Control of NF-κB activity by proteolysis

Anti-inflammatory effects of Beopje curly dock (Rumex crispus L.) in LPS-induced RAW 264.7 cells and its active compounds

Inflammation is a defense response of the body to stimuli. Curly dock (CD) is an herbal food with anti-inflammatory effects. Beopje is an herbal food processing method that reduces toxicity and enhances beneficial effects. This study investigated the effects of CD and Beopje curly dock (CD-B) extracts on lipopolysaccharide (LPS)-induced inflammatory damage in RAW 264.7 cells. Cell survival rate and nitrite concentration were determined using the MTT assay and Griess method, respectively. Enzyme-linked immunosorbent assay was used to detect the inflammatory cytokine levels. The mRNA and protein expression levels of inflammatory associated genes were detected by qPCR and Western blot, respectively. CD and CD-B extracts compositions were assessed by UPLC-Q-TOF MS analysis. Our results indicate that CD-B has a more significant inhibitory effect on the LPS-induced inflammatory response in RAW 264.7 cells than CD, suggesting that the Beopje process potentially enhances the anti-inflammatory effect of CD. PRACTICAL APPLICATIONS: Long-term inflammation can cause a variety of chronic diseases. Therefore, it is necessary to suppress the occurrence of body inflammation in time. This study preliminarily clarified the mechanism of herbal foods to alleviate inflammation by regulating the immune response, and further confirms that applying the Beopje process enhances the anti-inflammatory effect. This research can serve as a significant reference for future research, prevention and treatment of inflammation-related diseases, and the development of functional foods with anti-inflammatory activity. It also provides a theoretical basis for the further reasonable application of Beopje processing method.

Deletion of the Capn1 Gene Results in Alterations in Signaling Pathways Related to Alzheimer's Disease, Protein Quality Control and Synaptic Plasticity in Mouse Brain

Calpains represent a family of calcium-dependent proteases participating in a multitude of functions under physiological or pathological conditions. Calpain-1 is one of the most studied members of the family, is ubiquitously distributed in organs and tissues, and has been shown to be involved in synaptic plasticity and neuroprotection in mammalian brain. Calpain-1 deletion results in a number of phenotypic alterations. While some of these alterations can be explained by the acute functions of calpain-1, the present study was directed at studying alterations in gene expression that could also account for these phenotypic modifications. RNA-seq analysis identified 354 differentially expressed genes (DEGs) in brain of calpain-1 knock-out mice, as compared to their wild-type strain. Most DEGs were classified in 10 KEGG pathways, with the highest representations in Protein Processing in Endoplasmic Reticulum, MAP kinase and Alzheimer's disease pathways. Most DEGs were down-regulated and validation of a number of these genes indicated a corresponding decreased expression of their encoded proteins. The results indicate that calpain-1 is involved in the regulation of a significant number of genes affecting multiple brain functions. They also indicate that mutations in calpain-1 are likely to be involved in a number of brain disorders.

Proteasome serves as pivotal regulator in Angiostrongylus cantonensis-induced eosinophilic meningoencephalitis

Proteasome primarily degrades the unneeded or damaged proteins by proteolysis. Disruption of the brain barrier and its resulting meningoencephalitis caused by Angiostrongylus cantonensis are important pathological events in non-permissive hosts. In this study, the results showed upregulated proteasome during A. cantonensis infection. Occludin degradation and matrix metalloproteinase-9 (MMP-9) activity were significantly increased in infected mice than in uninfected mice. Moreover, confocal immunoflourescence microscopy showed that occludin was co-localized with MMP-9. The infected-mice were treated with proteasomal activity inhibitor MG132 by 1.5 and 3.0 mg/kg/day, which resulted in significantly reduced protein levels of phosphorylated IκBα (P<0.05) compared with the untreated control. The phosphorylated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) showed similar result. In addition, MMP-9 activity and occludin degradation were reduced because of MG132 treatment. These results suggested that the proteasome in A. cantonensis infection degraded phosphorylated IκBα, modulated phosphorylated NF-κB, and then regulated the activation of MMP-9 and occludin degradation. Proteasome alterations were presented in eosinophilic meningitis of BALB/c mice and may contribute to the pathophysiology of eosinophilic meningitis by increasing occludin degradation. This molecule would serve as pivotal regulator in A. cantonensis-induced eosinophilic meningoencephalitis.

