Identification of EGF receptor C-terminal sequences 1005–1017 and di-leucine motif 1010LL 1011 as essential in EGF receptor endocytosis

Abstract

Most studies regarding the role of epidermal growth factor (EGF) receptor (EGFR) C-terminal domain in EGFR internalization are done in the context of EGFR kinase activation. We recently showed that EGF-induced EGFR internalization is directly controlled by receptor dimerization, rather than kinase activation. Here we studied the role of EGFR C-terminus in EGF-induced EGFR internalization with or without EGFR kinase activation. We showed that graduate truncation of EGFR from C-terminus to 1044 did not affect EGF-induced EGFR endocytosis with or without kinase activation. However, truncation to 991 or further completely inhibited EGFR endocytosis. Graduate truncation within 991–1044 progressively lower EGF-induced EGFR endocytosis with most significant effects observed for residues 1005–1017. The endocytosis patterns of mutant EGFRs are independent of EGFR kinase activation. The residues 1005–1017 were also required for EGFR internalization triggered by non-ligand-induced receptor dimerization. This indicates that residues 1005–1017 function as an internalization motif, rather than a dimerization motif, to mediate EGFR internalization. Furthermore, we showed that the di-leucine motif 1010LL 1011 within this region is essential in mediating EGF-induced rapid EGFR internalization independent of kinase activation. We conclude that EGFR C-terminal sequences 1005–1017 and the 1010LL 1011 motif are essential for EGF-induced EGFR endoytosis independent of EGFR kinase activation and autophosphorylation.