Negative regulation of RIG-I-mediated innate antiviral signaling by SEC14L1

Nuclear morphology is shaped by loop-extrusion programs

It is well established that neutrophils adopt malleable polymorphonuclear shapes to migrate through narrow interstitial tissue spaces1-3. However, how polymorphonuclear structures are assembled remains unknown4. Here we show that in neutrophil progenitors, halting loop extrusion-a motor-powered process that generates DNA loops by pulling in chromatin5-leads to the assembly of polymorphonuclear genomes. Specifically, we found that in mononuclear neutrophil progenitors, acute depletion of the loop-extrusion loading factor nipped-B-like protein (NIPBL) induced the assembly of horseshoe, banded, ringed and hypersegmented nuclear structures and led to a reduction in nuclear volume, mirroring what is observed during the differentiation of neutrophils. Depletion of NIPBL also induced cell-cycle arrest, activated a neutrophil-specific gene program and conditioned a loss of interactions across topologically associating domains to generate a chromatin architecture that resembled that of differentiated neutrophils. Removing NIPBL resulted in enrichment for mega-loops and interchromosomal hubs that contain genes associated with neutrophil-specific enhancer repertoires and an inflammatory gene program. On the basis of these observations, we propose that in neutrophil progenitors, loop-extrusion programs produce lineage-specific chromatin architectures that permit the packing of chromosomes into geometrically confined lobular structures. Our data also provide a blueprint for the assembly of polymorphonuclear structures, and point to the possibility of engineering de novo nuclear shapes to facilitate the migration of effector cells in densely populated tumorigenic environments.

Longitudinal analysis of influenza vaccination implicates regulation of RIG-I signaling by DNA methylation

Influenza virus infection alters the promoter DNA methylation of key immune response-related genes, including type-1 interferons and proinflammatory cytokines. However, less is known about the effect of the influenza vaccine on the epigenome. We utilized a targeted DNA methylation approach to study the longitudinal effects (day 0 pre-vaccination and day 28 post-vaccination) on influenza vaccination responses in peripheral blood mononuclear cells. We found that baseline, pre-vaccination methylation profiles are associated with pre-existing, protective serological immunity. Additionally, we identified 481 sites that were differentially methylated between baseline and day 28 post-vaccination. These were enriched for genes involved in the regulation of the RIG-I signaling pathway, an important regulator of viral responses. Our results suggest that DNA methylation changes to components of the RIG-I pathway are associated with vaccine effectiveness. Therefore, immunization strategies that target this pathway may improve serological responses to influenza vaccination.

Transcriptome-based analysis of human peripheral blood reveals regulators of immune response in different viral infections

Introduction

There are difficulties in creating direct antiviral drugs for all viruses, including new, suddenly arising infections, such as COVID-19. Therefore, pathogenesis-directed therapy is often necessary to treat severe viral infections and comorbidities associated with them. Despite significant differences in the etiopathogenesis of viral diseases, in general, they are associated with significant dysfunction of the immune system. Study of common mechanisms of immune dysfunction caused by different viral infections can help develop novel therapeutic strategies to combat infections and associated comorbidities.

Methods

To identify common mechanisms of immune functions disruption during infection by nine different viruses (cytomegalovirus, Ebstein-Barr virus, human T-cell leukemia virus type 1, Hepatitis B and C viruses, human immunodeficiency virus, Dengue virus, SARS-CoV, and SARS-CoV-2), we analyzed the corresponding transcription profiles from peripheral blood mononuclear cells (PBMC) using the originally developed pipeline that include transcriptome data collection, processing, normalization, analysis and search for master regulators of several viral infections. The ten datasets containing transcription data from patients infected by nine viruses and healthy people were obtained from Gene Expression Omnibus. The analysis of the data was performed by Genome Enhancer pipeline.

Results

We revealed common pathways, cellular processes, and master regulators for studied viral infections. We found that all nine viral infections cause immune activation, exhaustion, cell proliferation disruption, and increased susceptibility to apoptosis. Using network analysis, we identified PBMC receptors, representing proteins at the top of signaling pathways that may be responsible for the observed transcriptional changes and maintain the current functional state of cells.

Discussion

The identified relationships between some of them and virus-induced alteration of immune functions are new and have not been found earlier, e.g., receptors for autocrine motility factor, insulin, prolactin, angiotensin II, and immunoglobulin epsilon. Modulation of the identified receptors can be investigated as one of therapeutic strategies for the treatment of severe viral infections.

