Inhibition of epidermal growth factor receptor aggregation by an antibody directed against the epidermal growth factor receptor extracellular domain.
We have examined the perturbation of epidermal growth factor (EGF) receptor-receptor interactions by a monoclonal antibody (13A9) that binds to the receptor extracellular domain. While 13A9 did not inhibit EGF binding, it inhibited energy transfer between fluorescent-labeled EGF molecules bound to receptors in membranes from human A431 cells by 70-100%. This antibody also inhibited EGF-stimulated receptor dimerization in membranes as assessed by chemical cross-linking and Fab fragments of the antibody strongly inhibited the EGF-stimulated dimerization of solubilized receptors when assessed by velocity sedimentation. However, under conditions where 13A9 inhibited receptor-receptor interactions within the plasma membranes, the antibody had no effect on EGF-stimulated receptor autophosphorylation or tyrosine kinase activity toward an exogenous substrate. Moreover, although the antibody significantly inhibited receptor dimerization in A431 cells, it had no effect on EGF-stimulated changes in cytosolic free [Ca2+] or 125I-EGF uptake in these cells, or on EGF-stimulated DNA synthesis in Swiss 3T3 cells. We conclude that the dimerization of the EGF receptors in a membrane environment is not required for full activation of tyrosine kinase activity and that inhibition of the dimerization of a large fraction of EGF receptors in cells does not necessarily inhibit several EGF-mediated cellular responses.
Carraway
K L
KL
Department of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853.
Cerione
R A
RA
D016475:3T3 Cells; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D002478:Cells, Cultured; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000378:metabolism / Q000502:physiology; D005456:Fluorescent Dyes; D006801:Humans; D051379:Mice; D011940:Receptor Aggregation / Q000276:immunology*
D000911:Antibodies, Monoclonal; D005456:Fluorescent Dyes; D066246:ErbB Receptors