Structural Investigations of Interactions between the Influenza a Virus NS1 and Host Cellular Proteins

The Influenza A virus is a continuous threat to public health that causes yearly epidemics with the ever-present threat of the virus becoming the next pandemic. Due to increasing levels of resistance, several of our previously used antivirals have been rendered useless. There is a strong need for new antivirals that are less likely to be susceptible to mutations. One strategy to achieve this goal is structure-based drug development. By understanding the minute details of protein structure, we can develop antivirals that target the most conserved, crucial regions to yield the highest chances of long-lasting success. One promising IAV target is the virulence protein non-structural protein 1 (NS1). NS1 contributes to pathogenicity through interactions with numerous host proteins, and many of the resulting complexes have been shown to be crucial for virulence. In this review, we cover the NS1-host protein complexes that have been structurally characterized to date. By bringing these structures together in one place, we aim to highlight the strength of this field for drug discovery along with the gaps that remain to be filled.

Dynamic phospho-modification of viral proteins as a crucial regulatory layer of influenza A virus replication and innate immune responses

Influenza viruses are small RNA viruses with a genome of about 13 kb. Because of this limited coding capacity, viral proteins have evolved to fulfil multiple functions in the infected cell. This implies that there must be mechanisms allowing to dynamically direct protein action to a distinct activity in a spatio-temporal manner. Furthermore, viruses exploit many cellular processes, which also have to be dynamically regulated during the viral replication cycle. Phosphorylation and dephosphorylation of proteins are fundamental for the control of many cellular responses. There is accumulating evidence that this mechanism represents a so far underestimated level of regulation in influenza virus replication. Here, we focus on the current knowledge of dynamics of phospho-modifications in influenza virus replication and show recent examples of findings underlining the crucial role of phosphorylation in viral transport processes as well as activation and counteraction of the innate immune response.

Exploring multiple mechanisms of Qingjie Fanggan prescription for prevention and treatment of influenza based on systems pharmacology

Influenza is a type of acute disease characterized by strong contagiousness and short incubation period, which have posed a large potential threat to public health. Traditional Chinese Medicine (TCM) advocates to the aim of combating complex diseases from a holistic view, which has shown effectiveness in anti-influenza. However, the mechanism of TCM prescription remains puzzling. Here, we applied a system pharmacology approach to reveal the underlying molecular mechanisms of Qingjie Fanggan prescription (QFP) in the prevention and treatment of influenza. In this study, we identified 228 potential active compounds by means of absorption, distribution, metabolism, and excretion (ADME) evaluation system and literature research. Then, the targets of the potential active compounds were predicted by using the WES (Weighted Ensemble Similarity) method, and the influenza-related targets were obtained according to some existing gene databases. Next, an herb-component-target network was constructed to further dissect the multi-directional therapeutic approach for QFP. Meanwhile, we also performed gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation analysis on 344 potential targets. Finally, a target-pathway network was constructed to further dissect the core pathways and targets in treatment of influenza for QFP. And the key components and targets were docked by AutoDock Vina to explore their binding mode. All of these demonstrated that QFP had multi-scale curative activity in regulating influenza-related biological processes, which facilitates the application of traditional medicine in modern medicine.

Regulation of Apoptosis by Enteroviruses

Enterovirus infection can cause a variety of diseases and severely impair the health of humans, animals, poultry, and other organisms. To resist viral infection, host organisms clear infected cells and viruses via apoptosis. However, throughout their long-term competition with host cells, enteroviruses have evolved a series of mechanisms to regulate the balance of apoptosis in order to replicate and proliferate. In the early stage of infection, enteroviruses mainly inhibit apoptosis by regulating the PI3K/Akt pathway and the autophagy pathway and by impairing cell sensors, thereby delaying viral replication. In the late stage of infection, enteroviruses mainly regulate apoptotic pathways and the host translation process via various viral proteins, ultimately inducing apoptosis. This paper discusses the means by which these two phenomena are balanced in enteroviruses to produce virus-favoring conditions – in a temporal sequence or through competition with each other. This information is important for further elucidation of the relevant mechanisms of acute infection by enteroviruses and other members of the picornavirus family.

The roles of apoptosis, autophagy and unfolded protein response in arbovirus, influenza virus, and HIV infections

Virus infection induces different cellular responses in infected cells. These include cellular stress responses like autophagy and unfolded protein response (UPR). Both autophagy and UPR are connected to programed cell death I (apoptosis) in chronic stress conditions to regulate cellular homeostasis via Bcl2 family proteins, CHOP and Beclin-1. In this review article we first briefly discuss arboviruses, influenza virus, and HIV and then describe the concepts of apoptosis, autophagy, and UPR. Finally, we focus upon how apoptosis, autophagy, and UPR are involved in the regulation of cellular responses to arboviruses, influenza virus and HIV infections.

