The role of the IKK complex in viral infections

Cytokine-like-Vago-mediated antiviral response in Penaeus monodon via IKK-NF-κB signaling pathway

Interferon (IFN) system is the primary mechanism of innate antiviral defense in immune response. To date, limited studies of IFN system were conducted in crustaceans. Previous report in Penaeus monodon demonstrated the interconnection of cytokine-like molecule Vago and inhibitor of kappa B kinase-nuclear factor κB (IKK-NF-κB) cascade against white spot syndrome virus (WSSV). This study further identified five different PmVago isoforms. Upon immune stimulation, PmVagos expressed against shrimp pathogens. PmVago1, PmVago4, and PmVago5 highly responded to WSSV, whereas, PmVago1 and PmVago4 RNAi exhibited a rapid mortality with elevated WSSV replication. Suppression of PmVago1 and PmVago4 negatively affected proPO system, genes in signal transduction, and AMPs. WSSV infection additionally induced PmVaog4 granule accumulation and cellular translocation to the area of cell membrane. More importantly, PmVago1 and PmVago4 promoters were stimulated by PmIKK overexpression; meanwhile, they further activated Dorsal and Relish promoter activities. These results suggested the possible roles of the cytokine-like PmVago via IKK-NF-κB cascade against WSSV infection.

TLR5S negatively regulates the TLR5M-mediated NF-κB signaling pathway in Epinephelus coioides

Nuclear factor kappa-B (NF-κB) pathway is a key mediator of inflammation response that plays a role in host defense for pathogen elimination, but excessive activation may lead to tissue damage or pathogen transmission. The negative regulation of NF-κB in lower vertebrates is largely unknown, hindering further understanding of immune signaling evolution. Here, we provided evidence that Epinephelus coioides soluble toll-like receptor 5 (TLR5S), a member of the TLR5 subfamily, has been newly identified as a negative regulator of NF-κB signaling. EcTLR5S was a cytoplasmic protein consisting of 17 leucine-rich repeat domains, which specifically responded to Vibrio flagellin and suppressed flagellin-induced NF-κB signaling activation and cytokine expression. The amino-terminal LRR 1-5 region was necessary for its negative regulatory function. Dual-luciferase reporter assay showed that EcTLR5S significantly inhibited the NF-κB-luc activity induced by inhibitor of NF-κB kinase α (IKKα) and IKKβ. Subsequently, the functional relationship between EcTLR5M and EcTLR5S was analyzed, revealing that the negative regulatory function of EcTLR5S targeted the activation of the NF-κB pathway mediated by EcTLR5M. The above results reveal that EcTLR5S negatively regulates the flagellin-induced EcTLR5M-NF-κB pathway activation, which may prevent over-activation of immune signaling and restore homeostasis.

A genome-wide CRISPR screen in human prostate cancer cells reveals drivers of macrophage-mediated cell killing and positions AR as a tumor-intrinsic immunomodulator

The crosstalk between prostate cancer (PCa) cells and the tumor microenvironment plays a pivotal role in disease progression and metastasis and could provide novel opportunities for patient treatment. Macrophages are the most abundant immune cells in the prostate tumor microenvironment (TME) and are capable of killing tumor cells. To identify genes in the tumor cells that are critical for macrophage-mediated killing, we performed a genome-wide co-culture CRISPR screen and identified AR, PRKCD, and multiple components of the NF-κB pathway as hits, whose expression in the tumor cell are essential for being targeted and killed by macrophages. These data position AR signaling as an immunomodulator, and confirmed by androgen-deprivation experiments, that rendered hormone-deprived tumor cells resistant to macrophage-mediated killing. Proteomic analyses showed a downregulation of oxidative phosphorylation in the PRKCD- and IKBKG-KO cells compared to the control, suggesting impaired mitochondrial function, which was confirmed by electron microscopy analyses. Furthermore, phosphoproteomic analyses revealed that all hits impaired ferroptosis signaling, which was validated transcriptionally using samples from a neoadjuvant clinical trial with the AR-inhibitor enzalutamide. Collectively, our data demonstrate that AR functions together with the PRKCD and the NF-κB pathway to evade macrophage-mediated killing. As hormonal intervention represents the mainstay therapy for treatment of prostate cancer patients, our findings may have direct implications and provide a plausible explanation for the clinically observed persistence of tumor cells despite androgen deprivation therapy.

Interactions of Equine Viruses with the Host Kinase Machinery and Implications for One Health and Human Disease

Zoonotic pathogens that are vector-transmitted have and continue to contribute to several emerging infections globally. In recent years, spillover events of such zoonotic pathogens have increased in frequency as a result of direct contact with livestock, wildlife, and urbanization, forcing animals from their natural habitats. Equines serve as reservoir hosts for vector-transmitted zoonotic viruses that are also capable of infecting humans and causing disease. From a One Health perspective, equine viruses, therefore, pose major concerns for periodic outbreaks globally. Several equine viruses have spread out of their indigenous regions, such as West Nile virus (WNV) and equine encephalitis viruses (EEVs), making them of paramount concern to public health. Viruses have evolved many mechanisms to support the establishment of productive infection and to avoid host defense mechanisms, including promoting or decreasing inflammatory responses and regulating host machinery for protein synthesis. Viral interactions with the host enzymatic machinery, specifically kinases, can support the viral infectious process and downplay innate immune mechanisms, cumulatively leading to a more severe course of the disease. In this review, we will focus on how select equine viruses interact with host kinases to support viral multiplication.

