Sam68 is required for both NF-?B activation and apoptosis signaling by the TNF receptor.
Ontology highlight
ABSTRACT:
SUBMITTER: Ramakrishnan P
PROVIDER: S-EPMC3142289 | biostudies-literature | 2011 Jul
REPOSITORIES: biostudies-literature
Publications
Sam68 is required for both NF-κB activation and apoptosis signaling by the TNF receptor.
Ramakrishnan Parameswaran P Baltimore David D
Molecular cell 20110527 2
The RNA-binding protein Sam68 is implicated in various cellular processes including RNA metabolism, apoptosis, and signal transduction. Here we identify a role of Sam68 in TNF-induced NF-κB activation and apoptosis. We found that Sam68 is recruited to the TNF receptor, and its deficiency dramatically reduces RIP recruitment and ubiquitylation. It also impairs cIAP1 recruitment and maintenance of recruited TRAF2 at the TNF receptor. In its absence, activation of the TAK1-IKK kinase complex is def ...[more]
Similar Datasets
Project description:Tumor necrosis factor-? (TNF?) is a proinflammatory cytokine that is closely linked to the development of cardiovascular disease. TNF? activates NADPH oxidase 1 (Nox1) and reactive oxygen species (ROS), including superoxide (O2·-), production extracellularly is required for subsequent signaling in vascular smooth muscle cells (VSMCs). Apoptosis signal-regulating kinase 1 (ASK1) is a mitogen-activated protein kinase kinase kinase that is activated by oxidation of associated thioredoxin. The role of ASK1 in Nox1-mediated signaling by TNF? is poorly defined. We hypothesized that ASK1 is required for TNF? receptor endocytosis and subsequent inflammatory TNF? signaling. We employed a knockdown strategy to explore the role of ASK1 in TNF? signaling in VSMCs. siRNA targeting ASK1 had no effect on TNF?-induced extracellular O2·- production. However, siASK1 inhibited receptor endocytosis as well as phosphorylation of two endocytosis-related proteins, dynamin1 and caveolin1. Intracellular O2·- production was subsequently reduced, as were other inflammatory signaling steps including NF-?B activation, IL-6 production, inducible nitric oxide synthase and VCAM expression, and VSMC proliferation. Prolonged exposure to TNF? (24 h) increased tumor necrosis factor receptor (TNFR) subtype 1 and 2 expression, and these effects were also attenuated by siASK1. ASK1 coimmunoprecipitated with both Nox1 and the leucine rich repeat containing 8A anion channel, two essential components of the TNFR1 signaling complex. Activation of ASK1 by autophosphorylation at Thr845 occurs following thioredoxin dissociation, and this requires the presence of Nox1. Thus, Nox1 is part of the multiprotein ASK1 signaling complex. In response to TNF?, ASK1 is activated by Nox1-derived oxidants, and this plays a critical role in translating these ROS into a physiologic response in VSMCs. NEW & NOTEWORTHY Apoptosis signal-regulating kinase 1 (ASK1) drives dynamin1 and caveolin1 phosphorylation and TNF? receptor endocytosis. ASK1 modulates TNF?-induced NF-?B activation, survival, and proliferation. ASK1 and NADPH oxidase 1 (Nox1) physically associate in a multiprotein signaling complex. Nox1 is required for TNF?-induced ASK1 activation.
| S-EPMC6620688 | biostudies-literature
Project description:Background and aimsTumor necrosis factor (TNF) is a major pathogenic effector and a therapeutic target in inflammatory bowel disease (IBD), yet the basis for TNF-induced intestinal epithelial cell (IEC) death is unknown, because TNF does not kill normal IECs. Here, we investigated how chronic nuclear factor (NF)- κB activation, which occurs in human IBD, promotes TNF-dependent IEC death in mice.MethodsHuman IBD specimens were stained for p65 and cleaved caspase-3. C57BL/6 mice with constitutively active IKKβ in IEC (Ikkβ(EE)IEC), Ripk1D138N/D138N knockin mice, and Ripk3-/- mice were injected with TNF or lipopolysaccharide. Enteroids were also isolated from these mice and challenged with TNF with or without RIPK1 and RIPK3 inhibitors or butylated hydroxyanisole. Ripoptosome-mediated caspase-8 activation was assessed by immunoprecipitation.ResultsNF-κB activation in human IBD correlated with appearance of cleaved caspase-3. Congruently, unlike normal mouse IECs that are TNF-resistant, IECs in Ikkβ(EE)IEC mice and enteroids were susceptible to TNF-dependent apoptosis, which depended on the protein kinase function of RIPK1. Constitutively active IKKβ facilitated ripoptosome formation, a RIPK1 signaling complex that mediates caspase-8 activation by TNF. Butylated hydroxyanisole treatment and RIPK1 inhibitors attenuated TNF-induced and ripoptosome-mediated caspase-8 activation and IEC death in vitro and in vivo.ConclusionsContrary to common expectations, chronic NF-κB activation induced intestinal crypt apoptosis after TNF stimulation, resulting in severe mucosal erosion. RIPK1 kinase inhibitors selectively inhibited TNF destructive properties while preserving its survival and proliferative properties, which do not require RIPK1 kinase activity. RIPK1 kinase inhibition could be a potential treatment for IBD.
