Inducible phosphorylation of NF-kappa B p65 at serine 468 by T cell costimulation is mediated by IKK epsilon

PTPN20 promotes metastasis through activating NF-κB signaling in triple-negative breast cancer

BACKGROUND

Cancer metastasis remains a major challenge in the clinical management of triple-negative breast cancer (TNBC). The NF-κB signaling pathway has been implicated as a crucial factor in the development of metastases, but the underlying molecular mechanisms remain largely unclear.

METHODS

PTPN20 expression was evaluated using data from the Sweden Cancerome Analysis Network-Breast and The Cancer Genome Atlas database, as well as by western blotting and immunohistochemistry in 88 TNBC patients. The ability of PTPN20 to activate NF-κB was assessed by luciferase reporter assays. The effects of PTPN20 overexpression and knockdown via short hairpin RNA were examined in TNBC cell lines by wound healing and transwell matrix penetration assays. Additionally, we analyzed the growth and metastasis abilitiy of 4T1 xenograft tumors in nude mice.

RESULTS

PTPN20 levels were elevated in TNBC cell lines and patient samples compared to controls, and higher protein levels correlated with metastasis-free survival. Overexpression of PTPN20 enhanced migration and invasion in vitro, and promoted lung metastasis in vivo. Our finding revealed that PTPN20 activates NF-κB signaling by dephosphorylating p65 at Ser468, preventing its binding to COMMD1, thereby protecting p65 from degradation. Downregulation of PTPN20 effectively inhibit, while p65 S468A mutant restored the migratory and invasive abilities of TNBC cells.

CONCLUSIONS

Collectively, our results demonstrate that PTPN20 plays a critical role in TNBC metastasis through the activation of NF-κB signaling. We propose that PTPN20 may serve as a novel prognostic marker and potential therapeutic target for the treatment of TNBC.

Knock-Out of IKKepsilon Ameliorates Atherosclerosis and Fatty Liver Disease by Alterations of Lipid Metabolism in the PCSK9 Model in Mice

The inhibitor-kappaB kinase epsilon (IKKε) represents a non-canonical IκB kinase that modulates NF-κB activity and interferon I responses. Inhibition of this pathway has been linked with atherosclerosis and metabolic dysfunction-associated steatotic liver disease (MASLD), yet the results are contradictory. In this study, we employed a combined model of hepatic PCSK9D377Y overexpression and a high-fat diet for 16 weeks to induce atherosclerosis and liver steatosis. The development of atherosclerotic plaques, serum lipid concentrations, and lipid metabolism in the liver and adipose tissue were compared between wild-type and IKKε knock-out mice. The formation and progression of plaques were markedly reduced in IKKε knockout mice, accompanied by reduced serum cholesterol levels, fat deposition, and macrophage infiltration within the plaque. Additionally, the development of a fatty liver was diminished in these mice, which may be attributed to decreased levels of multiple lipid species, particularly monounsaturated fatty acids, triglycerides, and ceramides in the serum. The modulation of several proteins within the liver and adipose tissue suggests that de novo lipogenesis and the inflammatory response are suppressed as a consequence of IKKε inhibition. In conclusion, our data suggest that the knockout of IKKε is involved in mechanisms of both atherosclerosis and MASLD. Inhibition of this pathway may therefore represent a novel approach to the treatment of cardiovascular and metabolic diseases.

Post-translational modifications of p65: state of the art

P65, a protein subunit of NF-κB, is a widely distributed transcription factor in eukaryotic cells and exerts diverse regulatory functions. Post-translational modifications such as phosphorylation, acetylation, methylation and ubiquitination modulate p65 transcriptional activity and function, impacting various physiological and pathological processes including inflammation, immune response, cell death, proliferation, differentiation and tumorigenesis. The intricate interplay between these modifications can be antagonistic or synergistic. Understanding p65 post-translational modifications not only elucidates NF-κB pathway regulation but also facilitates the identification of therapeutic targets and diagnostic markers for associated clinical conditions.

Molecular cloning and functional characterization of pigeon IKKε

Inhibitor of nuclear factor kappa-B kinase ε (IKKε), a member of the non-canonical IκB kinase family, plays a critical role in connecting various signaling pathways associated with the initiation of type I interferon (IFN) production. Although the importance of IKKε in innate immunity has been well established in mammals and fish, its characterization and function in pigeons have remained largely unexplored. In this study, we successfully cloned pigeon IKKε (piIKKε) from pigeon embryo fibroblasts (PEFs) for the first time. This gene encodes 722 amino acids and shares high amino acid similarity with its duck and goose counterparts. piIKKε showed a diffuse cytoplasmic distribution and broad expression in all tissues examined. Overexpression of piIKKε in PEFs significantly activated the IFN-β promoter, with both the kinase and CC domains of piIKKε playing key roles in initiating IFN-β expression. Knockdown of piIKKε using small interfering RNA significantly reduced the levels of IFN-β induced by NDV, AIV, poly (I:C), or SeV. Furthermore, the presence of piIKKε resulted in a remarkable reduction in the replication of both avian influenza virus (AIV) H9N2 and Newcastle disease virus (NDV) in PEFs. Our results demonstrate that piIKKε plays a critical role in mediating antiviral innate immunity in pigeons.

Downstream STING pathways IRF3 and NF-κB differentially regulate CCL22 in response to cytosolic dsDNA

Double-stranded DNA (dsDNA) in the cytoplasm of eukaryotic cells is abnormal and typically indicates the presence of pathogens or mislocalized self-DNA. Multiple sensors detect cytosolic dsDNA and trigger robust immune responses via activation of type I interferons. Several cancer immunotherapy treatments also activate cytosolic nucleic acid sensing pathways, including oncolytic viruses, nucleic acid-based cancer vaccines, and pharmacological agonists. We report here that cytosolic dsDNA introduced into malignant cells can robustly upregulate expression of CCL22, a chemokine responsible for the recruitment of regulatory T cells (Tregs). Tregs in the tumor microenvironment are thought to repress anti-tumor immune responses and contribute to tumor immune evasion. Surprisingly, we found that CCL22 upregulation by dsDNA was mediated primarily by interferon regulatory factor 3 (IRF3), a key transcription factor that activates type I interferons. This finding was unexpected given previous reports that type I interferon alpha (IFN-α) inhibits CCL22 and that IRF3 is associated with strong anti-tumor immune responses, not Treg recruitment. We also found that CCL22 upregulation by dsDNA occurred concurrently with type I interferon beta (IFN-β) upregulation. IRF3 is one of two transcription factors downstream of the STimulator of INterferon Genes (STING), a hub adaptor protein through which multiple dsDNA sensors transmit their signals. The other transcription factor downstream of STING, NF-κB, has been reported to regulate CCL22 expression in other contexts, and NF-κB has also been associated with multiple pro-tumor functions, including Treg recruitment. However, we found that NF-κB in the context of activation by cytosolic dsDNA contributed minimally to CCL22 upregulation compared with IRF3. Lastly, we observed that two strains of the same cell line differed profoundly in their capacity to upregulate CCL22 and IFN-β in response to dsDNA, despite apparent STING activation in both cell lines. This finding suggests that during tumor evolution, cells can acquire, or lose, the ability to upregulate CCL22. This study adds to our understanding of factors that may modulate immune activation in response to cytosolic DNA and has implications for immunotherapy strategies that activate DNA sensing pathways in cancer cells.