Identification and Expression Analysis of Phosphatidylinositol Transfer Proteins Genes in Rice

The family of phosphatidylinositol transfer proteins (PITPs) is able to bind specific lipids to carry out various biological functions throughout different stages of plant life. But the function of PITPs in rice plant is unclear. In this study, 30 PITPs were identified from rice genome, which showed differences in physicochemical properties, gene structure, conservation domains, and subcellular localization. The promoter region of the OsPITPs genes included at least one type of hormone response element, such as methyl jasmonate (Me JA) and salicylic acid (SA). Furthermore, the expression level of OsML-1, OsSEC14-3, OsSEC14-4, OsSEC14-15, and OsSEC14-19 genes were significantly affected by infection of rice blast fungus Magnaporthe oryzae. Based on these findings, it is possible that OsPITPs may be involved in rice innate immunity in response to M. oryzae infection through the Me JA and SA pathway.

Role of SEC14-like phosphatidylinositol transfer proteins in membrane identity and dynamics

Membrane identity and dynamic processes, that act at membrane sites, provide important cues for regulating transport, signal transduction and communication across membranes. There are still numerous open questions as to how membrane identity changes and the dynamic processes acting at the surface of membranes are regulated in diverse eukaryotes in particular plants and which roles are being played by protein interaction complexes composed of peripheral and integral membrane proteins. One class of peripheral membrane proteins conserved across eukaryotes comprises the SEC14-like phosphatidylinositol transfer proteins (SEC14L-PITPs). These proteins share a SEC14 domain that contributes to membrane identity and fulfills regulatory functions in membrane trafficking by its ability to sense, bind, transport and exchange lipophilic substances between membranes, such as phosphoinositides and diverse other lipophilic substances. SEC14L-PITPs can occur as single-domain SEC14-only proteins in all investigated organisms or with a modular domain structure as multi-domain proteins in animals and streptophytes (comprising charales and land plants). Here, we present an overview on the functional roles of SEC14L-PITPs, with a special focus on the multi-domain SEC14L-PITPs of the SEC14-nodulin and SEC14-GOLD group (PATELLINs, PATLs in plants). This indicates that SEC14L-PITPs play diverse roles from membrane trafficking to organism fitness in plants. We concentrate on the structure of SEC14L-PITPs, their ability to not only bind phospholipids but also other lipophilic ligands, and their ability to regulate complex cellular responses through interacting with proteins at membrane sites.

Proteins in pregnant swine serum promote the African swine fever virus replication: an iTRAQ-based quantitative proteomic analysis

African swine fever (ASF) is a severe infectious disease caused by the African swine fever virus (ASFV), seriously endangering the global pig industry. ASFV possesses a large genome, strong mutation ability, and complex immune escape mechanisms. Since the first case of ASF was reported in China in August 2018, it has had a significant impact on social economy and food safety. In the present study, pregnant swine serum (PSS) was found to promote viral replication; differentially expressed proteins (DEPs) in PSS were screened and identified using the isobaric tags for relative and absolute quantitation technology and compared with those in non-pregnant swine serum (NPSS). The DEPs were analyzed using Gene Ontology functional annotation, Kyoto Protocol Encyclopedia of Genes and Genome pathway enrichment, and protein-protein interaction networks. In addition, the DEPs were validated via western blot and RT-qPCR experiments. And the 342 of DEPs were identified in bone marrow-derived macrophages cultured with PSS compared with the NPSS. The 256 were upregulated and 86 of DEPs were downregulated. The primary biological functions of these DEPs involved signaling pathways that regulate cellular immune responses, growth cycles, and metabolism-related pathways. An overexpression experiment showed that the PCNA could promote ASFV replication whereas MASP1 and BST2 could inhibit it. These results further indicated that some protein molecules in PSS were involved in the regulation of ASFV replication. In the present study, the role of PSS in ASFV replication was analyzed using proteomics, and the study will be provided a basis for future detailed research on the pathogenic mechanism and host interactions of ASFV as well as new insights for the development of small-molecule compounds to inhibit ASFV.

Evaluation of Saccharomyces cerevisiae -like 1 (SEC14L1) in Gynecologic Malignancies Shows Overexpression in Endometrial Serous Carcinoma

Saccharomyces cerevisiae -like 1 ( SEC14L1 ) is a member of the SEC14 family and is involved in liposoluble vitamin transfer, and in a large cohort of breast cancer cases, was one of the genes most significantly associated with lymphovascular invasion (LVI), and had a significant relationship with human epidermal growth factor receptor 2 status, survival, and histologic grade. In this study, 111 separate gynecologic tumors were studied for SEC14L1 protein expression, including: uterine adenosarcoma, ovarian clear cell carcinoma, endometrial stromal sarcoma, endometrioid carcinoma of the uterus, high-grade serous carcinoma, ovarian endometrioid carcinoma, uterine leiomyosarcoma, low-grade serous carcinoma, uterine carcinosarcoma, and uterine serous carcinoma (USC). Overall, LVI was noted in 31/111 (28%) cases, highest in uterine carcinosarcoma (5/11; 45%), high-grade serous carcinoma (9/21; 43%), and ovarian clear cell carcinoma (4/10; 40%). SEC14L1 was positive in 25/111 (23%) cases; the highest percentage and only statistically significant finding by tumor type was USC at 9/12 (75%) cases positive. No relation between LVI or survival and SEC14L1 expression was noted. The relation between USC, a tumor known to show human epidermal growth factor receptor 2 overexpression and SEC14L1 is a novel finding, the significance of which warrants further study.

