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Dimerization of internalized epidermal growth factor receptors
1Department of Biochemistry and Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146.
The Journal of Biological Chemistry
|December 5, 1991
Summary
Epidermal growth factor (EGF) binding to EGF receptors causes receptor dimerization. Internalized EGF receptors maintain their dimeric form and tyrosine kinase activity, suggesting sustained receptor interactions after internalization.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Epidermal growth factor (EGF) binding to its receptor (EGFR) on the cell surface triggers receptor dimerization.
- This dimerization is crucial for initiating intracellular signaling pathways.
- Low pH conditions can cause EGF dissociation and receptor monomerization.
Purpose of the Study:
- To investigate the dimerization status of internalized EGF receptors.
- To determine if internalized EGF receptors retain their tyrosine kinase activity.
- To understand the conformational state of EGF receptors within the endosomal compartment.
Main Methods:
- Utilizing chemical cross-linking techniques on intact and solubilized cells.
- Employing mild permeabilization and cell solubilization protocols.
- Analyzing tyrosine phosphorylation levels of EGF receptor monomers and dimers.
Main Results:
- Dimeric forms of internalized EGF receptors were detected in A-431 and NIH 3T3 cells.
- The proportion of internalized dimeric receptors mirrored that of surface receptors.
- Both dimeric and monomeric internalized EGF receptors exhibited similar tyrosine phosphorylation levels.
- Kinase-negative EGF receptors showed similar dimerization and internalization rates compared to wild-type.
Conclusions:
- EGF remains bound to its receptor for a period after internalization.
- Internalized EGF receptors preserve a conformation that maintains receptor-receptor interactions.
- Tyrosine kinase activity is maintained intracellularly in EGF receptor dimers.