| S-EPMC6957844 | biostudies-literature
Project description:NF-?B is a key transcription factor that regulates innate immune response. Its activity is tightly controlled by numerous feedback loops, including two negative loops mediated by NF-?B inducible inhibitors, I?B? and A20, which assure oscillatory responses, and by positive feedback loops arising due to the paracrine and autocrine regulation via TNF?, IL-1 and other cytokines. We study the NF-?B system of interlinked negative and positive feedback loops, combining bifurcation analysis of the deterministic approximation with stochastic numerical modeling. Positive feedback assures the existence of limit cycle oscillations in unstimulated wild-type cells and introduces bistability in A20-deficient cells. We demonstrated that cells of significant autocrine potential, i.e., cells characterized by high secretion of TNF? and its receptor TNFR1, may exhibit sustained cytoplasmic-nuclear NF-?B oscillations which start spontaneously due to stochastic fluctuations. In A20-deficient cells even a small TNF? expression rate qualitatively influences system kinetics, leading to long-lasting NF-?B activation in response to a short-pulsed TNF? stimulation. As a consequence, cells with impaired A20 expression or increased TNF? secretion rate are expected to have elevated NF-?B activity even in the absence of stimulation. This may lead to chronic inflammation and promote cancer due to the persistent activation of antiapoptotic genes induced by NF-?B. There is growing evidence that A20 mutations correlate with several types of lymphomas and elevated TNF? secretion is characteristic of many cancers. Interestingly, A20 loss or dysfunction also leaves the organism vulnerable to septic shock and massive apoptosis triggered by the uncontrolled TNF? secretion, which at high levels overcomes the antiapoptotic action of NF-?B. It is thus tempting to speculate that some cancers of deregulated NF-?B signaling may be prone to the pathogen-induced apoptosis.
| S-EPMC3855823 | biostudies-literature
Project description:The microtubule cytoskeleton is known to play a role in cell structure and serve as a scaffold for a variety of active molecules in processes as diverse as motility and cell division. The literature on the role of microtubules in signal transduction, however, is marked by inconsistencies. We have investigated a well-studied signaling pathway, TNF-alpha-induced NF-kappaB activation, and found a connection between the stability of microtubules and the regulation of NF-kappaB signaling in C2C12 myotubes. When microtubules are stabilized by paclitaxel (taxol), there is a strong induction of NF-kappaB even in the absence of TNF-alpha . Although there was no additive effect of taxol and TNF-alpha on NF-kappaB activity suggesting a shared mechanism of activation, taxol strongly induced the NF-kappaB reporter in the presence of a TNF receptor (TNFR) blocking antibody while TNF-alpha did not. Both TNF-alpha and taxol induce the degradation of endogenous IkappaBalpha and either taxol or TNF-alpha induction of NF-kappaB activity was blocked by inhibitors of NF-kappaB acting at different sites in the signaling pathway. Both TNF-alpha and taxol strongly induce known NF-kappaB chemokine target genes. On the other hand, if microtubules are destabilized by colchicine, then the induction of NF-kappaB by TNF-alpha or taxol is greatly reduced. Taken together, we surmise that the activity of microtubules is at the level of the TNFR intracellular domain. This phenomenon may indicate a new level of signaling organization in cell biology, actively created by the state of the cytoskeleton, and has ramifications for therapies where microtubule regulating drugs are used.