Molluscum Contagiosum Virus Protein MC008 Targets NF-κB Activation by Inhibiting Ubiquitination of NEMO

Molluscum contagiosum virus (MCV) is a human-adapted poxvirus that causes a common and persistent yet mild infection characterized by distinct, contagious, papular skin lesions. These lesions are notable for having little or no inflammation associated with them and can persist for long periods without an effective clearance response from the host. Like all poxviruses, MCV encodes potent immunosuppressive proteins that perturb innate immune pathways involved in virus sensing, the interferon response, and inflammation, which collectively orchestrate antiviral immunity and clearance, with several of these pathways converging at common signaling nodes. One such node is the regulator of canonical nuclear factor kappa B (NF-κB) activation, NF-κB essential modulator (NEMO). Here, we report that the MCV protein MC008 specifically inhibits NF-κB through its interaction with NEMO, disrupting its early ubiquitin-mediated activation and subsequent downstream signaling. MC008 is the third NEMO-targeting inhibitor to be described in MCV to date, with each inhibiting NEMO activation in distinct ways, highlighting strong selective pressure to evolve multiple ways of disabling this key signaling protein. IMPORTANCE Inflammation lies at the heart of most human diseases. Understanding the pathways that drive this response is the key to new anti-inflammatory therapies. Viruses evolve to target inflammation; thus, understanding how they do this reveals how inflammation is controlled and, potentially, how to disable it when it drives disease. Molluscum contagiosum virus (MCV) has specifically evolved to infect humans and displays an unprecedented ability to suppress inflammation in our tissue. We have identified a novel inhibitor of human innate signaling from MCV, MC008, which targets NEMO, a core regulator of proinflammatory signaling. Furthermore, MC008 appears to inhibit early ubiquitination, thus interrupting later events in NEMO activation, thereby validating current models of IκB kinase (IKK) complex regulation.

Genome-wide identification and functional characterization of inhibitor of nuclear factor-κB (IκB) kinase (IKK) in turbot (Scophthalmus maximus)

The inhibitor of nuclear factor-κB (IκB) kinase (IKK) is involved in a variety of intracellular cell signaling pathways and is an important component of the NF-κB signaling pathway. IKK genes have been suggested to play important roles in the innate immune response to pathogen infection in both vertebrates and invertebrates. However, little information is available about IKK genes in turbot (Scophthalmus maximus). In this study, six IKK genes were identified including SmIKKα, SmIKKα2, SmIKKβ, SmIKKε, SmIKKγ, and SmTBK1. The IKK genes of turbot showed the highest identity and similarity with Cynoglossus semilaevis. Then, phylogenetic analysis showed that the IKK genes of turbot were most closely related to C. semilaevis. In addition, IKK genes were widely expressed in all the examined tissues. Meanwhile, the expression patterns of IKK genes were investigated by QRT-PCR after Vibrio anguillarum and Aeromonas salmonicida infection. The results showed that IKK genes had varying expression patterns in mucosal tissues after bacteria infection, indicating that they may play key roles in maintaining the integrity of the mucosal barrier. Subsequently, protein and protein interaction (PPI) network analysis showed that most proteins interacting with IKK genes were located in the NF-κB signaling pathway. Finally, the double luciferase report and overexpression experiments showed that SmIKKα/SmIKKα2/SmIKKβ involved in the activation of NF-κB in turbot. In summary, our results suggested that IKK genes of turbot played important roles in the innate immune response of teleost, and provide valuable information for further study of the function of IKK genes.

Emerging roles of interferon-stimulated gene-15 in age-related telomere attrition, the DNA damage response, and cardiovascular disease

Population aging and age-related cardiovascular disease (CVD) are becoming increasingly prevalent worldwide, generating a huge medical and socioeconomic burden. The complex regulation of aging and CVD and the interaction between these processes are crucially dependent on cellular stress responses. Interferon-stimulated gene-15 (ISG15) encodes a ubiquitin-like protein expressed in many vertebrate cell types that can be found both free and conjugated to lysine residues of target proteins via a post-translational process termed ISGylation. Deconjugation of ISG15 (deISGylation) is catalyzed by the ubiquitin-specific peptidase 18 (USP18). The ISG15 pathway has mostly been studied in the context of viral and bacterial infections and in cancer. This minireview summarizes current knowledge on the role of ISG15 in age-related telomere shortening, genomic instability, and DNA damage accumulation, as well as in hypertension, diabetes, and obesity, major CVD risk factors prevalent in the elderly population.

TGFβ1 and POSTN as biomarkers of postinfectious bronchiolitis obliterans and asthma in children

RATIONALE

Asthma and postinfectious bronchiolitis obliterans (PIBO) are common chronic lung diseases in company with wheezing in children. However, it is not clear what is common and unique mechanisms between the two diseases. Thus, we used proteomic analysis to compare differences in biomarkers between children with asthma and PIBO.