Abbreviation: AIDS: Acquired Immunodeficiency Syndrome; ATF6: Activating Transcription Factor 6; ATG6: Autophagy-specific Gene 6; BAG3: BCL Associated Athanogene 3; Bak: BCL-2-Anatagonist/Killer1; Bax; BCL-2: Associated X protein; Bcl-2: B cell Lymphoma 2x; BiP: Chaperon immunoglobulin heavy chain binding Protein; CARD: Caspase Recruitment Domain; cART: combination Antiretroviral Therapy; CCR5: C-C Chemokine Receptor type 5; CD4: Cluster of Differentiation 4; CHOP: C/EBP homologous protein; CXCR4: C-X-C Chemokine Receptor Type 4; Cyto c: Cytochrome C; DCs: Dendritic Cells; EDEM1: ER-degradation enhancing-a-mannosidase-like protein 1; ENV: Envelope; ER: Endoplasmic Reticulum; FasR: Fas Receptor;G2: Gap 2; G2/M: Gap2/Mitosis; GFAP: Glial Fibrillary Acidic Protein; GP120: Glycoprotein120; GP41: Glycoprotein41; HAND: HIV Associated Neurodegenerative Disease; HEK: Human Embryonic Kidney; HeLa: Human Cervical Epithelial Carcinoma; HIV: Human Immunodeficiency Virus; IPS-1: IFN-β promoter stimulator 1; IRE-1: Inositol Requiring Enzyme 1; IRGM: Immunity Related GTPase Family M protein; LAMP2A: Lysosome Associated Membrane Protein 2A; LC3: Microtubule Associated Light Chain 3; MDA5: Melanoma Differentiation Associated gene 5; MEF: Mouse Embryonic Fibroblast; MMP: Mitochondrial Membrane Permeabilization; Nef: Negative Regulatory Factor; OASIS: Old Astrocyte Specifically Induced Substrate; PAMP: Pathogen-Associated Molecular Pattern; PERK: Pancreatic Endoplasmic Reticulum Kinase; PRR: Pattern Recognition Receptor; Puma: P53 Upregulated Modulator of Apoptosis; RIG-I: Retinoic acid-Inducible Gene-I; Tat: Transactivator Protein of HIV; TLR: Toll-like receptor; ULK1: Unc51 Like Autophagy Activating Kinase 1; UPR: Unfolded Protein Response; Vpr: Viral Protein Regulatory; XBP1: X-Box Binding Protein 1

Acetyl-11-Keto-β-Boswellic Acid Exerts the Anti-Cancer Effects via Cell Cycle Arrest, Apoptosis Induction and Autophagy Suppression in Non-Small Cell Lung Cancer Cells

Objective

Acetyl-11-keto-β-boswellic acid (AKBA) is a triterpenoid, which is the main component of boswellic acid from Boswellia Serrata, a medicinal plant that has shown immense potential in anti-cancer therapy. This study aims to explore the roles and molecular mechanisms of AKBA on cell behavior in non-small cell lung cancer (NSCLC) cells.

Materials and Methods

The effects of AKBA on the cell viability in A549, H460, H1299, and BEAS-2B cells were determined by the CCK-8 assay. The colony formation assay was used to identify the effects of AKBA on cell proliferation. Potential roles of AKBA in regulating the cell cycle, apoptosis, and autophagy in A549 were evaluated by flow cytometry, Western blotting, reverse transcription-polymerase chain reaction (PCR) and immunofluorescence (IF).

Results

AKBA reduced cell viability in A549, H460, H1299, and BEAS-2B. In A549 cells, AKBA suppressed the clone formation, arrested the cell cycle at the G₀/G₁ phase, induced cellular apoptosis. We found that AKBA suppressed the formation of autolysosome, and decreased the expression levels of Beclin-1, LC3A/B-I, and LC3A/B-II proteins. Furthermore, AKBA also inhibited the expression levels of PI3K/Akt signaling pathway proteins.

Conclusion

AKBA exerts the anti-cancer effects via cell cycle arrest, apoptosis induction, and autophagy suppression in NSCLC cells. This body of evidence supports the potential of AKBA as a promising drug in the treatment of NSCLC.

Role of TGF-β-activated kinase 1 (TAK1) activation in H5N1 influenza A virus-induced c-Jun terminal kinase activation and virus replication

Activation of c-Jun terminal kinase (JNK) by the nonstructural protein 1 (NS1) of the H5N1 subtype of influenza A virus (IAV) plays an important role in inducing autophagy and virus replication. However, the mechanisms of NS1-induced JNK activation remain elusive. Here we first confirmed the ability of H5N1 (A/mallard/Huadong/S/2005) to activate JNK and to induce autophagy in 293T cells, a human embryonic kidney cell line. We further showed that TAK1, MAP kinase kinase 4 (MKK4), and JNK were activated in 293T cells transfected with the NS1 gene of the H5N1 virus. JNK activation by the NS1 protein or by H5N1 virus was blocked by 5Z-7-Oxozeaenol (5Z), a TAK1-specific inhibitor, and by TAK1 siRNA. Further study showed that 5Z and TAK1 siRNA suppressed H5N1 virus-induced autophagy and inhibited virus replication. Our study unveiled a previously unrecognized role of TAK1 in IAV replication, IAV-induced JNK activation, and autophagy.

New therapeutic targets for the prevention of infectious acute exacerbations of COPD: role of epithelial adhesion molecules and inflammatory pathways

Chronic respiratory diseases are among the leading causes of mortality worldwide, with the major contributor, chronic obstructive pulmonary disease (COPD) accounting for approximately 3 million deaths annually. Frequent acute exacerbations (AEs) of COPD (AECOPD) drive clinical and functional decline in COPD and are associated with accelerated loss of lung function, increased mortality, decreased health-related quality of life and significant economic costs. Infections with a small subgroup of pathogens precipitate the majority of AEs and consequently constitute a significant comorbidity in COPD. However, current pharmacological interventions are ineffective in preventing infectious exacerbations and their treatment is compromised by the rapid development of antibiotic resistance. Thus, alternative preventative therapies need to be considered. Pathogen adherence to the pulmonary epithelium through host receptors is the prerequisite step for invasion and subsequent infection of surrounding structures. Thus, disruption of bacterial-host cell interactions with receptor antagonists or modulation of the ensuing inflammatory profile present attractive avenues for therapeutic development. This review explores key mediators of pathogen-host interactions that may offer new therapeutic targets with the potential to prevent viral/bacterial-mediated AECOPD. There are several conceptual and methodological hurdles hampering the development of new therapies that require further research and resolution.

