Epidermal growth factor receptor is a common mediator of quinone-induced signaling leading to phosphorylation of connexin-43: role of glutathione and tyrosine phosphatases.
Rat liver epithelial cells were exposed to three quinones with different properties: menadione (2-methyl-1,4-naphthoquinone, vitamin K3), an alkylating as well as redox-cycling quinone, the strongly alkylating p-benzoquinone (BQ), and the non-arylating redox-cycler, 2,3-dimethoxy-1,4-naphthoquinone (DMNQ). All three quinones induced the activation of extracellular signal-regulated kinase (ERK) 1 and ERK 2 via the activation of epidermal growth factor receptor (EGFR) and MAPK/ERK kinases (MEK) 1/2. ERK activation resulted in phosphorylation at Ser-279 and Ser-282 of the gap junctional protein, connexin-43, known to result in the loss of gap junctional intercellular communication. Another EGFR-dependent pathway was stimulated, leading to the activation of the antiapoptotic kinase Akt via phosphoinositide 3-kinase. The activation of EGFR-dependent signaling by these quinones was by different mechanisms: (i) menadione, but not BQ or DMNQ, inhibited a protein-tyrosine phosphatase regulating the EGFR, as concluded from an EGFR dephosphorylation assay; (ii) although menadione-induced activation of ERK was unimpaired by pretreatment of cells with N-acetyl cysteine, activation by BQ and DMNQ was prevented; (iii) cellular glutathione (GSH) levels were strongly depleted by BQ. The mere depletion of GSH by application of diethyl maleate EGFR-dependently activated ERK and Akt, thus mimicking BQ effects. GSH levels were only moderately decreased by menadione and not affected by DMNQ. In summary, EGFR-dependent signaling was mediated by protein-tyrosine phosphatase inactivation (menadione), GSH depletion (BQ), and redox-cycling (DMNQ), funneling into the same signaling pathway.
Abdelmohsen
Kotb
K
Institut für Biochemie und Molekularbiologie I, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany.
Gerber
P Arne
PA
von Montfort
Claudia
C
Sies
Helmut
H
Klotz
Lars-Oliver
LO
D000818:Animals; D016227:Benzoquinones / Q000494:pharmacology*; D015153:Blotting, Western; D002460:Cell Line; D018031:Connexin 43 / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology; D066246:ErbB Receptors / Q000502:physiology*; D017629:Gap Junctions; D005978:Glutathione / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D007202:Indicators and Reagents / Q000494:pharmacology; D008099:Liver / Q000166:cytology; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D009285:Naphthoquinones / Q000494:pharmacology; D010084:Oxidation-Reduction; D010766:Phosphorylation; D011233:Precipitin Tests; D051381:Rats; D015398:Signal Transduction; D013997:Time Factors; D014466:Ultraviolet Rays; D024483:Vitamin K 3 / Q000494:pharmacology
D016227:Benzoquinones; D018031:Connexin 43; D007202:Indicators and Reagents; D009285:Naphthoquinones; C004532:quinone; C063002:2,3-dimethoxy-1,4-naphthoquinone; D024483:Vitamin K 3; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D005978:Glutathione