BS69 negatively regulates the canonical NF-κB activation induced by Epstein-Barr virus-derived LMP1

Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) activates NF-κB signaling pathways through the two C-terminal regions, CTAR1 and CTAR2. BS69 has previously been shown to be involved in LMP1-induced c-Jun N-terminal kinase activation through CTAR2 by interacting with tumor necrosis factor (TNFR) receptor-associated factor 6. In the present study, our manipulation of BS69 expression clearly indicates that BS69 negatively regulates LMP1-mediated NF-κB activation and up-regulates IL-6 mRNA expression and IκB degradation. Our immunoprecipitation experiments suggest that BS69 decreases complex formation between LMP1 and TNFR-associated death domain protein (TRADD).

Structured summary

MINT-7032462: LMP1 (uniprotkb:P03230) physically interacts (MI:0218) with TRADD (uniprotkb:Q15628) by anti bait coimmunoprecipitation (MI:0006)MINT-7032451: BS69 (uniprotkb:Q15326) and LMP1 (uniprotkb:P03230) colocalize (MI:0403) by fluorescence microscopy (MI:0416)MINT-7032478: LMP1 (uniprotkb:P03230) physically interacts (MI:0218) with BRAM1 (uniprotkb:Q15326) by anti bait coimmunoprecipitation (MI:0006)     

An LKB1-interacting protein negatively regulates TNFα-induced NF-κB activation

The Peutz-Jeghers syndrome (PJS) is a hereditary disorder that predisposes an individual to benign and malignant tumors in multiple organ systems. Recently, the locus responsible for PJS was mapped genetically to the LKB1 gene, with a subsequent investigation proving that it is responsible for most cases of PJS. LKB1 encodes a nuclear serine/threonine protein kinase, and potential tumor-suppressing activity has been attributed to LKB1 kinase. However, how LKB1 exerts its tumor-suppressing function remains to be determined. In this report, we describe the identification of a putative human LKB1-interacting protein, FLIP1, using the yeast two-hybrid system. Two regions of the LKB1 sequence have been determined to be crucial for the interaction with FLIP1. FLIP1 encodes a protein of 429 amino acids with a predicted molecular weight of 47 kd. In contrast to LKB1, which is mainly nuclear, FLIP1 is a cytoplasmic protein, and its expression is ubiquitous in all human tissues examined to date. Interestingly, deletion of the 195 N- terminal amino acids allows FLIP1 to enter the nucleus, suggesting the presence of a regulatory mechanism through its N-terminus for nuclear entry. In addition, we found that ectopic expression of FLIP1 selectively blocks cytokine-induced NF-kappaB activation. The involvement of FLIP1 in the regulation of NF-kappaB activity may shed new light on the role of LKB1 in tumor suppression.     

TAK1 ubiquitination regulates doxorubicin-induced NF-κB activation

Chemotherapeutic agents- and radiation therapy-induced NF-κB activation in cancer cells contributes to aggressive tumor growth and resistance to chemotherapy and ionizing radiation during cancer treatment. TAK1 has been shown to be required for genotoxic stress-induced NF-κB activation. However, whether TAK1 ubiquitination is involved in genotoxic stress-induced NF-κB activation remains unknown. Herein, we demonstrate that TAK1 ubiquitination plays an important role in the positive and negative regulation of doxorubicin (Dox)-induced NF-κB activation. We found that TAK1 was required for Dox-induced NF-κB activation. At the early stage of Dox treatment, Dox induced Lys63-linked TAK1 polyubiquitination at lysine 158 residue. USP4 inhibited Dox-induced TAK1 Lys63-linked polyubiquitination and knockdown of USP4 enhanced Dox-induced NF-κB activation. At the late stage of Dox treatment, Dox induced Lys48-linked TAK1 polyubiquitination to promote TAK1 degradation. ITCH inhibited Dox-induced NF-κB activation by promoting Lys48-linked TAK1 polyubiquitination and its subsequent degradation. Our study indicates that TAK1 ubiquitination plays critical roles in the regulation of Dox-induced NF-κB activation. Thus, intervention of TAK1 kinase activity or TAK1 Lys63-linked polyubiquitination pathways might greatly enhance the therapeutic efficacy of Dox.     

Oxaliplatin antagonizes HIV-1 latency by activating NF-κB without causing global T cell activation

Reactivation of latent HIV-1 is a promising strategy for the clearance of the viral reservoirs. Because of the limitations of current agents, identification of new latency activators is urgently required. Using an established model of HIV-1 latency, we examined the effect of Oxaliplatin on latent HIV-1 reactivation. We showed that Oxaliplatin, alone or in combination with valproic acid (VPA), was able to reactivate HIV-1 without inducing global T cell activation. We also provided evidence that Oxaliplatin reactivated HIV-1 expression by inducing nuclear factor kappa B (NF-κB) nuclear translocation. Our results indicated that Oxaliplatin could be a potential drug candidate for anti-latency therapies.     