Commensal microbiota modulates phenotypic characteristics and gene expression in piglet Peyer's patches

The gastrointestinal tract contains a complex microbial community. Peyer's patches (PPs) play an important role in inducing mucosal immune responses in the gastrointestinal tract. However, little is known about the effect of commensal microbiota on the host's PPs. Here, we analyzed the phenotypic-to-transcriptome changes in the intestine PPs of specific pathogen-free (SPF) and germ-free (GF) piglets (fed in an environment with and without commensal microbiota, respectively) to elucidate the role of commensal microbiota in host intestine mucosal immunity. Analyses of anatomical and histological characteristics showed that commensal microbiota deficiency led to PP hypoplasia, especially regarding B and T cells. A total of 12,444 mRNAs were expressed in 12 libraries; 2,156 and 425 differentially expressed (DE) mRNAs were detected in the jejunal PP (JPP) and ileal PP (IPP), respectively (SPF vs. GF). The shared DE mRNAs of the JPP and IPP were mainly involved in basic physiological and metabolic processes, while the specific DE mRNAs were enriched in regulating immune cells in the JPP and microbial responses and cellular immunity in the IPP. Commensal microbiota significantly modulated the expression of genes related to B-cell functions, including activation, proliferation, differentiation, apoptosis, receptor signaling, germinal center formation, and IgA isotype class switching, particularly in the JPP. TLR4 pathway-related genes were induced in response to microbial colonization and in LPS/SCFA-treated B cells. We also detected 69 and 21 DE lncRNAs in the JPP and IPP, respectively, and four one-to-one lncRNA-mRNA pairs were identified. These findings might represent key regulatory axes for host intestine mucosal immunity development during microbial colonization. Overall, the findings of this study revealed that commensal microbiota modulated phenotypic characteristics and gene expression in the piglet intestine PPs and underscored the importance of early microbial colonization for host mucosal immunity development.

Duck TRIM35 Promotes Tembusu Virus Replication by Interfering with RIG-I-Mediated Antiviral Signaling in Duck Embryo Fibroblasts

In China, the duck industry has been severely impacted by the newly emerging duck Tembusu virus (DTMUV). For DTMUV to successfully infect host cells, it employs several strategies that subvert the host's innate immune response. It has been found that several viral proteins encoded by DTMUV have strategically targeted the crucial molecules of the RIG-I-like Receptor (RLR) signaling pathway to antagonize host antiviral responses. However, it is not well known how the host proteins manipulated by DTMUV contribute to innate immune evasion. The present study reports that duck TRIM35 (duTRIM35) antagonizes DTMUV-induced innate immune responses by targeting duck RIG-I (duRIG-I) in duck embryo fibroblasts. A significant increase in duTRIM35 expression occurred during DTMUV infection. DuTRIM35 overexpression suppressed DTMUV-triggered expression of interferon beta (IFN-β) and interferon-stimulated genes (ISGs), promoting viral replication, whereas knockdown of duTRIM35 augments the innate immune response, reducing viral replication. Furthermore, duTRIM35 significantly impaired the IFN-β expression mediated by duRIG-I but not by other RLR signaling molecules. Mechanistically, duTRIM35 interfered with duRIG-I-duTRIM25 interaction and impeded duTRIM25-mediated duRIG-I ubiquitination by interacting with both duRIG-I and duTRIM25. Our findings indicate that duTRIM35 expression induced by DTMUV infection interfered with the duRIG-I-mediated antiviral response, illustrating a novel strategy in which DTMUV can evade the host's innate immunity. IMPORTANCE Duck Tembusu virus (DTMUV), an emerging flavivirus pathogen causing a substantial drop in egg production and severe neurological disorders in duck populations, has led to massive economic losses in the global duck industry. DTMUV has employed various strategies to subvert the host's innate immune response to establish a productive infection in host cells. In this study, we report that duck TRIM35 (duTRIM35) expression was upregulated upon DTMUV infection in vitro and in vivo, and its expression antagonized DTMUV-induced innate immune responses by targeting duck RIG-I (duRIG-I) in duck embryo fibroblasts. Further studies suggest that duTRIM35 interfered with duRIG-I-duTRIM25 interaction and impeded duTRIM25-mediated duRIG-I ubiquitination by interacting with both duRIG-I and duTRIM25. Together, these results revealed that duTRIM35 expression induced by DTMUV infection downregulated duRIG-I-mediated host antiviral response, which elucidated a novel strategy of DTMUV for innate immune evasion.

