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Characterization of the epidermal growth factor receptor and the erbB oncogene product by site-specific antibodies
Abstract:
Site-specific antibodies to the src-homologous domain (residues 373-383) of the erbB gene product neutralized the tyrosine kinase activity of the epidermal growth factor receptor, suggesting that the region against which the antibodies were directed may be functionally important for the kinase activity. In the immunofluorescence experiment, the site-specific antibodies detected the epidermal growth factor receptor and the erbB gene product only when the cells were permeabilized prior to staining, while monoclonal anti-epidermal growth factor receptor antibody, which recognizes the epidermal growth factor binding domain, gave a positive surface stain with viable nonpermeabilized A431 cells. This result supports the view that the epidermal growth factor binding domain and the src-homologous domain are located at the cell surface and inner face of the plasma membrane, respectively.
Insights
Site-specific antibodies targeting the src-homologous domain of the erbB gene product inhibited epidermal growth factor receptor kinase activity. This suggests the src-homologous domain is crucial for kinase function and located internally.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- The epidermal growth factor receptor (EGFR) is a key regulator of cell growth and is often implicated in cancer.
- The erbB gene product, also known as EGFR, possesses tyrosine kinase activity essential for its signaling.
- Understanding the functional domains of EGFR is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the functional importance of the src-homologous (SH) domain of the erbB gene product.
- To determine the cellular localization of the SH domain and the epidermal growth factor (EGF) binding domain of EGFR.
Main Methods:
- Generation and use of site-specific antibodies targeting the SH domain (residues 373-383) of the erbB gene product.
- Neutralization assays to assess the effect of antibodies on tyrosine kinase activity.
- Immunofluorescence experiments on A431 cells using site-specific and monoclonal antibodies with and without cell permeabilization.
Main Results:
- Site-specific antibodies against the SH domain neutralized EGFR tyrosine kinase activity.
- EGFR and erbB protein were detected by site-specific antibodies only in permeabilized cells.
- Monoclonal antibodies recognizing the EGF binding domain stained non-permeabilized viable cells.
Conclusions:
- The src-homologous domain of the erbB gene product is functionally important for EGFR tyrosine kinase activity.
- The EGF binding domain is located on the cell surface.
- The src-homologous domain is located on the inner face of the plasma membrane.