Abstract
Raf-1 is a regulator of cellular proliferation, differentiation, and apoptosis. Activation of the Raf-1 kinase activity is tightly regulated and involves targeting to the membrane by Ras and phosphorylation by various kinases, including the tyrosine kinase Src. Here we demonstrate that the connector enhancer of Ksr1, CNK1, mediates Src-dependent tyrosine phosphorylation and activation of Raf-1. CNK1 binds preactivated Raf-1 and activated Src and forms a trimeric complex. CNK1 regulates the activation of Raf-1 by Src in a concentration-dependent manner typical for a scaffold protein. Down-regulation of endogenously expressed CNK1 by small inhibitory RNA interferes with Src-dependent activation of ERK. Thus, CNK1 allows cross-talk between Src and Raf-1 and is essential for the full activation of Raf-1.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Base Sequence
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Cell Line
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DNA Primers
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Dimerization
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Humans
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Immunoprecipitation
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Intracellular Signaling Peptides and Proteins / chemistry
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Intracellular Signaling Peptides and Proteins / metabolism
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Intracellular Signaling Peptides and Proteins / physiology*
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Mitogen-Activated Protein Kinases / metabolism
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Phosphorylation
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Protein Binding
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Proto-Oncogene Proteins c-raf / metabolism
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Proto-Oncogene Proteins c-raf / physiology*
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Proto-Oncogene Proteins pp60(c-src) / metabolism
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Proto-Oncogene Proteins pp60(c-src) / physiology*
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Vascular Endothelial Growth Factor A / metabolism
Substances
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CNKSR1 protein, human
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DNA Primers
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Intracellular Signaling Peptides and Proteins
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Vascular Endothelial Growth Factor A
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Proto-Oncogene Proteins pp60(c-src)
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Proto-Oncogene Proteins c-raf
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Mitogen-Activated Protein Kinases