Single-nucleus transcriptomic profiling of multiple organs in a rhesus macaque model of SARS-CoV-2 infection

Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes diverse clinical manifestations and tissue injuries in multiple organs. However, cellular and molecular understanding of SARS-CoV-2 infection-associated pathology and immune defense features in different organs remains incomplete. Here, we profiled approximately 77 000 single-nucleus transcriptomes of the lung, liver, kidney, and cerebral cortex in rhesus macaques ( Macaca mulatta) infected with SARS-CoV-2 and healthy controls. Integrated analysis of the multi-organ dataset suggested that the liver harbored the strongest global transcriptional alterations. We observed prominent impairment in lung epithelial cells, especially in AT2 and ciliated cells, and evident signs of fibrosis in fibroblasts. These lung injury characteristics are similar to those reported in patients with coronavirus disease 2019 (COVID-19). Furthermore, we found suppressed MHC class I/II molecular activity in the lung, inflammatory response in the liver, and activation of the kynurenine pathway, which induced the development of an immunosuppressive microenvironment. Analysis of the kidney dataset highlighted tropism of tubule cells to SARS-CoV-2, and we found membranous nephropathy (an autoimmune disease) caused by podocyte dysregulation. In addition, we identified the pathological states of astrocytes and oligodendrocytes in the cerebral cortex, providing molecular insights into COVID-19-related neurological implications. Overall, our multi-organ single-nucleus transcriptomic survey of SARS-CoV-2-infected rhesus macaques broadens our understanding of disease features and antiviral immune defects caused by SARS-CoV-2 infection, which may facilitate the development of therapeutic interventions for COVID-19.

A gold revision of the Golgi Dynamics (GOLD) domain structure and associated cell functionalities

The classical secretory pathway is the key membrane-based delivery system in eukaryotic cells. Several families of proteins involved in the secretory pathway, with functionalities going from cargo sorting receptors to the maintenance and dynamics of secretory organelles, share soluble globular domains predicted to mediate protein-protein interactions. One of them is "Golgi Dynamics" (GOLD) domain, named after its strong association with the Golgi apparatus. There are many GOLD-containing protein families, such as the Transmembrane emp24 domain-containing proteins (TMED/p24 family), animal SEC14-like proteins, Human Golgi resident protein ACBD3, a splice variant of TICAM2 called TRAM with GOLD domain and FYCO1. Here, we critically review the state-of-the-art knowledge of the structures and functions of the main representatives of GOLD-containing proteins in vertebrates. We provide the first unified description of the GOLD domain structure across different families since the first high-resolution structure was determined. With a brand-new update on the definition of the GOLD domain, we also discuss how its tertiary structure fits the β-sandwich-like fold map and give exciting new directions for forthcoming studies.

Monocyte biology conserved across species: Functional insights from cattle

Similar to human monocytes, bovine monocytes can be split into CD14^highCD16^- classical, CD14^highCD16^high intermediate and CD14^-/dimCD16^high nonclassical monocytes (cM, intM, and ncM, respectively). Here, we present an in-depth analysis of their steady-state bulk- and single-cell transcriptomes, highlighting both pronounced functional specializations and transcriptomic relatedness. Bulk gene transcription indicates pro-inflammatory and antibacterial roles of cM, while ncM and intM appear to be specialized in regulatory/anti-inflammatory functions and tissue repair, as well as antiviral responses and T-cell immunomodulation. Notably, intM stood out by high expression of several genes associated with antigen presentation. Anti-inflammatory and antiviral functions of ncM are further supported by dominant oxidative phosphorylation and selective strong responses to TLR7/8 ligands, respectively. Moreover, single-cell RNA-seq revealed previously unappreciated heterogeneity within cM and proposes intM as a transient differentiation intermediate between cM and ncM.

