Antibody-induced activation of the epidermal growth factor receptor tyrosine kinase requires the presence of detergent

Activation of the epidermal growth factor receptor (EGF-R) tyrosine kinase was investigated in membrane preparations as well as intact A431 cells, using anti-EGF-R antibodies directed against extra- and intracellular receptor domains. In vitro assay conditions were mimicked on whole cells by a mild detergent treatment. We show that, irrespective of the recognition site on the EGF-R, antibodies induce EGF-R autophosphorylation and tyrosine kinase activity towards other endogenous and exogenous substrates, but only when detergent is present. We propose that the primary effect of detergent is to create conditions in the lipid environment of the EGF-R that allow antibodies to induce receptor-receptor interactions necessary for tyrosine kinase activation.