Vallabhapurapu S, Matsuzawa A, Zhang W, Tseng PH, Keats JJ, Wang H et al.. Nonredundant and complementary functions of TRAF2 and TRAF3 in a ubiquitination cascade that activates NIK-dependent alternative NF-κB signaling. Nat Immunol 9: 1364-1370

Laboratory of Gene Regulation and Signal Transduction, Departments of Pharmacology and Pathology, Cancer Center, University of California, San Diego, California 93093, USA.
Nature Immunology (Impact Factor: 20). 01/2009; 9(12):1364-70. DOI: 10.1038/ni.1678
Source: PubMed

ABSTRACT The adaptor and signaling proteins TRAF2, TRAF3, cIAP1 and cIAP2 may inhibit alternative nuclear factor-kappaB (NF-kappaB) signaling in resting cells by targeting NF-kappaB-inducing kinase (NIK) for ubiquitin-dependent degradation, thus preventing processing of the NF-kappaB2 precursor protein p100 to release p52. However, the respective functions of TRAF2 and TRAF3 in NIK degradation and activation of alternative NF-kappaB signaling have remained elusive. We now show that CD40 or BAFF receptor activation result in TRAF3 degradation in a cIAP1-cIAP2- and TRAF2-dependent way owing to enhanced cIAP1, cIAP2 TRAF3-directed ubiquitin ligase activity. Receptor-induced activation of cIAP1 and cIAP2 correlated with their K63-linked ubiquitination by TRAF2. Degradation of TRAF3 prevented association of NIK with the cIAP1-cIAP2-TRAF2 ubiquitin ligase complex, which resulted in NIK stabilization and NF-kappaB2-p100 processing. Constitutive activation of this pathway causes perinatal lethality and lymphoid defects.

