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Developments in the mechanism of growth factor action: activation of protein kinase by epidermal growth factor
Abstract:
The interaction between epidermal growth factor (EGF) and its target cells has been used as a model for studying the regulation of cell proliferation. Many of the details of binding and subsequent internalization and degradation of this growth factor have been elucidated by following the fate of [125I]EGF in the presence of responsive cells. To investigate the membrane-localized biochemical consequences of EGF-receptor complex formation, a subcellular membrane system has been developed. In this system, EGF enhances phosphorylation of its receptor as well as other endogenous proteins. This EGF-stimulable protein kinase activity is not separated from the EGF receptor activity either by detergent solubilization or by affinity purification of the solubilized membranes. The data suggest that the EGF-binding activity and EGF-sensitive protein kinase activity reside in a single membrane protein.
Insights
Epidermal growth factor (EGF) binding to its receptor enhances receptor phosphorylation. This suggests EGF receptor activity and kinase activity are part of a single membrane protein, crucial for cell proliferation studies.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Epidermal growth factor (EGF) interactions with target cells model cell proliferation regulation.
- Previous studies tracked [125I]EGF to understand binding, internalization, and degradation.
Purpose of the Study:
- Investigate membrane-localized biochemical events following EGF-receptor complex formation.
- Characterize the EGF-receptor complex's enzymatic activity.
Main Methods:
- Developed a subcellular membrane system to study EGF-receptor interactions.
- Utilized detergent solubilization and affinity purification techniques.
- Assayed protein phosphorylation in response to EGF.
Main Results:
- EGF stimulation enhanced phosphorylation of the EGF receptor and other endogenous proteins.
- EGF-stimulable protein kinase activity remained associated with the EGF receptor after solubilization and purification.
- EGF-binding and EGF-sensitive kinase activities were inseparable.
Conclusions:
- The data strongly suggest that EGF-binding activity and EGF-sensitive protein kinase activity are intrinsic to a single membrane protein.
- This finding provides a molecular basis for understanding EGF-mediated cell signaling and proliferation.