IκB Kinase ε Phosphorylates TRAF2 To Promote Mammary Epithelial Cell Transformation

Molecular and Cellular Biology (Impact Factor: 4.78). 12/2012; 32(23). DOI: 10.1128/MCB.00468-12


NF-κB transcription factors are central regulators of inflammation and when dysregulated contribute to malignant transformation.
IκB kinase ε (IKKε; IKKi, encoded by IKBKE) is a breast oncogene that is amplified in 30% of breast cancers and drives transformation in an NF-κB-dependent manner.
Here we demonstrate that IKKε interacts with and phosphorylates tumor necrosis factor receptor-associated factor 2 (TRAF2)
at Ser11 in vitro and in vivo. This activity promotes Lys63-linked TRAF2 ubiquitination and NF-κB activation and is essential for IKKε transformation.
Breast cancer cells that depend on IKKε expression for survival are also dependent on TRAF2. This work defines TRAF2 phosphorylation
to be one key effector of IKKε-induced mammary epithelial cell transformation.

Download full-text


Available from: Elgene Lim, Jul 13, 2014
  • Source
    • "IKKε-mediated mammary epithelial cell transformation is dependent on the phosphorylation of the cylindromatosis tumor suppressor (CYLD), the estrogen receptor α (ERα), the tumor necrosis factor receptor-associated factor 2 (TRAF2) E3 ligase and of the Forkhead box O 3a (FOXO3a) transcription factor [8] [9] [10] [11]. Expression of the CCND1 (Cyclin D1), MMP-9 (metalloproteinase-9) and Bcl-2 genes was found to be dependent on IKKε activity [5] [6] [9]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Oxidative stress is considered a causative factor in carcinogenesis, but also in the development of resistance to current chemotherapies. The appropriate usage of redox-modulating compounds is limited by the lack of knowledge of their impact on specific molecular pathways. Increased levels of the IKKε kinase, as a result of gene amplification or aberrant expression, are observed in a substantial number of breast carcinomas. IKKε not only plays a key role in cell transformation and invasiveness, but also in the development of resistance to tamoxifen. Here, we studied the effect of in vitro treatment with the redox-modulating triphenylmethane dyes, Gentian Violet and Brilliant Green, and nitroxide Tempol on IKKε expression and cell proliferation in the human breast cancer epithelial cell lines exhibiting amplification of IKKε, MCF-7 and ZR75.1. We show that Gentian Violet, Brilliant Green and Tempol significantly decrease intracellular superoxide anion levels and inhibit IKKε expression and cell viability. Treatment with Gentian Violet and Brilliant Green was associated with a reduced cyclin D1 expression and activation of caspase 3 and/or 7. Tempol decreased cyclin D1 expression in both cell lines, while activation of caspase 7 was only observed in MCF-7 cells. Silencing of the superoxide-generating NOX2 NADPH oxidase expressed in breast cancer cells resulted in the significant reduction of IKKε expression. Taken together, our results suggest that redox-modulating compounds targeting NOX2 could present a particular therapeutic interest in combination therapy against breast carcinomas exhibiting IKKε amplification. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.
    Full-text · Article · Jun 2015
  • [Show abstract] [Hide abstract]
    ABSTRACT: The innate immune system forms our first line of defense against invading pathogens and relies for a major part on the activation of two transcription factors, NF-κB and IRF3. Signaling pathways that activate these transcription factors are intertwined at the level of the canonical IκB kinases (IKKα, IKKβ) and non-canonical IKK-related kinases (IKKɛ, TBK1). Recently, significant progress has been made in understanding the function and mechanism of action of IKKɛ in immune signaling. In addition, IKKɛ impacts on cell proliferation and transformation, and is thereby also classified as an oncogene. Studies with IKKɛ knockout mice have illustrated a key role for IKKɛ in inflammatory and metabolic diseases. In this review we will highlight the mechanisms by which IKKɛ impacts on signaling pathways involved in disease development and discuss its potential as a novel therapeutic target.
    No preview · Article · Jan 2013 · Biochemical pharmacology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Upon stimulation by pathogen-associated inflammatory signals, TANK-binding kinase 1 (TBK1) induces type I interferon expression and modulates nuclear factor κB (NF-κB) signaling. Here, we describe the 2.4 Å-resolution crystal structure of nearly full-length TBK1 in complex with specific inhibitors. The structure reveals a dimeric assembly created by an extensive network of interactions among the kinase, ubiquitin-like, and scaffold/dimerization domains. An intact TBK1 dimer undergoes K63-linked polyubiquitination on lysines 30 and 401, and these modifications are required for TBK1 activity. The ubiquitination sites and dimer contacts are conserved in the close homolog inhibitor of κB kinase ε (IKKε) but not in IKKβ, a canonical IKK that assembles in an unrelated manner. The multidomain architecture of TBK1 provides a structural platform for integrating ubiquitination with kinase activation and IRF3 phosphorylation. The structure of TBK1 will facilitate studies of the atypical IKKs in normal and disease physiology and further the development of more specific inhibitors that may be useful as anticancer or anti-inflammatory agents.
    Full-text · Article · Feb 2013 · Cell Reports
Show more