title: Protein kinase C down-regulation enhances cAMP-mediated induction of urokinase-type plasminogen activator mRNA in LLC-PK1 cells.
abstract: Expression of the urokinase-type plasminogen activator (uPA) gene in LLC-PK1 cells can be induced by signals mediated by both cAMP-dependent protein kinase (PKA) and Ca(2+)- and phospholipid-dependent protein kinase (PKC). We have utilized the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) to down-regulate PKC, in order to test for an effect on the PKA-mediated induction of the uPA gene expression. Incubation of cells for 24 h with 100 ng/ml TPA caused a marked decrease of PKC protein, both in cytosolic and particulate fractions, and an 85% reduction of total PKC activity. After down-regulation of PKC, uPA mRNA accumulation induced by 8-Br-cAMP was 5-10-fold higher than in control cells. Both uPA mRNA stability and uPA gene transcription rates induced by 8-Br-cAMP were increased by PKC down-regulation (6- and 1.8-fold, respectively). Although total PKA activity was reduced by 20% in extracts from PKC-depleted cells, activation of PKA by 8-Br-cAMP was 2.5-fold higher than in control cells. This enhanced activation of PKA in PKC-depleted cells also occurred in response to other cAMP derivatives and to cAMP induced endogenously by the activation of adenylate cyclase with forskolin, but was not due to down-regulation-associated changes in the rate of cAMP synthesis. Our results demonstrate that in LLC-PK1 cells, down-regulation of PKC results in an enhanced induction of uPA gene expression by cAMP-mediated signals without alterations in adenylate cyclase activity, suggesting a mechanism distal to adenylate cyclase.
authors.affiliation: Friedrich Miescher-Institut, Basel, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Ziegler
authors.forename: J
authors.initials: J
authors.lastname: Knesel
authors.forename: D
authors.initials: D
authors.lastname: Fabbro
authors.forename: Y
authors.initials: Y
authors.lastname: Nagamine
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D015152:Blotting, Northern; D003994:Bucladesine / Q000494:pharmacology; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D011493:Protein Kinase C / Q000502:physiology*; D011494:Protein Kinases / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics*
chemical_list: D012333:RNA, Messenger; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D003994:Bucladesine; D000242:Cyclic AMP; D011494:Protein Kinases; D011493:Protein Kinase C; D014568:Urokinase-Type Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate; D015056:1-Methyl-3-isobutylxanthine