Differential network analysis and protein-protein interaction study reveals active protein modules in glucocorticoid resistance for infant acute lymphoblastic leukemia

BACKGROUND

Acute lymphoblastic leukemia (ALL) is the most common type of cancer diagnosed in children and Glucocorticoids (GCs) form an essential component of the standard chemotherapy in most treatment regimens. The category of infant ALL patients carrying a translocation involving the mixed lineage leukemia (MLL) gene (gene KMT2A) is characterized by resistance to GCs and poor clinical outcome. Although some studies examined GC-resistance in infant ALL patients, the understanding of this phenomenon remains limited and impede the efforts to improve prognosis.

METHODS

This study integrates differential co-expression (DC) and protein-protein interaction (PPI) networks to find active protein modules associated with GC-resistance in MLL-rearranged infant ALL patients. A network was constructed by linking differentially co-expressed gene pairs between GC-resistance and GC-sensitive samples and later integrated with PPI networks by keeping the links that are also present in the PPI network. The resulting network was decomposed into two sub-networks, specific to each phenotype. Finally, both sub-networks were clustered into modules using weighted gene co-expression network analysis (WGCNA) and further analyzed with functional enrichment analysis.

RESULTS

Through the integration of DC analysis and PPI network, four protein modules were found active under the GC-resistance phenotype but not under the GC-sensitive. Functional enrichment analysis revealed that these modules are related to proteasome, electron transport chain, tRNA-aminoacyl biosynthesis, and peroxisome signaling pathways. These findings are in accordance with previous findings related to GC-resistance in other hematological malignancies such as pediatric ALL.

CONCLUSIONS

Differential co-expression analysis is a promising approach to incorporate the dynamic context of gene expression profiles into the well-documented protein interaction networks. The approach allows the detection of relevant protein modules that are highly enriched with DC gene pairs. Functional enrichment analysis of detected protein modules generates new biological hypotheses and may help in explaining the GC-resistance in MLL-rearranged infant ALL patients.

IKK phosphorylates RelB to modulate its promoter specificity and promote fibroblast migration downstream of TNF receptors

TNFα is a potent cytokine that plays a critical role in numerous cellular processes, particularly immune and inflammatory responses, programmed cell death, angiogenesis, and cell migration. Thus, understanding the molecular mechanisms that mediate TNFα-induced cellular responses is a crucial issue. It is generally accepted that global DNA binding activity of the NF-κB avian reticuloendotheliosis viral (v-rel) oncogene related B (RelB) subunit is not induced upon TNFα treatment in fibroblasts, despite its TNFα-induced nuclear accumulation. Here, we demonstrate that RelB plays a critical role in promoting fibroblast migration upon prolonged TNFα treatment. We identified the two kinases IκB kinase α (IKKα) and IκB kinase β (IKKβ) as RelB interacting partners whose activation by TNFα promotes RelB phosphorylation at serine 472. Once phosphorylated on serine 472, nuclear RelB dissociates from its interaction with the inhibitory protein IκBα and binds to the promoter of critical migration-associated genes, such as the matrix metallopeptidase 3 (MMP3). Further, we show that RelB serine 472 phosphorylation status controls MMP3 expression and promigration activity downstream of TNF receptors. Our findings provide new insights into the regulation of RelB activity and reveal a novel link between selective NF-κB target gene expression and cellular response in response to TNFα.

