Chronic regulation of the expression of the gap junction protein connexin 43 in transfected HeLa cells.
Gap junction channels are essential for intercellular communication. Among the most abundant gap junction channel proteins is connexin 43 (Cx43). The goal of our study was to find out, whether Cx43 content may be regulated via adenylyl cyclase (AC)/cAMP/protein kinase A (PKA), protein kinase C (PKC) pathways or by a tyrosine kinase coupled pathway, i.e. TNF alpha-receptor dependent pathway. Therefore, we used HeLa cells transfected with Cx43 and exposed these cells for 24 h to either db-cAMP (10(-4)M), forskolin (10(-5)M), the phorbolester phorbol-12,13-didecanoate PDD (10(-7)M) (or its inactive form 4 alpha-PDD), TNF alpha (10 U/ml) with or without additional treatment with the MAP kinase inhibitors SB203580 (10(-5) M, p38 MAP-kinase inhibitor) or the MEK1-inhibitor PD98059 (10(-5)M). Cx43 content was analysed using Western blot analysis. All results were confirmed by a second series of identical experiments using Cx43 immunohistochemistry. We found significantly enhanced Cx43 content in cells treated with db-cAMP, forskolin, PDD or TNF alpha (p<0.05), while 4 alpha-PDD or the solvent DMSO exerted no effect. These increases in Cx43 content could be completely suppressed by SB203580 (p<0.05) but not by PD98059. In absence of a stimulating drug, these inhibitors (SB203580 or PD98059) did not affect Cx43 content. Additional PCR experiments revealed increases in Cx43-mRNA under the influence of db-cAMP, forskolin, PDD or TNFalpha (p<0.05), which all could be completely suppressed by SB203580. From these results we conclude that 1.Cx43 content can be regulated via AC/cAMP/PKA, PKC and TNF alpha-receptor-dependent pathways 2. Activation of p38 MAP kinase is a common pathway for regulation of Cx43 content in HeLa cells
Salameh
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Medizinische Klinik I, Abteilung Kardiologie, Universitätsklinik Leipzig, Johannisallee 32, 04103 Leipzig, Germany. sala@medizin.uni-leipzig.de
Polontchouk
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Dhein
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S
Hagendorff
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A
Pfeiffer
D
D
D000262:Adenylyl Cyclases / Q000378:metabolism; D015153:Blotting, Western; D005576:Colforsin / Q000494:pharmacology; D018031:Connexin 43 / Q000096:biosynthesis* / Q000235:genetics; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D017629:Gap Junctions / Q000378:metabolism*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D018031:Connexin 43; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D011725:Pyridines; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D000242:Cyclic AMP; D011505:Protein-Tyrosine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D000262:Adenylyl Cyclases; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one