Oxoaporphine Pr(III) complex inhibits hepatocellular carcinoma progression and metastasis by disrupting tumor cell-macrophage crosstalk

Tumor cells and macrophages communicate through the secretion of various cytokines to jointly promote the malignant development of cancers. We synthesized and characterized an oxoaporphine Pr(III) complex (PrL3(NO3)3) and found that it inhibits hepatocellular carcinoma (HCC) progression and metastasis by disrupting HCC cell-macrophage crosstalk. PrL3(NO3)3 treatment upregulated CD86, TNF-α, and IL-1β and downregulated CD163, CD206, CCL2, and VEGFA in macrophages. Our mRNA-Seq results demonstrated that PrL3(NO3)3 inhibited macrophage M2-like polarization by inhibiting the AMPK pathway and activating the NF-κB pathway by upregulating RelA/p65 Ser536 phosphorylation. This kind of macrophage polarization significantly inhibited HCC cell proliferation, migration, and invasion. In addition, PrL3(NO3)3 inhibited the migration, invasion, and chemotaxis of HCC cells by downregulating the expression of EMT-related markers and CCL2. hTFtarget database analysis revealed that PrL3(NO3)3 inhibited NF-κB nuclear translocation by upregulating RelA/p65 Ser536 phosphorylation in HCC cells, thereby downregulating the expression of Snail and CCL2. HCC tissue microarray analysis revealed that downregulation of RelA/p65 Ser536 phosphorylation is a driving event in HCC malignant progression. In conclusion, PrL3(NO3)3 effectively inhibits HCC cell-macrophage crosstalk by upregulating RelA/p65 Ser536 phosphorylation. This is the first report of a lanthanide complex exerting regulatory effects on both tumors and tumor-associated macrophages, providing a new strategy for the development of effective antitumor drugs.

Sanguinarine Inhibition of TNF-α-Induced CCL2, IKBKE/NF-κB/ERK1/2 Signaling Pathway, and Cell Migration in Human Triple-Negative Breast Cancer Cells

Angiogenesis is a process that drives breast cancer (BC) progression and metastasis, which is linked to the altered inflammatory process, particularly in triple-negative breast cancer (TNBC). In targeting inflammatory angiogenesis, natural compounds are a promising option for managing BC. Thus, this study was designed to determine the natural alkaloid sanguinarine (SANG) potential for its antiangiogenic and antimetastatic properties in triple-negative breast cancer (TNBC) cells. The cytotoxic effect of SANG was examined in MDA-MB-231 and MDA-MB-468 cell models at a low molecular level. In this study, SANG remarkably inhibited the inflammatory mediator chemokine CCL2 in MDA-MB-231 and MDA-MB-468 cells. Furthermore, qRT-PCR confirmed with Western analysis studies showed that mRNA CCL2 repression was concurrent with reducing its main regulator IKBKE and NF-κB signaling pathway proteins in both TNBC cell lines. The total ERK1/2 protein was inhibited in the more responsive MDA-MB-231 cells. SANG exhibited a higher potential to inhibit cell migration in MDA-MB-231 cells compared to MDA-MB-468 cells. Data obtained in this study suggest a unique antiangiogenic and antimetastatic effect of SANG in the MDA-MB-231 cell model. These effects are related to the compound’s ability to inhibit the angiogenic CCL2 and impact the ERK1/2 pathway. Therefore, SANG use may be recommended as a component of the therapeutic strategy for TNBC.

Development of (4-Phenylamino)quinazoline Alkylthiourea Derivatives as Novel NF-κB Inhibitors

For many inflammatory diseases, new effective drugs with fewer side effects are needed. While it appears promising to target the activation of the central pro-inflammatory transcription factor NF-κB, many previously discovered agents suffered from cytotoxicity. In this study, new alkylthiourea quinazoline derivatives were developed that selectively inhibit the activation of NF-κB in macrophage-like THP−1 cells while showing low general cytotoxicity. One of the best compounds, 19, strongly inhibited the production of IL-6 (IC50 = 0.84 µM) and, less potently, of TNFα (IC50 = 4.0 µM); in comparison, the reference compound, caffeic acid phenethyl ester (CAPE), showed IC50s of 1.1 and 11.4 µM, respectively. Interestingly, 19 was found to block the translocation of the NF-κB dimer to the nucleus, although its release from the IκB complex was unaffected. Furthermore, 19 suppressed the phosphorylation of NF-κB-p65 at Ser468 but not at Ser536; however, 19 did not inhibit any kinase involved in NF-κB activation. The only partial suppression of p65 phosphorylation might be associated with fewer side effects. Since several compounds selectively induced cell death in activated macrophage-like THP−1 cells, they might be particularly effective in various inflammatory diseases that are exacerbated by excess activated macrophages, such as arteriosclerosis and autoimmune diseases.

Role of IKKε in the Metabolic Diseases: Physiology, Pathophysiology, and Pharmacology

IKKε (inhibitor of nuclear factor kappa-B kinase ε) is a member of the noncanonical NF-κB pathway. It participates in the inflammatory response and innate immunity against bacteria. In recent decades, IKKε has been closely associated with metabolic regulation. Inhibition of the IKKε pathway can improve fat deposition in the liver, reduce subcutaneous fat inflammation, and improve liver gluconeogenesis in obesity. IKKε is expected to be a new therapeutic target for metabolic diseases such as nonalcoholic fatty liver disease, diabetes, and obesity. Herein, we summarize the structural characterization, physiological function, and pathological role of IKKε in metabolic diseases and small molecule inhibitors of IKKε.

Therapeutic targeting of TANK-binding kinase signaling towards anticancer drug development: Challenges and opportunities

TANK-binding kinase 1 (TBK1) plays a fundamental role in regulating the cellular responses and controlling several signaling cascades. It regulates inflammatory, interferon, NF-κB, autophagy, and Akt pathways. Post-translational modifications (PTM) of TBK1 control its action and subsequent cellular signaling. The dysregulation of the TBK1 pathway is correlated to many pathophysiological conditions, including cancer, that implicates the promising therapeutic advantage for targeting TBK1. The present study summarizes current updates on the molecular mechanisms and cancer-inducing roles of TBK1. Designed inhibitors of TBK1 are considered a potential therapeutic agent for several diseases, including cancer. Data from pre-clinical tumor models recommend that the targeting of TBK1 could be an attractive strategy for anti-tumor therapy. This review further highlighted the therapeutic potential of potent and selective TBK1 inhibitors, including Amlexanox, Compound II, BX795, MRT67307, SR8185 AZ13102909, CYT387, GSK8612, BAY985, and Domainex. These inhibitors may be implicated to facilitate therapeutic management of cancer and TBK1-associated diseases in the future.

Regulation of IRF3 activation in Human Antiviral Signalling Pathways

The interferon regulatory factor (IRF) family of transcription factors play a vital role in the human innate antiviral immune responses with production of interferons (IFNs) as a hallmark outcome of activation. In recent years, IRF3 has been considered a principal early regulator of type I IFNs (TI-IFNs) directly downstream of intracellular virus sensing. Despite decades of research on IRF-activating pathways, many questions remain on the regulation of IRF3 activation. The kinases IκB kinase epsilon (IKKε) and TANK-binding kinase-1 (TBK1) and the scaffold proteins TRAF family member-associated NF-kappa-B activator (TANK), NF-kappa-B-activating kinase-associated protein 1 (NAP1) and TANK-binding kinase 1-binding protein 1 (TBKBP1)/similar to NAP1 TBK1 adaptor (SINTBAD) are believed to be core components of an IRF3-activation complex yet their contextual involvement and complex composition are still unclear. This review will give an overview of antiviral signaling pathways leading to the activation of IRF3 and discuss recent developments in our understanding of its proximal regulation.

