## Abstract ErbB2 has been implicated in numerous functions, including normal and aberrant development of a variety of tissues. Although no soluble ligand has been identified for ErbB2, we have recently shown that ASGPโ2, the transmembrane subunit of the cell surface glycoprotein Muc4 (also called
Structural analysis of the ErbB-2 receptor using monoclonal antibodies: Implications for receptor signalling
โ Scribed by Yum L. Yip; Jiri Novotny; Michael Edwards; Robyn L. Ward
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- French
- Weight
- 253 KB
- Volume
- 104
- Category
- Article
- ISSN
- 0020-7136
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โฆ Synopsis
Abstract
The extracellular part of ErbBโ2 is formed by 4 domains, specifically, L1, L2 that adopt a ฮฒโhelical structure and S1, S2 that consist of several cysteineโrich, EGFโfold modules. These ectodomains mediate ErbBโ2 dimerisation with itself or with other members of the epidermal growth factor receptor (EGFR) family, events essential to both ErbBโ2 signaling and the development of certain malignancies. The antiโErbBโ2 monoclonal antibodies N12, N28 and L87 bind to the polypeptides C531โA586, T216โC235 and C220โC235 respectively. In this study, glycine walking and random mutagenesis were used to further delineate the critical residues involved in antibody binding. A molecular model of ErbBโ2 ectodomains was then constructed based on the recently published coordinates of the EGFR (EGFR) model. This model rationalized successfully many features of our epitope mapping, including their location in modules within the S1 and S2 domains and the importance of Arg545, Gln548 and Leu561 for N12 binding. Further investigation of the functional effects of the antiโErbBโ2 monoclonal antibodies demonstrated that N28 strongly stimulated ErbBโ2 phosphorylation and MAPK activation whereas N12 had no effect. As bivalency is required for the action of these antibodies we propose that at least 2 different kinds of ErbBโ2 homodimers can be formed as relative rotational isomers and that the S1 and S2 domains are instrumental in determining the relative orientations of the ErbBโ2 homodimers, such that different signaling effects are induced. ยฉ 2003 WileyโLiss, Inc.
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