title: The antibody zalutumumab inhibits epidermal growth factor receptor signaling by limiting intra- and intermolecular flexibility.
abstract: The epidermal growth factor receptor (EGFR) activates cellular pathways controlling cell proliferation, differentiation, migration, and survival. It thus represents a valid therapeutic target for treating solid cancers. Here, we used an electron microscopy-based technique (Protein Tomography) to study the structural rearrangement accompanying activation and inhibition of native, individual, EGFR molecules. Reconstructed tomograms (3D density maps) showed a level of detail that allowed individual domains to be discerned. Monomeric, resting EGFR ectodomains demonstrated large flexibility, and a number of distinct conformations were observed. In contrast, ligand-activated EGFR complexes were detected only as receptor dimers with ring-like conformations. Zalutumumab, a therapeutic inhibitory EGFR antibody directed against domain III, locked EGFR molecules into a very compact, inactive conformation. Biochemical analyses showed bivalent binding of zalutumumab to provide potent inhibition of EGFR signaling. The structure of EGFR-zalutumumab complexes on the cell surface visualized by Protein Tomography indicates that the cross-linking spatially separates the EGFR molecules' intracellular kinase domains to an extent that appears incompatible with the induction of signaling. These insights into the mechanisms of action of receptor inhibition may also apply to other cell-surface tyrosine kinase receptors of the ErbB family.
authors.affiliation: Genmab, 3508 AD, Utrecht, The Netherlands.
authors.forename: Jeroen J
authors.initials: JJ
authors.lastname: Lammerts van Bueren
authors.forename: Wim K
authors.initials: WK
authors.lastname: Bleeker
authors.forename: Annika
authors.initials: A
authors.lastname: Brännström
authors.forename: Anne
authors.initials: A
authors.lastname: von Euler
authors.forename: Magnus
authors.initials: M
authors.lastname: Jansson
authors.forename: Matthias
authors.initials: M
authors.lastname: Peipp
authors.forename: Tanja
authors.initials: T
authors.lastname: Schneider-Merck
authors.forename: Thomas
authors.initials: T
authors.lastname: Valerius
authors.forename: Jan G J
authors.initials: JG
authors.lastname: van de Winkel
authors.forename: Paul W H I
authors.initials: PW
authors.lastname: Parren
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D001665:Binding Sites; D045744:Cell Line, Tumor; D004815:Epidermal Growth Factor / Q000737:chemistry / Q000494:pharmacology; D018604:Epitope Mapping; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D008024:Ligands; D051379:Mice; D008854:Microscopy, Electron; D009154:Mutation; D011487:Protein Conformation; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D008024:Ligands; D004815:Epidermal Growth Factor; C546618:zalutumumab; D066246:ErbB Receptors