Human MicroRNAs Attenuate the Expression of Immediate Early Proteins and HCMV Replication during Lytic and Latent Infection in Connection with Enhancement of Phosphorylated RelA/p65 (Serine 536) That Binds to MIEP

Attenuating the expression of immediate early (IE) proteins is essential for controlling the lytic replication of human cytomegalovirus (HCMV). The human microRNAs (hsa-miRs), miR-200b-3p and miR-200c-3p, have been identified to bind the 3′-untranslated region (3′-UTR) of the mRNA encoding IE proteins. However, whether hsa-miRs can reduce IE72 expression and HCMV viral load or exhibit a crosstalk with the host cellular signaling machinery, most importantly the NF-κB cascade, has not been evaluated. In this study, argonaute-crosslinking and immunoprecipitation-seq revealed that miR-200b-3p and miR-200c-3p bind the 3′-UTR of UL123, which is a gene that encodes IE72. The binding of these miRNAs to the 3′-UTR of UL123 was verified in transfected cells stably expressing GFP. We used miR-200b-3p/miR-200c-3p mimics to counteract the downregulation of these miRNA after acute HCMV infection. This resulted in reduced IE72/IE86 expression and HCMV VL during lytic infection. We determined that IE72/IE86 alone can inhibit the phosphorylation of RelA/p65 at the Ser⁵³⁶ residue and that p-Ser⁵³⁶ RelA/p65 binds to the major IE promoter/enhancer (MIEP). The upregulation of miR-200b-3p and miR-200c-3p resulted in the phosphorylation of RelA/p65 at Ser⁵³⁶ through the downregulation of IE, and the binding of the resultant p-Ser⁵³⁶ RelA/p65 to MIEP resulted in a decreased production of pro-inflammatory cytokines. Overall, miR-200b-3p and miR-200c-3p—together with p-Ser⁵³⁶ RelA/p65—can prevent lytic HCMV replication during acute and latent infection

Human Metapneumovirus Induces IRF1 via TANK-Binding Kinase 1 and Type I IFN

The innate immune and host-protective responses to viruses, such as the airway pathogen human metapneumovirus (HMPV), depend on interferons (IFNs) that is induced through TANK-binding kinase 1 (TBK1) and IFN regulatory factors (IRFs). The transcription factor IRF1 is important for host resistance against several viruses and has a key role in induction of IFN-λ at mucosal surfaces. In most cell types IRF1 is expressed at very low levels, but its mRNA is rapidly induced when the demand for IRF1 activity arises. Despite general recognition of the importance of IRF1 to antiviral responses, the molecular mechanisms by which IRF1 is regulated during viral infections are not well understood. Here we identify the serine/threonine kinase TBK1 and IFN-β as critical regulators of IRF1 mRNA and protein levels in human monocyte-derived macrophages. We find that inhibition of TBK1 activity either by the semi-selective TBK1/IKKε inhibitor BX795 or by siRNA-mediated knockdown abrogates HMPV-induced expression of IRF1. Moreover, we show that canonical NF-κB signaling is involved in IRF1 induction and that the TBK1/IKKε inhibitor BX795, but not siTBK1 treatment, impairs HMPV-induced phosphorylation of the NF-κB subunit p65. At later time-points of the infection, IRF1 expression depended heavily on IFN-β-mediated signaling via the IFNAR-STAT1 pathway. Hence, our results suggest that TBK1 activation and TBK1/IKKε-mediated phosphorylation of the NF-κB subunit p65 control transcription of IRF1. Our study identifies a novel mechanism for IRF1 induction in response to viral infection of human macrophages that could be relevant not only to defense against HMPV, but also to other viral, bacterial and fungal pathogens.

A review on the role of TANK-binding kinase 1 signaling in cancer

TANK-binding kinase 1 (TBK1) regulates various biological processes including, NF-κB signaling, immune response, autophagy, cell division, Ras-mediated oncogenesis, and AKT pro-survival signaling. Enhanced TBK1 activity is associated with autoimmune diseases and cancer, suggesting its role in therapeutic targeting of interferonopathies. In addition, dysregulation of TBK1 activity promotes several inflammatory disorders and oncogenesis. Structural and biochemical study reports provide the molecular process of TBK1 activation and recap the substrate selection about TBK1. This review summarizes recent findings on the molecular mechanisms by which TBK1 is involved in cancer signaling. The IKK-ε and TBK1 are together associated with inflammatory diseases by inducing type I IFNs. Furthermore, TBK1 signaling regulates radiation-induced epithelial-mesenchymal transition by controlling phosphorylation of GSK-3β and expression of Zinc finger E-box-binding homeobox 1, suggesting, TBK1 could be targeted for radiotherapy-induced metastasis therapy. Despite a considerable increase in the list of TBK1 inhibitors, only a few has potential to control cancer. Among them, a compound BX795 is considered a potent and selective inhibitor of TBK1. We discussed the therapeutic potential of small-molecule inhibitors of TBK1, particularly those with high selectivity, which will enable further exploration in the therapeutic management of cancer and inflammatory diseases.

ERα-dependent estrogen-TNFα signaling crosstalk increases cisplatin tolerance and migration of lung adenocarcinoma cells

Lung adenocarcinoma is the most common type of lung cancer in women. Our previous studies demonstrated that 17β-estradiol (E2) promoted lung adenocarcinoma cell proliferation and tumor growth through estrogen receptor ERα. Transcriptomic analysis suggested that E2 potentiated TNFα-NFκB signaling in ERα-expressing lung adenocarcinoma cells. This study further demonstrated that E2 increased TNFα receptor expression and TNFα-triggered NFκB activity in ERα-expressing cells. E2-activated ERα had no physical association with NFκB p65/p50 heterodimer but facilitated TNFα-initiated IκBα degradation, NFκB nuclear translocation, and S468/S536 phosphorylation of p65 essential for NFκB activity. While knockdown of ERα prevented E2 from boosting NFκB activity, antiestrogen ICI 182,780 stimulated NFκB activity like E2. Inhibition of GSK3β hampered E2:ERα-promoted NFκB activity and abolished S468 phosphorylation of p65, suggesting that GSK3β played a role in the E2-TNFα signaling crosstalk. In ERα-expressing cells, E2 and TNFα synergistically regulated many genes that were not typically responsive to either E2 or TNFα. Functional analysis of microarray data inferred that E2/TNFα-induced transcriptomic changes improved cell survival and movement. Viability and colony formation assays validated that E2 and TNFα together increased cisplatin tolerance of ERα-expressing cells. Wound healing assays also confirmed that E2/TNFα cotreatment increased cell migration in an ERα-dependent manner. E2/TNFα-induced dysregulation of genes such as cell survival and movement-associated genes, proto-oncogenes, metallothioneins and histone core genes was correlated with poor overall survival in patients. In summary, E2 and TNFα engaged in an ERα-dependent positive crosstalk in lung adenocarcinoma cells, consequently increasing NFκB activation, cisplatin tolerance and cell migration and worsening prognosis.

Interaction of Adipocyte Metabolic and Immune Functions Through TBK1

Adipocytes and adipose tissue play critical roles in the regulation of metabolic homeostasis. In obesity and obesity-associated metabolic diseases, immune cells infiltrate into adipose tissues. Interaction between adipocytes and immune cells re-shapes both metabolic and immune properties of adipose tissue and dramatically changes metabolic set points. Both the expression and activity of the non-canonical IKK family member TBK1 are induced in adipose tissues during diet-induced obesity. TBK1 plays important roles in the regulation of both metabolism and inflammation in adipose tissue and thus affects glucose and energy metabolism. Here we review the regulation and functions of TBK1 and the molecular mechanisms by which TBK1 regulates both metabolism and inflammation in adipose tissue. Finally, we discuss the potential of a TBK1/IKKε inhibitor as a new therapy for metabolic diseases.

IκB kinase-ε-mediated phosphorylation triggers IRF-1 degradation in breast cancer cells

Interferon Regulatory Factors (IRFs) are key regulators of immunity, cell survival and apoptosis. IRF transcriptional activity and subcellular localization are tightly regulated by posttranscriptional modifications including phosphorylation. The IκB kinase family member IKK-ε is essential in regulating antiviral innate immunity mediated by IRFs but is now also recognized as an oncoprotein amplified and overexpressed in breast cancer cell lines and patient-derived tumors. In the present study, we report that the tumor suppressor IRF-1 is a specific target of IKK-ε in breast cancer cells. IKK-ε-mediated phosphorylation of IRF-1 dramatically decreases IRF-1 protein stability, accelerating IRF-1 degradation and quenching IRF-1 transcriptional activity. Chemical inhibition of IKK-ε activity, fully restores IRF-1 levels and function and positively correlates with inhibition of cell growth and proliferation of breast cancer cells. By using a breast cancer cell line stably expressing a dominant negative version of IRF-1 we were able to demonstrate that IKK-ε preferentially exerts its oncogenic potential in breast cancer through the regulation of IRF-1 and point to the IKK-ε-mediated phosphorylation of IRF-1 as a therapeutic target to overcome IKK-ε-mediated tumorigenesis.

