title: 12-O-tetradecanoyl-phorbol-13-acetate (TPA) counteracts the cAMP up-regulation of the expression of the stimulatory guanine nucleotide binding protein (Gs alpha) and Gs alpha messenger RNA in cultured pig thyroid cells.
abstract: In this study, we examined whether the protein kinase C (PKC) pathway could interfere with the regulation of Gs protein in porcine thyroid cells. The two days culture of cells with 12-O-tetradecanoylphorbol 13-acetate (TPA) (0.1 microM) alone neither affected adenylyl cyclase activity, nor the level of Gs alpha protein in membranes when compared with control cells. The co-addition of TPA with thyrotropin (TSH) (1 mU/ml) or forskolin (fk) (10 microM) in the culture medium, abolished the stimulatory effects of either agonists on the activation of adenylyl cyclase by fk or [AlF4]- and on the increase of Gs alpha protein. By contrast, TPA had effects neither on the Gi-dependent inhibition of adenylyl cyclase nor on Gi alpha proteins levels. The level of Gs alpha mRNA measured by Northern blot analysis was increased (200%) in TSH- or fk-treated cells and this increase was counteracted by TPA. The effects of TPA observed after 6-9 h of contact with cells were mimicked by mezerezin, a non-phorbol protein kinase C activator and blocked by bisindolylmaleimide a specific protein kinase C inhibitor (GF 109203X). These results suggest that the activation of the PKC pathway prevents the cAMP-dependent up-regulation of Gs alpha protein and Gs alpha mRNA expression.
authors.affiliation: Unité de Recherche sur la glande thyröide et la régulation hormonale, U96 INSERM, Le Kremlin-Bicêtre, France.
authors.forename: K
authors.initials: K
authors.lastname: Dib
authors.forename: B
authors.initials: B
authors.lastname: Delemer
authors.forename: A
authors.initials: A
authors.lastname: el Jamali
authors.forename: B
authors.initials: B
authors.lastname: Haye
authors.forename: C
authors.initials: C
authors.lastname: Jacquemin
authors.forename: C
authors.initials: C
authors.lastname: Corrèze
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D004224:Diterpenes; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects*; D007700:Kinetics; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D013552:Swine; D013729:Terpenes / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology
chemical_list: D004224:Diterpenes; D012333:RNA, Messenger; D013729:Terpenes; D005576:Colforsin; C011309:mezerein; D013972:Thyrotropin; D000242:Cyclic AMP; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D013755:Tetradecanoylphorbol Acetate