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Since their identification more than 20 years ago, the death receptors CD95, TRAILR1, and TRAILR2 have been intensively studied with respect to their cell death-inducing activities. These receptors, however, can also trigger a variety of cell death-independent cellular responses reaching from the activation of proinflammatory gene transcription programs over the stimulation of proliferation and differentiation to induction of cell migration. The cell death-inducing signaling mechanisms of CD95 and the TRAIL death receptors are well understood. In contrast, despite the increasing recognition of the biological and pathophysiological relevance of the cell death-independent activities of CD95, TRAILR1, and TRAILR2, the corresponding signaling mechanisms are less understood and give no fully coherent picture. This review is focused on the cell death-independent activities of CD95 and the TRAIL death receptors and addresses mainly three questions: (a) how are these receptors linked to noncell death pathways at the molecular level, (b) which factors determine the balance of cell death and cell death-independent activities of CD95 and the TRAIL death receptors at the cellular level, and (c) what are the consequences of the cell death-independent functions of these receptors for their role in cancer and inflammatory diseases. [ABSTRACT FROM AUTHOR]

Background and Purpose MLN4924 prevents the formation of active cullin- RING ubiquitin ligase complexes and thus inhibits NF-κB signalling. Here, we evaluated the effects of this compound on monocytes and dendritic cells ( DCs). Experimental Approach Monocytes and DCs were challenged with TNF or LPS in the presence and absence of MLN4924. The effects of MLN4924 on cellular viability, pro-inflammatory gene induction and DC maturation were investigated using the MTT assay, elisa and FACS analysis. Mechanisms of cell death induction were evaluated by using inhibitors of caspases, RIPK1 and MLKL. Key Results MLN4924 inhibited NF-κB activation and sensitized monocytes and immature DCs ( iDCs) for TNFR1-induced cell death. Neither the caspase inhibitor zVAD-fmk, the RIPK1 inhibitor necrostatin-1 (nec-1) nor the MLKL inhibitor necrosulfonamide ( NSA) alone prevented TNF-induced cell death. A combination of zVAD-fmk and nec-1 or NSA, however, rescued monocytes and iDCs from MLN4924/ TNF-induced cell death indicating that MLN4924 affects anti-apoptotic and anti-necrotic activities in TNFR1 signalling. MLN4924 also converted the response of iDCs to LPS from maturation to cell death. LPS-induced cell death in MLN4924-treated iDCs was again only effectively blocked by cotreatment with zVAD-fmk and nec-1 or NSA. Noteworthy, MLN4924/ LPS-induced cell death was almost completely independent of endogenous TNF. MLN4924 also strongly inhibited maturation and activation of iDCs that were rescued from cell death by zVAD-fmk and nec-1. Conclusions and Implications Our data reveal a strong dual suppressive effect of MLN4924 on DC activity. The targeting of NAE by MLN4924 could be a new way to treat inflammatory diseases. [ABSTRACT FROM AUTHOR]

The oligomerization status of soluble tumor necrosis factor-related apoptosis inducing ligand (TRAIL) trimers has an overwhelming impact on cell death induction in a cell-type dependent fashion. Thus, we evaluated the ability of single and oligomerized TRAIL trimers to induce cell death in human myeloma cells. In all myeloma cell lines analyzed, oligomerized TRAIL trimers induced caspase activation and complete cell death, whereas non-oligomerized TRAIL trimers showed no or only a modest effect. Caspase activation induced by oligomerized TRAIL was blocked in all cell lines by the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone (z-VAD-fmk). Cell death induction was largely blocked in two cell lines by z-VAD-fmk, but was only marginally attenuated in three other cell lines, indicating that TRAIL induces caspase-dependent and caspase-independent cell death in myeloma cells. Preceding cell death, TRAIL activated nuclear factor κB, c-Jun N-terminal kinase, p38 and p42/44. Although TRAIL-induced stimulation of c-Jun N-terminal kinase and p38 was caspase-dependent in a cell type-specific fashion, activation of nuclear factor κB and p42/44 was caspase-independent in all cases. In accordance with activation of the nuclear factor κB pathway, we observed transcriptional up-regulation of several well established nuclear factor κB target genes. Furthermore, we found that TRAIL activates proinflammatory pathways in approximately 50% of primary myeloma samples. Taken together, our data suggest (a) that oligomerized TRAIL variants are necessary to ensure maximal cell death induction in myeloma cells and (b) TRAIL should be used in combination with anti-inflammatory drugs for treatment of myeloma to avoid and/or minimize any potential side-effects arising from the proinflammatory properties of the molecule. [ABSTRACT FROM AUTHOR]