Mutual regulation of metabolic processes and proinflammatory NF-κB signaling

The nuclear factor kappa B (NF-κB) signaling system, a key regulator of immunologic processes, also affects a plethora of metabolic changes associated with inflammation and the immune response. NF-κB-regulating signaling cascades, in concert with NF-κB-mediated transcriptional events, control the metabolism at several levels. NF-κB modulates apical components of metabolic processes including metabolic hormones such as insulin and glucagon, the cellular master switches 5' AMP-activated protein kinase and mTOR, and also numerous metabolic enzymes and their respective regulators. Vice versa, metabolic enzymes and their products also exert multilevel control of NF-κB activity, thereby creating a highly connected regulatory network. These insights have resulted in the identification of the noncanonical IκB kinase kinases IκB kinase ɛ and TBK1, which are upregulated by overnutrition, and may therefore be suitable potential therapeutic targets for metabolic syndromes. An inhibitor interfering with the activity of both kinases reduces obesity-related metabolic dysfunctions in mouse models and the encouraging results from a recent clinical trial indicate that targeting these NF-κB pathway components improves glucose homeostasis in a subset of patients with type 2 diabetes.

The Specific IKKε/TBK1 Inhibitor Amlexanox Suppresses Human Melanoma by the Inhibition of Autophagy, NF-κB and MAP Kinase Pathways

Inhibitor-kappaB kinase epsilon (IKKε) and TANK-binding kinase 1 (TBK1) are non-canonical IκB kinases, both described as contributors to tumor growth and metastasis in different cancer types. Several hints indicate that they are also involved in the pathogenesis of melanoma; however, the impact of their inhibition as a potential therapeutic measure in this "difficult-to-treat" cancer type has not been investigated so far. We assessed IKKε and TBK1 expression in human malignant melanoma cells, primary tumors and the metastasis of melanoma patients. Both kinases were expressed in the primary tumor and in metastasis and showed a significant overexpression in tumor cells in comparison to melanocytes. The pharmacological inhibition of IKKε/TBK1 by the approved drug amlexanox reduced cell proliferation, migration and invasion. Amlexanox did not affect the cell cycle progression nor apoptosis induction but significantly suppressed autophagy in melanoma cells. The analysis of potential functional downstream targets revealed that NF-кB and ERK pathways might be involved in kinase-mediated effects. In an in vivo xenograft model in nude mice, amlexanox treatment significantly reduced tumor growth. In conclusion, amlexanox was able to suppress tumor progression potentially by the inhibition of autophagy as well as NF-кB and MAP kinase pathways and might therefore constitute a promising candidate for melanoma therapy.

Role of Chondrocytes in the Development of Rheumatoid Arthritis Via Transmembrane Protein 147-Mediated NF-κB Activation

OBJECTIVE

We have previously reported that the coactivation of NF-κB and STAT3 in nonimmune cells, including synovial fibroblasts, enhances the expression of NF-κB target genes and plays a role in chronic inflammation and rheumatoid arthritis (RA). This study was undertaken to examine the role of NF-κB activation in chondrocytes and better understand the pathogenesis of RA. Furthermore, transmembrane protein 147 (TMEM147) was investigated as a representative NF-κB activator in chondrocytes.

METHODS

Clinical samples from RA patients were analyzed by immunohistochemistry. Specimens obtained from patients with polydactyly were used as control samples. The functional contribution of chondrocytes and TMEM147 to arthritis was examined in several murine models of RA. In vitro experiments (quantitative polymerase chain reaction, RNA interference, immunoprecipitation, and confocal microscopy) were performed to investigate the mechanism of action of TMEM147 in chondrocytes.

RESULTS

Samples obtained from RA patients and mouse models of RA showed coactivation of NF-κB and STAT3 in chondrocytes (P < 0.001). This coactivation induced a synergistic expression of NF-κB targets in vitro (P < 0.01). Chondrocyte-specific deletion of STAT3 significantly suppressed the development of cytokine-induced RA (P < 0.01). TMEM147 was highly expressed in chondrocytes from RA patient samples and the mouse models of RA. Gene silencing of TMEM147 or anti-TMEM147 antibody treatment inhibited the cytokine-mediated activation of NF-κB in vitro (P < 0.01) and suppressed cytokine-induced RA in vivo (P < 0.01). Mechanistically, TMEM147 molecules acted as scaffold proteins for the NF-κB complex, which included breakpoint cluster region and casein kinase 2, and enhanced NF-κB activity.

CONCLUSION

These results suggest that chondrocytes play a role in the development of RA via TMEM147-mediated NF-κB activation and indicate a novel therapeutic strategy for RA.

Essential Roles for the Non-Canonical IκB Kinases in Linking Inflammation to Cancer, Obesity, and Diabetes

Non-canonical IκB kinases (IKKs) TBK1 and IKKε have essential roles as regulators of innate immunity and cancer. Recent work has also implicated these kinases in distinctively controlling glucose homeostasis and repressing adaptive thermogenic and mitochondrial biogenic response upon obesity-induced inflammation. Additionally, TBK1 and IKKε regulate pancreatic β-cell regeneration. In this review, we summarize current data on the functions and molecular mechanisms of TBK1 and IKKε in orchestrating inflammation to cancer, obesity, and diabetes.

Inhibition of the protein kinase IKKepsilon attenuates neuropathic pain in mice

Inhibitor-kappaB kinase epsilon (IKKε, Ikbke) constitutes an NF-κB activating kinase with high homology to the classical I-κB kinase subunits, IKKα and IKKβ. It is expressed in nociceptive neurons in the spinal cord and in dorsal root ganglia (DRG) and involved in inflammatory nociception. Under inflammatory conditions, IKKε deficient mice show significantly less nociceptive behavior in comparison to wild type mice associated with reduced activation of NF-κB and attenuated NF-κB-dependent gene expression. The role of IKKε in neuropathic pain has not been investigated so far. We applied the spared nerve injury (SNI) model of neuropathic pain in mice and found an increased expression of IKKε in the spinal cord, the DRGs and the sciatic nerve after induction of neuropathy. Genetic depletion of IKKε or pharmacological inhibition by amlexanox led to a significant reduction of mechanical hyperalgesia and cold allodynia in comparison to control mice. Transcription factor ELISA indicated that the effects are mediated by reduced activation of NF-κB. Furthermore, immunofluorescence staining, qPCR and Western Blot analyses revealed that the decreased pain-like behavior was associated with a reduced activation of microglia, diminished expression of c-fos as well as a decreased activation of MAP-Kinases. In summary, we conclude that IKKε modulates mechanisms of neuropathic pain by activating NF-κB. The administration of IKKε inhibitors might therefore constitute a new and promising approach for the therapy of neuropathic pain.

Mechanisms of NF-κB p65 and strategies for therapeutic manipulation

The transcription factor NF-κB is a critical regulator of immune and inflammatory responses. In mammals, the NF-κB/Rel family comprises five members: p50, p52, p65 (Rel-A), c-Rel, and Rel-B proteins, which form homo- or heterodimers and remain as an inactive complex with the inhibitory molecules called IκB proteins in resting cells. Two distinct NF-κB signaling pathways have been described: 1) the canonical pathway primarily activated by pathogens and inflammatory mediators, and 2) the noncanonical pathway mostly activated by developmental cues. The most abundant form of NF-κB activated by pathologic stimuli via the canonical pathway is the p65:p50 heterodimer. Disproportionate increase in activated p65 and subsequent transactivation of effector molecules is integral to the pathogenesis of many chronic diseases such as the rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis, and even neurodegenerative pathologies. Hence, the NF-κB p65 signaling pathway has been a pivotal point for intense drug discovery and development. This review begins with an overview of p65-mediated signaling followed by discussion of strategies that directly target NF-κB p65 in the context of chronic inflammation.