Caspase-8 as a regulator of tumor cell motility

The caspases are a family of ubiquitously expressed cysteine proteases best known for their roles in programmed cell death. However, caspases play a number of other roles in vertebrates. In the case of caspase-8, loss of expression is an embryonic lethal phenotype, and caspase-8 plays roles in suppressing cellular necrosis, promoting differentiation and immune signaling, regulating autophagy, and promoting cellular migration. Apoptosis and migration require localization of caspase-8 in the periphery of the cells, where caspase-8 acts as part of distinct biosensory complexes that either promote migration in appropriate cellular microenvironments, or cell death in inappropriate settings. In the cellular periphery, caspase-8 interacts with components of the focal adhesion complex in a tyrosine-kinase dependent manner, promoting both cell migration in vitro and metastasis in vivo. Mechanistically, caspase-8 interacts with components of both focal adhesions and early endosomes, enhancing focal adhesion turnover and promoting rapid integrin recycling to the cell surface. Clinically, this suggests that the expression of caspase-8 may not always be a positive prognostic sign, and that the role of caspase-8 in cancer progression is likely context-dependent.

Calpain A modulates Toll responses by limited Cactus/IκB proteolysis

Calcium-dependent cysteine proteases of the calpain family are modulatory proteases that cleave their substrates in a limited manner. Among their substrates, calpains target vertebrate and invertebrate IκB proteins. Because proteolysis by calpains potentially generates novel protein functions, it is important to understand how this affects NFκB activity. We investigate the action of Calpain A (CalpA) on the Drosophila melanogaster IκB homologue Cactus in vivo. CalpA alters the absolute amounts of Cactus protein. Our data indicate, however, that CalpA uses additional mechanisms to regulate NFκB function. We provide evidence that CalpA interacts physically with Cactus, recognizing a Cactus pool that is not bound to Dorsal, a fly NFκB/Rel homologue. We show that proteolytic cleavage by CalpA generates Cactus fragments lacking an N-terminal region required for Toll responsiveness. These fragments are generated in vivo and display properties distinct from those of full-length Cactus. We propose that CalpA targets free Cactus, which is incorporated into and modulates Toll-responsive complexes in the embryo and immune system.

The increased transcriptional response and translocation of a Rel/NF-κB homologue in scallop Chlamys farreri during the immune stimulation

The Rel/NF-κB transcription factors can function as key regulators to modulate the expression of immune-related genes in response to immune challenge or environmental stress. In the present study, a gene coding Rel/NF-κB homologue was identified from scallop Chlamys farreri (designated CfRel). Its deduced protein comprised 359 amino acids, and contained a conserved N-terminal Rel homology domain (RHD) and an IPT domain. There was an NF-κB/Rel/dorsal domain signature sequence in the RHD domain. The mRNA transcripts of CfRel could be detected in all the tested tissues including adductor muscle, mantle, gill, gonad, haemocytes, kidney and hepatopancreas, with the highest expression level in hepatopancreas. After LPS stimulation, there were two peaks of CfRel mRNA expression level in haemocytes at 6 h (25.25-fold, P < 0.05) and 24 h (59.66-fold, P < 0.05) respectively, while the mRNA expression of CfRel was only up-regulated at 3 h after PGN stimulation (2.35-fold, P < 0.05). By Western blotting technique, CfRel protein was observed in the cytoplasm and nucleus of scallop haemocytes, and its concentration in the haemocyte nucleus increased significantly at 3 h and 12 h after LPS stimulation. The noticeable NF-κB transcription activity of CfRel protein was determined by NF-κB luciferase reporter assays (122.43%, P < 0.05), and it decreased significantly (17.61%, P < 0.05) after the coexpression of scallop IκB protein. These results collectively suggested that CfRel mRNA transcripts and protein were induced by immune stimulation, and CfRel protein could extricate itself from IκB protein and transfer into the haemocyte nucleus to modulate the immune response in scallop.