| S-EPMC3131200 | biostudies-literature
Project description:The I?B kinase complex (IKK) is a key regulator of immune responses, inflammation, cell survival, and tumorigenesis. The prosurvival function of IKK centers on activation of the transcription factor NF-?B, whose target gene products inhibit caspases and prevent prolonged JNK activation. Here, we report that inactivation of the BH3-only protein BAD by IKK independently of NF-?B activation suppresses TNF?-induced apoptosis. TNF?-treated Ikk?(-/-) mouse embryonic fibroblasts (MEFs) undergo apoptosis significantly faster than MEFs deficient in both RelA and cRel due to lack of inhibition of BAD by IKK. IKK phosphorylates BAD at serine-26 (Ser26) and primes it for inactivation. Elimination of Ser26 phosphorylation promotes BAD proapoptotic activity, thereby accelerating TNF?-induced apoptosis in cultured cells and increasing mortality in animals. Our results reveal that IKK inhibits TNF?-induced apoptosis through two distinct but cooperative mechanisms: activation of the survival factor NF-?B and inactivation of the proapoptotic BH3-only BAD protein.
| S-EPMC3586589 | biostudies-literature
Project description:Cell fate decisions regulating survival and death are essential for maintaining tissue homeostasis; dysregulation thereof can lead to tumor development. In some cases, survival and death are triggered by the same receptor, e.g., tumor necrosis factor (TNF)-receptor 1 (TNFR1). We identified a prominent role for the cold shock Y-box binding protein-1 (YB-1) in the TNF-induced activation and nuclear translocation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-?B) p65. In the absence of YB-1, the expression of TNF receptor-associated factor 2 (TRAF2), a central component of the TNF receptor signaling complex required for NF-?B activation, is significantly reduced. Therefore, we hypothesized that the loss of YB-1 results in a destabilization of TRAF2. Consistent with this hypothesis, we observed that YB-1-deficient cells were more prone to TNF-induced apoptotic cell death. We observed enhanced effector caspase-3 activation and could successfully rescue the cells using the pan-caspase inhibitor zVAD-fmk, but not necrostatin-1. Taken together, our results indicate that YB-1 plays a central role in promoting cell survival through NF-?B activation and identifies a novel mechanism by which enhanced YB-1 expression may contribute to tumor development.
| S-EPMC7464034 | biostudies-literature
Project description:BACKGROUND: TNF-related lymphotoxin alpha (LTalpha) is essential for the development of Plasmodium berghei ANKA (PbA)-induced experimental cerebral malaria (ECM). The pathway involved has been attributed to TNFR2. Here we show a second arm of LTalpha-signaling essential for ECM development through LTbeta-R, receptor of LTalpha1beta2 heterotrimer. METHODOLOGY/PRINCIPAL FINDINGS: LTbetaR deficient mice did not develop the neurological signs seen in PbA induced ECM but died at three weeks with high parasitaemia and severe anemia like LTalphabeta deficient mice. Resistance of LTalphabeta or LTbetaR deficient mice correlated with unaltered cerebral microcirculation and absence of ischemia, as documented by magnetic resonance imaging and angiography, associated with lack of microvascular obstruction, while wild-type mice developed distinct microvascular pathology. Recruitment and activation of perforin(+) CD8(+) T cells, and their ICAM-1 expression were clearly attenuated in the brain of resistant mice. An essential contribution of LIGHT, another LTbetaR ligand, could be excluded, as LIGHT deficient mice rapidly succumbed to ECM. CONCLUSIONS/SIGNIFICANCE: LTbetaR expressed on radioresistant resident stromal, probably endothelial cells, rather than hematopoietic cells, are essential for the development of ECM, as assessed by hematopoietic reconstitution experiment. Therefore, the data suggest that both functional LTbetaR and TNFR2 signaling are required and non-redundant for the development of microvascular pathology resulting in fatal ECM.
