A RelA(p65) Thr505 phospho-site mutation reveals an important mechanism regulating NF-κB-dependent liver regeneration and cancer.
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ABSTRACT:
SUBMITTER: Moles A
PROVIDER: S-EPMC4862573 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Post-translational modification of NF-κB subunits provides a mechanism to differentially regulate their activity in response to the many stimuli that can induce this pathway. However, the physiological significance of these modifications is largely unknown and it remains unclear if these have a critical role in the normal and pathological functions of NF-κB in vivo. Among these, phosphorylation of the RelA(p65) Thr505 residue has been described as an important regulator of NF-κB activity in cell lines but its physiological significance was not known. Therefore, to learn more about the role of this pathway in vivo, we generated a knockin mouse with a RelA T505A mutation. Unlike RelA knockout mice, the RelA T505A mice develop normally but exhibit aberrant hepatocyte proliferation following liver partial hepatectomy or damage resulting from carbon tetrachloride treatment. Consistent with these effects, RelA T505A mice exhibit earlier onset of cancer in the N-nitrosodiethylamine (DEN) model of hepatocellular carcinoma. This data reveals a critical pathway controlling NF-κB function in the liver that acts to suppress tumour-promoting activities of RelA.
2015-11-30 | E-MTAB-3596 | biostudies-arrayexpress
Project description:BackgroundThe transcription factor NF-κB consisting of the subunits RelA/p65 and p50 is known to be quickly activated after partial hepatectomy (PH), the functional relevance of which is still a matter of debate. Current concepts suggest that activation of NF-κB is especially critical in non-parenchymal cells to produce cytokines (TNF, IL-6) to adequately prime hepatocytes to proliferate after PH, while NF-κB within hepatocytes mainly bears cytoprotective functions.MethodsTo study the role of the NF-κB pathway in different liver cell compartments, we generated conditional knockout mice in which the transactivating NF-κB subunit RelA/p65 can be inactivated specifically in hepatocytes (Rela(F/F)AlbCre) or both in hepatocytes plus non-parenchymal cells including Kupffer cells (Rela(F/F)MxCre). 2/3 and 80% PH were performed in controls (Rela(F/F)) and conditional knockout mice (Rela(F/F)AlbCre and Rela(F/F)MxCre) and analyzed for regeneration.ResultsHepatocyte-specific deletion of RelA/p65 in Rela(F/F)AlbCre mice resulted in an accelerated cell cycle progression without altering liver mass regeneration after 2/3 PH. Surprisingly, hepatocyte apoptosis or liver damage were not enhanced in Rela(F/F)AlbCre mice, even when performing 80% PH. The additional inactivation of RelA/p65 in non-parenchymal cells in Rela(F/F)MxCre mice reversed the small proliferative advantage observed after hepatocyte-specific deletion of RelA/p65 so that Rela(F/F)MxCre mice displayed normal cell cycle progression, DNA-synthesis and liver mass regeneration.ConclusionThe NF-κB subunit RelA/p65 fulfills opposite functions in different liver cell compartments in liver regeneration after PH. However, the effects observed after conditional deletion of RelA/p65 are small and do not alter liver mass regeneration after PH. We therefore do not consider RelA/p65-containing canonical NF-κB signalling to be essential for successful liver regeneration after PH.
| S-EPMC3462179 | biostudies-literature
Project description:BackgroundGlioblastoma (GBM) harbors significant genetic heterogeneity, high infiltrative capacity, and patterns of relapse following many therapies. The expression of nuclear factor kappa-B (NF-κB p65 (RelA)) and signaling pathways is constitutively activated in GBM through inflammatory stimulation such as tumor necrosis factor-alpha (TNFα), cell invasion, motility, abnormal physiological stimuli, and inducible chemoresistance. However, the underlying anti-tumor and anti-proliferative mechanisms of NF-κB p65 (RelA) and TNFα are still poorly defined. This study aimed to investigate the expression profiling of NF-κB p65 (RelA) and TNFα as well as the effectiveness of celecoxib along with temozolomide (TMZ) in reducing the growth of the human GBM cell line SF-767.Methodsgenome-wide expression profiling, enrichment analysis, immune infiltration, quantitative expression, and the Microculture Tetrazolium Test (MTT) proliferation assay were performed to appraise the effects of celecoxib and TMZ.Resultsdemonstrated the upregulation of NF-κB p65 (RelA) and TNFα and celecoxib reduced the viability of the human glioblastoma cell line SF-767, cell proliferation, and NF-κB p65 (RelA) and TNFα expression in a dose-dependent manner. Overall, these findings demonstrate for the first time how celecoxib therapy could mitigate the invasive characteristics of the human GBM cell line SF-767 by inhibiting the NF-κB mediated stimulation of the inflammatory cascade.Conclusionbased on current findings, we propose that celecoxib as a drug candidate in combination with temozolomide might dampen the transcriptional and enzymatic activities associated with the aggressiveness of GBM and reduce the expression of GBM-associated NF-κB p65 (RelA) and TNFα inflammatory genes expression.
