Different EGF‐induced receptor dimer conformations for signaling and internalization

The structural basis of the activation and internalization of EGF receptors (EGFR) is still a matter of debate despite the importance of this target in cancer treatment. Whether agonists induce dimer formation or act on preformed dimers remains discussed. Here, we provide direct evidence that EGF‐induced EGFR dimer formation as best illustrated by the very large increase in FRET between snap‐tagged EGFR subunits induced by agonists. We confirm that Erlotinib‐related TK (tyrosine kinase) inhibitors also induce dimer formation despite the inactive state of the binding domain. Surprisingly, TK inhibitors do not inhibit EGF‐induced EGFR internalization despite their ability to fully block EGFR signaling. Only Erlotinib‐related TK inhibitors promoting asymmetric dimers could slow down this process while the lapatinib‐related ones have almost no effect. These results reveal that the conformation of the intracellular TK dimer, rather than the known EGFR signaling, is critical for EGFR internalization. These results also illustrate clear differences in the mode of action of TK inhibitors on the EGFR and open novel possibilities to control EGFR signaling for cancer treatment. EGF induces EGF receptor (EGFR) dimer formation. Erlotinib‐related (group I) TK inhibitors (TKIs) also induce dimer formation despite the inactive EGF binding domain. Surprisingly, TKIs block EGFR signaling but not EGF‐induced EGFR internalization. Only Erlotinib‐related TKIs promoting asymmetric dimers slow down internalization. Group I TKIs stabilize both Activator and Receiver conformations and group II TKIs only Activator conformations of the TK domain. The conformation of the intracellular TK dimer appears critical for EGFR internalization rather than the known EGFR signaling.