title: Inhibition of connexin43 gap junctional intercellular communication by TPA requires ERK activation.
abstract: The phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), is a potent inhibitor of gap junctional intercellular communication (GJIC). This inhibition requires activation of protein kinase C (PKC), but the events downstream of this kinase are not known. Since PKC can activate extracellular signal regulated kinases (ERKs) and these also downregulate GJIC, we hypothesized that the inhibition of GJIC by TPA involved ERKs. TPA treatment (10 ng/ml for 30 min) of WB-F344 rat liver epithelial cells strongly activated p42 and p44 ERK-1 and -2, blocked gap junction-mediated fluorescent dye-coupling, and induced connexin43 hyperphosphorylation and gap junction internalization. These effects were completely prevented by inhibitors of PKC (bis-indolylmaleimide I; 2 microM) and ERK activation (U-0126; 10 microM). These data suggest that ERKs are activated by PKC in response to TPA treatment and are downstream mediators of the gap junction effects of the phorbol ester.
authors.affiliation: Department of Pathology, Medical College of Ohio, 3055 Arlington Avenue, Toledo, OH 43614, USA. rruch@mco.edu
authors.forename: R J
authors.initials: RJ
authors.lastname: Ruch
authors.forename: J E
authors.initials: JE
authors.lastname: Trosko
authors.forename: B V
authors.initials: BV
authors.lastname: Madhukar
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002450:Cell Communication / Q000187:drug effects*; D002478:Cells, Cultured; D018031:Connexin 43 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D017629:Gap Junctions / Q000187:drug effects* / Q000378:metabolism; D007546:Isoquinolines / Q000378:metabolism; D008099:Liver; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D018031:Connexin 43; D007546:Isoquinolines; C017475:lucifer yellow; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate