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Epidermal growth factor stimulates mitogen-activated protein kinase by a PKC-dependent pathway in human keratinocytes
V Mitev1, R Le Panse, B Coulomb
1INSERM unité 312-Laboratoire de Dermatologie, Hôpital Henri Mondor, Créteil, France.
Abstract:
Epidermal growth factor (EGF), 20 ng/ml, stimulated myelin basic protein (MBP) phosphorylation in crude extracts from human keratinocyte primary cultures. In order to identify the involved kinases, we separated by fast protein liquid chromatography proteins participating in MBP phosphorylation. We detected three MBP kinase activities in the keratinocyte crude extracts. The first MBP kinase activity was the only one stimulated by EGF and reacted with anti-mitogen-activated protein kinase (MAPK) antiserum recognising p42mapk and p44mapk isoforms. However, when protein kinase C (PKC) was either inhibited by the PKC inhibitor GF 109203X or depleted by a prolonged TPA treatment, the stimulation of MBP phosphorylation by EGF was strongly inhibited. The second MBP kinase activity eluted was due to a PKC isoform reacting with an anti-PKC zeta antibody, and the third was not identified. With this work, we have thus shown that, in human keratinocytes, EGF activates MAPK activity by a PKC-dependent pathway.
Insights
Epidermal growth factor (EGF) activates mitogen-activated protein kinase (MAPK) in human skin cells. This activation relies on protein kinase C (PKC) signaling, revealing a novel signaling pathway in keratinocytes.
Area of Science:
- Cellular Biology
- Molecular Biology
- Dermatology
Background:
- Human keratinocytes play a crucial role in skin structure and function.
- Epidermal growth factor (EGF) is a key signaling molecule in keratinocyte biology.
- Understanding growth factor-induced signaling pathways is vital for skin research.
Purpose of the Study:
- To identify kinases involved in myelin basic protein (MBP) phosphorylation stimulated by EGF in human keratinocytes.
- To elucidate the signaling pathway mediating EGF-induced MBP phosphorylation.
Main Methods:
- Primary human keratinocyte cultures were used.
- Fast protein liquid chromatography (FPLC) was employed to separate proteins.
- Mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) activities were assessed using specific antibodies and inhibitors (GF 109203X, TPA).
Main Results:
- Three distinct MBP kinase activities were detected in keratinocyte extracts.
- EGF specifically stimulated one MBP kinase activity, identified as MAPK (p42mapk and p44mapk isoforms).
- EGF-induced MBP phosphorylation was significantly inhibited by blocking or depleting PKC, indicating a PKC-dependent pathway.
Conclusions:
- EGF activates MAPK signaling in human keratinocytes.
- This EGF-induced MAPK activation is dependent on protein kinase C (PKC) activity.
- The study reveals a novel PKC-dependent pathway for EGF-mediated MAPK activation in keratinocytes.