The Src family kinase Hck interacts with Bcr-Abl by a kinase-independent mechanism and phosphorylates the Grb2-binding site of Bcr.

bcr-abl, the oncogene causing chronic myeloid leukemia, encodes a fusion protein with constitutively active tyrosine kinase and transforming capacity in hematopoietic cells. Various intracellular signaling intermediates become activated and/or associate by/with Bcr-Abl, including the Src family kinase Hck. To elucidate some of the structural requirements and functional consequences of the ...
association of Bcr-Abl with Hck, their interaction was investigated in transiently transfected COS7 cells. Neither the complex formation of Hck kinase with Bcr-Abl nor the activation of Hck by Bcr-Abl was dependent on the Abl kinase activity. Both inactivating point mutations of Hck and dephosphorylation of Hck enhanced its complex formation with Bcr-Abl, indicating that their physical interaction was negatively regulated by Hck (auto)phosphorylation. Finally, experiments with a series of kinase negative Bcr-Abl mutants showed that Hck phosphorylated Bcr-Abl and induced the binding of Grb2 to Tyr177 of Bcr-Abl. Taken together, our results suggest that Bcr-Abl preferentially binds inactive forms of Hck by an Abl kinase-independent mechanism. This physical interaction stimulates the Hck tyrosine kinase, which may then phosphorylate the Grb2-binding site in Bcr-Abl.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Animals, Binding Sites, COS Cells, Fusion Proteins, bcr-abl, GRB2 Adaptor Protein, Humans, Phosphorylation, Point Mutation, Protein-Tyrosine Kinases, Proteins, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-hck, Proto-Oncogene Proteins pp60(c-src), Receptor, Epidermal Growth Factor
J. Biol. Chem.
Date: Dec. 26, 1997
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