Functional heterogeneity of proto-oncogene tyrosine kinases: the C terminus of the human epidermal growth factor receptor facilitates cell proliferation.
Previous reports have indicated that the C termini of the membrane-associated tyrosine kinases encoded by c-src and c-fms proto-oncogenes have a negative effect on their biological activity and that this effect is mediated by their C-terminal tyrosine residue. To determine whether this was true for the human epidermal growth factor (EGF) receptor, which is also a membrane-associated tyrosine kinase proto-oncogene, we have constructed two premature termination mutants, dc19 and dc63, that delete the C-terminal 19 and 63 amino acids, respectively, from the human full-length receptor (hEGFR). The smaller deletion removes the C-terminal tyrosine residue, while the larger deletion removes the two most C-terminal tyrosines; similar deletions are found in v-erbB. As previously shown for the gene encoding the full-length EGF receptor, the two C-terminal mutants induced EGF-dependent focal transformation and anchorage-independent growth of NIH 3T3 cells. However, both dc19 and dc63 were quantitatively less efficient than the gene encoding the full-length receptor, with dc63 being less active than dc19. Although the C-terminal mutants displayed lower biological activity than the gene encoding the full-length receptor, the mutant receptors were found to be similar in several respects to the full-length receptor. These parameters included receptor localization, stability in the absence of EGF, receptor half-life in the presence of EGF, EGF binding, extent of EGF-dependent autophosphorylation in vitro, and EGF-dependent phosphorylation of an exogenous substrate in vitro. Therefore, the C-terminal 63 amino acids of the human receptor have no detectable influence on EGF-dependent early events. We conclude that in contrast
Velu
T J
TJ
Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, Maryland 20892.
Vass
W C
WC
Lowy
D R
DR
Beguinot
L
L
D000818:Animals; D002455:Cell Division; D002478:Cells, Cultured; D002872:Chromosome Deletion; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000235:genetics / Q000502:physiology*; D006801:Humans; D009154:Mutation; D010641:Phenotype; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000502:physiology*; D000090063:Proto-Oncogene Mas; D011519:Proto-Oncogenes; D014162:Transfection
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases