Ley, R., Balmanno, K., Hadfield, K., Weston, C.R. & Cook, S.J. Activation of the ERK1/2 signalling pathway promotes phosphorylation and proteasome-dependent degradation of the BH3-only protein Bim. J. Biol. Chem. 278, 18811-18816

Babraham Institute, Cambridge, England, United Kingdom
Journal of Biological Chemistry (Impact Factor: 4.57). 06/2003; 278(21):18811-6. DOI: 10.1074/jbc.M301010200
Source: PubMed


Both the ERK and phosphatidylinositol 3′-kinase (PI3K) signaling pathways can protect cells from apoptosis following withdrawal
of survival factors. We have previously shown that the ERK1/2 pathway acts independently of PI3K to block expression of
the BH3-only protein, BimEL, and prevent serum withdrawal-induced cell death, although the precise mechanism by which ERK reduced BimEL levels was unclear. By comparing Bim mRNA and Bim protein, expression we now show that the rapid expression of BimEL following serum withdrawal cannot be accounted for simply by increases in mRNA following inhibition of PI3K. In cells maintained
in serum BimEL is a phosphoprotein. We show that activation of the ERK1/2 pathway is both necessary and sufficient to promote BimEL phosphorylation and that this leads to a substantial increase in turnover of the BimEL protein. ERK1/2-dependent degradation of BimEL proceeds via the proteasome pathway because it is blocked by proteasome inhibitors and is defective at the restrictive temperature
in cells with a temperature-sensitive mutation in the E1 component of the ubiquitin-conjugating system. Finally, co-transfection
of BimEL and FLAG-ubiquitin causes the accumulation of polyubiquitinated forms of Bim, and this requires the ERK1/2 pathway. Our
findings provide new insights into the regulation of Bim and the role of the ERK pathway in cell survival.

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Available from: Kathryn Balmanno
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    • "Both the RAF/MEK/ERK and the PI3K/AKT pathways modulate several key apoptotic players thereby transducing a survival signal. The ERK pathway regulates BcL-2, Bad, Mcl-1, Bim, Survivin and Caspase 9 [20], [21], [22]. The PI3K/AKT pathway phosphorylates Bim, Bad, XIAP and p21 [23], [24], [25]. "
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    ABSTRACT: The late endosomal LAMTOR complex serves as a convergence point for both the RAF/MEK/ERK and the PI3K/AKT/mTOR pathways. Interestingly, both of these signalling cascades play a significant role in the aetiology of breast cancer. Our aim was to address the possible role of genetic polymorphisms in LAMTOR2 and LAMTOR3 as genetic risk factors for breast cancer. We sequenced the exons and exon-intron boundaries of LAMTOR2 (p14) and LAMTOR3 (MP1) in 50 prospectively collected pairs of cancerous tissue and blood samples from breast cancer patients and compared their genetic variability. We found one single nucleotide polymorphism (SNP) in LAMTOR2 (rs7541) and two SNPs in LAMTOR3 (rs2298735 and rs148972953) in both tumour and blood samples, but no somatic mutations in cancerous tissues. In addition, we genotyped all three SNPs in 296 samples from the Risk Prediction of Breast Cancer Metastasis Study and found evidence of a genetic association between rs148972953 and oestrogen (ER) and progesterone receptor negative status (PR) (ER: OR = 3.60 (1.15-11.28); PR: OR = 4.27 (1.43-12.72)). However, when we additionally genotyped rs148972953 in the MARIE study including 2,715 breast cancer cases and 5,216 controls, we observed neither a difference in genotype frequencies between patients and controls nor was the SNP associated with ER or PR. Finally, all three SNPs were equally frequent in breast cancer samples and female participants (n = 640) of the population-based SAPHIR Study. The identified polymorphisms in LAMTOR2 and LAMTOR3 do not seem to play a relevant role in breast cancer. Our work does not exclude a role of other not yet identified SNPs or that the here annotated polymorphism may in fact play a relevant role in other diseases. Our results underscore the importance of replication in association studies.
    Full-text · Article · Jan 2013 · PLoS ONE
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    • "The inhibition of the MAPK pathway might represent a link between EGFR inhibition and EGFR accumulation since U0126, a well known MEK1/2 inhibitor, induced EGFR accumulation in Calu-3 cells, while none of PI3K/AKT/mTOR inhibitors tested was effective. A correlation between MAPK pathway and protein degradation by the ubiquitin system was described for the pro-apoptotic BH3-only protein BIM, indeed in the absence of MAPK activation, BIM protein accumulated in the cell promoting activation of apoptotic cell death [30]. "
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    ABSTRACT: Background The epidermal growth factor receptor (EGFR) is an established target for anti-cancer treatment in different tumour types. Two different strategies have been explored to inhibit this pivotal molecule in epithelial cancer development: small molecules TKIs and monoclonal antibodies. ErbB/HER-targeting by monoclonal antibodies such as cetuximab and trastuzumab or tyrosine-kinase inhibitors as gefitinib or erlotinib has been proven effective in the treatment of advanced NSCLC. Results In this study we explored the potential of combining either erlotinib with cetuximab or trastuzumab to improve the efficacy of EGFR targeted therapy in EGFR wild-type NSCLC cell lines. Erlotinib treatment was observed to increase EGFR and/or HER2 expression at the plasma membrane level only in NSCLC cell lines sensitive to the drug inducing protein stabilization. The combined treatment had marginal effect on cell proliferation but markedly increased antibody-dependent, NK mediated, cytotoxicity in vitro. Moreover, in the Calu-3 xenograft model, the combination significantly inhibited tumour growth when compared with erlotinib and cetuximab alone. Conclusion Our results indicate that erlotinib increases surface expression of EGFR and/or HER2 only in EGFR-TKI sensitive NSCLC cell lines and, in turns, leads to increased susceptibility to ADCC both in vitro and in a xenograft models. The combination of erlotinib with monoclonal antibodies represents a potential strategy to improve the treatment of wild-type EGFR NSCLC patients sensitive to erlotinib.
    Full-text · Article · Dec 2012 · Molecular Cancer
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    • "The mechanisms for regulating Bim expression vary according to the apoptotic stimulus and the cell type. One mechanism initiated in response to Erk1/2 activation is the proteasomal degradation of the phosphorylated form of BimEL [17], [22]. To check this possibility, we treated HS2 cells with the proteasome inhibitor MG132 and monitored expression of BimEL by immunoblotting. "
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    ABSTRACT: Oncogenic mutations leading to persistent kinase activities are implicated in various human malignancies. Thereby, signaling pathway-targeted therapies are powerful customized treatment to eradicate cancer cells. In murine and human leukemia cells harboring mutations in Kit, we previously showed that distinct and independent pathways controlled resistance to apoptosis or cell cycle. A treatment with PI3Kinase inhibitors to reduce cell proliferation combined with inhibitors of Erk1/2 activity to promote apoptosis had synergistic effects allowing eradication of leukemia cell growth. We reported here that Bim(EL), a pro-apoptotic member of the Bcl2 family proteins, is the target of Erk1/2 signaling and that its down-regulation is responsible for the apoptosis resistance of murine and human leukemic cells. Downstream of Kit mutant, the tyrosine phosphatase Shp2 maintains Bim(EL) expression at a low level, through Erk/2 activation and proteosomal Bim(EL) degradation. This process is controlled by Shp2 independently of other signaling pathways activated downstream of oncogenic Kit, demonstrating that Shp2 is a key regulator of Bim expression in the context of an oncogenic signaling. The increase in Bim(EL) expression is associated to an increased apoptosis. Moreover, the depletion of Bim overcomes apoptosis associated with Erk1/2 inactivation in UO126-treated leukemic cells, thereby establishing the contribution of Bim to drug-induced apoptosis. These data provide a molecular rationale for using BH3 mimetics in combination with PI3K inhibitors to treat leukemia, especially in the case of an oncogenic signaling refractory to Tyrosine Kinase inhibitors.
    Preview · Article · Nov 2012 · PLoS ONE
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