Lipid metabolism-related proteins of relevant evolutionary and lymphoid interest (PRELI) domain containing family proteins in cancer

Metabolic reprogramming of tumor cells plays a critical role in the tumor microenvironment, including disorder of lipid metabolism. Recently, lipid metabolism has received increasing attention in cancer research. The proteins of relevant evolutionary and lymphoid interest (PRELI) domain containing family contains 6 proteins. Functionally, the PRELI-like family proteins were mainly involved in mitochondrial lipid transport and correlated with several types of diseases and malignant tumors. Here we review current knowledge of the functions, structures, biological functions and underlying mechanisms of the PRELI-like family proteins in cancer progression, which provide insights into the clinical translational application.

hnRNPH2 as an Inhibitor of Chicken MDA5-Mediated Type I Interferon Response: Analysis Using Chicken MDA5-Host Interactome

RIG-I and MDA5 are two key pattern recognition receptors that sense the invasion of RNA viruses and initiate type I interferon (IFN) response. Although these receptors are generally conserved in vertebrates, RIG-I is absent in chickens, whereas MDA5 is present. Chicken MDA5 (chMDA5) plays a pivotal role in sensing the invasion of RNA viruses into cells. However, unlike mammalian MDA5, where there are in-depth and extensive studies, regulation of the chMDA5-mediated signaling pathway remains unexplored. In this study, we performed a pulldown assay and mass spectrometry analysis to identify chicken proteins that could interact with the N terminal of chMDA5 (chMDA5-N) that contained two CARDs responsible for binding of the well-known downstream adaptor MAVS. We found that 337 host proteins could potentially interact with chMDA5-N, which were integrated to build a chMDA5-N–host association network and analyzed by KEGG pathway and Gene Ontology annotation. Results of our analysis revealed that diverse cellular processes, such as RNA binding and transport and protein translation, ribosome, chaperones, and proteasomes are critical cellular factors regulating the chMDA5-mediated signaling pathway. We cloned 64 chicken genes to investigate their effects on chMDA5-mediated chicken IFN-β production and confirmed the association of chicken DDX5, HSPA8, HSP79, IFIT5, PRDX1, and hnRNPH2 with chMDA5-N. In particular, we found that chicken hnRNPH2 impairs the association between chMDA5-N and MAVS and thus acts as a check on the chMDA5-mediated signaling pathway. To our knowledge, this study is the first to analyze the chicken MDA5–host interactome, which provides fundamental but significant insights to further explore the mechanism of chicken MDA5 signaling regulation in detail.

SNX5 inhibits RLR-mediated antiviral signaling by targeting RIG-I-VISA signalosome

Upon invading the cell, the viral RNA is recognized by the RIG-I receptor located in the cytoplasm, causing the RIG-I receptor to be activated. The activated RIG-I receptor transmits downstream antiviral signals by interacting with the adaptor protein VISA located on the mitochondria, leading to the production of type Ⅰ interferons and crude inflammatory cytokine genes. Although there have been many studies on antiviral signal transduction of RIG-I receptors in recent years, the mechanism of RIG-I-VISA-mediated antiviral regulation is still not fully understood. In this study, we identified SNX5 as a negative regulator of RLR-mediated antiviral signaling. Our results show that overexpression of SNX5 inhibits viral-induced activation of the IFN-β promoter, ISRE, NF-κB, and IRF3, whereas RNAi knockdown of SNX5 expression shows opposite results. We also found that overexpression of SNX5 enhanced RIG-I's K48 ubiquitination and attenuated its K63 ubiquitination, resulting in inhibition of virus-induced RIG-I expression. Besides, further studies show that SNX5 overexpression weakens the interaction between VISA and TRAF2/5. Our findings suggest that SNX5 negatively regulates RLR-mediated antiviral signaling by targeting the RIG-I-VISA signalosome and provide new evidence for the negative regulation of RIG-I-mediated innate immune response mechanisms.

Interactome networks between the human respiratory syncytial virus (HRSV), the human metapneumovirus (ΗMPV), and their host: In silico investigation and comparative functional enrichment analysis

BACKGROUND AND OBJECTIVES

Human respiratory syncytial virus (HRSV) and human metapneumovirus (HMPV) are leading causes of upper and lower respiratory tract infections in non-immunocompetent subjects, yet the mechanisms by which they induce their pathogenicity differ significantly and remain elusive. In this study we aimed at identifying the gene interaction networks between the HRSV, HMPV respiratory pathogens and their host along with the different cell-signaling pathways associated with the above interactomes.

MATERIALS AND METHODS

The Viruses STRING database (http://viruses.string-db.org/) was used for the identification of the host-viruses interaction networks. The two lists of the predicted functional partners were entered in the FunRich tool (http://www.funrich.org) for the construction of the Venn diagram and the comparative Funcional Enrichment Analysis (FEA) with respect to biological pathways. The sets of the common and unique human genes identified in the two networks were also analyzed. The computational predictions regarding the shared human genes in the host-HRSV and the host-HMPV interactomes were further evaluated via the analysis of the GSE111732 dataset. miRNA transcriptomics data were mapped to gene targets using the miRNomics pipeline of the GeneTrail2 database (https://genetrail2.bioinf.uni-sb.de/).