METHODS

Overall, 30 healthy children without respiratory underlying diseases, 18 children with asthma and 15 with PIBO were included for this study. Sequential window acquisition of all theoretical mass spectra (SWATH)-mass spectrometry (MS) was used to measure proteins in plasma samples. To identify specific pathways of each groups, we used the ingenuity pathway analysis (IPA) software.

RESULTS

We identified and quantified 354 proteins across all 63 samples in the SWATH-MS analysis. Forty eight proteins were significantly different among 3 groups. The upstream analysis of IPA suggested that inhibitor of nuclear factor kappa B kinase subunit beta (IKBKB) was the upstream inhibitor of 4 differentially expressed proteins (DEPs) in asthma, while the upstream activator in PIBO subjects. Among 4 DEPs, TGF-β1 in PIBO and periostin in asthma were negatively correlated with forced expiratory volume in 1 s (FEV1), FEV1/forced vital capacity, maximal med-expiratory flow, and PC20, respectively.

CONCLUSION

These findings demonstrate that transforming growth factor β1 and periostin were unique biomarkers of PIBO and asthma in children, respectively. The mechanism regulated by IKBKB may be therapeutically relevant for PIBO and asthma.

Pharmacological Inhibition of IKK to Tackle Latency and Hyperinflammation in Chronic HIV-1 Infection

HIV latent infection may be associated with disrupted viral RNA sensing, interferon (IFN) signaling, and/or IFN stimulating genes (ISG) activation. Here, we evaluated the use of compounds selectively targeting at the inhibitor of nuclear factor-κB (IκB) kinase (IKK) complex subunits and related kinases (TBK1) as a novel pathway to reverse HIV-1 latency in latently infected non-clonal lymphoid and myeloid cell in vitro models. IKK inhibitors (IKKis) triggered up to a 1.8-fold increase in HIV reactivation in both, myeloid and lymphoid cell models. The best-in-class IKKis, targeting TBK-1 (MRT67307) and IKKβ (TCPA-1) respectively, were also able to significantly induce viral reactivation in CD4+ T cells from people living with HIV (PLWH) ex vivo. More importantly, although none of the compounds tested showed antiviral activity, the combination of the distinct IKKis with ART did not affect the latency reactivation nor blockade of HIV infection by ART. Finally, as expected, IKKis did not upregulate cell activation markers in primary lymphocytes and innate immune signaling was blocked, resulting in downregulation of inflammatory cytokines. Overall, our results support a dual role of IKKis as immune modulators being able to tackle the HIV latent reservoir in lymphoid and myeloid cellular models and putatively control the hyperinflammatory responses in chronic HIV-1 infection.

Transient blockade of TBK1/IKKε allows efficient transduction of primary human natural killer cells with vesicular stomatitis virus G-pseudotyped lentiviral vectors

BACKGROUND AIMS

Vesicular stomatitis virus G (VSV-G)-pseudotyped lentiviral vectors (LVs) are widely used to reliably generate genetically modified, clinical-grade T-cell products. However, the results of genetically modifying natural killer (NK) cells with VSV-G LVs have been variable. The authors explored whether inhibition of the IKK-related protein kinases TBK1 and IKKε, key signaling molecules of the endosomal TLR4 pathway, which is activated by VSV-G, would enable the reliable transduction of NK cells by VSV-G LVs.

METHODS

The authors activated NK cells from peripheral blood mononuclear cells using standard procedures and transduced them with VSV-G LVs encoding a marker gene (yellow fluorescent protein [YFP]) or functional genes (chimeric antigen receptors [CARs], co-stimulatory molecules) in the presence of three TBK1/IKKε inhibitors (MRT67307, BX-795, amlexanox). NK cell transduction was evaluated by flow cytometry and/or western blot and the functionality of expressed CARs was evaluated in vitro.

RESULTS

Blocking TBK1/IKKε during transduction of NK cells enabled their efficient transduction by VSV-G LVs as judged by YFPexpression of 40-50%, with half maximal effective concentrations of 1.1 µM (MRT67307), 5 µM (BX-795) and 24.8 µM (amlexanox). Focusing on MRT67307, the authors successfully generated NK cells expressing CD19-CARs or HER2-CARs with an inducible co-stimulatory molecule. CAR NK cells exhibited increased cytolytic activity and ability to produce cytokines in comparison to untreated controls, confirming CAR functionality.

CONCLUSIONS

The authors demonstrate that inhibition of TBK1/IKKε enables the reliable generation of genetically modified NK cells using VSV-G LVs. The authors' protocol can be readily adapted to generate clinical-grade NK cells and thus has the potential to facilitate the clinical evaluation of genetically modified NK cell-based therapeutics in the future.

