Coexistence of phosphotyrosine-dependent and -independent interactions between Cbl and Bcr-Abl

Isabelle Gaston, Kara J. Johnson, Tsukasa Oda, Arun Bhat, Margaret Reis, Wallace Langdon, Lei Shen, Michael W. Deininger, Brian J. Druker

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Objectives. Cbl is one of the major tyrosine-phosphorylated proteins in Bcr-Abl-expressing cells. A direct association between the SH2 domain of Bcr-Abl and tyrosine-phosphorylated Cbl has been demonstrated. The purpose of this study was to determine if and how unphosphorylated Cbl and Bcr-Abl may associate. Methods. Interactions between Cbl and Bcr-Abl were investigated in yeast two- and three-hybrid systems, gel overlay assays, and immunoprecipitates from mammalian cells expressing wild-type and the Y177F mutant of Bcr-Abl. Results. No direct interaction between Bcr-Abl and unphosphorylated Cbl was observed. Bcr-Abl did, however, associate with Grb2, an adaptor protein that binds tyrosine 177 of Bcr-Abl. Additionally, Grb2 interacted with Cbl. In a yeast three-hybrid assay, Grb2 mediated an interaction between Cbl and Bcr-Abl that was dependent on a functional Grb2 binding site. This interaction was confirmed in vitro using purified proteins. In cells expressing Bcr-Abl with a mutation in the Grb2 binding site, binding of Cbl to Bcr-Abl was significantly reduced, but Cbl tyrosine phosphorylation was maintained. Imatinib treatment of these cells further reduced but did not abrogate Cbl binding, reflecting residual kinase activity. Conclusion. Multiple phosphotyrosine-dependent and -independent interactions stabilize the interaction between Cbl and Abl. Grb2 or another, yet unidentified, protein may mediate an initial interaction between Cbl and Bcr-Abl that is independent of Cbl tyrosine phosphorylation. Following this initial interaction, Cbl can then become tyrosine phosphorylated and interact with the SH2 domain of Bcr-Abl, further stabilizing the complex.

Original languageEnglish (US)
Pages (from-to)113-121
Number of pages9
JournalExperimental hematology
Volume32
Issue number1
DOIs
StatePublished - Jan 2004

ASJC Scopus subject areas

  • Molecular Biology
  • Hematology
  • Genetics
  • Cell Biology
  • Cancer Research

Fingerprint Dive into the research topics of 'Coexistence of phosphotyrosine-dependent and -independent interactions between Cbl and Bcr-Abl'. Together they form a unique fingerprint.

  • Cite this

    Gaston, I., Johnson, K. J., Oda, T., Bhat, A., Reis, M., Langdon, W., Shen, L., Deininger, M. W., & Druker, B. J. (2004). Coexistence of phosphotyrosine-dependent and -independent interactions between Cbl and Bcr-Abl. Experimental hematology, 32(1), 113-121. https://doi.org/10.1016/j.exphem.2003.09.018