Wehrman, T. S. et al. A system for quantifying dynamic protein interactions defines a role for Herceptin in modulating ErbB2 interactions. Proc. Natl Acad. Sci. USA 103, 19063-19068

Baxter Laboratory in Genetic Pharmacology, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305-5175, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 01/2007; 103(50):19063-8. DOI: 10.1073/pnas.0605218103
Source: PubMed


The orphan receptor tyrosine kinase ErbB2 is activated by each of the EGFR family members upon ligand binding. However, difficulties monitoring the dynamic interactions of the membrane receptors have hindered the elucidation of the mechanism of ErbB2 activation. We have engineered a system to monitor protein-protein interactions in intact mammalian cells such that different sets of protein interactions can be quantitatively compared. Application of this system to the interactions of the EGFR family showed that ErbB2 interacts stably with the EGFR and ErbB3, but fails to spontaneously homooligomerize. The widely used anti-cancer antibody Herceptin was found to effectively inhibit the interaction of the EGFR and ErbB2 but not to interfere with the interaction of ErbB2-ErbB3. Treatment of cells expressing EGFR and ErbB2 with Herceptin results in increased EGFR homooligomerization in the presence of EGF and a subsequent rapid internalization and down-regulation of the EGFR. In summary, the protein interaction system described here enabled the characterization of ErbB2 interactions within the biological context of the plasma membrane and provides insight into the mechanism of Herceptin action on cells overexpressing ErbB2.

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    • "Since trastuzumab does not prevent HER3 dimerization (Wehrman et al., 2006), the overexpression of HER3 could overcome trastuzumab-mediated inhibition of HER2 signaling. It was previously found that co-expression of HER3 and HER2 is required for the transformation of NIH-3T3 cells (Alimandi et al., 1995) and that HER2-HER3 dimerization results in increased tyrosine phosphorylation of HER3 which subsequently increases PI3K recruitment and downstream activation (Alimandi et al., 1995; Holbro et al., 2003). "
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    • "The oligomerization properties of the HER receptors confirmed that interactions between EGFR/HER2 and HER2/HER3 are detected in the presence of ligand. In addition, they found that trastuzumab is ineffective in blocking HER2/HER3 dimerization [84]. "
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    • "To further investigate the role of HER2-mediated interactions, we used another HER2 blocking antibody, Herceptin [57] in our HER2+/3+ cells. Like 2C4, 4D5/Herceptin also inhibits HER2 dimerization but in a selective fashion; it disrupts the interaction between EGFR and HER2 but does not markedly interfere with the HER2-HER3 interaction [58]. This is most likely due to the differential involvement of HER2 cell surface residues in the formation of the various dimer types [59,60]. "
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