Direct interaction of Cbl with pTyr 1045 of the EGF receptor (EGFR) is required to sort the EGFR to lysosomes for degradation

Mutation of the binding site for Cb1 (Tyr1045) in the EGF receptor (EGFR) results in impaired ubiquitination but does not affect EGFR internalization. However, the Y1045F mutation resulted in strongly decreased degradation of the EGFR, as well as efficient recycling of EGER to the plasma membrane. Significantly, more wild-type EGFR than Y1045F EGER was found localizing to multivesicular late endosomes. Ubiquitination of the EGFR was in HeLa cells inhibited both upon overexpressing the N-terminal part of Cb1 and upon overexpressing a double mutant Grb2 incapable of interacting with Cb1 and thereby being incapable of indirectly recruiting Cb1 to the EGER. Collectively, these data suggest that the ubiquitination resulting from direct binding of Cb1 to pTyr1045 of the EGFR is critical for lysosomal sorting of the EGER in contrast to ubiquitination resulting from Grb2-mediated binding of Cb1 to the EGFR. (C) 2004 Elsevier Inc. All rights reserved.