Roles for the IKK-Related Kinases TBK1 and IKKε in Cancer

While primarily studied for their roles in innate immune response, the IκB kinase (IKK)-related kinases TANK-binding kinase 1 (TBK1) and IKKε also promote the oncogenic phenotype in a variety of cancers. Additionally, several substrates of these kinases control proliferation, autophagy, cell survival, and cancer immune responses. Here we review the involvement of TBK1 and IKKε in controlling different cancers and in regulating responses to cancer immunotherapy.

Hippocampal nuclear factor kappa B accounts for stress-induced anxiety behaviors via enhancing neuronal nitric oxide synthase (nNOS)-carboxy-terminal PDZ ligand of nNOS-Dexras1 coupling

Anxiety disorders are associated with a high social burden worldwide. Recently, increasing evidence suggests that nuclear factor kappa B (NF-κB) has significant implications for psychiatric diseases, including anxiety and depressive disorders. However, the molecular mechanisms underlying the role of NF-κB in stress-induced anxiety behaviors are poorly understood. In this study, we show that chronic mild stress (CMS) and glucocorticoids dramatically increased the expression of NF-κB subunits p50 and p65, phosphorylation and acetylation of p65, and the level of nuclear p65 in vivo and in vitro, implicating activation of NF-κB signaling in chronic stress-induced pathological processes. Using the novelty-suppressed feeding (NSF) and elevated-plus maze (EPM) tests, we found that treatment with pyrrolidine dithiocarbamate (PDTC; intra-hippocampal infusion), an inhibitor of NF-κB, rescued the CMS- or glucocorticoid-induced anxiogenic behaviors in mice. Microinjection of PDTC into the hippocampus reversed CMS-induced up-regulation of neuronal nitric oxide synthase (nNOS), carboxy-terminal PDZ ligand of nNOS (CAPON), and dexamethasone-induced ras protein 1 (Dexras1) and dendritic spine loss of dentate gyrus (DG) granule cells. Moreover, over-expression of CAPON by infusing LV-CAPON-L-GFP into the hippocampus induced nNOS-Dexras1 interaction and anxiety-like behaviors, and inhibition of NF-κB by PDTC reduced the LV-CAPON-L-GFP-induced increases in nNOS-Dexras1 complex and anxiogenic-like effects in mice. These findings indicate that hippocampal NF-κB mediates anxiogenic behaviors, probably via regulating the association of nNOS-CAPON-Dexras1, and uncover a novel approach to the treatment of anxiety disorders.

vFLIP upregulates IKKε, leading to spindle morphology formation through RelA activation

Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) vFLIP, a latent gene of KSHV, was first identified as a FLICE-inhibitory protein (FLIP) protecting cells from apoptosis. The vFLIP protein has been shown to activate the NF-κB signaling involved in spindle morphology formation both in HUVECs infected with KSHV and Kaposi's sarcoma (KS) itself. In this study, we independently established stably vFLIP-expressing cells and showed that they exhibited upregulated NF-κB family protein expression independent of the ability of IKKs to bind vFLIP. Further, vFLIP induced upregulation of IKKε, phosphorylation of RelA at Ser468 (p-RelA S468) and nuclear localization of Re1A concomitant with spindle morphology formation, and these effects were reversed by knockdown of IKKε and treatment with Bay-11. Overexpression of IKKε alone also showed spindle morphology formation with p-RelA S468. In conclusion, the spindle cell morphology in KS should be induced by RelA activation (p-RelA S468) by IKKε upregulation in vFLIP-expressing EA hy926 cells.

STIM- and Orai-mediated calcium entry controls NF-κB activity and function in lymphocytes

The central role of Ca²⁺ signaling in the development of functional immunity and tolerance is well established. These signals are initiated by antigen binding to cognate receptors on lymphocytes that trigger store operated Ca²⁺ entry (SOCE). The underlying mechanism of SOCE in lymphocytes involves TCR and BCR mediated activation of Stromal Interaction Molecule 1 and 2 (STIM1/2) molecules embedded in the ER membrane leading to their activation of Orai channels in the plasma membrane. STIM/Orai dependent Ca²⁺ signals guide key antigen induced lymphocyte development and function principally through direct regulation of Ca²⁺ dependent transcription factors. The role of Ca²⁺ signaling in NFAT activation and signaling is well known and has been studied extensively, but a wide appreciation and mechanistic understanding of how Ca²⁺ signals also shape the activation and specificity of NF-κB dependent gene expression has lagged. Here we discuss and interpret what is known about Ca²⁺ dependent mechanisms of NF-kB activation, including what is known and the gaps in our understanding of how these signals control lymphocyte development and function.

Prognostic significance of preoperative IKBKE expression in esophageal squamous cell carcinoma

Purpose

IκB kinase epsilon (IKBKE; IKKε), a member of the nuclear factor-κB kinase inhibitor family, is upregulated in several human cancers, including breast cancer, prostate cancer, and ovarian cancer. Esophageal squamous cell carcinoma (ESCC) is one of the most common and most aggressively malignant cancers with dismal prognosis. However, the state of IKBKE expression in ESCC is still unknown and its potential value remains unexplored.

Patients and methods

IKBKE protein expression was evaluated by immunohistochemistry in 118 paraffin specimens of ESCC treated by curative surgery. All patients were regularly followed up by telephone over 3 years after surgery. The chi-square test, Kaplan–Meier method, and Cox proportional hazard regression model were used to analyze the relationship of IKBKE expression, clinicopathological characteristics, and prognostic value for ESCC.

Results

IKBKE expression was 61.9% (73/118) in paraffin-embedded archived ESCC. Its expression was significantly associated with tumor differentiation grade (p=0.045) and advanced TNM (pathologic tumor node metastasis) stages (p=0.023). In univariate analysis, IKBKE expression was closely associated with decreased 3-year disease-free survival (HR 1.804, 95% CI 1.076–3.027; p=0.023) and overall survival (HR 2.118, 95% CI 1.189–3.773; p=0.009). Meanwhile, in multivariate analysis it was identified as an independent prognostic factor for 3-year disease-free survival (HR 1.777, 95% CI 1.034–3.054; p=0.037) and overall survival (HR 2.078, 95% CI 1.138–3.796; p=0.017).

Conclusion

Our data indicated for the first time that IKKε expression is a highly recurrent event in ESCC and could play a pivotal role in the evaluation of prognosis. IKBKE upregulation is negatively associated with disease-free survival and overall survival. Therefore, IKBKE could serve as a prognostic variable and potential therapeutic target for this malignancy.

Detection of IKKε by immunohistochemistry in primary breast cancer: association with EGFR expression and absence of lymph node metastasis

Background

IKKε is an oncogenic kinase that was found amplified and overexpressed in a substantial percentage of human breast cancer cell lines and primary tumors using genomic and gene expression analyses. Molecular studies have provided the rational for a key implication of IKKε in breast cancer cells proliferation and invasiveness through the phosphorylation of several substrates.

Methods

Here, we performed immunohistochemical detection of IKKε expression on tissue microarrays constituted of 154 characterized human breast cancer tumors. We further determined the association with multiple clinicopathological parameters and 5-years overall, disease-free and distant disease free survival.

Results

We observed expression of IKKε in 60.4% of the breast cancer tumors. IKKε expression status showed no association with a panel of markers used for molecular classification of the tumors, including ER/PR/HER2 status, or with the molecular subtypes. However, IKKε expression was inversely associated with lymph node metastasis status (p = 0.0032). Additionally, we identified a novel association between IKKε and EGFR expression (p = 0.0011).

Conclusions

The unexpected observation of an inverse association between IKKε and lymph node metastasis advocates for larger scale immunohistochemical profiling of primary breast tumors to clarify the role of IKKε in metastasis. This study suggests that breast cancer tumors expressing EGFR and IKKε may be potential targets for drugs aiming at inhibiting IKKε activity or expression.

