Project description:Host defense and inflammation are regulated by the NF-kB essential modulator (NEMO), a scaffolding protein with a broad immune cell and tissue expression profile. Hypomorphic mutations in inhibitor of nuclear factor kappa B kinase regulatory subunit gamma (IKBKG) encoding NEMO typically present with immunodeficiency. Here we characterized a novel pediatric autoinflammatory syndrome in 3 unrelated male patients with distinct X-linked IKBKG germ-line mutations that led to overexpression of a NEMO protein isoform lacking the domain encoded by exon 5 (NEMO-Dex5). This isoform failed to associate with TANK binding kinase 1 (TBK1), and dermal fibroblasts from affected patients activated NF-kB in response to TNF, but not TLR3 or RIG-I-like-receptor (RLR) stimulation when isoform levels were high. By contrast, T cells, monocytes and macrophages that expressed NEMO-Dex5 exhibited increased NF-kB activation and IFN production, and blood cells from these patients expressed a strong interferon and NF-kB transcriptional signature. Immune cells and TNF-stimulated dermal fibroblasts upregulated the inducible IKK protein (IKKi) that was stabilized by NEMO-Dex5, promoting type I IFN induction and antiviral responses. These data reveal how IKBKG mutations that lead to alternative splicing of skipping exon 5 cause a clinical phenotype we name NEMO Deleted exon 5 Autoinflammatory Syndrome (NDAS), distinct from the immunodeficiency syndrome resulting from loss-of-function IKBKG mutations.
Project description:We report here that KSHV viral infection targets the NF-kB pathway which is crucial for cell survival. KSHV protein vFLIP K13 is known to directly interact with cellular protein NEMO of the NF-kB pathway. We used gene expression array to suggets that the interaction of K13 with NEMO is important to activate NF-kB pathway.
Project description:Many immune responses depend upon activation of NF-κB, a key transcription factor in the elicitation of a cytokine response. Here we show that N4BP1 inhibits TLR-dependent activation of NF-κB by interacting with the NF-κB signaling essential modulator (NEMO, also known as IκB kinase γ) to attenuate NEMO-NEMO dimerization or oligomerization. The UBA-like (ubiquitin associated-like) and CUE-like (ubiquitin conjugation to ER degradation) domains in N4BP1 mediate the interaction with the NEMO COZI domain. Both in vitro and in mice, N4bp1 deficiency specifically enhances TRIF-independent (TLR2, TLR7, or TLR9-mediated), but not TRIF-dependent (TLR3 or TLR4-mediated), NF-κB activation leading to increased production of proinflammatory cytokines. In response to TLR4 or TLR3 activation, TRIF causes activation of caspase-8, which cleaves N4BP1 distal to residues D424 and D490 and abolishes its inhibitory effect. N4bp1-/- mice also exhibit diminished numbers of T cells in the peripheral blood. Our work identifies N4BP1 as an inhibitory checkpoint protein that must be overcome to activate NF-κB, and a TRIF-initiated caspase-8-dependent mechanism by which this is accomplished.
Project description:Death receptor-mediated hepatocyte apoptosis is implicated in a wide range of liver diseases including viral hepatitis, alcoholic hepatitis, ischemia/reperfusion injury, fulminant hepatic failure, cholestatic liver injury and cancer. Deletion of NF-ĸB essential modulator in hepatocytes (NemoΔhepa) causes the spontaneous development of hepatocellular carcinoma preceded by steatohepatitis in mice and thus serves as an excellent model for the progression from chronic hepatitis to liver cancer. In the present study we aimed to dissect the death-receptor mediated pathways that contribute to liver injury in NemoΔhepa mice. Therefore, we generated NemoΔhepa/TRAIL-/- and NemoΔhepa/TNFR1-/- animals and analyzed the progression of liver injury. NemoΔhepa/TRAIL-/- displayed a similar phenotype to NemoΔhepa mice characteristic of high apoptosis, infiltration of immune cells, hepatocyte proliferation and steatohepatitis. These pathophysiological features were significantly ameliorated in NemoΔhepa/TNFR1-/- livers. Hepatocyte apoptosis was increased in NemoΔhepa and NemoΔhepa/TRAIL-/- mice while NemoΔhepa/TNFR1-/- animals showed reduced cell death concomitant with a strong reduction in pJNK levels. Cell cycle parameters were significantly less activated in NemoΔhepa/TNFR1-/- livers. Additionally, markers of liver fibrosis and indicators of tumour progression were significantly decreased in these animals. The present data demonstrate that the death receptor TNFR1 but not TRAIL is important in determining progression of liver injury in hepatocyte-specific Nemo knockout mice. Expression profiling of livers from wild type, NEMO, NEMO-TRIAL, and NEMO-TNFR null mice
Project description:We report here that KSHV viral infection targets the NF-kB pathway which is crucial for cell survival. KSHV protein vFLIP K13 is known to directly interact with cellular protein NEMO of the NF-kB pathway. We used gene expression array to suggets that the interaction of K13 with NEMO is important to activate NF-kB pathway. We employed gene array analysis followed by bioinformatics analyses as well as biological pathways to determine the effect of K13 interaction with Nemo in Jurkat cell line system. Total RNA was isolated isolated using standard RNAeasy kit protocol (Qiagen). Their gene expression profiles were obtained using the Affymetrix Human Genome U133A 2.0 Array.
