Abstract
The ability of cells to adapt their response to growth factors in relation to their environment is an essential aspect of tissue development and homeostasis. We found that signaling mediated by the Eph family of receptor tyrosine kinases from cell-cell contacts changed the cellular response to the growth factor EGF by modulating the vesicular trafficking of its receptor, EGFR. Eph receptor activation trapped EGFR in Rab5-positive early endosomes by inhibiting Akt-dependent vesicular recycling. By altering the spatial distribution of EGFR activity, EGF-promoted Akt signaling from the plasma membrane was suppressed, thereby inhibiting cell migration. In contrast, ERK signaling from endosomal EGFR was preserved to maintain a proliferative response to EGF stimulation. We also found that soluble extracellular signals engaging the G protein-coupled receptor Kiss1 (Kiss1R) similarly suppressed EGFR vesicular recycling to inhibit EGF-promoted migration. Eph or Kiss1R activation also suppressed EGF-promoted migration in Pten-/- mouse embryonic fibroblasts, which exhibit increased constitutive Akt activity, and in MDA-MB-231 triple-negative breast cancer cells, which overexpress EGFR. The cellular environment can thus generate context-dependent responses to EGF stimulation by modulating EGFR vesicular trafficking dynamics.