Novel Serine 176 Phosphorylation of YBX1 Activates NF-κB in Colon Cancer

Y box protein 1 (YBX1) is a well known oncoprotein that has tumor-promoting functions. YBX1 is widely considered to be an attractive therapeutic target in cancer. To develop novel therapeutics to target YBX1, it is of great importance to understand how YBX1 is finely regulated in cancer. Previously, we have shown that YBX1 could function as a tumor promoter through phosphorylation of its Ser-165 residue, leading to the activation of the NF-κB signaling pathway (1). In this study, using mass spectrometry analysis, we discovered a distinct phosphorylation site, Ser-176, on YBX1. Overexpression of the YBX1-S176A (serine-to-alanine) mutant in either HEK293 cells or colon cancer HT29 cells showed dramatically reduced NF-κB-activating ability compared with that of WT-YBX1, confirming that Ser-176 phosphorylation is critical for the activation of NF-κB by YBX1. Importantly, the mutant of Ser-176 and the previously reported Ser-165 sites regulate distinct groups of NF-κB target genes, suggesting the unique and irreplaceable function of each of these two phosphorylated serine residues. Our important findings could provide a novel cancer therapy strategy by blocking either Ser-176 or Ser-165 phosphorylation or both of YBX1 in colon cancer.

Natural Compound Histone Deacetylase Inhibitors (HDACi): Synergy with Inflammatory Signaling Pathway Modulators and Clinical Applications in Cancer

The remarkable complexity of cancer involving multiple mechanisms of action and specific organs led researchers Hanahan and Weinberg to distinguish biological capabilities acquired by cancer cells during the multistep development of human tumors to simplify its understanding. These characteristic hallmarks include the abilities to sustain proliferative signaling, evade growth suppressors, resist cell death, enable replicative immortality, induce angiogenesis, activate invasion and metastasis, avoid immune destruction, and deregulate cellular energetics. Furthermore, two important characteristics of tumor cells that facilitate the acquisition of emerging hallmarks are tumor-promoting inflammation and genome instability. To treat a multifactorial disease such as cancer, a combination treatment strategy seems to be the best approach. Here we focus on natural histone deacetylase inhibitors (HDACi), their clinical uses as well as synergies with modulators of the pro-inflammatory transcription factor signaling pathways.

The Regulation of NF-κB Subunits by Phosphorylation

The NF-κB transcription factor is the master regulator of the inflammatory response and is essential for the homeostasis of the immune system. NF-κB regulates the transcription of genes that control inflammation, immune cell development, cell cycle, proliferation, and cell death. The fundamental role that NF-κB plays in key physiological processes makes it an important factor in determining health and disease. The importance of NF-κB in tissue homeostasis and immunity has frustrated therapeutic approaches aimed at inhibiting NF-κB activation. However, significant research efforts have revealed the crucial contribution of NF-κB phosphorylation to controlling NF-κB directed transactivation. Importantly, NF-κB phosphorylation controls transcription in a gene-specific manner, offering new opportunities to selectively target NF-κB for therapeutic benefit. This review will focus on the phosphorylation of the NF-κB subunits and the impact on NF-κB function.

T Cell Receptor-induced Nuclear Factor κB (NF-κB) Signaling and Transcriptional Activation Are Regulated by STIM1- and Orai1-mediated Calcium Entry

T cell activation following antigen binding to the T cell receptor (TCR) involves the mobilization of intracellular Ca(2+) to activate the key transcription factors nuclear factor of activated T lymphocytes (NFAT) and NF-κB. The mechanism of NFAT activation by Ca(2+) has been determined. However, the role of Ca(2+) in controlling NF-κB signaling is poorly understood, and the source of Ca(2+) required for NF-κB activation is unknown. We demonstrate that TCR- but not TNF-induced NF-κB signaling upstream of IκB kinase activation absolutely requires the influx of extracellular Ca(2+) via STIM1-dependent Ca(2+) release-activated Ca(2+)/Orai channels. We further show that Ca(2+) influx controls phosphorylation of the NF-κB protein p65 on Ser-536 and that this posttranslational modification controls its nuclear localization and transcriptional activation. Notably, our data reveal that this role for Ca(2+) is entirely separate from its upstream control of IκBα degradation, thereby identifying a novel Ca(2+)-dependent distal step in TCR-induced NF-κB activation. Finally, we demonstrate that this control of distal signaling occurs via Ca(2+)-dependent PKCα-mediated phosphorylation of p65. Thus, we establish the source of Ca(2+) required for TCR-induced NF-κB activation and define a new distal Ca(2+)-dependent checkpoint in TCR-induced NF-κB signaling that has broad implications for the control of immune cell development and T cell functional specificity.

COMMD7 as a novel NEMO interacting protein involved in the termination of NF-κB signaling

NEMO/IKKγ is the regulatory subunit of the IκB Kinase (IKK) complex, required for the activation of the NF-κB pathway, which is involved in a variety of key processes, including immunity, inflammation, differentiation, and cell survival. Termination of NF-κB activity on specific -κB responsive genes, which is crucial for the resolution of inflammatory responses, can be achieved by direct degradation of the chromatin-bound NF-κB subunit RelA/p65, a process mediated by a protein complex that contains Copper Metabolism Murr1 Domain 1 (COMMD1). In this study, we identify COMMD7, another member of the COMMDs protein family, as a novel NEMO-interacting protein. We show that COMMD7 exerts an inhibitory effect on NF-κB activation upon TNFα stimulation. COMMD7 interacts with COMMD1 and together they cooperate to down-regulate NF-κB activity. Accordingly, termination of TNFα-induced NF-κB activity on the -κB responsive gene, Icam1, is defective in cells silenced for COMMD7 expression. Furthermore, this impairment is not greatly increased when we silence the expression of both COMMD7 and COMMD1 indicating that the two proteins participate in the same pathway of termination of TNFα-induced NF-κB activity. Importantly, we have demonstrated that COMMD7's binding to NEMO does not interfere with the binding to the IKKs, and that the disruption of the IKK complex through the use of the NBP competitor impairs the termination of NF-κB activity. We propose that an intact IKK complex is required for the termination of NF-κB-dependent transcription and that COMMD7 acts as a scaffold in the IKK-mediated NF-κB termination.

The protein kinase IKKepsilon contributes to tumour growth and tumour pain in a melanoma model

Inhibitor-kappaB kinase epsilon (IKKε) constitutes a non-canonical I-κB kinase, which amongst others modulates NF-κB activity. IKKε and NF-κB have both been described for their role in cell proliferation and their dysregulation has been associated with tumourigenesis and metastasis in multiple cancer types. Accordingly, overexpression and constitutive activation of NF-κB have also been shown in melanoma, however, the role of IKKε in this cancer type has not been investigated so far. Thus, we determined IKKε expression in malignant melanoma cells and we were able to show a significant overexpression of IKKε in tumour cells in comparison to melanocytes. Inhibition of IKKε either by shRNA or the pharmacological inhibitor amlexanox resulted in reduced cell proliferation associated with a cell cycle block in the G1-phase. Functional analysis indicated that NF-κB, Akt1 and MAPK pathways might be involved in the IKKε-mediated effects. In vivo, we applied a mouse melanoma skin cancer model to assess tumour growth and melanoma-associated pain in IKKε knockout mice as well as C57BL/6 mice after inoculation with IKKε-negative cells. In IKKε knockout mice, tumour growth was not altered as compared to IKKε wild type mice. However, melanoma associated pain was strongly suppressed accompanied by a reduced mRNA expression of a number of pain-relevant genes. In contrast, after inoculation of IKKε-depleted tumour cells, the development of melanoma was almost completely prevented. In conclusion, our data suggest that IKKε in the tumour plays an essential role in tumour initiation and progression while IKKε expression in tumour surrounding tissues contributes to melanoma-associated pain.