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Available from: Ping-Hui Tseng, Jul 22, 2014
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    • "In B lymphocytes, it has been demonstrated that TRAF3 interacts with TRAF2, cIAP1 and cIAP2 and negatively regulates the non-canonical NF-κB2 pathway [26], [27]. Depletion of TRAF3 results in constitutive activation of the NF-κB2 pathway in all cell types examined to date [19]–[21]. "
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    ABSTRACT: Our laboratory reported previously that TNF receptor associated factor 3 (TRAF3) is a positive regulator of TCR signaling and T cell function. In the current study, we present new findings that reveal differential roles for TRAF3 in the regulation of CD4+ and CD8+ T cells. In response to TCR stimulation in vitro, TRAF3 has greater impact in CD4+ T cells than in CD8+ T cells. However, T cell-specific TRAF3 deficient mice (CD4Cre TRAF3fl°x/fl°x; T-TRAF3-/-) have a greater number of CD4+CD44hi effector/memory T cells than littermate control (LMC) mice, possibly due to an inefficient suppressive effect of TRAF3 deficient Foxp3+ regulatory T cells. In contrast, CD8+CD44hiCD62Lhi central memory (Tcm) cells are markedly reduced in T-TRAF3-/- mice in comparison to LMC mice, although CD8+CD44hiCD62Ll°w effector memory T (Tem) cells and naïve T cells (CD8+CD44l°wCD62Lhi) do not show significant differences in number. Importantly, TRAF3-deficient Tcm cells exhibit defective homeostasis due to impaired IL-15 signaling. These results indicate that the involvement of TRAF3 in IL-15 mediated signaling to T cells plays a previously unappreciated and critical role in CD8+ Tcm cell regulation and maintenance.
    PLoS ONE 07/2014; 9(7):e102120. DOI:10.1371/journal.pone.0102120 · 3.23 Impact Factor
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    • "In agreement with the observation that PACS-2 is a substrate for cIAPs, immunoprecipitation studies identified direct binding between PACS-2 and cIAP-1 and cIAP-2 both in vivo and in cell-free systems. TRAF2 has been shown to stabilize cIAP-1 [36], and is required for cIAP-mediated degradation of NIK, as well as for SMAC mimetic-induced cIAP autoubiquitination and degradation [42], [43]. Interestingly, although TRAF2 co-precipitates with PACS-2 in cell-free systems, in the presence or absence of cIAP-1 and/or cIAP-2, it seems to be dispensable for cIAP ubiquitination and downregulation of PACS-2. "
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    ABSTRACT: Lysosomal membrane permeabilization is an essential step in TRAIL-induced apoptosis of liver cancer cell lines. TRAIL-induced lysosomal membrane permeabilization is mediated by the multifunctional sorting protein PACS-2 and repressed by the E3 ligases cIAP-1 and cIAP-2. Despite the opposing roles for PACS-2 and cIAPs in TRAIL-induced apoptosis, an interaction between these proteins has yet to be examined. Herein, we report that cIAP-1 and cIAP-2 confer TRAIL resistance to hepatobiliary cancer cell lines by reducing PACS-2 levels. Under basal conditions, PACS-2 underwent K48-linked poly-ubiquitination, resulting in PACS-2 proteasomal degradation. Biochemical assays showed cIAP-1 and cIAP-2 interacted with PACS-2 in vitro and co-immunoprecipitation studies demonstrated that the two cIAPs bound PACS-2 in vivo. More importantly, both cIAP-1 and cIAP-2 directly mediated PACS-2 ubiquitination in a cell-free assay. Single c-Iap-1 or c-Iap-2 gene knock-outs in mouse hepatocytes did not lead to PACS-2 accumulation. However, deletion of both cIAP-1 and cIAP-2 reduced PACS-2 ubiquitination, which increased PACS-2 levels and sensitized HuH-7 cells to TRAIL-induced lysosomal membrane permeabilization and apoptosis. Correspondingly, deletion of cIAPs sensitized wild-type, but not PACS-2-deficient hepatocarcinoma cells or Pacs-2-/- mouse hepatocytes to TRAIL-induced apoptosis. Together, these data suggest cIAPs constitutively downregulate PACS-2 by polyubiquitination and proteasomal degradation, thereby restraining TRAIL-induced killing of liver cancer cells.
    PLoS ONE 03/2014; 9(3):e92124. DOI:10.1371/journal.pone.0092124 · 3.23 Impact Factor
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    • "In response to stimulation with cytokines such as BAFF or CD40 ligand, TRAF3 is recruited to the receptor and undergoes ubiquitination-mediated proteasomal degradation. This results in stabilization and accumulation of newly synthesized NIK, while these stimuli do not increase the NIK mRNA level [3], [4]. In hematopoietic cancer cells such as multiple myeloma and adult T-cell leukemia as well as lung cancer cells, either stabilization of the NIK protein through impaired negative regulation by the TRAF3/TRAF2/cIAP complex or aberrant expression of the NIK mRNA have been reported [5], [6], [7], [8]. "
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    ABSTRACT: Ovarian cancer is one of the leading causes of female death and the development of novel therapeutic approaches is urgently required. Nuclear factor-κB (NF-κB) is constitutively activated in several types of cancer including ovarian cancer and is known to support the survival of cancer cells. However, molecular mechanisms of persistent activation of NF-κB in ovarian cancer remain largely unknown. We report here that, in addition to the previously reported canonical activation, NF-κB is activated through the noncanonical pathway in ovarian cancer cells. RNA interference-mediated silencing of NF-κB inducing kinase (NIK), a central regulator of the noncanonical pathway, reduced the NF-κB2/p52 DNA binding activity and NF-κB-dependent reporter gene expression as well as NF-κB target gene expression. Notably, anchorage-dependent and -independent cell growth was impaired in NIK-depleted cells. Depletion of NIK also suppressed tumor formation in the nude mouse xenograft assay. These results indicate that NIK plays a key role in constitutive NF-κB activation and the progression of ovarian cancer cells and suggest that NIK represents an attractive therapeutic target for ovarian cancer.
    PLoS ONE 02/2014; 9(2):e88347. DOI:10.1371/journal.pone.0088347 · 3.23 Impact Factor
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