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A single autophosphorylation site confers oncogenicity to the Neu/ErbB-2 receptor and enables coupling to the MAP
R Ben-Levy1, H F Paterson, C J Marshall
1Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel.
Abstract:
The transforming potential of the Neu/ErbB-2 receptor tyrosine kinase undergoes inactivation by deletion of the non-catalytic C-terminal tail, which contains five autophosphorylation sites. To determine which site is essential for oncogenicity, we tailed the C-terminally-deleted mutant with individual autophosphorylation sites. Complete restoration of the transforming action in vitro and in vivo was conferred by a stretch of 12 amino acids that contained the most C-terminal tyrosine autophosphorylation site (Y1253). Reconstitution of transformation was specific to this amino acid sequence because none of the other autophosphorylation sites, when grafted individually, caused transformation, and replacement of the tyrosine with a phenylalanine residue significantly reduced the oncogenic potential of both the full-length and the tailed proteins. When present alone the most C-terminal sequence enabled coupling to a biochemical pathway that includes Ras, MAP kinase and transactivation of Jun. These results indicate that the multiplicity of autophosphorylation sites on a receptor tyrosine kinase is not essential for transformability, and implicate the MAP kinase pathway in transduction of the oncogenic signal of Neu/ErbB-2.
Insights
The Neu/ErbB-2 receptor tyrosine kinase
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- The Neu/ErbB-2 receptor tyrosine kinase plays a crucial role in cell transformation and oncogenesis.
- Its transforming potential is regulated by autophosphorylation sites within its C-terminal tail.
- Deletion of this tail inactivates the receptor's oncogenic activity.
Purpose of the Study:
- To identify the specific autophosphorylation site(s) essential for Neu/ErbB-2-mediated oncogenicity.
- To elucidate the downstream signaling pathways involved in Neu/ErbB-2-induced transformation.
Main Methods:
- Constructing C-terminally-deleted Neu/ErbB-2 mutants.
- Reintroducing individual autophosphorylation sites into the deleted mutants.
- Assessing the transforming potential of these mutants in vitro and in vivo.
- Investigating the involvement of Ras-MAP kinase pathway components.
Main Results:
- A 12-amino acid sequence containing the C-terminal tyrosine autophosphorylation site (Y1253) fully restored transforming activity.
- Other autophosphorylation sites individually failed to confer transformation.
- Mutation of Y1253 to phenylalanine significantly reduced oncogenic potential.
- The Y1253-containing sequence activated the Ras-MAP kinase pathway, leading to Jun transactivation.
Conclusions:
- The multiplicity of autophosphorylation sites is not required for receptor tyrosine kinase transformability.
- The C-terminal autophosphorylation site Y1253 is critical for Neu/ErbB-2 oncogenicity.
- The MAP kinase pathway is implicated in transducing the oncogenic signal of Neu/ErbB-2.