c-Abl Has High Intrinsic Tyrosine Kinase Activity That Is Stimulated by Mutation of the Src Homology 3 Domain and by Autophosphorylation at Two Distinct Regulatory Tyrosines

Abstract

Titlec-Abl has high intrinsic tyrosine kinase activity that is stimulated by mutation of the Src homology 3 domain and by autophosphorylation at two distinct regulatory tyrosines. c-Abl is a non-receptor tyrosine kinase of which the precise functions are not known, but roles for Abl in growth factor and integrin signaling, cell cycle regulation, neurogenesis, and responses to DNA damage and oxidative stress have been suggested (1). c-Abl kinase activity is increased in vivo by diverse physiological stimuli including ionizing radiation (2), entry into S phase (3), integrin activation (4), and platelet-derived growth factor stimulation (5). The mechanism of regulation of Abl tyrosine kinase activity by these processes is not well understood. Ionizing radiation may activate Abl kinase activity through phosphorylation of the Abl catalytic domain at Ser-465 by the Atm kinase (6), whereas platelet-derived growth factor stimulation is associated with tyrosine phosphorylation of cAbl by c-Src (5). In contrast, the activation of nuclear c-Abl in S phase is through the detachment of the inhibitor Rb protein (3), whereas Abl may be activated by free radicals through dissociation of Pag/Msp23, an antioxidant protein that also inhibits Abl (7). Abl kinase activity can also be stimulated by the binding of several activator proteins, including the transcription factors c-Jun (8) and RFX1 (9), and the adapter protein Nck (10). These observations suggest complex regulation of c-Abl at multiple levels through binding or dissociation of activators and inhibitors and via direct phosphorylation.Although the NH 2 -terminal sequence of c-Abl is very similar to members of the Src family, biochemical and genetic studies suggest that the structural basis of regulation of c-Abl catalytic activity is significantly different from the catalytic activity of Src. When co-expressed with another kinase, such as Csk, that can phosphorylate the COOH-terminal regulatory tyrosine 527, c-Src (and the Src family member Hck) can be purified as an inactive monomer in which the phosphorylated Tyr-527 residue binds the SH2 1 domain in an intramolecular fashion. In this structure, the SH3 domain contacts the linker region between SH2 and the catalytic domain (the SH2-CD linker) in an atypical interaction involving a single proline (Pro-250) (11,12). Mutation or deletion of 14) or mutation of the SH2 or SH3 domains (15, 16) dysregulates and increases Src kinase activity both in vitro and in vivo. The precise mechanism of physiological activation of Src kinases is unknown, but in vitro studies demonstrate that activation may involve discrete steps that independently increase catalytic activity. In the presence of ATP and magnesium, Src or Hck that is monophosphorylated at the Tyr-527 homologue undergoes slow autophosphorylation at Tyr-412 that increases kinase activity about 10-fold (17-19). Dissociation of the SH2-Tyr-527 interaction by dephosphorylation or a competing SH2 ligand stimulates activity 2.5-fold, whereas the disruption of the SH3-linker interac...

c-ABL tyrosine kinase stabilizes RAD51 chromatin association

“…Interestingly, we detected the phosphorylation of Tyr-54 and Tyr-315 by c-ABL only in the chromatin fraction. This is consistent with the findings that c-ABL auto-phosphorylation, which is required for c-ABL activation [22,23], is detected only in the chromatin fraction, as described above. To test the generality of this finding that c-ABL restore the defective chromatin association of selfassociation-defective RAD51-R167G, GFP-tagged RAD51-WT or RAD51-F86E were transiently co-expressed with Flag-tagged c-ABL-wt or c-ABL-kd in 293T cells and the cytoplasmic and chromatin fractions were subjected to immunoblot analysis.…”

Oncogenic activation of c-Abl in non-small cell lung cancer cells lacking FUS1 expression: inhibition of c-Abl by the tumor suppressor gene product Fus1

“…Functional interaction of wild-type Fus1 and c-Abl was shown in cells by co-expression assays in COS1 cells (Figure 3). Phosphorylation of tyrosine 412 is a critical step that leads to the activation of c-Abl kinase (Brasher and Van Etten, 2000). Co-expression of wild-type FUS1 and c-ABL led to a significant decrease in both the total (Kondo et al, 2001), or the EV (Figure 3).…”

F-actin-binding domain of c-Abl regulates localized phosphorylation of C3G: role of C3G in c-Abl-mediated cell death

“…SH3 domain deletion or mutation results in its activation (Brasher and Van Etten, 2000;Wang, 2004). Phosphorylation of Y412 and Y245 of c-Abl corresponds with its activation.…”