| S-EPMC10607796 | biostudies-literature
Project description:Viruses evolve multiple ways to interfere with NF-κB signaling, a key regulator of innate and adaptive immunity. Enterovirus 71 (EV71) is one of primary pathogens that cause hand-foot-mouth disease. Here, we identify RelA(p65) as a novel binding partner for EV71 2C protein from yeast two-hybrid screen. By interaction with IPT domain of p65, 2C reduces the formation of heterodimer p65/p50, the predominant form of NF-κB. We also show that picornavirus 2C family proteins inhibit NF-κB activation and associate with p65 and IKKβ. Our findings provide a novel mechanism how EV71 antagonizes innate immunity.
| S-EPMC4585786 | biostudies-literature
Project description:The NF-κB signaling pathway is central to the innate and adaptive immune responses. Upon their detection of pathogen-associated molecular patterns, Toll-like receptors on the cell surface initiate signal transduction and activate the NF-κB pathway, leading to the production of a wide array of inflammatory cytokines, in attempt to eradicate the invaders. As a countermeasure, pathogens have evolved ways to subvert and manipulate this system to their advantage. Enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) are closely related bacteria responsible for major food-borne diseases worldwide. Via a needle-like protein complex called the type three secretion system (T3SS), these pathogens deliver virulence factors directly to host cells and modify cellular functions, including by suppressing the inflammatory response. Using gain- and loss-of-function screenings, we identified two bacterial effectors, NleC and NleE, that down-regulate the NF-κB signal upon being injected into a host cell via the T3SS. A recent report showed that NleE inhibits NF-κB activation, although an NleE-deficient pathogen was still immune-suppressive, indicating that other anti-inflammatory effectors are involved. In agreement, our present results showed that NleC was also required to inhibit inflammation. We found that NleC is a zinc protease that disrupts NF-κB activation by the direct cleavage of NF-κB's p65 subunit in the cytoplasm, thereby decreasing the available p65 and reducing the total nuclear entry of active p65. More importantly, we showed that a mutant EPEC/EHEC lacking both NleC and NleE (ΔnleC ΔnleE) caused greater inflammatory response than bacteria carrying ΔnleC or ΔnleE alone. This effect was similar to that of a T3SS-defective mutant. In conclusion, we found that NleC is an anti-inflammatory bacterial zinc protease, and that the cooperative function of NleE and NleC disrupts the NF-κB pathway and accounts for most of the immune suppression caused by EHEC/EPEC.
| S-EPMC3002990 | biostudies-literature
Project description:Nuclear factor κB (NF-κB) plays important roles in innate immune responses by regulating the expression of a large number of target genes involved in the immune and inflammatory response, apoptosis, cell proliferation, differentiation, and survival. To survive in the host cells, viruses have evolved multiple strategies to evade and subvert the host immune response. Herpes simplex virus 1 (HSV-1) bears a large DNA genome, with the capacity to encode many different viral proteins to counteract the host immune responses. In the present study, we demonstrated that HSV-1 protein kinase US3 significantly inhibited NF-κB activation and decreased the expression of inflammatory chemokine interleukin-8 (IL-8). US3 was also shown to hyperphosphorylate p65 at serine 75 and block its nuclear translocation. Two US3 mutants, K220M and D305A, still interacted with p65; however, they could not hyperphosphorylate p65, indicating that the kinase activity of US3 was indispensable for the function. The attenuation of NF-κB activation by HSV-1 US3 protein kinase may represent a critical adaptation to enable virus persistence within the host. Importance: This study demonstrated that HSV-1 protein kinase US3 significantly inhibited NF-κB activation and decreased the expression of inflammatory chemokine interleukin-8 (IL-8). US3 hyperphosphorylated p65 at serine 75 to inhibit NF-κB activation. The kinase activity of US3 was indispensable for its hyperphosphorylation of p65 and abrogation of the nuclear translocation of p65. The present study elaborated a novel mechanism of HSV-1 US3 to evade the host innate immunity.