ESM-1 regulates cell growth and metastatic process through activation of NF-κB in colorectal cancer

In our previous study, we reported that endothelial cell specific molecule-1 (ESM-1) was increased in tissue and serum from colorectal cancer patients and suggested that ESM-1 can be used as a potential serum marker for early detection of colorectal cancer. The aim of this study was to evaluate the role of ESM-1 as an intracellular molecule in colorectal cancer. ESM-1 expression was knocked down by small interfering RNA (siRNA) in colorectal cancer cells. Expression of ESM-1 siRNA decreased cell survival through the Akt-dependent inhibition of NF-κB/IκB pathway and an interconnected reduction in phospho-Akt, -p38, -ERK1, -RSK1, -GSK-3α/β and -HSP27, as determined by a phospho-MAPK array. ESM-1 silencing induced G(1) phase cell cycle arrest by induction of PTEN, resulting in the inhibition of cyclin D1 and inhibited cell migration and invasion of COLO205 cells. Consistently, ESM-1 overexpression in HCT-116 cells enhanced cell proliferation through the Akt-dependent activation of NF-κB pathway. In addition, ESM-1 interacted with NF-κB and activated NF-κB promoter. This study demonstrates that ESM-1 is involved in cell survival, cell cycle progression, migration, invasion and EMT during tumor invasion in colorectal cancer. Based on our results, ESM-1 may be a useful therapeutic target for colorectal cancer.     

microRNA-210 negatively regulates LPS-induced production of proinflammatory cytokines by targeting NF-κB1 in murine macrophages

Ligation of TLR4 with LPS in macrophages leads to the production of proinflammatory cytokines, which are central to eliminate viral and bacterial infection. However, uncontrolled TLR4 activation may contribute to pathogenesis of inflammatory diseases such as septic shock. In this study, we found microRNA-210 was induced in murine macrophages by LPS. Transfection of miR-210 mimics significantly inhibited LPS-induced production of inflammatory cytokines. In contrast, transfection of anti-miR-210 inhibitors increased LPS-induced expression of proinflammatory cytokines. Furthermore, we demonstrated that miR-210 targets NF-κB1. Therefore, our data identify miR-210 as a very important feedback negative regulator for LPS-induced production of proinflammatory cytokines.     

Beyond NF-κB activation: nuclear functions of IκB kinase α

IκB kinase (IKK) complex, the master kinase for NF-κB activation, contains two kinase subunits, IKKα and IKKβ. In addition to mediating NF-κB signaling by phosphorylating IκB proteins during inflammatory and immune responses, the activation of the IKK complex also responds to various stimuli to regulate diverse functions independently of NF-κB. Although these two kinases share structural and biochemical similarities, different sub-cellular localization and phosphorylation targets between IKKα and IKKβ account for their distinct physiological and pathological roles. While IKKβ is predominantly cytoplasmic, IKKα has been found to shuttle between the cytoplasm and the nucleus. The nuclear-specific roles of IKKα have brought increasing complexity to its biological function. This review highlights major advances in the studies of the nuclear functions of IKKα and the mechanisms of IKKα nuclear translocation. Understanding the nuclear activity is essential for targeting IKKα for therapeutics.     

Autophagy in the intestinal epithelium reduces endotoxin-induced inflammatory responses by inhibiting NF-κB activation

Autophagy is a lysosomal degradation pathway that is essential for survival, differentiation, development and homeostasis. There is growing evidence that impaired autophagy leads to the pathogenesis of diverse diseases. However, the role of autophagy in intestinal epithelium is not clearly understood, although previous studies have pointed out the possibility for the relationships of autophagy with bowel inflammation. In this study, we investigated the involvement of autophagy in intestinal epithelium with inflammatory responses. We generated the mice with a conditional deletion of Atg7, which is one of the autophagy regulated gene, in intestinal epithelium. In Atg7-deficient small intestinal epithelium, LPS-induced production of TNF-α and IL-1β mRNA was enhanced in comparison to the control small intestinal tissues. In addition, the degree of LPS-induced activation of NF-κB was promoted in Atg7-deficient intestinal epithelium. These results demonstrate that autophagy can attenuate endotoxin-induced inflammatory responses in intestinal epithelium resulting in the maintenance of intestinal homeostasis.     

TNFR1-induced activation of the classical NF-κB pathway

The molecular mechanisms underlying activation of the IκB kinase (IKK) complex are presumably best understood in the context of tumor necrosis factor (TNF) receptor-1 (TNFR1) signaling. In fact, it seems that most, if not all, proteins relevant for this process have been identified and extensive biochemical and genetic data are available for the role of these factors in TNF-induced IKK activation. There is evidence that protein modification-independent assembly of a core TNFR1 signaling complex containing TNFR1-associated death domain, receptor interacting kinase?1, TNF receptor-associated factor?2 and cellular inhibitor of apoptosis protein?1 and 2 starts a chain of nondegrading ubiquitination events that culminate in the recruitment and activation of IKK complex-stimulating kinases and the IKK complex itself. Here, we sum up the known details of TNFR1-induced IKK activation, address arising contradictions and discuss possible explanations resolving the apparent discrepancies.