Serine mutations that abrogate ligand-induced ubiquitination and internalization of the EGF receptor do not affect c-Cbl association with the receptor.
In the present study, we examined EGF-induced internalization, degradation and trafficking of the epidermal growth factor receptor (EGFR) mutated at serines 1046, 1047, 1057 and 1142 located in its cytoplasmic carboxy-terminal region. We found the serine-mutated EGFR to be inhibited in EGF-induced internalization and degradation in NIH3T3 cells. We therefore tested the hypothesis that these mutations affect ligand-induced c-Cbl association with the receptor, leading to inhibited receptor ubiquitination. EGF was unable to induce ubiquitination of the serine-mutated EGFR, yet EGF-induced phosphorylation of the c-Cbl-binding site at tyrosine 1045, and c-Cbl-EGFR association, was unaffected. To compare the relevance of these serine residues with tyrosine 1045 in their regulation of c-Cbl binding and receptor ubiquitination, we analysed an EGFR mutated at tyrosine 1045 (Y1045F). EGF-induced c-Cbl-EGFR binding was partially inhibited, and receptor ubiquitination was abrogated in cells expressing Y1045F-EGFR. In contrast, ligand-induced internalization and degradation of the Y1045F mutant was similar to that of wild-type EGFR. Together, our data indicate that the serine residues and tyrosine 1045 are essential for EGF-induced receptor ubiquitination, but only the serine residues are critical for EGFR internalization and degradation.
Oksvold
Morten P
MP
Department of Pathology, University of Western Australia, Queen Elizabeth II Medical Center, Nedlands, Western Australia 6009, Australia. m.p.oksvold@labmed.uio.no
Thien
Christine B F
CB
Widerberg
Jannicke
J
Chantry
Andrew
A
Huitfeldt
Henrik S
HS
Langdon
Wallace Y
WY
D019943:Amino Acid Substitution; D000818:Animals; D066246:ErbB Receptors / Q000235:genetics* / Q000378:metabolism; D008024:Ligands; D051379:Mice; D009154:Mutation; D041681:NIH 3T3 Cells; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D050721:Proto-Oncogene Proteins c-cbl; D012694:Serine / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases
D008024:Ligands; D011518:Proto-Oncogene Proteins; D025801:Ubiquitin; D014443:Tyrosine; D012694:Serine; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; D066246:ErbB Receptors; C493849:Cbl protein, mouse