1. Src42 binding activity regulates Drosophila RAF by a novel CNK-dependent derepression mechanism.
- Author
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Laberge G, Douziech M, and Therrien M
- Subjects
- Adaptor Proteins, Signal Transducing chemistry, Adaptor Proteins, Signal Transducing genetics, Amino Acid Sequence, Animals, Drosophila genetics, Drosophila growth & development, Drosophila metabolism, Drosophila Proteins chemistry, Drosophila Proteins genetics, Enzyme Activation, Eye growth & development, In Vitro Techniques, MAP Kinase Signaling System, Models, Biological, Molecular Sequence Data, Mutation, Phosphorylation, Protein Binding, Protein-Tyrosine Kinases chemistry, Protein-Tyrosine Kinases genetics, Proto-Oncogene Proteins pp60(c-src) chemistry, Proto-Oncogene Proteins pp60(c-src) genetics, Recombinant Proteins chemistry, Recombinant Proteins genetics, Recombinant Proteins metabolism, Sequence Homology, Amino Acid, Tyrosine chemistry, raf Kinases chemistry, raf Kinases genetics, src Homology Domains, Adaptor Proteins, Signal Transducing metabolism, Drosophila Proteins metabolism, Protein-Tyrosine Kinases metabolism, Proto-Oncogene Proteins pp60(c-src) metabolism, raf Kinases metabolism
- Abstract
Connector enhancer of KSR (CNK), an essential component of Drosophila receptor tyrosine kinase/mitogen-activated protein kinase pathways, regulates oppositely RAF function. This bimodal property depends on the N-terminal region of CNK, which integrates RAS activity to stimulate RAF and a bipartite element, called the RAF-inhibitory region (RIR), which binds and inhibits RAF catalytic activity. Here, we show that the repressive effect of the RIR is counteracted by the ability of Src42 to associate, in an RTK-dependent manner, with a conserved region located immediately C-terminal to the RIR. Strikingly, we found that several cnk loss-of-function alleles have mutations clustered in this area and provide evidence that these mutations impair Src42 binding. Surprisingly, the derepressing effect of Src42 does not appear to involve its catalytic function, but critically depends on the ability of its SH3 and SH2 domains to associate with CNK. Together, these findings suggest that the integration of RTK-induced RAS and Src42 signals by CNK as a two-component input is essential for RAF activation in Drosophila.
- Published
- 2005
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