Role of c-Jun terminal kinase (JNK) activation in influenza A virus-induced autophagy and replication

The non-structural protein 1 (NS1) of different influenza A virus (IAV) strains can differentially regulate the activity of c-Jun terminal kinase (JNK) and PI-3 kinase (PI3K). Whether varying JNK and PI3K activation impacts autophagy and IAV replication differently remains uncertain. Here we report that H5N1 (A/mallard/Huadong/S/2005) influenza A virus induced functional autophagy, as evidenced by increased LC3 lipidation and decreased p62 levels, and the presence of autolysosomes in chicken fibroblast cells. H9N2 (A/chicken/Shanghai/F/98) virus weakly induced autophagy, whereas H1N1 virus (A/PR/8/34, PR8) blocked autophagic flux. H5N1 virus activated JNK but inhibited the PI-3 kinase pathway. In contrast, N9N2 virus infection led to modest JNK activation and strong PI-3 kinase activation; whereas H1N1 virus activated the PI-3 kinase pathway but did not activate JNK. SP600125, a JNK inhibitor, inhibited H5N1 virus-induced autophagy and virus replication in a DF-1 chicken fibroblast cell line. Our study uncovered a previously unrecognized role of JNK in IAV replication and autophagy.

Effects of mutations in the effector domain of influenza A virus NS1 protein

OBJECTIVE

The multifunctional NS1 protein of influenza A virus has roles in antagonising cellular innate immune responses and promoting viral gene expression. To better understand the interplay between these functions, we tested the effects of NS1 effector domain mutations known to affect homo-dimerisation or interactions with cellular PI3 kinase or Trim25 on NS1 ability to promote nuclear export of viral mRNAs.

RESULTS

The NS1 dimerisation mutant W187R retained the functions of binding cellular NXF1 as well as stabilising NXF1 interaction with viral segment 7 mRNAs and promoting their nuclear export. Two PI3K-binding mutants, NS1 Y89F and Y89A still bound NXF1 but no longer promoted NXF1 interactions with segment 7 mRNA or its nuclear export. The Trim25-binding mutant NS1 E96A/E97A bound NXF1 and supported NXF1 interactions with segment 7 mRNA but no longer supported mRNA nuclear export. Analysis of WT and mutant NS1 interaction partners identified hsp70 as specifically binding to NS1 E96A/E97A. Whilst these data suggest the possibility of functional links between NS1's effects on intracellular signalling and its role in viral mRNA nuclear export, they also indicate potential pleiotropic effects of the NS1 mutations; in the case of E96A/E97A possibly via disrupted protein folding leading to chaperone recruitment.

MiR-31 regulates the cisplatin resistance by targeting Src in gallbladder cancer

Background

Gallbladder cancer (GBC) is a malignant tumor highly resistant to chemotherapy. MicroRNAs (miRNAs) are found extensively involved in modulation of carcinogenesis and chemoresistance. This study aimed to investigate cisplatin (DDP)-susceptibility regulated by expression of the miRNAs and underlying pathways in GBC.

Results

The microRNA-31 (miR-31) was selected by microarray due to the biggest fold change between DDP-resistant and parental cells. Ectopic overexpression of miR-31 decreased cell proliferation, viability and invasion capacity, but promoted apoptosis in DDP-resistant cells and in xenograft tumor models. Cell apoptosis and DDP-chemosensitivity was remarkably increased by knockdown of Src proto-oncogene (Src) expression, which was subsequently reversed by rescue of Src expression in miR-31-expressing cells.

Methods

The microarray was used to select the candidate miRNA in two DDP-resistant GBC cell lines. The effect of regulated expression of the miRNA on cell migration, invasion, proliferation and apoptosis was examined by wound healing, transwell assays, CCK-8 assays, colony formation and flow cytometry assays, respectively. Xenograft tumor models were used to validate the function of the downstream target.

Conclusion

Our results demonstrated that miR-31reduced significantly in GBC cells rendering resistance to cisplatin, and upregulated expression of miR-31 augmented chemosensitivity, presenting a therapeutic potential to overcome drug resistance in GBC.

ASK family in infection and inflammatory disease

Living organisms are continuously exposed to pathogens such as viruses and bacteria. Soon after a limited number of germline-encoded receptors, called pathogen recognition receptors, sense pathogen-associated molecular patterns, hosts trigger innate immune responses, including production of type Ⅰ interferons, proinflammatory cytokines, and cellular apoptosis, to limit propagation of invading pathogens. Importantly, these host responses are also activated during inflammatory diseases, irrespective of pathogen infection, and often play a causal role in pathogenesis and progression of these diseases, thereby implying an intimate link between immune responses and inflammatory disease. The apoptosis signal-regulating kinase (ASK) family belongs to the larger MAP3K family that controls various stress responses. Here, I summarize the critical roles of members of the ASK family during infection and inflammatory disease, and discuss the relationship between these two noxious conditions.

Autophagy activation is required for influenza A virus-induced apoptosis and replication

Autophagy and apoptosis are two major interconnected host cell responses to viral infection, including influenza A virus (IAV). Thus, delineating these events could facilitate the development of better treatment options and provide an effective anti-viral strategy for controlling IAV infection. We used A549 cells and mouse embryonic fibroblasts (MEF) to study the role of virus-induced autophagy and apoptosis, the cross-talk between both pathways, and their relation to IAV infection [ATCC strain A/Puerto Rico/8/34(H1N1) (hereafter; PR8)]. PR8-infected and mock-infected cells were analyzed by immunoblotting, immunofluorescence confocal microscopy, electron microscopy and flow cytometry (FACS). We found that PR8 infection simultaneously induced autophagy and apoptosis in A549 cells. Autophagy was associated with Bax and Bak activation, intrinsic caspase cleavage and subsequent PARP-1 and BID cleavage. Both Bax knockout (KO) and Bax/Bak double knockout MEFs displayed inhibition of virus-induced cytopathology and cell death and diminished virus-mediated caspase activation, suggesting that virus-induced apoptosis is Bax/Bak-dependent. Biochemical inhibition of autophagy induction with 3-methyladenine blocked both virus replication and apoptosis pathways. These effects were replicated using autophagy-refractory Atg3 KO and Atg5 KO cells. Taken together, our data indicate that PR8 infection simultaneously induces autophagy and Bax/caspase-dependent apoptosis, with autophagy playing a role to support PR8 replication, in part, by modulating virus-induced apoptosis.

