Antibody-induced dimerization activates the epidermal growth factor receptor tyrosine kinase

• Published in: The Journal of biological chemistry 1991-01, Vol.266 (3), p.1733-1739
• Main Authors: SPAARGAREN, M, DEFIZE, L. H. K, BOONSTRA, J, DE LAAT, S. W
• Format: Article
• Language: English
• Subjects: Antibodies, Monoclonal; Biological and medical sciences; Cell Line; Cell Membrane - enzymology; Cell physiology; Detergents - chemistry; Enzyme Activation; ErbB Receptors - metabolism; Fundamental and applied biological sciences. Psychology; Humans; Molecular and cellular biology; Molecular Structure; Phosphorylation; Protein Binding; Protein-Tyrosine Kinases - metabolism; Receptor Aggregation; Responses to growth factors, tumor promotors, other factors; Structure-Activity Relationship
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(18)52357-7

The relationship between epidermal growth factor receptor (EGF-R) protein tyrosine kinase activation and ligand-induced receptor dimerization was investigated using several bivalent anti-EGF-R antibodies directed against various receptor epitopes. In A431 membrane preparations and permeabilized cells, all antibodies were able to activate the EGF-R tyrosine kinase, as measured by EGF-R autophosphorylation and phosphorylation of other substrates on tyrosine residues. EGF-R tyrosine kinase activation correlated strongly with the induction of EGF-R dimerization. (i) Both processes specifically occurred in a narrow antibody concentration range; (ii) both processes required the presence of detergent; and (iii) both processes depended on antibody bivalence since monovalent Fab fragments were inactive yet regained full activity after cross-linking by a second bivalent antibody. These data demonstrate that antibody bivalence is essential and sufficient for EGF-R activation and that activation occurs regardless of the EGF-R epitope recognized. Finally, EGF-R dimerization was shown not to depend on receptor autophosphorylation since it still occurred in the absence of ATP. Also, partial inhibition of the tyrosine kinase activity by the specific EGF-R tyrosine kinase inhibitor tyrphostin AG 213 did not affect formation of EGF-R dimers. Taken together these results demonstrate that induction of EGF-R dimerization is sufficient and in case of antibody action, essential, for activation of the EGF-R tyrosine kinase and thus provide strong support for an intermolecular mechanism of EGF-R tyrosine kinase activation.