Roles of Inflammasomes in Epstein-Barr Virus-Associated Nasopharyngeal Cancer

Epstein-Barr virus (EBV) infection is recognised as one of the causative agents in most nasopharyngeal carcinoma (NPC) cases. Expression of EBV viral antigens can induce host's antiviral immune response by activating the inflammasomes to produce pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and IL-18. These cytokines are known to be detrimental to a wide range of virus-infected cells, in which they can activate an inflammatory cell death program, called pyroptosis. However, aberrant inflammasome activation and production of its downstream cytokines lead to chronic inflammation that may contribute to various diseases, including NPC. In this review, we summarise the roles of inflammasomes during viral infection, how EBV evades inflammasome-mediated immune response, and progress into tumourigenesis. The contrasting roles of inflammasomes in cancer, as well as the current therapeutic approaches used in targeting inflammasomes, are also discussed in this review. While the inflammasomes appear to have dual roles in carcinogenesis, there are still many questions that remain unanswered. In particular, the exact molecular mechanism responsible for the regulation of the inflammasomes during carcinogenesis of EBV-associated NPC has not been explored thoroughly. Furthermore, the current practical application of inflammasome inhibitors is limited to specific tumour types, hence, further studies are warranted to discover the potential of targeting the inflammasomes for the treatment of NPC.

Inhibitory effects of baicalein against herpes simplex virus type 1

Herpes simplex virus type 1 (HSV-1) is a ubiquitous and widespread human pathogen, which gives rise to a range of diseases, including cold sores, corneal blindness, and encephalitis. Currently, the use of nucleoside analogs, such as acyclovir and penciclovir, in treating HSV-1 infection often presents limitation due to their side effects and low efficacy for drug-resistance strains. Therefore, new anti-herpetic drugs and strategies should be urgently developed. Here, we reported that baicalein, a naturally derived compound widely used in Asian countries, strongly inhibited HSV-1 replication in several models. Baicalein was effective against the replication of both HSV-1/F and HSV-1/Blue (an acyclovir-resistant strain) in vitro. In the ocular inoculation mice model, baicalein markedly reduced in vivo HSV-1/F replication, receded inflammatory storm and attenuated histological changes in the cornea. Consistently, baicalein was found to reduce the mortality of mice, viral loads both in nose and trigeminal ganglia in HSV-1 intranasal infection model. Moreover, an ex vivo HSV-1-EGFP infection model established in isolated murine epidermal sheets confirmed that baicalein suppressed HSV-1 replication. Further investigations unraveled that dual mechanisms, inactivating viral particles and inhibiting IκB kinase beta (IKK-β) phosphorylation, were involved in the anti-HSV-1 effect of baicalein. Collectively, our findings identified baicalein as a promising therapy candidate against the infection of HSV-1, especially acyclovir-resistant strain.

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Baicalein is highly effective against HSV-1infection ex vivo and in vivo.

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Inactivation of viral particles and suppression of NF-κB activation were involved in the anti-viral effect of baicalein.

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Hence, our work offers experimental basis for baicalein as a potential drug in treating HSV-1 associated diseases.

Monkeypox Virus in Nigeria: Infection Biology, Epidemiology, and Evolution

Monkeypox is a zoonotic disease caused by monkeypox virus (MPXV), which is a member of orthopoxvirus genus. The reemergence of MPXV in 2017 (at Bayelsa state) after 39 years of no reported case in Nigeria, and the export of travelers' monkeypox (MPX) from Nigeria to other parts of the world, in 2018 and 2019, respectively, have raised concern that MPXV may have emerged to occupy the ecological and immunological niche vacated by smallpox virus. This review X-rays the current state of knowledge pertaining the infection biology, epidemiology, and evolution of MPXV in Nigeria and worldwide, especially with regard to the human, cellular, and viral factors that modulate the virus transmission dynamics, infection, and its maintenance in nature. This paper also elucidates the role of recombination, gene loss and gene gain in MPXV evolution, chronicles the role of signaling in MPXV infection, and reviews the current therapeutic options available for the treatment and prevention of MPX. Additionally, genome-wide phylogenetic analysis was undertaken, and we show that MPXV isolates from recent 2017 outbreak in Nigeria were monophyletic with the isolate exported to Israel from Nigeria but do not share the most recent common ancestor with isolates obtained from earlier outbreaks, in 1971 and 1978, respectively. Finally, the review highlighted gaps in knowledge particularly the non-identification of a definitive reservoir host animal for MPXV and proposed future research endeavors to address the unresolved questions.

Venezuelan Equine Encephalitis Virus nsP3 Phosphorylation Can Be Mediated by IKKβ Kinase Activity and Abrogation of Phosphorylation Inhibits Negative-Strand Synthesis