Transcriptional profile of breast muscle in heat stressed layers is similar to that of broiler chickens at control temperature

BACKGROUND

In recent years, the commercial importance of changes in muscle function of broiler chickens and of the corresponding effects on meat quality has increased. Furthermore, broilers are more sensitive to heat stress during transport and at high ambient temperatures than smaller egg-laying chickens. We hypothesised that heat stress would amplify muscle damage and expression of genes that are involved in such changes and, thus, lead to the identification of pathways and networks associated with broiler muscle and meat quality traits. Broiler and layer chickens were exposed to control or high ambient temperatures to characterise differences in gene expression between the two genotypes and the two environments.

RESULTS

Whole-genome expression studies in breast muscles of broiler and layer chickens were conducted before and after heat stress; 2213 differentially-expressed genes were detected based on a significant (P < 0.05) genotype × treatment interaction. This gene set was analysed with the BioLayout Express^3D and Ingenuity Pathway Analysis software and relevant biological pathways and networks were identified. Genes involved in functions related to inflammatory reactions, cell death, oxidative stress and tissue damage were upregulated in control broilers compared with control and heat-stressed layers. Expression of these genes was further increased in heat-stressed broilers.

CONCLUSIONS

Differences in gene expression between broiler and layer chickens under control and heat stress conditions suggest that damage of breast muscles in broilers at normal ambient temperatures is similar to that in heat-stressed layers and is amplified when broilers are exposed to heat stress. The patterns of gene expression of the two genotypes under heat stress were almost the polar opposite of each other, which is consistent with the conclusion that broiler chickens were not able to cope with heat stress by dissipating their body heat. The differentially expressed gene networks and pathways were consistent with the pathological changes that are observed in the breast muscle of heat-stressed broilers.

Selenium protects against cadmium-induced kidney apoptosis in chickens by activating the PI3K/AKT/Bcl-2 signaling pathway

Cadmium (Cd) is a toxic heavy metal that can induce apoptosis. Selenium (Se) is a necessary trace element and can antagonize the toxicity of many heavy metals, including Cd. PI3K/AKT/Bcl-2 is a key survival signaling pathway that regulates cellular defense system against oxidative injury as well as cell proliferation, survival, and apoptosis. The antagonistic effects of Se on Cd-induced toxicity have been reported. However, little is known about the effect of Se on Cd-induced apoptosis in chicken kidneys via the PI3K/AKT/Bcl-2 signaling pathway. In the present study, we fed chickens with Se, Cd, or both Se and Cd supplements, and after 90 days of treatment, we detected the related index. The results showed that the activity of inducible nitric oxide synthase (iNOS) and concentration of nitric oxide (NO) were increased; activities of the mitochondrial respiratory chain complexes (complexes I, II, and V) and ATPases (the Na⁺-K⁺-ATPase, the Mg²⁺-ATPase, and the Ca²⁺-ATPase) were decreased; expression of PI3K, AKT, and Bcl-2 were decreased; and expression of Bax, Bak, P53, Caspase-3, Caspase-9, and cytochrome c (Cyt c) were increased. Additionally, the results of the TUNEL assay showed that the number of apoptotic cells was increased in the Cd group. By contrast, there was a significant improvement of the correlation indicators and occurrence of apoptosis in the Se + Cd group compared to the Cd group. In conclusion, our results confirmed that Se had a positive effect on ameliorating Cd-induced apoptosis in chicken kidney tissue by activating the PI3K/AKT/Bcl-2 signaling pathway.

Influenza A Virus and Influenza B Virus Can Induce Apoptosis via Intrinsic or Extrinsic Pathways and Also via NF-κB in a Time and Dose Dependent Manner

Influenza viruses are able to cause annual epidemics and pandemics due to their mutation rates and reassortment capabilities leading to antigenic shifts and drifts. To identify host response to influenza A and B viruses on A549 and MDCK II cells at low and high MOIs, expressions of MxA and caspases 3, 8, and 9 and BAD, TNFα, and IκBα genes were measured in the cells supernatants. H1N1 and H3N2 prefer to initially enhance the intrinsic pathway, determined by higher caspase 9 activity in MDCK II cells compared to caspase 8 activity and vice versa in A549 cells at different MOIs, while INF B prefers extrinsic pathway in A549 cells according to significant low or undetectable caspase 9 activity and high activity of caspase 8 but also can induce intrinsic pathway in MDCK II cells as determined by significant low or undetectable activity of caspase 8 and high caspase 9 activity at different MOIs; the considerable MxA expression was found in influenza A and B viruses infected A549 and MDCK II cells at low MOIs. In conclusion, influenza A and B viruses induced extrinsic and intrinsic apoptosis in parallel, and the induction was associated with viral infection in a dose dependent manner.

Cross-talk between Arg methylation and Ser phosphorylation modulates apoptosis signal-regulating kinase 1 activation in endothelial cells

Protein arginine methyltransferase 5 interacts with and methylates apoptosis signal–regulating kinase 1 at arginine residue 89, thereby negatively regulating its activity by promoting the interaction between ASK1 and Akt and thus phosphorylating ASK1 at serine residue 83.

We describe a novel functional interaction between ASK1 and PRMT5. We show that PRMT5 interacts with and methylates ASK1 at arginine residue 89 and thereby negatively regulates its activity by promoting the interaction between ASK1 and Akt and thus phosphorylating ASK1 at serine residue 83. Furthermore, the association between ASK1 and Akt is enhanced by VEGF stimulation, and PRMT5 is required for this association. Moreover, PRMT5-mediated ASK1 methylation impaired the H₂O₂-induced activity of ASK1, and this inhibitory effect of PRMT5 was abolished by replacement of arginine 89 with Trp or depletion of PRMT5 expression by RNA interference. Together the results demonstrate cross-talk between arginine methylation and serine phosphorylation in ASK1.

