Global Phosphoproteomics Reveals Crosstalk Between Bcr-Abl and Negative Feedback Mechanisms Controlling Src Signaling

Crump Institute for Molecular Imaging, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.
Science Signaling (Impact Factor: 6.28). 07/2011; 4(166):ra18. DOI: 10.1126/scisignal.2001314
Source: PubMed


In subtypes and late stages of leukemias driven by the tyrosine kinase fusion protein Bcr-Abl, signaling by the Src family kinases (SFKs) critically contributes to the leukemic phenotype. We performed global tyrosine phosphoprofiling by quantitative mass spectrometry of Bcr-Abl-transformed cells in which the activities of the SFKs were perturbed to build a detailed context-dependent network of cancer signaling. Perturbation of the SFKs Lyn and Hck with genetics or inhibitors revealed Bcr-Abl downstream phosphorylation events either mediated by or independent of SFKs. We identified multiple negative feedback mechanisms within the network of signaling events affected by Bcr-Abl and SFKs and found that Bcr-Abl attenuated these inhibitory mechanisms. The C-terminal Src kinase (Csk)-binding protein Pag1 (also known as Cbp) and the tyrosine phosphatase Ptpn18 both mediated negative feedback to SFKs. We observed Bcr-Abl-mediated phosphorylation of the phosphatase Shp2 (Ptpn11), and this may contribute to the suppression of these negative feedback mechanisms to promote Bcr-Abl-activated SFK signaling. Csk and a kinase-deficient Csk mutant both produced similar globally repressive signaling consequences, suggesting a critical role for the adaptor protein function of Csk in its inhibition of Bcr-Abl and SFK signaling. The identified Bcr-Abl-activated SFK regulatory mechanisms are candidates for dysregulation during leukemia progression and acquisition of SFK-mediated drug resistance.

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Available from: Matteo Pellegrini, Jan 12, 2014
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    • "PTPN18 is an interesting candidate for several reasons. First, it is involved in the negative feedback mechanisms controlling the Bcr-Abl fusion tyrosine kinase-signalling network by inhibiting the phosphorylation of Src family kinase (Rubbi et al, 2011). Second, PTPN18 can induce actin cytoskeleton reorganisation (Shiota et al, 2003), suggesting a plausible explanation of the morphological changes observed in the imatinib-resistant GIST cells (Mahadevan et al, 2007). "
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    • "Metformin increases amyloid-␤ production and secretion by AMPK activation and increased BACE1 level, suggesting that it is potentially accelerating Alzheimer's manifestation in patients with T2D [12]. Phosphoproteomic analysis is particularly useful in recognizing the alteration of signaling pathways by a drug [13] [14]. Herein, we determined the alteration of phosphoproteome in the brain of metformin-administrated mice to understand the action of metformin in the CNS. "
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    • "The protein Cbp/PAG1 [15,17,18] is a scaffold molecule involved in recruiting both the inhibitory kinase Csk, which inturn also recruits the inhibitory phosphatase PTPN18 [93], as well as E3 ubiquitin ligase SOCS1 to active Lyn, via facilitating the enzymatic inactivation of Lyn (through Csk phosphorylation of the C-terminal tyrosine of Lyn, and PTPN18 dephosphorylation of the activation loop motif) as well as degradation of Lyn via the proteasome through its poly-ubiquitination mediated by SOCS1. In these CML cells the Bcr-Abl kinase overpowers the negative feedback loops initiated by its activation of Lyn through activation of the phosphatase Shp2 that is able to dephosphorylate Cbp/PAG1 thus mitigating its ability to turn off the Lyn signals [92]. It is also very interesting to note that the second generation (T315I non-effective, e.g. "
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