos becomes up regulated after cAMP elevation. However an electrophoretic mobility shift assay with the activator protein-1 motif present in the promoter of the rat NPP1 gene indicates that this motif is not involved in the cAMP-dependent inhibition of NPP1 expression. In conclusion, these results indicate that intracellular cAMP levels regulate the expression of NPP1 in rat C6 glioma cells by a signalling pathway that is different from the GFAP signal transduction pathway.
authors.affiliation: Department of Biomedical Science, Cellular Biochemistry, Campus Drie Eiken, University of Antwerp, Belgium. indra.aerts@telenet.be
authors.forename: Indra
authors.initials: I
authors.lastname: Aerts
authors.forename: Bert
authors.initials: B
authors.lastname: Grobben
authors.forename: Xaveer
authors.initials: X
authors.lastname: Van Ostade
authors.forename: Herman
authors.initials: H
authors.lastname: Slegers
mesh_terms: D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics*; D005910:Glioma / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011755:Pyrophosphatases / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D005904:Glial Fibrillary Acidic Protein; D012333:RNA, Messenger; D003994:Bucladesine; D000242:Cyclic AMP; D010727:Phosphoric Diester Hydrolases; C065962:ectonucleotide pyrophosphatase phosphodiesterase 1; D011755:Pyrophosphatases; D007545:Isoproterenol