Characterization of a novel mutation in NS1 protein of influenza A virus induced by a chemical substance for the attenuation of pathogenicity

It is generally accepted that live attenuated influenza vaccine (LAIV) has the potential for use as a vaccination against flu. In this study, we demonstrated the nature of an influenza A virus (IAV) mutant induced by treating the IAV with a stable furan derivative, (1R,2R)-1-(5’-methylfur-3’-yl)propane-1,2,3-triol (MFPT), which had been isolated from Streptomyces sp. strain FV60 with the objective of it being an LAIV candidate. The resulting MFPT-resistant (MFPT^r) IAVs possessed attenuated pathogenicity in vitro and in vivo when compared with that of the parent virus (H1N1 subtype, NWS strain). Sequencing analysis revealed that a novel mutation, C490U in ns gene (P164S in NS1), was detected in all MFPT^r virus clones tested. Therefore, NS1 might be a main target of MFPT, and it was suggested that the P164S mutation contributed to the attenuated pathogenicity of the mutants. Although the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway is one of the targets of NS1, the MFPT^r virus suppressed the phosphorylation of Akt when compared with the wild-type (WT) virus. It was suggested that this might lead to the subsequent inhibition of the cleavage of PARP-1 and caspase-3, which is important for the progression of apoptosis. At the same time, nucleoprotein (NP) was found to be retained in the nuclei in MFPT^r virus-infected cells while nuclear export of NP was detected in WT virus-infected cells. In addition, the expression levels of interferon-β transcripts were significantly decreased in MFPT^r virus-infected cells. From these results it can be shown that the mutation, NS1^P164S, might be one of the key residues to control NS1 function concerning the induction of apoptosis. In conclusion, MFPT induced favorable mutation in the ns gene for the attenuation of IAV, and therefore might provide the novel methodology for preparing LAIVs.

Platelet-derived growth factor-C (PDGF-C) induces anti-apoptotic effects on macrophages through Akt and Bad phosphorylation

PDGF-C, which is abundant in the malignant breast tumor microenvironment, plays an important role in cell growth and survival. Because tumor-associated macrophages (TAMs) contribute to cancer malignancy, macrophage survival mechanisms are an attractive area of research into controlling tumor progression. In this study, we investigated PDGF-C-mediated signaling pathways involved in anti-apoptotic effects in macrophages. We found that the human malignant breast cancer cell line MDA-MB-231 produced high quantities of PDGF-C, whereas benign MCF-7 cells did not. Recombinant PDGF-C induced PDGF receptor α chain phosphorylation, followed by Akt and Bad phosphorylation in THP-1-derived macrophages. MDA-MB-231 culture supernatants also activated macrophage PDGF-Rα. PDGF-C prevented staurosporine-induced macrophage apoptosis by inhibiting the activation of caspase-3, -7, -8, and -9 and cleavage of poly(ADP-ribose) polymerase. Finally, TAMs isolated from the PDGF-C knockdown murine breast cancer cell line 4T1 and PDGF-C knockdown MDA-MB-231-derived tumor mass showed higher rates of apoptosis than the respective WT controls. Collectively, our results suggest that tumor cell-derived PDGF-C enhances TAM survival, promoting tumor malignancy.

DAMP molecule S100A9 acts as a molecular pattern to enhance inflammation during influenza A virus infection: role of DDX21-TRIF-TLR4-MyD88 pathway

Pathogen-associated molecular patterns (PAMPs) trigger host immune response by activating pattern recognition receptors like toll-like receptors (TLRs). However, the mechanism whereby several pathogens, including viruses, activate TLRs via a non-PAMP mechanism is unclear. Endogenous “inflammatory mediators” called damage-associated molecular patterns (DAMPs) have been implicated in regulating immune response and inflammation. However, the role of DAMPs in inflammation/immunity during virus infection has not been studied. We have identified a DAMP molecule, S100A9 (also known as Calgranulin B or MRP-14), as an endogenous non-PAMP activator of TLR signaling during influenza A virus (IAV) infection. S100A9 was released from undamaged IAV-infected cells and extracellular S100A9 acted as a critical host-derived molecular pattern to regulate inflammatory response outcome and disease during infection by exaggerating pro-inflammatory response, cell-death and virus pathogenesis. Genetic studies showed that the DDX21-TRIF signaling pathway is required for S100A9 gene expression/production during infection. Furthermore, the inflammatory activity of extracellular S100A9 was mediated by activation of the TLR4-MyD88 pathway. Our studies have thus, underscored the role of a DAMP molecule (i.e. extracellular S100A9) in regulating virus-associated inflammation and uncovered a previously unknown function of the DDX21-TRIF-S100A9-TLR4-MyD88 signaling network in regulating inflammation during infection.

The lung disease severity following influenza A virus (IAV) infection is dependent on the extent of inflammation in the respiratory tract. Severe inflammation in the lung manifests in development of pneumonia. Therefore, it is very critical to identify cellular factors and dissect the molecular/cellular mechanism controlling inflammation in the respiratory tract during IAV infection. Knowledge derived from these studies will be instrumental in development of therapeutics to combat the lung disease associated with IAV infection. Towards that end, in the current study we have identified a cellular factor S100A9 which is responsible for enhanced inflammation during IAV infection. In addition, we have characterized a signal transduction pathway involving various cellular receptors and signaling adaptors that are involved in mediating S100A9-dependent inflammatory response. Thus, our studies have illuminated a cellular/molecular mechanism that can be intervened by therapeutics to reduce and control IAV-associated lung inflammatory disease like pneumonia.

Regulatory role of ASK1 in porcine circovirus type 2-induced apoptosis

Porcine circovirus type 2 (PCV2), a major causative agent of postweaning multisystemic wasting syndrome which is an emerging and important swine disease, can induce apoptotic responses in vitro and in vivo. However, the molecular mechanism of PCV2-induced apoptosis is not well understood. Apoptosis signal-regulating kinase 1 (ASK1), serves as an upstream enzyme that activates the JNK and p38 MAPK pathways, has been shown to play a target role in the regulation of apoptosis. Here, we showed that PCV2 infection induced ASK1 phosphorylation which preceded activation of JNK1/2 and p38 signaling in the cultured cells, and that the phosphatidylinostol 3-kinase (PI3K)/Akt signaling triggered by PCV2 infection limited the extent of JNK1/2 and p38 activation and thereby apoptotic cell death. Furthermore, inhibition of JNK and p38 activation is associated with PI3K-dependent negative-regulation of ASK1 in the PCV2-infected cells. These results indicate an important regulatory role of ASK1 in PCV2-induced apoptotic responses.