RESULTS

Eleven out of twenty predicted human genes were common in the two interactomes (TLR4, SOCS3, SFXN1, AKT1, SFXN3, LY96, SFXN2, SOCS7, CISH, SOCS6, SOCS1). FEA of these common genes identified the kit receptor and the GH receptor signaling pathways as the most significantly enriched annotations. The remaining nine genes of the host-HRSV and the host-HMPV interaction networks were the IFIH1, DDX58, NCL, IRF3, STAT2, HSPA4, CD209, KLF6, CHKA and the MYD88, SOCS4, SOCS2, SOCS5 AKT2, AKT3, SFXN4, SFXN5 and TLR3 respectively. Distinct cell-signaling pathways were enriched per interactome. The comparative FEA highlighted the association of the host-HRSV functional partners with the negative regulation of RIG-I/MDA5 signaling. The analysis with respect to miRNAs mapping to gene targets of the GSE111732 dataset indicated that nine out of the eleven common host genes are either enriched or depleted in the sample sets (HRSV or HMPV infected) as compared with the reference set (non-infected), although with no significant scores.

CONCLUSIONS

We have identified both shared and unique host genes as members of the HRSV and HMPV interaction networks. The disparate human genes likely contribute to distinct responses in airway epithelial cells.

Intracellular sensing of viral genomes and viral evasion

During viral infection, virus-derived cytosolic nucleic acids are recognized by host intracellular specific sensors. The efficacy of this recognition system is crucial for triggering innate host defenses, which then stimulate more specific adaptive immune responses against the virus. Recent studies show that signal transduction pathways activated by sensing proteins are positively or negatively regulated by many modulators to maintain host immune homeostasis. However, viruses have evolved several strategies to counteract/evade host immune reactions. These systems involve viral proteins that interact with host sensor proteins and prevent them from detecting the viral genome or from initiating immune signaling. In this review, we discuss key regulators of cytosolic sensor proteins and viral proteins based on experimental evidence.

Homologs of Human Dengue-Resistance Genes, FKBP1B and ATCAY, Confer Antiviral Resistance in Aedes aegypti Mosquitoes

Dengue virus (DENV) is transmitted by mosquitoes and is a major public health concern. The study of innate mosquito defense mechanisms against DENV have revealed crucial roles for the Toll, Imd, JAK-STAT, and RNAi pathways in mediating DENV in the mosquito. Often overlooked in such studies is the role of intrinsic cellular defense mechanisms that we hypothesize to work in concert with the classical immune pathways to affect organismal defense. Our understanding of the molecular interaction of DENV with mosquito host cells is limited, and we propose to expand upon the recent results from a genome-scale, small interfering RNA (siRNA)-based study that identified mammalian host proteins associated with resistance to dengue/West Nile virus (DENV/WNV) infection. The study identified 22 human DENV/WNV resistance genes (DVR), and we hypothesized that a subset would be functionally conserved in Aedes aegypti mosquitoes, imparting cellular defense against flaviviruses in this species. We identified 12 homologs of 22 human DVR genes in the Ae. aegypti genome. To evaluate their possible role in cellular resistance/antiviral defense against DENV, we used siRNA silencing targeted against each of the 12 homologs in an Ae. aegypti cell line (Aag2) infected with DENV2 and identified that silencing of the two candidates, AeFKBP1 and AeATCAY, homologs of human FKBP1B and ATCAY, were associated with a viral increase. We then used dsRNA to silence each of the two genes in adult mosquitoes to validate the observed antiviral functions in vivo. Depletion of AeFKBP1 or AeATCAY increased viral dissemination through the mosquito at 14 days post-infection. Our results demonstrated that AeFKBP1 and AeATCAY mediate resistance to DENV akin to what has been described for their homologs in humans. AeFKBP1 and AeATCAY provide a rare opportunity to elucidate a DENV-resistance mechanism that may be evolutionarily conserved between humans and Ae. aegypti.

Saccharomyces cerevisiae-like 1 (SEC14L1) is a prognostic factor in breast cancer associated with lymphovascular invasion