The essential role of FADD/MORT1 and caspase-8 in 'death-receptor'-induced apoptosis is well characterized. Surprisingly, these proteins also play a critical role in antigen- or mitogen-induced activation and proliferation of T cells. We report the results of gene expression profiling in T cells from mice defective in FADD-signaling due to transgenic expression of a dominant negative mutant of FADD (FADDdn T cells). Of the tested genes, 159 were differentially expressed in mutant cells prior to or, more often, after mitogenic stimulation for 20 h. No obvious regulator of proliferation was changed in expression. However, a number of T cell effector genes such as IL-2 and IL-9 were up-regulated upon stimulation. Analysis of IL-2 regulation showed enhanced mRNA induction but normal protein production in activated FADDdn T cells. Activation of the nuclear factor of activated T cells was normal upon stimulation but the activity of the activator protein 1 (AP-1) family was strongly increased in resting FADDdn T cells. Expression and transcriptional activity of classical AP-1 family members was unaltered in FADDdn cells, suggesting the involvement of other AP-1 family members. The constitutive activation of AP-1 may thus serve to precondition resting T cells for an enhanced expression of many immunologically relevant genes during activation. [ABSTRACT FROM AUTHOR]

To gain insight in the subcellular localization of tumor necrosis factor receptor-associated factor (TRAF4) we analyzed GFP chimeras of full-length TRAF4 and various deletion mutants derived thereof. While TRAF4–GFP (T4–GFP) was clearly localized in the cytoplasm, the N-terminal deletion mutant, T4(259–470), comprising the TRAF domain of the molecule, and a C-terminal deletion mutant consisting mainly of the RING and zinc finger domains of TRAF4 were both localized predominantly to the nucleus. Passive nuclear localization of T4(259–470) can be ruled out as the TRAF domain of TRAF4 was sufficient to form high molecular weight complexes. T4(259–470) recruited full-length TRAF4 into the nucleus whereas TRAF4 was unable to change the nuclear localization of T4(259–470). Thus, it seems that individual T4(259–470) mutant molecules are sufficient to direct the respective TRAF4–T4(259–470) heteromeric complexes into the nucleus. In cells forming cell–cell contacts, TRAF4 was recruited to the sites of contact via its C-TRAF domain. The expression of some TRAF proteins is regulated by the NF-κB pathway. Thus, we investigated whether this pathway is also involved in the regulation of the TRAF4 gene. Indeed, in primary T-cells and Jurkat cells stimulated with the NF-κB inducers TNF or phorbol 12-myristate 13-acetate (PMA), TRAF4-mRNA was rapidly up-regulated. In Jurkat T-cells deficient for I-κB kinase γ (IKKγ, also known as NEMO), an essential component of the NF-κB-inducing–IKK complex, induction of TRAF4 was completely inhibited. In cells deficient for RIP (receptor interactive protein), an essential signaling intermediate of TNF-dependent NF-κB activation, TNF-, but not PMA-induced up-regulation of TRAF4 was blocked. These data suggest that activation of the NF-κB pathway is involved in up-regulation of TRAF4 in T-cells. [ABSTRACT FROM AUTHOR]

Presents a study on the ability of CD95 and TRAF2 to promote invasiveness of pancreatic cancer cells. Method used to determine the expression levels of TRAF2 in pancreatic tumor cells; Adaptor molecule that interacts with death receptors; Enhancement of the invasive potential of pancreatic tumor cells through stimulation of CD95.