Venezuelan equine encephalitis virus (VEEV), a mosquito transmitted alphavirus of the Togaviridae family, can cause a highly inflammatory and encephalitic disease upon infection. Although a category B select agent, no FDA-approved vaccines or therapeutics against VEEV currently exist. We previously demonstrated NF-κB activation and macromolecular reorganization of the IKK complex upon VEEV infection in vitro, with IKKβ inhibition reducing viral replication. Mass spectrometry and confocal microscopy revealed an interaction between IKKβ and VEEV non-structural protein 3 (nsP3). Here, using western blotting, a cell-free kinase activity assay, and mass spectrometry, we demonstrate that IKKβ kinase activity can directly phosphorylate VEEV nsP3 at sites 204/5, 142, and 134/5. Alanine substitution mutations at sites 204/5, 142, or 134/5 reduced VEEV replication by >30-100,000-fold corresponding to a severe decrease in negative-strand synthesis. Serial passaging rescued viral replication and negative-strand synthesis, and sequencing of revertant viruses revealed reversion to the wild-type TC-83 phosphorylation capable amino acid sequences at nsP3 sites 204/5, 142, and 135. Generation of phosphomimetic mutants using aspartic acid substitutions at site 204/5 resulted in rescue of both viral replication and negative-strand RNA production, whereas phosphomimetic mutant 134/5 rescued viral replication but failed to restore negative-strand RNA levels, and phosphomimetic mutant 142 did not rescue VEEV replication. Together, these data demonstrate that IKKβ can phosphorylate VEEV nsP3 at sites 204/5, 142, and 134/5, and suggest that phosphorylation is essential for negative-strand RNA synthesis at site 204/5, but may be important for infectious particle production at site 134/5.

Molecular characterization and functional analysis of IKKα in orange-spotted grouper (Epinephelus coioides)

Inhibitor of nuclear factor kappa-B kinase subunit alpha (IKKα) plays crucial roles in regulating activation of nuclear factor kappa-B (NF-κB) in response to pathogens infections. Here, we cloned and identified IKKα gene of orange-spotted grouper (Epinephelus coioides), named as EcIKKα. The gene transcript contained a 2262 bp open reading frame, which encoded 753 amino acids. The typically conserved IKKα structure, including serine kinase domain (KD), leucine chain (LZ) structure, helix-loop-helix (HLH) motif and IKKβ-NEMO-binding domain, was identified in EcIKKα. Phylogenetic analysis suggested that EcIKKα had the closest relationship with large yellow croaker (Larimichthy crocea) IKKα. Ecikkα was ubiquitously expressed in all tissues tested and the highest expression level was in ovary. After lipopolysaccharide (LPS), flagellin, polyinosinic-polycytidylic acid (poly I:C), polyadenylic-polyuridylic acid (poly A:U), and Vibrio parahaemolyticus stimulation, the expression of Ecikkα increased in grouper spleen (GS) cells. In the luciferase assay, NF-κB-luc activity was significantly up-regulated when human embryonic kidney 293T (HEK 293T) cells were transfected with EcIKKα plasmid. Moreover, overexpression of EcIKKα significantly increased LPS- and flagellin-induced proinflammatory cytokines (interleukin-6 (il-6) and tumor necrosis factor-α (tnf-α)) expression, but did not significantly affect poly I:C- and poly A:U-induced cytokines (il-6 and tnf-α) expression. Overall, these results suggested that EcIKKα functions like that of mammals to activate NF-κB, and it could be involved in host defense against invading pathogens.

PSMB1 Negatively Regulates the Innate Antiviral Immunity by Facilitating Degradation of IKK-ε

Proteasome is a large protein complex, which degrades most intracellular proteins. It regulates numerous cellular processes, including the removal of misfolded or unfolded proteins, cell cycle control, and regulation of apoptosis. However, the function of proteasome subunits in viral immunity has not been well characterized. In this study, we identified PSMB1, a member of the proteasome β subunits (PSMB) family, as a negative regulator of innate immune responses during viral infection. Knockdown of PSMB1 enhanced the RNA virus-induced cytokine and chemokine production. Overexpression of PSMB1 abolished virus-induced activation of the interferon-stimulated response element (ISRE) and interferon beta (IFNβ) promoters. Mechanistically, PSMB1 inhibited the activation of RIG-I-like receptor (RLR) and Toll-like receptor 3 (TLR3) signaling pathways. PSMB1 was induced after viral infection and its interaction with IKK-ε promoted degradation of IKK-ε through the ubiquitin-proteasome system. Collectively, our study demonstrates PSMB1 is an important regulator of innate immune signaling.

The levels of NF-κB p50 and NF-κB p65 play a role in thyroid carcinoma malignancy in vivo

Background To investigate the relationship between the levels of nuclear factor (NF)-κB p50 and NF-κB p65 and tumour characteristics in patients with thyroid carcinoma. Methods This prospective study enrolled consecutive patients with thyroid carcinoma. Tumour samples were collected and the levels of NF-κB p50 and NF-κB p65 protein and mRNA were measured using immunohistochemistry and quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). Results A total of 73 patients with thyroid carcinoma were included in the study (20 males; 53 females; mean ± SD age, 44.8 ± 12.7 years, range, 18-76 years). There were no significant differences in sex, age and pathological type between the NF-κB p50 positive group and the NF-κB p50 negative group, but tumour diameter and lymph node metastasis were significantly higher in the NF-κB p50 positive group compared with the NF-κB p50 negative group. Similar findings were observed for NF-κB p65. The levels of NF-κB p50 were positively correlated with NF-κB p65 in samples of thyroid carcinoma ( rs = 0.653). Conclusion The levels of NF-κB p50 and NF-κB p65 in samples of thyroid carcinoma were positively associated with tumour diameter and the presence of lymph node metastasis.