Lymphovascular invasion is strongly related to breast cancer metastasis. However, the underlying mechanisms of lymphovascular invasion and its driver molecules in breast cancer remain to be defined. In this study, we explore differential expression of genes in large molecularly characterized and clinically annotated datasets of invasive breast cancer patients (n = 8056) coupled with histological review and strict definition for lymphovascular invasion status. The METABRIC series was used to identify genes associated with lymphovascular invasion, as defined using hematoxylin and eosin staining supplemented by immunohistochemistry, at the genomic/transcriptomic levels. Saccharomyces cerevisiae-like 1 (SEC14L1) was identified as one of the most significant genes associated with lymphovascular invasion. The prognostic significance of SEC14L1 gene copy number and mRNA expression was further investigated in the METABRIC series and externally validated using the Breast Cancer Gene-Expression Miner v4.0. Protein expression of SEC14L1 was also assessed using immunohistochemistry in series of early stage breast cancer using tissue microarrays. SEC14L1 gene copy number gain was significantly associated with high histological grade and poor outcome. SEC14L1 mRNA expression showed positive association with higher grade, lymph node metastasis, and poor outcome. SEC14L1 protein overexpression was significantly associated with lymphovascular invasion (p < 0.0001), higher grade (p = 0.011), HER2 positivity (p = 0.036), and shorter survival (p = 0.00075). Our findings specify SEC14L1 as an independent prognostic factor in breast cancer. Its association, at both transcriptome and protein expression levels, with lymphovascular invasion and outcome could imply an important role in tumor progression. A further mechanistic insight into its molecular roles including potential therapeutic utility is warranted.

Region-specific innate antiviral responses of the human epididymis

Viral infections of the epididymis are associated with epididymitis, which damages the epithelium and impairs fertility. We showed previously that innate immune response genes were differentially expressed in the corpus and cauda region of the human epididymis in comparison to the caput. Here we investigate the antiviral defense response mechanisms of human epididymis epithelial (HEE) cells. Toll-like receptor (TLR) 3 and retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) are enriched in HEE cells from the corpus and cauda region. These HEE cells show an enhanced response to antiviral ligands (poly(I:C) and HSV-60), as shown by increased IFN-β mRNA expression and IFN-β secretion. Nuclear translocation of phosphorylated p65 occurs after poly(I:C) exposure. In addition, paired box 2 (PAX2), which was implicated in regulating antiviral response pathways, is required for basal expression of the DNA sensor, Z-DNA binding protein (ZBP1) and type I interferon, in caput but not in cauda cells.

Negative regulators of the RIG-I-like receptor signaling pathway

Upon recognition of specific molecular patterns on microbes, host cells trigger an innate immune response, which culminates in the production of type I interferons, proinflammatory cytokines and chemokines, and restricts pathogen replication and spread within the host. At each stage of this response, there are stimulatory and inhibitory signals that regulate the magnitude, quality, and character of the response. Positive regulation promotes an antiviral state to control and eventually clear infection, whereas negative regulation dampens inflammation and prevents immune-mediated tissue damage. An overexuberant innate response can lead to cell and tissue destruction, and the development of spontaneous autoimmunity. The retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), RIG-I and melanoma differentiation-associated gene 5 (MDA5), belong to a family of cytosolic host RNA helicases that recognize distinct nonself RNA signatures and trigger innate immune responses against several RNA viruses by signaling through the essential adaptor protein mitochondrial antiviral signaling (MAVS). The RLR signaling pathway is tightly regulated to maximize antiviral immunity and minimize immune-mediated pathology. This review highlights contemporary findings on negative regulators of the RLR signaling pathway, with specific focus on the proteins and biological processes that directly regulate RIG-I, MDA5 and MAVS signaling function.

Host and Viral Modulation of RIG-I-Mediated Antiviral Immunity

Innate immunity is the first line of defense against invading pathogens. Rapid and efficient detection of pathogen-associated molecular patterns via pattern-recognition receptors is essential for the host to mount defensive and protective responses. Retinoic acid-inducible gene-I (RIG-I) is critical in triggering antiviral and inflammatory responses for the control of viral replication in response to cytoplasmic virus-specific RNA structures. Upon viral RNA recognition, RIG-I recruits the mitochondrial adaptor protein mitochondrial antiviral signaling protein, which leads to a signaling cascade that coordinates the induction of type I interferons (IFNs), as well as a large variety of antiviral interferon-stimulated genes. The RIG-I activation is tightly regulated via various posttranslational modifications for the prevention of aberrant innate immune signaling. By contrast, viruses have evolved mechanisms of evasion, such as sequestrating viral structures from RIG-I detections and targeting receptor or signaling molecules for degradation. These virus–host interactions have broadened our understanding of viral pathogenesis and provided insights into the function of the RIG-I pathway. In this review, we summarize the recent advances regarding RIG-I pathogen recognition and signaling transduction, cell-intrinsic control of RIG-I activation, and the viral antagonism of RIG-I signaling.