A comprehensive map of the influenza A virus replication cycle

Background

Influenza is a common infectious disease caused by influenza viruses. Annual epidemics cause severe illnesses, deaths, and economic loss around the world. To better defend against influenza viral infection, it is essential to understand its mechanisms and associated host responses. Many studies have been conducted to elucidate these mechanisms, however, the overall picture remains incompletely understood. A systematic understanding of influenza viral infection in host cells is needed to facilitate the identification of influential host response mechanisms and potential drug targets.

Description

We constructed a comprehensive map of the influenza A virus (‘IAV’) life cycle (‘FluMap’) by undertaking a literature-based, manual curation approach. Based on information obtained from publicly available pathway databases, updated with literature-based information and input from expert virologists and immunologists, FluMap is currently composed of 960 factors (i.e., proteins, mRNAs etc.) and 456 reactions, and is annotated with ~500 papers and curation comments. In addition to detailing the type of molecular interactions, isolate/strain specific data are also available. The FluMap was built with the pathway editor CellDesigner in standard SBML (Systems Biology Markup Language) format and visualized as an SBGN (Systems Biology Graphical Notation) diagram. It is also available as a web service (online map) based on the iPathways+ system to enable community discussion by influenza researchers. We also demonstrate computational network analyses to identify targets using the FluMap.

Conclusion

The FluMap is a comprehensive pathway map that can serve as a graphically presented knowledge-base and as a platform to analyze functional interactions between IAV and host factors. Publicly available webtools will allow continuous updating to ensure the most reliable representation of the host-virus interaction network. The FluMap is available at http://www.influenza-x.org/flumap/.

Influenza A virus proteins NS1 and hemagglutinin along with M2 are involved in stimulation of autophagy in infected cells

The NS1 protein of influenza A virus is known to downregulate apoptosis early in infection in order to support virus replication (O. P. Zhirnov, T. E. Konakova, T. Wolff, and H. D. Klenk, J. Virol. 76:1617-1625, 2002). In the present study, we analyzed the development of autophagy, another mechanism to protect cells from degradation that depends on NS1 expression. To this end, we compared autophagy in cells infected with wild-type (WT) influenza virus and virus lacking the NS1 gene (delNS1 virus). The results show that in WT-infected cells but not in delNS1 virus-infected cells, synthesis of the autophagy marker LC3-II, the lipidated form of microtubule light chain-associated protein LC3, is stimulated and that LC3-II accumulates in a perinuclear zone enriched with double-layered membrane vesicles characteristic of autophagosomes. Transfection experiments revealed that NS1 expressed alone was unable to upregulate autophagy, whereas hemagglutinin (HA) and M2 were. Proteolytic cleavage of HA increased autophagy. Taken together, these observations indicate that NS1 stimulates autophagy indirectly by upregulating the synthesis of HA and M2. Thus, it appears that NS1, besides downregulating apoptosis, is involved in upregulation of autophagy and that it supports the survival of infected cells by both mechanisms.

Involvement of unfolded protein response, p53 and Akt in modulation of porcine reproductive and respiratory syndrome virus-mediated JNK activation

Our previous study has shown that activation of JNK plays a critical role in Porcine reproductive and respiratory syndrome virus (PRRSV)-mediated apoptosis. In this follow-up study, we further investigated the mechanisms involved in modulation of PRRSV-mediated JNK activation and apoptosis. We found that unfolded protein response (UPR) was induced in response to PRRSV infection which in turn triggered JNK activation and apoptosis. We also found that p53 and Akt were activated at the early stage of infection and functioned as negative regulator of JNK activation to counteract the PRRSV-mediated apoptosis. Furthermore, induction of UPR, p53 and Akt was not only involved in modulation of PRRSV-mediated apoptosis, but also contributed to the virus replication. Our findings indicated that multiple signaling pathways were involved in modulation of PRRSV-mediated apoptosis of the host cells via regulating JNK signaling pathway and provided novel insights into understanding the mechanisms of pathogenesis of PRRSV infection.

PI3K/Akt-independent negative regulation of JNK signaling by MKP-7 after cerebral ischemia in rat hippocampus

Background

The inactivation of c-Jun N-terminal kinase (JNK) is associated with anti-apoptotic and anti-inflammatory effects in cerebral ischemia, which can be induced by an imbalance between upstream phosphatases and kinases.

Result

Mitogen-activated protein kinase phosphatase 7 (MKP-7) was upregulated significantly at 4 h of reperfusion postischemia in rat hippocampi. By administration of cycloheximide or siRNA against mitogen-activated protein kinase phosphatase 7 (MKP-7) in a rat model of ischemia/reperfusion, an obvious enhancement of JNK activity was observed in 4 h of reperfusion following ischemia, suggesting MKP-7 was involved in JNK inactivation after ischemia. The subcellular localization of MKP-7 altered after ischemia, and the inhibition of MKP-7 nuclear export by Leptomycin B up-regulated JNK activity. Although PI3K/Akt inhibition could block downregulation of JNK activity through SEK1 and MKK-7 activation, PI3K/Akt activity was not associated with the regulation of JNK by MKP-7.

Conclusions

MKP-7, independently of PI3K/Akt pathway, played a key role in downregulation of JNK activity after ischemia in the rat hippocampus, and the export of MKP-7 from the nucleus was involved in downregulation of cytoplasmic JNK activity in response to ischemic stimuli.