S100A4 suppresses cancer stem cell proliferation via interaction with the IKK/NF-κB signaling pathway

Background

Bladder cancer often recurs due to incomplete elimination of the cancer stem cells (CSCs). Therefore, new strategies targeting bladder CSCs are needed and the aim of this study was to investigate the effect of S100A4 on the proliferation capacity of MB49 bladder cancer stem cells (MCSCs).

Methods

MCSCs were established and validated. The expression level of S100A4 in MCSCs and MB49 cells was evaluated using Western blotting and quantitative polymerase chain reaction (QPCR). S100A4 was overexpressed or knocked-down by transfection of pCMV6-XL5-S100A4 plasmid or RNA interference (RNAi) respectively. Proliferation capacity of MCSC was evaluated by cell proliferation assay and in vivo tumorigenicity study. Transcriptional activity of nuclear factor kappa B (NF-κB) was analyzed using luciferase reporter assay, and the level of interleukin (IL)-2 as well as tumor necrosis factor (TNF) was quantified by QPCR. Protein-protein interaction of S100A4 and inhibitor of nuclear factor kappa B NF-κB kinase (IKK) was analyzed by immunoprecipitation.

Results

S100A4 was significantly up-regulated in MCSCs, which positively associated with the proliferation capacity, as well as the level of NF-κB, IKK, IL-2 and TNF in MCSCs. Knock-down of S100A4 could reverse such effects. Using immunoprecipitation assay, an interaction between S100A4 and IKK could be observed.

Conclusions

S100A4 is upregulated in MCSCs and possibly enhance the proliferation ability of MCSCs by way of activating the IKK/NF-κB signaling pathway, and S100A4 maybe a hopeful therapeutic target for MCSCs.

A parapoxviral virion protein targets the retinoblastoma protein to inhibit NF-κB signaling

Poxviruses have evolved multiple strategies to subvert signaling by Nuclear Factor κB (NF-κB), a crucial regulator of host innate immune responses. Here, we describe an orf virus (ORFV) virion-associated protein, ORFV119, which inhibits NF-κB signaling very early in infection (≤ 30 min post infection). ORFV119 NF-κB inhibitory activity was found unimpaired upon translation inhibition, suggesting that virion ORFV119 alone is responsible for early interference in signaling. A C-terminal LxCxE motif in ORFV119 enabled the protein to interact with the retinoblastoma protein (pRb) a multifunctional protein best known for its tumor suppressor activity. Notably, experiments using a recombinant virus containing an ORFV119 mutation which abrogates its interaction with pRb together with experiments performed in cells lacking or with reduced pRb levels indicate that ORFV119 mediated inhibition of NF-κB signaling is largely pRb dependent. ORFV119 was shown to inhibit IKK complex activation early in infection. Consistent with IKK inhibition, ORFV119 also interacted with TNF receptor associated factor 2 (TRAF2), an adaptor protein recruited to signaling complexes upstream of IKK in infected cells. ORFV119-TRAF2 interaction was enhanced in the presence of pRb, suggesting that ORFV119-pRb complex is required for efficient interaction with TRAF2. Additionally, transient expression of ORFV119 in uninfected cells was sufficient to inhibit TNFα-induced IKK activation and NF-κB signaling, indicating that no other viral proteins are required for the effect. Infection of sheep with ORFV lacking the ORFV119 gene led to attenuated disease phenotype, indicating that ORFV119 contributes to virulence in the natural host. ORFV119 represents the first poxviral protein to interfere with NF-κB signaling through interaction with pRb.

A parapoxviral virion protein inhibits NF-κB signaling early in infection

Poxviruses have evolved unique proteins and mechanisms to counteract the nuclear factor κB (NF-κB) signaling pathway, which is an essential regulatory pathway of host innate immune responses. Here, we describe a NF-κB inhibitory virion protein of orf virus (ORFV), ORFV073, which functions very early in infected cells. Infection with ORFV073 gene deletion virus (OV-IA82Δ073) led to increased accumulation of NF-κB essential modulator (NEMO), marked phosphorylation of IκB kinase (IKK) subunits IKKα and IKKβ, IκBα and NF-κB subunit p65 (NF-κB-p65), and to early nuclear translocation of NF-κB-p65 in virus-infected cells (≤ 30 min post infection). Expression of ORFV073 alone was sufficient to inhibit TNFα induced activation of the NF-κB signaling in uninfected cells. Consistent with observed inhibition of IKK complex activation, ORFV073 interacted with the regulatory subunit of the IKK complex NEMO. Infection of sheep with OV-IA82Δ073 led to virus attenuation, indicating that ORFV073 is a virulence determinant in the natural host. Notably, ORFV073 represents the first poxviral virion-associated NF-κB inhibitor described, highlighting the significance of viral inhibition of NF-κB signaling very early in infection.