ADAM17 mediates MMP9 expression in lung epithelial cells

The purposes were to study the role of lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF)-α/nuclear factor-κB (NF-κB) signaling in matrix metalloproteinase 9 (MMP9) expression in A549 cells and to investigate the effects of lentivirus-mediated RNAi targeting of the disintegrin and metalloproteinase 17 (ADAM17) gene on LPS-induced MMP9 expression. MMP9 expression induced by LPS in A549 cells was significantly increased in a dose- and time-dependent manner (p<0.05). Pyrrolidine dithiocarbamate (PDTC) and a TNFR1 blocking peptide (TNFR1BP) significantly inhibited LPS-induced MMP9 expression in A549 cells (p<0.05). TNFR1BP significantly inhibited LPS-induced TNF-α production (p<0.05). Both PDTC and TNFR1BP significantly inhibited the phosphorylation of IκBα and expression of phosphorylation p65 protein in response to LPS (p<0.05), and the level of IκBα in the cytoplasm was significantly increased (p<0.05). Lentivirus mediated RNA interference (RNAi) significantly inhibited ADAM17 expression in A549 cells. Lentivirus-mediated RNAi targeting of ADAM17 significantly inhibited TNF-α production in the supernatants (p<0.05), whereas the level of TNF-α in the cells was increased (p<0.05). Lentiviral ADAM17 RNAi inhibited MMP9 expression, IκBα phosphorylation and the expression of phosphorylation p65 protein in response to LPS (p<0.05). PDTC significantly inhibited the expression of MMP9 and the phosphorylation of IκBα, as well as the expression of phosphorylation p65 protein in response to TNF-α (p<0.05). Lentiviral RNAi targeting of ADAM17 down-regulates LPS-induced MMP9 expression in lung epithelial cells via inhibition of TNF-α/NF-κB signaling.

Nucleo-cytoplasmic trafficking of TRIM8, a novel oncogene, is involved in positive regulation of TNF induced NF-κB pathway

TNF induced nuclear factor kappa B (NF-κB) is one of the central signaling pathways that plays a critical role in carcinogenesis and inflammatory diseases. Post-translational modification through ubiquitin plays important role in the regulation of this pathway. In the current study, we investigated the role of TRIM8, member of RING family ubiquitin ligase in regulation of NF-κB pathway. We observed that TRIM8 positively regulates TNF induced NF-κB pathway. Different domains of TRIM8 showed discrete functions at the different steps in regulation of TNF induced NF-κB pathway. Ubiquitin ligase activity of TRIM8 is essential for regulation of NF-κB activation in both cytoplasm as well as nucleus. TRIM8 negates PIAS3 mediated negative repression of NF-κB at p65 by inducing translocation of PIAS3 from nucleus to cytoplasm as well as its turnover. TNF induces translocation of TRIM8 from nucleus to cytoplasm, which positively regulates NF-κB. The cytoplasmic translocation of TRIM8 is essential for TNF induced NF-κB but not for p65 mediated NF-κB regulation. TRIM8 also enhanced the clonogenic and migration ability of cells by modulating NF-κB. The further study will help to understand the role of TRIM8 in inflammation and cancer.

A20-binding inhibitor of nuclear factor-kappaB (NF-kappaB)-2 (ABIN-2) is an activator of inhibitor of NF-kappaB (IkappaB) kinase alpha (IKKalpha)-mediated NF-kappaB transcriptional activity

NF-κB transcription factors are pivotal players in controlling inflammatory and immune responses, as well as cell proliferation and apoptosis. Aberrant regulation of NF-κB and the signaling pathways that regulate its activity have been involved in various pathologies, particularly cancers, as well as inflammatory and autoimmune diseases. NF-κB activation is tightly regulated by the IκB kinase (IKK) complex, which is composed of two catalytic subunits IKKα and IKKβ, and a regulatory subunit IKKγ/NEMO. Although IKKα and IKKβ share structural similarities, IKKα has been shown to have distinct biological functions. However, the molecular mechanisms that modulate IKKα activity have not yet been fully elucidated. To understand better the regulation of IKKα activity, we purified IKKα-associated proteins and identified ABIN-2. Here, we demonstrate that IKKα and IKKβ both interact with ABIN-2 and impair its constitutive degradation by the proteasome. Nonetheless, ABIN-2 enhances IKKα- but not IKKβ-mediated NF-κB activation by specifically inducing IKKα autophosphorylation and kinase activity. Furthermore, we found that ABIN-2 serine 146 is critical for the ABIN-2-dependent IKKα transcriptional up-regulation of specific NF-κB target genes. These results imply that ABIN-2 acts as a positive regulator of NF-κB-dependent transcription by activating IKKα.