Activation mechanisms of ASK1 in response to various stresses and its significance in intracellular signaling

Apoptosis signal-regulating kinase 1 (ASK1) is a member of the mitogen-activated protein kinase kinase kinase family. ASK1 activates c-jun N-terminal kinase (JNK) and p38 in response to various stimuli such as oxidative stress, endoplasmic reticulum stress, infection and calcium influx. Under these stress conditions, ASK1 plays important roles in intracellular signaling pathways and biological functions. Diverse proteins are known to interact with ASK1 and regulate the activity of ASK1. However, activation mechanisms of ASK1 and ASK1-binding proteins which regulate the activity of ASK1 have not been completely understood. In this review, we focus on the recent findings on ASK1 and update the regulatory mechanisms of ASK1 activity.

Activation of the phosphatidylinositol 3-kinase/Akt signaling pathway during porcine circovirus type 2 infection facilitates cell survival and viral replication

Virus infection activates host cellular signaling pathways, including the phosphatidylinositol 3-kinase (PI3K)/Akt pathway, which regulates diverse cellular activities related to cell growth, survival, and apoptosis. The present study demonstrated for the first time that porcine circovirus type 2 (PCV2), a major causative agent of postweaning multisystemic wasting syndrome, which is an emerging and important swine disease, can transiently induce the PI3K/Akt pathway in cultured cells at an early step during PCV2 infection. Activation of the PI3K/Akt signal was also induced by UV-irradiated PCV2, indicating that virus replication was not required for this induction. Inhibition of PI3K activation leads to reduced virus yield, which is associated with decreased viral DNA replication and lower virus protein expression. However, inhibition of PI3K activation greatly enhanced apoptotic responses as evidenced by the cleavage of poly-ADP ribose polymerase and caspase-3 as well as DNA fragmentation using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling staining during the early stage of PCV2 infection. Furthermore, the pancaspase inhibitor zVAD.fmk alleviated the reduction in Akt phosphorylation levels by inhibiting PI3K activation, indicating that the signaling promotes cell survival and thereby favors viral replication. These results reveal that an antiapoptotic role for the PI3K/Akt pathway induced by PCV2 infection to suppress premature apoptosis for improved virus growth after infection, extending our understanding of the molecular mechanism of PCV2 infection.

Amplification of JNK signaling is necessary to complete the murine gammaherpesvirus 68 lytic replication cycle

Several studies have previously defined host-derived signaling events capable of driving lytic gammaherpesvirus replication or enhancing immediate-early viral gene expression. Yet signaling pathways that regulate later stages of the productive gammaherpesvirus replication cycle are still poorly defined. In this study, we utilized a mass spectrometric approach to identify c-Jun as an abundant cellular phosphoprotein present in late stages of lytic murine gammaherpesvirus 68 (MHV68) infection. Kinetically, c-Jun phosphorylation was enhanced as infection progressed, and this correlated with enhanced phosphorylation of the c-Jun amino-terminal kinases JNK1 and JNK2 and activation of AP-1 transcription. These events were dependent on progression beyond viral immediate-early gene expression, but not dependent on viral DNA replication. Both pharmacologic and dominant-negative blockade of JNK1/2 activity inhibited viral replication, and this correlated with inhibition of viral DNA synthesis and reduced viral gene expression. These data suggest a model in which MHV68 by necessity amplifies and usurps JNK/c-Jun signaling as infection progresses in order to facilitate late stages of the MHV68 lytic infection cycle.

Transactivation of inducible nitric oxide synthase gene by Kruppel-like factor 6 regulates apoptosis during influenza A virus infection

Influenza A virus (flu) is a respiratory tract pathogen causing high morbidity and mortality among the human population. NO is a cellular mediator involved in tissue damage through its apoptosis of target cells and resulting enhancement of local inflammation. Inducible NO synthase (iNOS) is involved in the production of NO following infection. Although NO is a key player in the development of exaggerated lung disease during flu infection, the underlying mechanism, including the role of NO in apoptosis during infection, has not been reported. Similarly, the mechanism of iNOS gene induction during flu infection is not well defined in terms of the host transactivator(s) required for iNOS gene expression. In the current study, we identified Kruppel-like factor 6 (KLF6) as a critical transcription factor essential for iNOS gene expression during flu infection. We also underscored the requirement for iNOS in inducing apoptosis during infection. KLF6 gene silencing in human lung epithelial cells resulted in the drastic loss of NO production, iNOS promoter-specific luciferase activity, and expression of iNOS mRNA following flu infection. Chromatin immunoprecipitation assay revealed a direct interaction of KLF6 with iNOS promoter during in vitro and in vivo flu infection of human lung cells and mouse respiratory tract, respectively. A significant reduction in flu-mediated apoptosis was noted in KLF6-silenced cells, cells treated with iNOS inhibitor, and primary murine macrophages derived from iNOS knockout mice. A similar reduction in apoptosis was noted in the lungs following intratracheal flu infection of iNOS knockout mice.

Differential requirement for c-Jun N-terminal kinase 1 in lung inflammation and host defense

The c-Jun N-terminal kinase (JNK) - 1 pathway has been implicated in the cellular response to stress in many tissues and models. JNK1 is known to play a role in a variety of signaling cascades, including those involved in lung disease pathogenesis. Recently, a role for JNK1 signaling in immune cell function has emerged. The goal of the present study was to determine the role of JNK1 in host defense against both bacterial and viral pneumonia, as well as the impact of JNK1 signaling on IL-17 mediated immunity. Wild type (WT) and JNK1 -/- mice were challenged with Escherichia coli, Staphylococcus aureus, or Influenza A. In addition, WT and JNK1 -/- mice and epithelial cells were stimulated with IL-17A. The impact of JNK1 deletion on pathogen clearance, inflammation, and histopathology was assessed. JNK1 was required for clearance of E. coli, inflammatory cell recruitment, and cytokine production. Interestingly, JNK1 deletion had only a small impact on the host response to S. aureus. JNK1 -/- mice had decreased Influenza A burden in viral pneumonia, yet displayed worsened morbidity. Finally, JNK1 was required for IL-17A mediated induction of inflammatory cytokines and antimicrobial peptides both in epithelial cells and the lung. These data identify JNK1 as an important signaling molecule in host defense and demonstrate a pathogen specific role in disease. Manipulation of the JNK1 pathway may represent a novel therapeutic target in pneumonia.