Neonatal High Bone Mass With First Mutation of the NF-κB Complex: Heterozygous De Novo Missense (p.Asp512Ser) RELA (Rela/p65)

Heritable disorders that feature high bone mass (HBM) are rare. The etiology is typically a mutation(s) within a gene that regulates the differentiation and function of osteoblasts (OBs) or osteoclasts (OCs). Nevertheless, the molecular basis is unknown for approximately one-fifth of such entities. NF-κB signaling is a key regulator of bone remodeling and acts by enhancing OC survival while impairing OB maturation and function. The NF-κB transcription complex comprises five subunits. In mice, deletion of the p50 and p52 subunits together causes osteopetrosis (OPT). In humans, however, mutations within the genes that encode the NF-κB complex, including the Rela/p65 subunit, have not been reported. We describe a neonate who died suddenly and unexpectedly and was found at postmortem to have HBM documented radiographically and by skeletal histopathology. Serum was not available for study. Radiographic changes resembled malignant OPT, but histopathological investigation showed morphologically normal OCs and evidence of intact bone resorption excluding OPT. Furthermore, mutation analysis was negative for eight genes associated with OPT or HBM. Instead, accelerated bone formation appeared to account for the HBM. Subsequently, trio-based whole exome sequencing revealed a heterozygous de novo missense mutation (c.1534_1535delinsAG, p.Asp512Ser) in exon 11 of RELA encoding Rela/p65. The mutation was then verified using bidirectional Sanger sequencing. Lipopolysaccharide stimulation of patient fibroblasts elicited impaired NF-κB responses compared with healthy control fibroblasts. Five unrelated patients with unexplained HBM did not show a RELA defect. Ours is apparently the first report of a mutation within the NF-κB complex in humans. The missense change is associated with neonatal osteosclerosis from in utero increased OB function rather than failed OC action. These findings demonstrate the importance of the Rela/p65 subunit within the NF-κB pathway for human skeletal homeostasis and represent a new genetic cause of HBM.

p97/VCP promotes Cullin-RING-ubiquitin-ligase/proteasome-dependent degradation of IκBα and the preceding liberation of RelA from ubiquitinated IκBα

Cullin‐RING‐ubiquitin‐ligase (CRL)‐dependent ubiquitination of the nuclear factor kappa B (NF‐κB) inhibitor IκBα and its subsequent degradation by the proteasome usually precede NF‐κB/RelA nuclear activity. Through removal of the CRL‐activating modification of their cullin subunit with the ubiquitin (Ub)‐like modifier NEDD8, the COP9 signalosome (CSN) opposes CRL Ub‐ligase activity. While RelA phosphorylation was observed to mediate NF‐κB activation independent of Ub‐proteasome‐pathway (UPP)‐dependent turnover of IκBα in some studies, a strict requirement of the p97/VCP ATPase for both, IκBα degradation and NF‐κB activation, was reported in others. In this study, we thus aimed to reconcile the mechanism for tumour necrosis factor (TNF)‐induced NF‐κB activation. We found that inducible phosphorylation of RelA is accomplished in an IKK‐complex‐dependent manner within the NF‐κB/RelA‐IκBα‐complex contemporaneous with the phosphorylation of IκBα, and that RelA phosphorylation is not sufficient to dissociate NF‐κB/RelA from IκBα. Subsequent to CRL‐dependent IκBα ubiquitination functional p97/VCP is essentially required for efficient liberation of (phosphorylated) RelA from IκBα, preceding p97/VCP‐promoted timely and efficient degradation of IκBα as well as simultaneous NF‐κB/RelA nuclear translocation. Collectively, our data add new facets to the knowledge about maintenance of IκBα and RelA expression, likely depending on p97/VCP‐supported scheduled basal NF‐κB activity, and the mechanism of TNF‐induced NF‐κB activation.

NOS1-derived nitric oxide promotes NF-κB transcriptional activity through inhibition of suppressor of cytokine signaling-1

The NF-κB pathway is central to the regulation of inflammation. Here, we demonstrate that the low-output nitric oxide (NO) synthase 1 (NOS1 or nNOS) plays a critical role in the inflammatory response by promoting the activity of NF-κB. Specifically, NOS1-derived NO production in macrophages leads to proteolysis of suppressor of cytokine signaling 1 (SOCS1), alleviating its repression of NF-κB transcriptional activity. As a result, NOS1(-/-) mice demonstrate reduced cytokine production, lung injury, and mortality when subjected to two different models of sepsis. Isolated NOS1(-/-) macrophages demonstrate similar defects in proinflammatory transcription on challenge with Gram-negative bacterial LPS. Consistently, we found that activated NOS1(-/-) macrophages contain increased SOCS1 protein and decreased levels of p65 protein compared with wild-type cells. NOS1-dependent S-nitrosation of SOCS1 impairs its binding to p65 and targets SOCS1 for proteolysis. Treatment of NOS1(-/-) cells with exogenous NO rescues both SOCS1 degradation and stabilization of p65 protein. Point mutation analysis demonstrated that both Cys147 and Cys179 on SOCS1 are required for its NO-dependent degradation. These findings demonstrate a fundamental role for NOS1-derived NO in regulating TLR4-mediated inflammatory gene transcription, as well as the intensity and duration of the resulting host immune response.

Local and Systemic IKKε and NF-κB Signaling Associated with Sjögren's Syndrome Immunopathogenesis

The activated NF-κB signaling pathway plays an important role in pathogenesis of primary Sjögren's syndrome (pSS). The inhibitor of κB (IκB) kinase (IKK) family such as IKKα, IKKβ, IKKγ, and IKKε, is required for this signaling. Our aim was to investigate the role of IKKα/β/γ/ε in patients with untreated pSS. In minor salivary glands from pSS patients, phosphorylated IKKε (pIKKε), pIκBα, and pNF-κB p65 (p-p65) were highly expressed in ductal epithelium and infiltrating mononuclear cells by immunohistochemistry, compared to healthy individuals. pIKKα/β and pIKKγ were both negative. And pIKKε positively related to expression of p-p65. Furthermore, pIKKε and p-p65 expression significantly correlated with biopsy focus score and overall disease activity. Meanwhile, in peripheral blood mononuclear cells from pSS patients, pIKKε, total IKKε, pIKKα/β, and p-p65 were significantly increased by western blot, compared to healthy controls. However, there was no difference in IKKγ and IκBα between pSS patients and healthy individuals. These results demonstrated an abnormality of IKKε, IκBα, and NF-κB in pSS, suggesting a potential target of treatment for pSS based on the downregulation of IKKε expression and deregulation of NF-κB pathway.

Role of Novel Serine 316 Phosphorylation of the p65 Subunit of NF-κB in Differential Gene Regulation

Nuclear factor κB (NF-κB) is a central coordinator in immune and inflammatory responses. Constitutive NF-κB is often found in some types of cancers, contributing to oncogenesis and tumor progression. Therefore, knowing how NF-κB is regulated is important for its therapeutic control. Post-translational modification of the p65 subunit of NF-κB is a well known approach for its regulation. Here, we reported that in response to interleukin 1β, the p65 subunit of NF-κB is phosphorylated on the novel serine 316. Overexpression of S316A (serine 316 → alanine) mutant exhibited significantly reduced ability to activate NF-κB and decreased cell growth as compared with wtp65 (wild type p65). Moreover, conditioned media from cells expressing the S316A-p65 mutant had a considerably lower ability to induce NF-κB than that of wtp65. Our data suggested that phosphorylation of p65 on Ser-316 controls the activity and function of NF-κB. Importantly, we found that phosphorylation at the novel Ser-316 site and other two known phosphorylation sites, Ser-529 and Ser-536, either individually or cooperatively, regulated distinct groups of NF-κB-dependent genes, suggesting the unique role of each individual phosphorylation site on NF-κB-dependent gene regulation. Our novel findings provide an important piece of evidence regarding differential regulation of NF-κB-dependent genes through phosphorylation of different p65 serine residues, thus shedding light on novel mechanisms for the pathway-specific control of NF-κB. This knowledge is key to develop strategies for prevention and treatment of constitutive NF-κB-driven inflammatory diseases and cancers.

