MOLECULAR DETERMINANTS OF THE ENDOCYTIC PROTEIN EPSIN CONTROLLING ITS LOCALIZATION AND FUNCTION IN CANCER CELL MIGRATION AND INVASION

Abstract

ABSTRACTEpsins are endocytic adaptor proteins with signaling and endocytic functions. The three mammalian epsin paralogs are made of an Epsin N-Terminal Homology (ENTH) domain and an unstructured C-terminal region. The highly conserved ENTH domain plays a role in signaling by blocking RhoGAP activity and is required for cell migration in mammalian cells. However, our lab has previously shown that only epsin full length overexpression can enhance cell migration, but the ENTH domain alone cannot. Among the three Epsin paralogs, epsin 3 followed by epsin 2 were able to substantially enhance cell migration. This study is the first one to systematically and comprehensibly address the contribution of different motifs within the epsin C-terminus to enhance protein localization and cell migration. We show that is not the lipid-binding ENTH domain, but the C-terminus of epsin the one playing a major role in epsin association with sites of endocytosis. Further, we dissected the contribution of individual C-terminal endocytic (clathrin-, AP2-, Ubiquitin- and EH domain-binding) motifs for epsin localization. We found that while all motifs show a degree of synergism, the clathrin-binding motifs are the most important for epsin localization. Our study also showed that, these motifs (particularly the clathrin binding site) play an important role in sustaining endocytic site dynamics and cell migration.