Tyrosine kinase activity of the EGF receptor is enhanced by the expression of oncogenic 70Z-Cbl

Christine Thien, Wallace Langdon

Research output: Contribution to journalArticle

55 Citations (Scopus)


The 120kD product of the c-Cbl oncogene is a prominent substrate of protein tyrosine kinases that lacks a known catalytic activity but possesses an array of binding sites for cytoplasmic signalling proteins, An oncogenic form of Cbl was recently identified in the 70Z/3 pre-B cell lymphoma which has a small deletion at the N-terminus of the Ring finger domain. This form of Cbl, termed 70Z-Cbl, exhibits an enhanced level of tyrosine phosphorylation compared with c-Cbl, Here we demonstrate that the expression of 70Z-Cbl induces a tenfold enhancement in the kinase activity of the EGF receptor in serum-starved and EGF-stimulated cells, In serum-starved cells this results in EGF receptor autophosphorylation and the recruitment of Grb2, Shc and Sos1 but does not induce a corresponding increase in MAP kinase activity, Furthermore the expression of 70Z-Cbl greatly enhances EGF-induced tyrosine phosphorylation of the protein tyrosine phosphatase SHP-2, We also show that the Cbl/EGF receptor complex is predominantly associated with CrkII and is distinct to the Grb2/Shc/Sos1 complex that associates with the EGF receptor. These findings therefore demonstrate a biochemical effect of an oncogenic Cbl protein and support predictions from C, elegans that Cbl functions as regulator of receptor tyrosine kinases.
Original languageEnglish
Pages (from-to)2909-2919
Publication statusPublished - 1997

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