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Characterization of a breast cancer cell differentiation factor that specifically activates the HER4/p180erbB4
J M Culouscou1, G D Plowman, G W Carlton
1Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, Washington 98121.
Abstract:
We recently reported the molecular cloning of HER4/p180erbB4, a new member of the epidermal growth factor receptor family, as well as its activation by a partially purified ligand (Plowman, G. D., Culouscou, J.-M., Whitney, G. S., Green, J. M., Carlton, G. W., Foy, L., Neubauer, M. G., and Shoyab, M. (1993) Proc. Natl. Acad. Sci. U. S. A. 90, 1746-1750). In this report we describe the purification to homogeneity of a 45-kDa protein (p45) that induces the differentiation of MDA-MB-453 human breast cancer cells and stimulates the tyrosine phosphorylation of p180erbB4, the HER4-encoded protein. Hydrophobic interaction, ion-exchange, heparin, and size exclusion chromatographies were used to purify this p180erbB4 activator to homogeneity. N-terminal amino acid sequencing suggests that p45 is related to heregulin, a recently reported ligand for p185erbB2. Binding and cross-linking experiments demonstrated that p45 specifically binds to cells expressing recombinant p180erbB4 and not cells expressing recombinant p185erbB2.
Insights
Researchers purified a 45-kDa protein (p45) that activates the HER4 receptor (p180erbB4), promoting breast cancer cell differentiation. This protein is related to heregulin and specifically binds to HER4-expressing cells.
Area of Science:
- Molecular biology
- Cell signaling
- Cancer research
Background:
- The epidermal growth factor receptor family member HER4/p180erbB4 was recently cloned.
- Activation of HER4 by partially purified ligands was previously reported.
Purpose of the Study:
- To purify and characterize a ligand that activates HER4/p180erbB4.
- To investigate the role of this ligand in human breast cancer cell differentiation.
Main Methods:
- Purification of a 45-kDa protein (p45) using multiple chromatography techniques (hydrophobic interaction, ion-exchange, heparin, size exclusion).
- Assessing p45's ability to induce differentiation in MDA-MB-453 breast cancer cells.
- Measuring tyrosine phosphorylation of p180erbB4 stimulated by p45.
- N-terminal amino acid sequencing of p45.
- Binding and cross-linking experiments to determine cell specificity.
Main Results:
- A 45-kDa protein (p45) was purified to homogeneity.
- p45 induces differentiation of MDA-MB-453 human breast cancer cells.
- p45 stimulates tyrosine phosphorylation of the HER4-encoded protein, p180erbB4.
- N-terminal sequencing indicates p45 is related to heregulin.
- p45 specifically binds to cells expressing recombinant p180erbB4, not p185erbB2.
Conclusions:
- A novel HER4/p180erbB4 activator, p45, has been purified.
- p45 plays a role in breast cancer cell differentiation and HER4 signaling.
- p45 represents a potential therapeutic target in HER4-related cancers.