1. Raf Activation Is Regulated by Tyrosine 510 Phosphorylation in Drosophila
- Author
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Xia, Fan, Li, Jinghong, Hickey, Gavin W, Tsurumi, Amy, Larson, Kimberly, Guo, Dongdong, Yan, Shian-Jang, Silver-Morse, Louis, and Li, Willis X
- Subjects
Genetics ,Generic health relevance ,Animals ,Cell Line ,Drosophila Proteins ,Drosophila melanogaster ,Enzyme Activation ,Gene Expression Regulation ,Developmental ,Glutamic Acid ,Phosphorylation ,Phosphotyrosine ,Protein-Tyrosine Kinases ,Proto-Oncogene Proteins ,Signal Transduction ,raf Kinases ,ras Proteins ,Biological Sciences ,Agricultural and Veterinary Sciences ,Medical and Health Sciences ,Developmental Biology - Abstract
The proto-oncoprotein Raf is pivotal for mitogen-activated protein kinase (MAPK) signaling, and its aberrant activation has been implicated in multiple human cancers. However, the precise molecular mechanism of Raf activation, especially for B-Raf, remains unresolved. By genetic and biochemical studies, we demonstrate that phosphorylation of tyrosine 510 is essential for activation of Drosophila Raf (Draf), which is an ortholog of mammalian B-Raf. Y510 of Draf is phosphorylated by the c-src homolog Src64B. Acidic substitution of Y510 promotes and phenylalanine substitution impairs Draf activation without affecting its enzymatic activity, suggesting that Y510 plays a purely regulatory role. We further show that Y510 regulates Draf activation by affecting the autoinhibitory interaction between the N- and C-terminal fragments of the protein. Finally, we show that Src64B is required for Draf activation in several developmental processes. Together, these results suggest a novel mechanism of Raf activation via Src-mediated tyrosine phosphorylation. Since Y510 is a conserved residue in the kinase domain of all Raf proteins, this mechanism is likely evolutionarily conserved.
- Published
- 2008