| First Author | Köhler M | Year | 2016 |
| Journal | EMBO J | Volume | 35 |
| Issue | 2 | Pages | 143-61 |
| PubMed ID | 26657898 | Mgi Jnum | J:229687 |
| Mgi Id | MGI:5753003 | Doi | 10.15252/embj.201592097 |
| Citation | Kohler M, et al. (2016) Activation loop phosphorylation regulates B-Raf in vivo and transformation by B-Raf mutants. EMBO J 35(2):143-61 |
| abstractText | Despite being mutated in cancer and RASopathies, the role of the activation segment (AS) has not been addressed for B-Raf signaling in vivo. Here, we generated a conditional knock-in mouse allowing the expression of the B-Raf(AVKA) mutant in which the AS phosphoacceptor sites T599 and S602 are replaced by alanine residues. Surprisingly, despite producing a kinase-impaired protein, the Braf(AVKA) allele does not phenocopy the lethality of Braf-knockout or paradoxically acting knock-in alleles. However, Braf(AVKA) mice display abnormalities in the hematopoietic system, a distinct facial morphology, reduced ERK pathway activity in the brain, and an abnormal gait. This phenotype suggests that maximum B-Raf activity is required for the proper development, function, and maintenance of certain cell populations. By establishing conditional murine embryonic fibroblast cultures, we further show that MEK/ERK phosphorylation and the immediate early gene response toward growth factors are impaired in the presence of B-Raf(AVKA). Importantly, alanine substitution of T599/S602 impairs the transformation potential of oncogenic non-V600E B-Raf mutants and a fusion protein, suggesting that blocking their phosphorylation could represent an alternative strategy to ATP-competitive inhibitors. |