| S-EPMC4097809 | biostudies-literature
Project description:Receptor-interacting protein kinase 3 (RIPK3) can induce necroptosis, apoptosis, or cell proliferation and is silenced in several hematological malignancies. We previously reported that RIPK3 activity independent of its kinase domain induces caspase-mediated p65/RelA cleavage, resulting in N-terminal 1-361 and C-terminal 362-549 fragments. We show here that a noncleavable p65/RelA D361E mutant expressed in DA1-3b leukemia cells decreases mouse survival times and that coexpression of p65/RelA fragments increases the tumorigenicity of B16F1 melanoma cells. This aggressiveness in vivo did not correlate with NF-κB activity measured in vitro. The fragments and p65/RelA D361E mutant induced different expression profiles in DA1-3b and B16F1 cells. Stemness markers were affected: p65/RelA D361E increased ALDH activity in DA1-3b cells, and fragment expression increased melanoma sphere formation in B16/F1 cells. p65/RelA fragments and the D361E noncleavable mutant decreased oxidative or glycolytic cell metabolism, with differences observed between models. Thus, p65/RelA cleavage initiated by kinase-independent RIPK3 activity in cancer cells is not neutral and induces pleiotropic effects in vitro and in vivo that may vary across tumor types.
| S-EPMC9299825 | biostudies-literature
Project description:Here we sought to identify transcription factors that induce ADAMTS5, a crucial proteinase for osteoarthritis development. Exhaustive comparison of the genomic sequences of human, macaque, and mouse ADAMTS5 genes revealed that the proximal 1.4 kb of the 5'-end-flanking regions containing several consensus motifs was highly conserved. Among putative transcription factors for these motifs, NF-κB family member RelA/p65 most strongly stimulated the promoter activity. In the ADAMTS5 gene, there were three NF-κB binding motifs, in which deletion, mutagenesis, and tandem repeat analyses of the luciferase assay identified the core responsive elements of RelA/p65 to be -896/-887 and -424/-415 bp with specific bindings. The endogenous Adamts5 expression in ATDC5 cells was increased by RelA/p65 overexpression and decreased by knockdown through its siRNA. The expression was also inhibited by the Rela deletion through Cre transfection in primary articular chondrocytes from Rela(fl/fl) mice. In the ex vivo culture of femoral head cartilage from mesenchymal cell-specific Rela knock-out (Prx1-Cre;Rela(fl/fl)) mice, aggrecanolysis was significantly lower than that in the Rela(fl/fl) cartilage. Finally, in the experimental mouse osteoarthritis model, ADAMTS5 and RelA were co-localized in chondrocytes of degraded articular cartilage. We conclude that RelA/p65 is a potent transcriptional activator of ADAMTS5 in chondrocytes during osteoarthritis development.
| S-EPMC3789961 | biostudies-literature
Project description:Increasing evidence shows that many transcription factors execute important biologic functions independent from their DNA-binding capacity. The NF-κB p65 (RELA) subunit is a central regulator of innate immunity. Here, we investigated the relative functional contribution of p65 DNA-binding and dimerization in p65-deficient human and murine cells reconstituted with single amino acid mutants preventing either DNA-binding (p65 E/I) or dimerization (p65 FL/DD). DNA-binding of p65 was required for RelB-dependent stabilization of the NF-κB p100 protein. The antiapoptotic function of p65 and expression of the majority of TNF-α-induced genes were dependent on p65's ability to bind DNA and to dimerize. Chromatin immunoprecipitation with massively parallel DNA sequencing experiments revealed that impaired DNA-binding and dimerization strongly diminish the chromatin association of p65. However, there were also p65-independent TNF-α-inducible genes and a subgroup of p65 binding sites still allowed some residual chromatin association of the mutants. These sites were enriched in activator protein 1 (AP-1) binding motifs and showed increased chromatin accessibility and basal transcription. This suggests a mechanism of assisted p65 chromatin association that can be in part facilitated by chromatin priming and cooperativity with other transcription factors such as AP-1.-Riedlinger, T., Liefke, R., Meier-Soelch, J., Jurida, L., Nist, A., Stiewe, T., Kracht, M., Schmitz, M. L. NF-κB p65 dimerization and DNA-binding is important for inflammatory gene expression.
| S-EPMC6404571 | biostudies-literature
Project description:Nuclear factor κB (NF-κB) is a family of critical transcription factors that play a critical role in innate immune responses and inflammation, yet the molecular mechanisms responsible for its tight regulation is not fully understood. In this study, we identified LRRC25, a member of leucine-rich repeat (LRR)-containing protein family, as a negative regulator in the NF-κB signaling pathway. Ectopic expression of LRRC25 impaired NF-κB activation, whereas knockout of LRRC25 potentiated NF-κB activation and enhanced the production of inflammatory cytokines. Further study demonstrated that the LRR domain of LRRC25 interacted with the Rel Homology domain (RHD) of p65/RelA and promotes the degradation of p65/RelA. Furthermore, LRRC25 enhanced the interaction between p65/RelA and cargo receptor p62, thus facilitating the degradation of p65/RelA through autophagy pathway. Our study has not only identified LRRC25 as a novel inhibitor of NF-κB signaling pathway, but also uncovers a new mechanism of crosstalk between NF-κB signaling and autophagy pathways.
| S-EPMC5647368 | biostudies-literature