Eps15 is recruited to the plasma membrane upon epidermal growth factor receptor activation and localizes to components of the endocytic pathway during receptor internalization

Eps15 is a substrate for the tyrosine kinase of the epidermal growth factor receptor (EGFR) and is characterized by the presence of a novel protein:pr otein interaction domain, the EH domain. Eps15 also stably binds the clathr in adaptor protein complex AP-2. Previous work demonstrated an essential ro le for eps15 in receptor-mediated endocytosis. In this study we show that, upon activation of the EGFR kinase, eps15 undergoes dramatic relocalization consisting of 1) initial relocalization to the plasma membrane and 2) subs equent colocalization with the EGFR in various intracellular compartments o f the endocytic pathway, with the notable exclusion of coated vesicles. Rel ocalization of eps15 is independent of its binding to the EGFR or of bindin g of the receptor to AP-2. Furthermore, eps15 appears to undergo tyrosine p hosphorylation both at the plasma membrane and in a nocodazole-sensitive co mpartment, suggesting sustained phosphorylation in endocytic compartments. Our results are consistent with a model in which eps15 undergoes cycles of association:dissociation with membranes and suggest multiple roles for this protein in the endocytic pathway.