Multilayered regulations of RIG-I in the anti-viral signaling pathway

RIG-I is a cytosolic receptor recognizing virus-specific RNA structures and initiates an antiviral signaling that induces the production of interferons and proinflammatory cytokines. Because inappropriate RIG-I signaling affects either viral clearance or immune toxicity, multiple regulations of RIG-I have been investigated since its discovery as the viral RNA detector. In this review, we describe the recent progress in research on the regulation of RIG-I activity or abundance. Specifically, we focus on the mechanism that modulates RIG-I-dependent antiviral response through post-translational modifications of or protein-protein interactions with RIG-I.

RNF123 has an E3 ligase-independent function in RIG-I-like receptor-mediated antiviral signaling

Retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are cytoplasmic sensors crucial for recognizing different species of viral RNAs, which triggers the production of type I interferons (IFNs) and inflammatory cytokines. Here, we identify RING finger protein 123 (RNF123) as a negative regulator of RIG-I and MDA5. Overexpression of RNF123 inhibits IFN-β production triggered by Sendai virus (SeV) and encephalomyocarditis picornavirus (EMCV). Knockdown or knockout of endogenous RNF123 potentiates IFN-β production triggered by SeV and EMCV, but not by the sensor of DNA viruses cGAS RNF123 associates with RIG-I and MDA5 in both endogenous and exogenous cases in a viral infection-inducible manner. The SPRY and coiled-coil, but not the RING, domains of RNF123 are required for the inhibitory function. RNF123 interacts with the N-terminal CARD domains of RIG-I/MDA5 and competes with the downstream adaptor VISA/MAVS/IPS-1/Cardif for RIG-I/MDA5 CARD binding. These findings suggest that RNF123 functions as a novel inhibitor of innate antiviral signaling mediated by RIG-I and MDA5, a function that does not depend on its E3 ligase activity.

Molecular etiology of an indolent lymphoproliferative disorder determined by whole-genome sequencing

In an attempt to assess potential treatment options, whole-genome and transcriptome sequencing were performed on a patient with an unclassifiable small lymphoproliferative disorder. Variants from genome sequencing were prioritized using a combination of comparative variant distributions in a spectrum of lymphomas, and meta-analyses of gene expression profiling. In this patient, the molecular variants that we believe to be most relevant to the disease presentation most strongly resemble a diffuse large B-cell lymphoma (DLBCL), whereas the gene expression data are most consistent with a low-grade chronic lymphocytic leukemia (CLL). The variant of greatest interest was a predicted NOTCH2-truncating mutation, which has been recently reported in various lymphomas.

RIG-I-like receptor regulation in virus infection and immunity

Mammalian cells have the intrinsic capacity to detect viral pathogens and to initiate an antiviral response that is characterized by the induction of interferons (IFNs) and proinflammatory cytokines. A delicate regulation of the signaling pathways that lead to cytokine production is needed to ensure effective clearance of the virus, while preventing tissue damage caused by excessive cytokine release. Here, we focus on the mechanisms that modulate the signal transduction triggered by RIG-I-like receptors (RLRs) and their adaptor protein MAVS, key components of the host machinery for sensing foreign RNA. Specifically, we summarize recent advances in understanding how RLR signaling is regulated by posttranslational and posttranscriptional mechanisms, microRNAs (miRNAs) and autophagy. We further discuss how viruses target these regulatory mechanisms for immune evasion.

Regulation of RIG-I-like receptor signaling by host and viral proteins

Vertebrate innate immunity is characterized by an effective immune surveillance apparatus, evolved to sense foreign structures, such as proteins or nucleic acids of invading microbes. RIG-I-like receptors (RLRs) are key sensors of viral RNA species in the host cell cytoplasm. Activation of RLRs in response to viral RNA triggers an antiviral defense program through the production of hundreds of antiviral effector proteins including cytokines, chemokines, and host restriction factors that directly interfere with distinct steps in the virus life cycle. To avoid premature or abnormal antiviral and proinflammatory responses, which could have harmful consequences for the host, the signaling activities of RLRs and their common adaptor molecule, MAVS, are delicately controlled by cell-intrinsic regulatory mechanisms. Furthermore, viruses have evolved multiple strategies to modulate RLR-MAVS signal transduction to escape from immune surveillance. Here, we summarize recent progress in our understanding of the regulation of RLR signaling through host factors and viral antagonistic proteins.

Systems biology unravels interferon responses to respiratory virus infections

Interferon production is an important defence against viral replication and its activation is an attractive therapeutic target. However, it has long been known that viruses perpetually evolve a multitude of strategies to evade these host immune responses. In recent years there has been an explosion of information on virus-induced alterations of the host immune response that have resulted from data-rich omics technologies. Unravelling how these systems interact and determining the overall outcome of the host response to viral infection will play an important role in future treatment and vaccine development. In this review we focus primarily on the interferon pathway and its regulation as well as mechanisms by which respiratory RNA viruses interfere with its signalling capacity.