Molluscum Contagiosum Virus Protein MC005 Inhibits NF-κB Activation by Targeting NEMO-Regulated IκB Kinase Activation

Molluscum contagiosum virus (MCV), the only known extant human-adapted poxvirus, causes a long-duration infection characterized by skin lesions that typically display an absence of inflammation despite containing high titers of live virus. Despite this curious presentation, MCV is very poorly characterized in terms of host-pathogen interactions. The absence of inflammation around MCV lesions suggests the presence of potent inhibitors of human antiviral immunity and inflammation. However, only a small number of MCV immunomodulatory genes have been characterized in detail. It is likely that many more remain to be discovered, given the density of such sequences in other poxvirus genomes. NF-κB activation occurs in response to both virus-induced pattern recognition receptor (PRR) signaling and cellular activation by virus-induced proinflammatory cytokines like tumor necrosis factor and interleukin-1. Activated NF-κB drives cytokine and interferon gene expression, leading to inflammation and virus clearance. We report that MC005, which has no orthologs in other poxvirus genomes, is a novel inhibitor of PRR- and cytokine-stimulated NF-κB activation. MC005 inhibited NF-κB proximal to the IκB kinase (IKK) complex, and unbiased affinity purification revealed that MC005 interacts with the IKK subunit NEMO (NF-κB essential modulator). MC005 binding to NEMO prevents the conformational priming of the IKK complex that occurs when NEMO binds to ubiquitin chains during pathway activation. These data reveal a novel mechanism of poxvirus inhibition of human innate immunity, validate current dynamic models of NEMO-dependent IKK complex activation, and further clarify how the human-adapted poxvirus MCV can so effectively evade antiviral immunity and suppress inflammation to persist in human skin lesions.IMPORTANCE Poxviruses adapt to specific hosts over time, evolving and tailoring elegantly precise inhibitors of the rate-limiting steps within the signaling pathways that control innate immunity and inflammation. These inhibitors reveal new features of the antiviral response, clarify existing models of signaling regulation while offering potent new tools for approaching therapeutic intervention in autoimmunity and inflammatory disease. Molluscum contagiosum virus (MCV) is the only known extant poxvirus specifically adapted to human infection and appears adept at evading normal human antiviral responses, yet it remains poorly characterized. We report the identification of MCV protein MC005 as an inhibitor of the pathways leading to the activation of NF-κB, an essential regulator of innate immunity. Further, identification of the mechanism of inhibition of NF-κB by MC005 confirms current models of the complex way in which NF-κB is regulated and greatly expands our understanding of how MCV so effectively evades human immunity.

Genomewide association of piglet responses to infection with one of two porcine reproductive and respiratory syndrome virus isolates

Porcine reproductive and respiratory syndrome (PRRS) is a devastating disease in the swine industry. Identification of host genetic factors that enable selection for improved performance during PRRS virus (PRRSV) infection would reduce the impact of this disease on animal welfare and production efficiency. We conducted genomewide association study (GWAS) analyses of data from 13 trials of approximately 200 commercial crossbred nursery-age piglets that were experimentally infected with 1 of 2 type 2 isolates of PRRSV (NVSL 97-7985 [NVSL] and KS2006-72109 [KS06]). Phenotypes analyzed were viral load (VL) in blood during the first 21 d after infection (dpi) and weight gain (WG) from 0 to 42 dpi. We accounted for the previously identified QTL in the region on SSC4 in our models to increase power to identify additional regions. Many regions identified by single-SNP analyses were not identified using Bayes-B, but both analyses identified the same regions on SSC3 and SSC5 to be associated with VL in the KS06 trials and on SSC6 in the NVSL trials ( < 5 × 10); for WG, regions on SSC5 and SSC17 were associated in the NVSL trials ( < 3 × 10). No regions were identified with either method for WG in the KS06 trials. Except for the region on SSC4, which was associated with VL for both isolates (but only with WG for NVSL), identified regions did not overlap between the 2 PRRSV isolate data sets, despite high estimates of the genetic correlation between isolates for traits based on these data. We also identified genomic regions whose associations with VL or WG interacted with either PRRSV isolate or with genotype at the SSC4 QTL. Gene ontology (GO) annotation terms for genes located near moderately associated SNP ( < 0.003) were enriched for multiple immunologically (VL) and metabolism- (WG) related GO terms. The biological relevance of these regions suggests that, although it may increase the number of false positives, the use of single-SNP analyses and a relaxed threshold also increased the identification of true positives. In conclusion, although only the SSC4 QTL was associated with response to both PRRSV isolates, genes near associated SNP were enriched for the same GO terms across PRRSV isolates, suggesting that host responses to these 2 isolates are affected by the actions of many genes that function together in similar biological processes.

Non-Canonical Role of IKKα in the Regulation of STAT1 Phosphorylation in Antiviral Signaling

Non-self RNA is recognized by retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), inducing type I interferons (IFNs). Type I IFN promotes the expression of IFN-stimulated genes (ISGs), which requires the activation of signal transducer and activator of transcription-1 (STAT1). We previously reported that dsRNA induced STAT1 phosphorylation via a type I IFN-independent pathway in addition to the well-known type I IFN-dependent pathway. IκB kinase α (IKKα) is involved in antiviral signaling induced by dsRNA; however, its role is incompletely understood. Here, we explored the function of IKKα in RLR-mediated STAT1 phosphorylation. Silencing of IKKα markedly decreased the level of IFN-β and STAT1 phosphorylation inHeH response to dsRNA. However, the inhibition of IKKα did not alter the RLR signaling-mediated dimerization of interferon responsive factor 3 (IRF3) or the nuclear translocation of nuclear factor-κB (NFκB). These results suggest a non-canonical role of IKKα in RLR signaling. Furthermore, phosphorylation of STAT1 was suppressed by IKKα knockdown in cells treated with a specific neutralizing antibody for the type I IFN receptor (IFNAR) and in IFNAR-deficient cells. Collectively, the dual regulation of STAT1 by IKKα in antiviral signaling suggests a role for IKKα in the fine-tuning of antiviral signaling in response to non-self RNA.

