Characterization of ligand-induced conformational changes in the EGF receptor

The epidermal growth factor (EGF) receptor is a classical receptor tyrosine kinase that mediates cellular processes such as proliferation, migration, and differentiation in response to growth factor stimulation. Crystal structures of the EGF receptor suggest that its activation is associated with extensive conformational changes in both the extracellular and intracellular domains. However, evidence of these structural dynamics in intact cells has been lacking. This thesis describes the characterization of sequential ligand-induced conformational changes in the EGF receptor in live cells in real time using luciferase fragment complementation imaging. We find that these conformational changes are unique to the full-length activated EGF receptor. These studies identified a novel conformational change that was dependent on MAP kinase activation and desensitization of the EGF receptor. It has been unclear how MAP kinase desensitizes the EGF receptor following activation. Mutational analysis was done to identify residues involved in the MAP kinase-mediated EGF receptor desensitization. We use these analyses to provide a structural explanation for the MAP kinase-mediated desensitization of the EGF receptor. The luciferase complementation assay was further utilized to test the ability of different ligands for the EGF receptor family to induce dimer formation and intracellular domain conformational changes.