Regulation of EGFR endocytosis by CBL during mitosis

Abstract

Endocytosis plays important roles in regulating EGFR signaling. We previously found that EGFR endocytosis during mitosis is mediated differently than during interphase. While the regulation of EGFR endocytosis in interphase is well understood, little is known regarding the regulation of EGFR endocytosis during mitosis. Here, we studied the mechanisms regulating mitotic EGFR endocytosis. We found that contrary to interphase cells, mitotic EGFR endocytosis is more reliant on the activation of the E3 ligase CBL. At high EGF doses, inhibition of inhibited EGFR endocytosis of mitotic cells, but not of interphase cells. Moreover, the endocytosis of mutant EGFR Y1045F-YFP was strongly delayed. The endocytosis of truncated EGFR {Delta}1044-YFP that does not bind to CBL was completely inhibited. EGF induced stronger ubiquitination of mitotic EGFR than interphase EGFR and mitotic EGFR is trafficked to lysosome for degradation. Furthermore, during mitosis low doses of EGF also stimulate EGFR endocytosis by NCE. Contrary to interphase, CBL and the CBL-binding regions of EGFR were required for mitotic EGFR endocytosis at low doses. This may be due to the mitotic ubiquitination of the EGFR even at low EGF doses. In conclusion, mitotic EGFR endocytosis solely proceed through CBL-mediated NCE.