| S-EPMC2442868 | biostudies-literature
Project description:To elucidate the mechanisms responsible for cytoprotective effects of TNF receptor-activated factor 2 (TRAF2) in the heart, we employed genetic gain- and loss-of-function studies ex vivo and in vivo in mice with cardiac-restricted overexpression of TRAF2 (Myh6-TRAF2LC). Crossing Myh6-TRAF2LC mice with mice lacking canonical signaling (Myh6-TRAF2LC/Myh6-IκBαΔN) abrogated the cytoprotective effects of TRAF2 ex vivo. In contrast, inhibiting the JAK/STAT pathway did not abrogate the cytoprotective effects of TRAF2. Transcriptional profiling of WT, Myh6-TRAF2LC, and Myh6-TRAF2LC/Myh6-IκBαΔN mouse hearts suggested that the noncanonical NF-κB signaling pathway was upregulated in the Myh6-TRAF2LC mouse hearts. Western blotting and ELISA for the NF-κB family proteins p50, p65, p52, and RelB on nuclear and cytoplasmic extracts from naive 12-week-old WT, Myh6-TRAF2LC, and Myh6-TRAF2LC/Myh6-IκBαΔN mouse hearts showed increased expression levels and increased DNA binding of p52 and RelB, whereas there was no increase in expression or DNA binding of the p50 and p65 subunits. Crossing Myh6-TRAF2LC mice with RelB-/+ mice (Myh6-TRAF2LC/RelB-/+) attenuated the cytoprotective effects of TRAF2 ex vivo and in vivo. Viewed together, these results suggest that crosstalk between the canonical and noncanonical NF-κB signaling pathways is required for mediating the cytoprotective effects of TRAF2.
| S-EPMC5821173 | biostudies-literature
Project description:Recognition of pathogens by Toll-like receptors (TLR) activate multiple signaling cascades and expression of genes tailored to mount a primary immune response, inflammation, cell survival and apoptosis. Although TLR-induced activation of pathways, such as nuclear factor kappaB (NF-κB) and mitogen-activated protein kinases (MAPK), has been well studied, molecular entities controlling quantitative regulation of these pathways during an immune response remain poorly defined. We identified Sam68 as a novel regulator of TLR-induced NF-κB and MAPK activation. We found that TLR2 and TLR3 are totally dependent, whereas TLR4 is only partially dependent on Sam68 to induce the activation of NF-κB c-Rel. Absence of Sam68 greatly decreased TLR2- and TLR3-induced NF-κB p65 activation, whereas TLR4-induced p65 activation in a Sam68-independent manner. In contrast, Sam68 appeared to be a negative regulator of MAPK pathways because absence of Sam68 enhanced TLR2-induced activation of extracellular signal-regulated kinases (ERK) and c-Jun N-terminal kinases (JNK). Interestingly, TLR2- and TLR3-induced gene expression showed a differential requirement of Sam68. Absence of Sam68 impaired TLR2-induced gene expression, suggesting that Sam68 has a critical role in myeloid differentiation primary response gene 88-dependent TLR2 signaling. TLR3-induced gene expression that utilize Toll/Interleukin-1 receptor-domain-containing adapter-inducing beta interferon pathway, depend only partially on Sam68. Our findings suggest that Sam68 may function as an immune rheostat that balances the activation of NF-κB p65 and c-Rel, as well as MAPK, revealing a potential novel target to manipulate TLR signaling.
| S-EPMC5214940 | biostudies-literature
Project description:Our previous studies have demonstrated that PMS1077, a platelet-activating factor (PAF) antagonist, could induce apoptosis of Raji cells. However, the mechanism of action has not yet been determined. The nuclear transcription factor-kappa B (NF-?B) signaling pathway plays a critical role in tumor cell survival, proliferation, invasion, metastasis, and angiogenesis, so we determined the effects of PMS1077 and its structural analogs on tumor necrosis factor-? (TNF-?) induced activation of NF-?B signaling. In this study, we found that PMS1077 inhibited TNF-? induced expression of the NF-?B regulated reporter gene in a dose dependent manner. Western blot assay indicated that PMS1077 suppressed the TNF-? induced inhibitor of ?B-? (I?B-?) phosphorylation, I?B-? degradation, and p65 phosphorylation. PMS1077 consistently blocked TNF-? induced p65 nuclear translocation as demonstrated in the immunofluorescence assay used. Docking studies by molecular modeling predicted that PMS1077 might interact directly with the I?B kinase-? (IKK-?) subunit. These results suggested that PMS1077 might suppress the activation of NF-?B by targeting IKK-? involved in the NF-?B signaling pathway. Finally, we showed that PMS1077 sensitized cells to TNF-? induced apoptosis by suppressing the expression of NF-?B regulated anti-apoptotic genes. Our results reveal a novel function of PMS1077 on the NF-?B signaling pathway and imply that PMS1077 can be considered as an anti-tumor lead compound.
| S-EPMC3621893 | biostudies-literature