Project description:In response to DNA double strand breaks (DSBs), the ATM kinase activates NF-κB factors to stimulate gene expression changes that promote survival and allow time for cells to repair damage. In cell lines, ATM can activate NF-κB transcription factors via two independent, convergent mechanisms. One is ATM-mediated phosphorylation of nuclear NF-κB essential modulator (Nemo) protein, which leads to monoubiquitylation and export of Nemo to the cytoplasm where it engages the IκB kinase (IKK) complex to activate NF-κB. Another is DSB-triggered migration of ATM into the cytoplasm where it promotes monoubiquitylation of Nemo and resulting IKK-mediated activation of NF-κB. ATM has many other functions in the DSB response beyond activation of NF-κB, and Nemo activates NF-κB downstream of diverse stimuli, including developmental or proinflammatory stimuli such as lipopolysaccharides (LPS). To elucidate the in vivo role of DSB-induced, ATM-dependent changes in expression of NF-κB-responsive genes, we generated mice expressing phosphomutant Nemo protein lacking consensus SQ sites for phosphorylation by ATM or related kinases. We demonstrate that these mice are viable/healthy, fertile, and exhibit overall normal B and T lymphocyte development. Moreover, treatment of their B lineage cells with LPS induces normal NF-κB-regulated gene expression changes. Furthermore, in marked contrast to results from a pre-B cell line, primary B lineage cells expressing phosphomutant Nemo treated with the genotoxic drug etoposide induce normal ATM- and Nemo-dependent changes in expression of NF-κB-regulated genes. Our data demonstrate that ATM-dependent phosphorylation of Nemo SQ motifs in vivo is dispensable for DSB-signaled changes in expression of NF-κB-regulated genes.
Project description:The transcription factor NF-kB is an important regulator of genes involved in inflammation and cell proliferation. Several studies previously showed that NF-kB transcription factor was constitutively activated in melanoma cell lines due to the up regulated activity of inhibitor of NF-kB kinases (IKK). In the present study, we tested the activation of NF-kB pathway following TNF stimulation in 9 melanoma cell lines and the subsequent inhibition after the treatment of a small–molecule IKK inhibitor NDB peptide using Secreated Alkaline Phosphate (SEAP) reporter gene assay. The pro-apoptotic effects induced by NBD peptide treatment were determined by flow cytometry as well as by Western Blot testing of PARP’s cleavage. Our findings showed that NBD peptide was able to block IKK-NFKB pathway in all tested cell lines by inducing apoptosis as confirmed by increased levels of active caspase 3 and PARP cleavage after treatment. Moreover, our finding provides the basis for the development of a novel therapeutic approach targeting NF-kB transcription factor to treat melanoma.
Project description:The canonical NF-κB pathway is active in 70% of all pancreatic cancer cases and NF-κB Essential Modulator (NEMO) is essential for the activation of this pathway. In our study, we used KC mice, which express the oncogenic KRAS and develop precancerous lesions termed Pancreatic Intraepithelial Neoplasias (PanINs), and KNeC mice, which express the oncogenic KRAS and have NEMO deleted in their pancreatic cells. These mice were injected with cerulein to promote the development of pancreatitis (cerulein dosage= 50μg/kg). Cerulein was injected at 8 hourly intervals for 2 days in total. The first injection day was when mice reached their sixth week of age and the second injection day was 3 days after the first injection day. Both KC and KNeC mice developed PanINs. At the age of 10 months, pancreata of KC and KNeC mice were analyzed. Using laser capture microdissection, PanINs from both groups were excised and their transcriptome was analyzed though RNA-seq.
Project description:HOIL-1L is an essential member of the linear ubiquitin assembly complex (LUBAC), which targets Nemo for linear ubiquitination during NF-kB activation in response to a variety of simuli, including LPS and TNFa treatment. HOIL-1L has also been suggested to function as a transcription factor. Here we analyzed changes in the global transcriptional profiles of primary bone marrow derived macrophage (BMDMs) from WT and HOIL-1L-/- mice upon treatment with NF-kB activating simuli.
Project description:Mitochondria are often essential for apoptosis through mitochondrial outer membrane permeabilization (MOMP). This central event enables cytochrome c release leading to caspase activation and rapid cell death. Recently, MOMP has been shown to be inherently pro-inflammatory, for instance, causing mitochondrial DNA-dependent activation of cGAS-STING signalling. Alongside having emerging functions in health and disease, MOMP associated inflammation can also elicit anti-tumour immunity. Nonetheless, how MOMP triggers inflammation and how the cell counteracts this remain poorly defined. Here, we find that upon MOMP, mitochondria are ubiquitylated in a promiscuous manner targeting proteins localised to both inner and outer mitochondrial membranes. Mitochondrial ubiquitylation serves to recruit the essential adaptor molecule, NEMO, leading to activation of pro-inflammatory NF-kB signalling. We find that disruption of mitochondrial outer membrane integrity through different means leads to engagement of a similar pro-inflammatory signalling platform. Thus, mitochondrial integrity directly controls inflammation, whereby permeabilised mitochondria initiate NF-?B signalling. This may be important for the various pathophysiological functions of MOMP-associated inflammation.