Dokument: Activation of the epidermal growth factor receptor (EGFR) by redox cycling and alkylating quinones: Mechanisms and consequences
| Titel: | Activation of the epidermal growth factor receptor (EGFR) by redox cycling and alkylating quinones: Mechanisms and consequences | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=2714 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20040126-000714-0 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Abdelmohsen, Kotb [Autor] | |||||||
| Dateien: |
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| Beitragender: | Prof. Dr. Dr. h.c. Sies, Helmut [Gutachter] | |||||||
| Stichwörter: | Menadion, Chinone, NAD(P)H-quinon-oxidoreductase, Doxorubicin, Mytomycin C, Glutathion, Dicoumarolepidermal growth factor receptor (EGFR), quinones, NAD(P)H-quinon-oxidoreductase, Doxorubicin, Mytomycin C, Redox cycling, ERK1/2, Protein kinase B (Akt), Glutathione, Dicoumarol, Menadione, Benzoquinone, 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), Connexins, Gap junctional Channels, Cell-cell communication, chemotherapy, Signal transduction, Neutral red, MTT, cytotoxicity | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 570 Biowissenschaften; Biologie | |||||||
| Beschreibungen: | The effect of redox cycling and alkylating quinones on epidermal growth factor receptor (EGFR) dependent signaling pathways and consequences thereof were investigated. 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 activation of epidermal growth factor receptor (EGFR) and MAPK/ERK kinases (MEK) 1/2. ERK activation resulted in phosphorylation at Ser279 and Ser282 of the gap junctional protein, connexin-43, known to result in loss of gap junctional intercellular communication (GJC). Another EGFR-dependent pathway was stimulated by the quinones, leading to activation of the antiapoptotic kinase Akt via phosphoinositide 3-kinase. Intrestingly, activation of EGFR-dependent signaling by these quinones occurred through different mechanisms: (i) menadione, but not BQ or DMNQ, inhibited a protein tyrosine phosphatase (PTPase) regulating the EGFR, as concluded from an EGFR-dephosphorylation assay; (ii) while 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. The chemotherapeutic quinones doxorubicin and mitomycin C also activated ERK1/2 via activation of EGFR and MEK1/2. Activation of this cascade by these quinones as well as by DMNQ was demonstrated to be dependent on NAD(P)H:quinone oxidoreductase-1, pointing to an important role of redox cycling in the process leading to activation of the signaling cascade. Cell exposure to doxorubicin led to a dose-dependent decrease in GJC that was due to phosphorylation of connexin-43 by ERK1/2. By contrast, ERK5 was not involved. In summary, different quinones affect the same signaling pathway leading to the regulation of intercellular communication, converging at the level of EGFR.The effect of redox cycling and alkylating quinones on epidermal growth factor receptor (EGFR) dependent signaling pathways and consequences thereof were investigated. 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 activation of epidermal growth factor receptor (EGFR) and MAPK/ERK kinases (MEK) 1/2. ERK activation resulted in phosphorylation at Ser279 and Ser282 of the gap junctional protein, connexin-43, known to result in loss of gap junctional intercellular communication (GJC). Another EGFR-dependent pathway was stimulated by the quinones, leading to activation of the antiapoptotic kinase Akt via phosphoinositide 3-kinase. Intrestingly, activation of EGFR-dependent signaling by these quinones occurred through different mechanisms: (i) menadione, but not BQ or DMNQ, inhibited a protein tyrosine phosphatase (PTPase) regulating the EGFR, as concluded from an EGFR-dephosphorylation assay; (ii) while 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. The chemotherapeutic quinones doxorubicin and mitomycin C also activated ERK1/2 via activation of EGFR and MEK1/2. Activation of this cascade by these quinones as well as by DMNQ was demonstrated to be dependent on NAD(P)H:quinone oxidoreductase-1, pointing to an important role of redox cycling in the process leading to activation of the signaling cascade. Cell exposure to doxorubicin led to a dose-dependent decrease in GJC that was due to phosphorylation of connexin-43 by ERK1/2. By contrast, ERK5 was not involved. In summary, different quinones affect the same signaling pathway leading to the regulation of intercellular communication, converging at the level of EGFR. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Biologie | |||||||
| Dokument erstellt am: | 26.01.2004 | |||||||
| Dateien geändert am: | 12.02.2007 | |||||||
| Promotionsantrag am: | 11.12.2003 | |||||||
| Datum der Promotion: | 11.12.2003 |