Apoptosis signaling in influenza virus propagation, innate host defense, and lung injury

Programmed cell death is a crucial cellular response frequently observed in IV-infected tissue. This article reviews the current knowledge on the molecular virus-host interactions that induce apoptosis pathways in an IV-infected cell and the functional implications of these cellular signaling events on viral propagation at distinct steps during the viral replication cycle. Furthermore, it summarizes the role of IV-induced apoptosis pathways in equilibrating the host's antiviral immune response between effective viral clearance and development of severe apoptotic lung injury.

From virus entry to release: the diverse functions of PI3K during RNA virus infections

RNA viruses are the causative agents of severe diseases in vertebrates. Upon viral infection, various intracellular signaling pathways are induced within the infected cells. While most of the different cellular signaling responses are initiated as antiviral defense mechanisms to counteract invading pathogens, they may also be exploited by viruses to support their replication. Recently, PI3K has been added to the growing list of signaling factors and pathways that are activated upon viral infections and regulate the replication process. Here, the current knowledge on RNA virus-induced PI3K-regulated signaling processes and how the pathogens take advantage of these activities within the infected cells is summarized.

Regulation of influenza A virus induced CXCL-10 gene expression requires PI3K/Akt pathway and IRF3 transcription factor

Influenza A virus infects human airway epithelial cells, and induces the CXC chemokine gamma interferon (IFN-γ)-inducible protein CXCL-10/IP-10 production. To understand the regulation of CXCL-10, we investigated the role of PI3K/AKT pathway in regulating virus induced CXCL-10 production. Previously we have shown that wild type (WT) influenza A virus infection activates PI3K/AKT pathway, whereas PR8-SH3-mf-1 mutant virus is unable to activate this pathway. Here we report that WT influenza A virus infection induced CXCL-10 production in A549 cells. PR8-SH3-mf-1 mutant virus infection led to reduced level of CXCL-10 mRNA transcription and protein expression. To define the transcriptional regulation factors that are important in this process, we performed studies using several mutant CXCL-10 promoter-luciferase constructs. Mutation of either of four Forkhead binding sites and two NF-κB response elements in CXCL-10 promoter did not alter promoter activity induced by WT virus. However, mutation of ISRE binding site markedly reduced luciferase activity. Our data suggested that PI3K/AKT pathway contributes to influenza A virus induced CXCL-10 production. This process is involved in binding of IRF3 to the ISRE binding site in CXCL-10 promoter region.

Host cellular signaling induced by influenza virus

A wide range of host cellular signal transduction pathways can be stimulated by influenza virus infection. Some of these signal transduction pathways induce the host cell's innate immune response against influenza virus, while others are essential for efficient influenza virus replication. This review examines the cellular signaling induced by influenza virus infection in host cells, including host pattern recognition receptor (PRR)-related signaling, protein kinase C (PKC), Raf/MEK/ERK and phosphatidy-linositol-3-kinase (PI3K)/Akt signaling, and the corresponding effects on the host cell and/or virus, such as recognition of virus by the host cell, viral absorption and entry, viral ribonucleoprotein (vRNP) export, translation control of cellular and viral proteins, and virus-induced cell apoptosis. Research into influenza virus-induced cell signaling promotes a clearer understanding of influenza virus-host interactions and assists in the identification of novel antiviral targets and antiviral strategies.

Influenza A virus-induced early activation of ERK and PI3K mediates V-ATPase-dependent intracellular pH change required for fusion

The vacuolar (H+)-ATPases (V-ATPases) facilitate the release of influenza A virus (IAV) genome into the cytoplasm by acidifying the endosomal interior. The regulation of V-ATPases by signalling pathways has been demonstrated in various model systems. However, little is known about signalling-regulated V-ATPase activation during IAV infection. Here we show that V-ATPase activity is elevated during infection of cell monolayers with IAV, as measured by intracellular pH change, via a mechanism mediated by extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3-kinase (PI3K). Inhibition of IAV-induced early activation of these kinases reduced V-ATPase activity and the acidification of intracellular compartments in infected cells. IAV-activated ERK and PI3K appear to interact directly, and they colocalize with the E subunit of V-ATPase V1 domain. Further, siRNAs targeting the E2 subunit isoform significantly reduced virus titres. Interestingly, suppression of PI3K early activation, but not that of ERK or V-ATPase, negatively affected virus internalization, suggesting the involvement of the pathway in earlier, V-ATPase-independent infection-promoting events. Cell treatment with a V-ATPase-specific inhibitor impaired the nuclear localization of incoming viral ribonucleoproteins, inhibiting replication/transcription of viral RNAs. These findings highlight the importance of IAV-induced ERK and PI3K early activation as signalling mediators in V-ATPase-stimulated endosomal acidification required for fusion.

Next generation sequencing in functional genomics

Genome-wide sequencing has enabled modern biomedical research to relate more and more events in healthy as well as disease-affected cells and tissues to the genomic sequence. Now next generation sequencing (NGS) extends that reach into multiple almost complete genomes of the same species, revealing more and more details about how individual genomes as well as individual aspects of their regulation differ from each other. The inclusion of NGS-based transcriptome sequencing, chromatin-immunoprecipitation (ChIP) of transcription factor binding and epigenetic analyses (usually based on DNA methylation or histone modification ChIP) completes the picture with unprecedented resolution enabling the detection of even subtle differences such as alternative splicing of individual exons. Functional genomics aims at the elucidation of the molecular basis of biological functions and requires analyses that go far beyond the primary analysis of the reads such as mapping to a genome template sequence. The various and complex interactions between the genome, gene products and metabolites define biological function, which necessitates inclusion of results other than sequence tags in quite elaborative approaches. However, the extra efforts pay off in revealing mechanisms as well as providing the foundation for new strategies in systems biology and personalized medicine. This review emphasizes the particular contribution NGS-based technologies make to functional genomics research with a special focus on gene regulation by transcription factor binding sites.