Activation of B-Raf kinase requires phosphorylation of the conserved residues Thr598 and Ser601
AUTOR(ES)
Zhang, Bao-Hong
FONTE
Oxford University Press
RESUMO
The Raf kinase family serves as a central intermediate to relay signals from Ras to ERK. The precise molecular mechanism for Raf activation is still not fully understood. Here we report that phosphorylation of Thr598 and Ser601, which lie between kinase subdomains VII and VIII, is essential for B-Raf activation by Ras. Substitution of these residues by alanine (B-RafAA) abolished Ras-induced B-Raf activation without altering the association of B-Raf with other signaling proteins. Phosphopeptide mapping and immunoblotting with phospho-specific antibodies confirmed that Thr598 and Ser601 are in vivo phosphorylation sites induced by Ras. Furthermore, replacement of these two sites by acidic residues (B-RafED) renders B-Raf constitutively active. Con sistent with these data, B-RafAA and B-RafED exhibited diminished and enhanced ability, respectively, to stimulate ERK activation and Elk-dependent transcription. Moreover, functional studies revealed that B-RafED was able to promote NIH 3T3 cell transformation and PC12 cell differentiation. Since Thr598 and Ser601 are conserved in all Raf family members from Caenorhabditis elegans to mammals, we propose that phosphorylation of these two residues may be a general mechanism for Raf activation.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=314015Documentos Relacionados
- Activation of MEK family kinases requires phosphorylation of two conserved Ser/Thr residues.
- Protein Kinase A and B-Raf Mediate Extracellular Signal-Regulated Kinase Activation by Thyrotropin
- Activation of B-Raf and Regulation of the Mitogen-activated Protein Kinase Pathway by the Go α chain
- 95-kilodalton B-Raf serine/threonine kinase: identification of the protein and its major autophosphorylation site.
- Differential regulation of Raf-1 and B-Raf and Ras-dependent activation of mitogen-activated protein kinase by cyclic AMP in PC12 cells.