Abstract
Bcr-Abl is a dysregulated tyrosine kinase whose mechanism of activation is unclear. Here, we demonstrate that, like c-Abl, Bcr-Abl is negatively regulated through its SH3 domain. Kinase activity, transformation, and leukemogenesis by Bcr-Abl are greatly impaired by mutations of the Bcr coiled-coil domain that disrupt oligomerization, but restored by an SH3 point mutation that blocks ligand binding or a complementary mutation at the intramolecular SH3 binding site defined in c-Abl. Phosphorylation of tyrosines in the activation loop of the catalytic domain and the linker between the SH2 and catalytic domains (SH2-CD linker) is dependent on oligomerization and required for leukemogenesis. These results suggest that Bcr-Abl has a monomeric, unphosphorylated state with the SH3 domain engaged intramolecularly to Pro1124 in the SH2-CD linker, the form that is sensitive to the inhibitor imatinib (STI-571). The sole function of the coiled-coil domain is to disrupt the autoinhibited conformation through oligomerization and intermolecular autophosphorylation.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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3T3 Cells
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Alanine / genetics
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Alanine / metabolism
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Amino Acid Sequence / genetics
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Animals
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Binding Sites / genetics
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Catalytic Domain / drug effects
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Catalytic Domain / genetics
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Cell Transformation, Neoplastic / genetics
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Cell Transformation, Neoplastic / metabolism*
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Enzyme Inhibitors / pharmacology
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Eukaryotic Cells / enzymology*
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Feedback, Physiological / drug effects
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Feedback, Physiological / genetics*
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Fusion Proteins, bcr-abl
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Humans
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Leukemia, Myelogenous, Chronic, BCR-ABL Positive / enzymology*
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Leukemia, Myelogenous, Chronic, BCR-ABL Positive / genetics
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Mice
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Mice, Inbred BALB C
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Models, Molecular
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Mutation / drug effects
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Mutation / genetics
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Phosphorylation / drug effects
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Proline / genetics
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Proline / metabolism
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Protein Binding / drug effects
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Protein Binding / genetics
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Protein Structure, Tertiary / drug effects
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Protein Structure, Tertiary / genetics
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Protein-Tyrosine Kinases / antagonists & inhibitors
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Protein-Tyrosine Kinases / genetics
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Protein-Tyrosine Kinases / metabolism*
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Tyrosine / metabolism
Substances
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Enzyme Inhibitors
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Tyrosine
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Proline
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Protein-Tyrosine Kinases
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Fusion Proteins, bcr-abl
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Alanine