2C Proteins of Enteroviruses Suppress IKKβ Phosphorylation by Recruiting Protein Phosphatase 1

The NF-κB signaling network, which is an ancient signaling pathway, plays a pivotal role in innate immunity and constitutes a first line of defense against invading pathogens, including viruses. However, numerous viruses possess evolved strategies to antagonize the activation of the NF-κB signaling pathway. Our previous study demonstrated that the nonstructural protein 2C of enterovirus 71 (EV71), which is the major pathogen of hand, foot, and mouth disease, inhibits tumor necrosis factor alpha (TNF-α)-mediated activation of NF-κB by suppressing IκB kinase β (IKKβ) phosphorylation. Nevertheless, the mechanism underlying the inhibition of IKKβ phosphorylation by EV71 2C remains largely elusive. We demonstrate that EV71 2C interacts with all isoforms of the protein phosphatase 1 (PP1) catalytic subunit (the PP1α, PP1β, and PP1γ isoforms) through PP1-docking motifs. EV71 2C has no influence on the subcellular localization of PP1. In addition, the PP1-binding-deficient EV71 2C mutant 3E3L nearly completely lost the ability to suppress IKKβ phosphorylation and NF-κB activation was markedly restored in the mutant, thereby indicating that PP1 binding is efficient for EV71 2C-mediated inhibition of IKKβ phosphorylation and NF-κB activation. We further demonstrate that 2C forms a complex with PP1 and IKKβ to dephosphorylate IKKβ. Notably, we reveal that other human enteroviruses, including poliovirus (PV), coxsackie A virus 16 (CVA16), and coxsackie B virus 3 (CVB3), use 2C proteins to recruit PP1, leading to the inhibition of IKKβ phosphorylation. Our findings indicate that enteroviruses exploit a novel mechanism to inhibit IKKβ phosphorylation by recruiting PP1 and IKKβ to form a complex through 2C proteins, which ultimately results in the inhibition of the NF-κB signaling pathway.

IMPORTANCE

The innate antiviral immunity system performs an essential function in recognizing and eliminating invading viruses. Enteroviruses include a number of important human pathogens, including poliovirus (PV), EV71, and coxsackieviruses (CVs). As 2C is the most conserved and complex nonstructural protein of enteroviruses, its biological function is largely unclear, whereas the 2A and 3C proteinases of enteroviruses are well characterized. We reveal that EV71 2C forms a complex with PP1 and IKKβ to maintain IKKβ in an unphosphorylated and inactive state, resulting in the inactivation of the TNF-α-mediated NF-κB signaling pathway. We provide evidence that the 2C proteins of the enteroviruses PV, CVA16, and CVB3 suppress IKKβ phosphorylation through the same mechanism involving PP1. We demonstrate that enteroviruses exploit a novel mechanism involving PP1 to regulate innate antiviral immunity, and our findings may be particularly important for understanding the pathogenicity of enteroviruses.

Inhibition of IκB Kinase Attenuates the Organ Injury and Dysfunction Associated with Hemorrhagic Shock

Nuclear factor-kappa B (NF-κB) activation is widely implicated in multiple organ failure (MOF); however, a direct inhibitor of IκB kinase (IKK), which plays a pivotal role in the activation of NF-κB, has not been investigated in shock. Thus, the aim of the present work was to investigate the effects of an IKK inhibitor on the MOF associated with hemorrhagic shock (HS). Therefore, rats were subjected to HS and were resuscitated with the shed blood. Rats were treated with the inhibitor of IKK or vehicle at resuscitation. Four hours later, blood and organs were assessed for organ injury and signaling events involved in the activation of NF-κB. Additionally, survival following serum deprivation was assessed in HK-2 cells treated with the inhibitor of IKK. HS resulted in renal dysfunction, lung, liver and muscular injury, and increases in serum inflammatory cytokines. Kidney and liver tissue from HS rats revealed increases in phosphorylation of IKKαβ and IκBα, nuclear translocation of NF-κB and expression of inducible isoform of nitric oxide synthase (iNOS). IKK16 treatment upon resuscitation attenuated NF-κB activation and activated the Akt survival pathway, leading to a significant attenuation of all of the above parameters. Furthermore, IKK16 exhibited cytoprotective effects in human kidney cells. In conclusion, the inhibitor of IKK complex attenuated the MOF associated with HS. This effect may be due to the inhibition of the NF-κB pathway and activation of the survival kinase Akt. Thus, the inhibition of the IKK complex might be an effective strategy for the prevention of MOF associated with HS.