NF-κB p65 Subunit Is Modulated by Latent Transforming Growth Factor-β Binding Protein 2 (LTBP2) in Nasopharyngeal Carcinoma HONE1 and HK1 Cells

NF-κB is a well-characterized transcription factor, widely known as a key player in tumor-derived inflammation and cancer development. Herein, we present the functional and molecular relevance of the canonical NF-κB p65 subunit in nasopharyngeal carcinoma (NPC). Loss- and gain-of-function approaches were utilized to reveal the functional characteristics of p65 in propagating tumor growth, tumor-associated angiogenesis, and epithelial-to-mesenchymal transition in NPC cells. Extracellular inflammatory stimuli are critical factors that trigger the NF-κB p65 signaling; hence, we investigated the components of the tumor microenvironment that might potentially influence the p65 signaling pathway. This led to the identification of an extracellular matrix (ECM) protein that was previously reported as a candidate tumor suppressor in NPC. Our studies on the Latent Transforming Growth Factor-β Binding Protein 2 (LTBP2) protein provides substantial evidence that it can modulate the p65 transcriptional activity. Re-expression of LTBP2 elicits tumor suppressive effects that parallel the inactivation of p65 in NPC cells. LTBP2 was able to reduce phosphorylation of p65 at Serine 536, inhibit nuclear localization of active phosphorylated p65, and impair the p65 DNA-binding ability. This results in a consequential down-regulation of p65-related gene expression. Therefore, the data suggest that the overall up-regulation of p65 expression and the loss of this candidate ECM tumor suppressor are milestone events contributing to NPC development.

Polymorphisms of IKBKE gene are associated with major depressive disorder and panic disorder

BACKGROUND

The immune system has been increasingly implicated in the development of mood and anxiety disorders. Inhibitor of kappa light polypeptide gene enhancer in B cells, kinase epsilon (IKBKE) gene encodes IKKε protein that is involved in innate immunity, predominantly antiviral response generation. It also bears pro-inflammatory properties that could affect psychiatric outcomes. In order to investigate the possible role of IKBKE gene in major depressive disorder (MDD) and panic disorder (PD), we conducted a case-control genetic association study concerning these disorders.

METHODS

In all, 14 SNPs of IKBKE gene were genotyped in groups of 391 patients with MDD and 190 patients with PD together with respective 389 and 371 healthy control individuals. The given groups were further divided by gender for additional analyses.

RESULTS

Substantial genetic associations were revealed between IKBKE SNPs and MDD (multiple testing adjusted P < 0.05) and suggestive associations in case of PD (P(adj) > 0.05). In addition, two SNPs that were only associated with PD among males, also displayed significantly different allele frequencies compared to PD females. This may indicate a specific role of these SNPs in male PD, but caution should be applied here due to the small size of the studied PD males group.

CONCLUSIONS

The results of this study confirm our initial findings and indicate a possible role of IKBKE gene in mood and anxiety disorders.

NF-kB as a key player in regulation of cellular radiation responses and identification of radiation countermeasures

Nuclear factor (NF)-κB is a transcription factor that plays significant role in immunity, cellular survival and inhibition of apoptosis, through the induction of genetic networks. Depending on the stimulus and the cell type, the members of NF-κB related family (RelA, c-Rel, RelB, p50, and p52), forms different combinations of homo and hetero-dimers. The activated complexes (Es) translocate into the nucleus and bind to the 10bp κB site of promoter region of target genes in stimulus specific manner. In response to radiation, NF-κB is known to reduce cell death by promoting the expression of anti-apoptotic proteins and activation of cellular antioxidant defense system. Constitutive activation of NF-κB associated genes in tumour cells are known to enhance radiation resistance, whereas deletion in mice results in hypersensitivity to IR-induced GI damage. NF-κB is also known to regulate the production of a wide variety of cytokines and chemokines, which contribute in enhancing cell proliferation and tissue regeneration in various organs, such as the GI crypts stem cells, bone marrow etc., following exposure to IR. Several other cytokines are also known to exert potent pro-inflammatory effects that may contribute to the increase of tissue damage following exposure to ionizing radiation. Till date there are a series of molecules or group of compounds that have been evaluated for their radio-protective potential, and very few have reached clinical trials. The failure or less success of identified agents in humans could be due to their reduced radiation protection efficacy. In this review we have considered activation of NF-κB as a potential marker in screening of radiation countermeasure agents (RCAs) and cellular radiation responses. Moreover, we have also focused on associated mechanisms of activation of NF-κB signaling and their specified family member activation with respect to stimuli. Furthermore, we have categorized their regulated gene expressions and their function in radiation response or modulation. In addition, we have discussed some recently developed radiation countermeasures in relation to NF-κB activation

To be an ally or an adversary in bladder cancer: the NF-κB story has not unfolded

Signaling and regulation of transcription factor nuclear factor-kappaB (NF-κB) has been an area of extensive research since its first discovery nearly three decades ago. Members of the NF-κB family have been reported to critically mediate a multitude of responses in normal cells. Therefore, it is not surprising that NF-κB function can go awry and result in pathological conditions including cancer. Despite its critical importance, the functional role of NF-κB has not received the same attention in cancers of all tissue types. In the case of cancer of the urinary bladder, which is the second most common urologic cancer, the involvement of NF-κB in the development of superficial or muscle invasive disease and during cancer recurrence is rudimentary at best. Nuclear expression of p65/RelA is seen in bladder cancer patients and has been found to negatively affect survival of patients with superficial and muscle invasive disease. Despite these observations, the exact mechanism of NF-κB upregulation and function remains unknown. Furthermore, the emergence of a tumor suppressive role for NF-κB in recent years suggests that the family may play the role of a double-edged sword in cancer, which remains unexplored in bladder cancer. The challenge now is to delineate the increasing complexity of this pathway in the development and progression of bladder cancer. Here, we review key aspects of the current knowledge of signaling and regulation by the NF-κB family focusing on its controversial role in cancer and highlight the importance of studying NF-κB in bladder cancer in particular.

HTLV-1 Tax protein recruitment into IKKε and TBK1 kinase complexes enhances IFN-I expression

The Tax protein expressed by human T-cell leukemia virus type 1 (HTLV-1) plays a pivotal role in the deregulation of cellular pathways involved in the immune response, inflammation, cell survival, and cancer. Many of these effects derive from Tax multiple interactions with host factors, including the subunits of the IKK-complex that are required for NF-κB activation. IKKɛ and TBK1 are two IKK-related kinases that allow the phosphorylation of interferon regulatory factors that trigger IFN type I gene expression. We observed that IKKɛ and TBK1 recruit Tax into cellular immunocomplexes. We also found that TRAF3, which regulates cell receptor signaling effectors, forms complexes with Tax. Transactivation analyses revealed that expression of Tax, in presence of IKKɛ and TBK1, enhances IFN-β promoter activity, whereas the activation of NF-κB promoter is not modified. We propose that Tax may be recruited into the TBK1/IKKɛ complexes as a scaffolding-adaptor protein that enhances IFN-I gene expression.

Downregulation of diacylglycerol kinase ζ enhances activation of cytokine-induced NF-κB signaling pathway

The transcription factor NF-κB family serves as a key component of many pathophysiological events such as innate and adaptive immune response, inflammation, apoptosis, and oncogenesis. Various cell signals trigger activation of the regulatory mechanisms of NF-κB, resulting in its nuclear translocation and transcriptional initiation. The diacylglycerol kinase (DGK) family, a lipid second messenger-metabolizing enzyme in phosphoinositide signaling, is shown to regulate widely various cellular processes. Results of recent studies suggest that one family member, DGKζ, is closely involved in immune and inflammatory responses. Nevertheless, little is known about the regulatory mechanism of DGKζ on NF-κB pathway in cytokine-induced inflammatory signaling. This study shows that siRNA-mediated DGKζ knockdown in HeLa cells facilitates degradation of IκB, followed by nuclear translocation of NF-κB p65 subunit. In addition, DGKζ-deficient MEFs show upregulation of p65 subunit phosphorylation at Serine 468 and 536 and its interaction with CBP transcriptional coactivator upon TNF-α stimulation. These modifications of p65 subunit might engender enhanced NF-κB transcriptional reporter assay of DGKζ knockdown cells. These findings provide further insight into the regulatory mechanisms of cytokine-induced NF-κB activation.