Raf activation is regulated by tyrosine 510 phosphorylation in Drosophila

• Published in: PLoS biology 2008-05, Vol.6 (5), p.e128-e128
• Main Authors: Xia, Fan, Li, Jinghong, Hickey, Gavin W, Tsurumi, Amy, Larson, Kimberly, Guo, Dongdong, Yan, Shian-Jang, Silver-Morse, Louis, Li, Willis X
• Format: Article
• Language: English
• Subjects: Animals; Cell Biology; Cell Line; Drosophila; Drosophila melanogaster - enzymology; Drosophila melanogaster - metabolism; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; Enzyme Activation; Enzymes; Gene Expression Regulation, Developmental; Glutamic Acid - metabolism; Kinases; Medical research; Metazoa; Mutation; Phosphorylation; Phosphotyrosine - metabolism; Protein-Tyrosine Kinases - genetics; Protein-Tyrosine Kinases - metabolism; Proteins; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins - metabolism; raf Kinases - genetics; raf Kinases - metabolism; ras Proteins - metabolism; Signal Transduction
• ISSN: 1545-7885; 1544-9173; 1545-7885
• DOI: 10.1371/journal.pbio.0060128

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.