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Grandvaux, N.

Publications and source records attributed to Grandvaux, N..

11 recordsLinked to original sources
bioRxiv2026

A Stable Reporter Cell Line to Study Respiratory Syncytial Virus NS2-Mediated Inhibition of IFNB Promoter Activation

Human respiratory syncytial virus (RSV) is an enveloped, non-segmented, negative-sense RNA virus and a major cause of severe lower respiratory tract disease in infants, older adults, and immunocompromised individuals. A hallmark of RSV pathogenesis is early evasion of innate immunity mediated by the non-structural proteins NS1 and NS2. NS2 is a multifunctional interferon (IFN) antagonist that dampens both IFN{beta} induction and type I IFN responsiveness by targeting multiple nodes of the RIG-I/IFN signaling axis. Because NS2 inhibition is typically partial and context dependent, its quantitative assessment in conventional cell-based assays can be challenging. Here, we report the generation and characterization of a stable, virus-free reporter system in human lung epithelial A549 cells to measure NS2-mediated inhibition of RIG-I-dependent activation of the human IFNB promoter. The platform combines stable NS2 expression with genomic integration of a dual cassette encoding (i) a non-targeting short hairpin RNA that constitutively activates RIG-I signaling and (ii) a firefly luciferase reporter driven by the IFNB promoter. This configuration provides a sensitive and reproducible luminescence readout of IFNB promoter activity under controlled, infection-free conditions, enabling robust quantification of NS2 antagonism with reduced experimental variability. The luminescence-based format is readily scalable for early-stage discovery and prioritization of small molecules or biologics that counteract NS2 function. More broadly, the modular design can be adapted to other viral immune antagonists, signaling pathways, or cell types, supporting comparative studies where pathway modulation must be evaluated under highly standardized and reproducible conditions.

microbiology↗
bioRxiv2025

No Evidence of Direct Activation of Human Neutrophil Responses by Multivalent Prefusion Trimeric SARS-CoV-2 Spike Protein ex vivo

The SARS-CoV-2 Spike (S) protein is essential for viral entry and serves as the primary immunogen in most COVID-19 vaccines. While its role in adaptive immunity is well defined, its potential to contribute directly to innate immune activation and remains incompletely understood. Neutrophils, in particular, are prominent effectors in COVID-19 severity, yet how they respond directly to the S protein presented in a multivalent format is unclear. Here, we investigated whether the S protein can directly activate human neutrophils ex vivo using two biologically relevant models: nanoparticles displaying multivalent stabilized prefusion trimeric S glycoprotein, and purified {beta}-propiolactone-inactivated SARS-CoV-2 virions. Neutrophils were exposed to nanoparticles or inactivated virus, either alone or pre-coated with monoclonal or polyclonal anti-S antibodies. Nanoparticles displaying Respiratory Syncytial Virus (RSV) Fusion (F) protein and purified {beta}-propiolactone-inactivated RSV served as comparators. Across all models and conditions tested, the S protein did not induce significant neutrophil responses. No consistent effects were observed on cell viability, surface marker expression, reactive oxygen species production, neutrophil extracellular trap formation, cytokine release, or inflammatory gene expression--even in the presence of anti-S antibodies mimicking immune complexes. Results with F-nanoparticles and inactivated RSV were similarly modest. These findings indicate that the trimeric prefusion S protein, whether displayed multivalently on nanoparticles or in the context of inactivated viral particles, is insufficient to trigger robust neutrophil activation. This work provides insight into the innate immune profile of the S protein and suggests that its use in vaccine platforms is unlikely to directly provoke neutrophil-mediated inflammatory responses.

immunology↗
bioRxiv2024

Comprehensive Proteomic Analysis of HCoV-OC43 Virions and Virus-Modulated Extracellular Vesicles

Viruses are obligate parasites that depend on the cellular machinery for their propagation. Several viruses also incorporate cellular proteins that facilitate viral spread. Defining these cellular proteins is critical to decipher viral life cycles and delineate novel therapeutic strategies. While numerous studies have explored the importance of host proteins in coronavirus spread, information about their presence in mature virions is limited. In this study, we developed a protocol to highly enrich mature HCoV-OC43 virions and characterize them by proteomics. Recognizing that cells release extracellular vesicles whose content is modulated by viruses, and given our ability to separate virions from these vesicles, we also analyzed their protein content in both uninfected and infected cells. We uncovered 69 unique cellular proteins associated with virions including 31 high confidence hits. These proteins primarily regulate RNA metabolism, enzymatic activities, vesicular transport, cell adhesion, metabolite interconversion and translation. We further discovered that the virus had a profound impact on exosome composition, incorporating 47 novel cellular proteins (11 high confidence) and excluding 92 others (61 high confidence) in virus-associated extracellular vesicles compared to uninfected cells. Moreover, a dsiRNA screen revealed that 11 of 18 select targets significantly impacted viral yields, including proteins found in virions or extracellular vesicles. Overall, this study provides new and important insights into the incorporation of numerous host proteins into HCoV-OC43 virions, their biological significance and the ability of the virus to modulate extracellular vesicles. ImportanceIn recent years, coronaviruses have dominated global attention, making it crucial to develop methods to control them and prevent future pandemics. Besides viral proteins, host proteins play a significant role in viral propagation and offer potential therapeutic targets. Targeting host proteins is advantageous because they are less likely to mutate and develop resistance compared to viral proteins, a common issue with many antiviral treatments. In this study, we examined the protein content of the less virulent biosafety level 2 HCoV-OC43 virus as a stand-in for the more virulent SARS-CoV-2. Our findings reveal that several cellular proteins incorporated into the virion regulate viral spread. Additionally, we report that the virus extensively modulates the content of extracellular vesicles, enhancing viral dissemination. This underscores the critical interplay between the virus, host proteins, and extracellular vesicles.

microbiology↗
bioRxiv2023

High-accuracy mapping of human and viral direct physical protein-protein interactions using the novel computational system AlphaFold-pairs

Protein-protein interactions are central, highly flexible components of regulatory mechanisms in all living cells. Over the years, diverse methods have been developed to map protein-protein interactions. These methods have revealed the organization of protein complexes and networks in numerous cells and conditions. However, these methods are also time consuming, costly and sensitive to various experimental artifacts. To avoid these caveats, we have taken advantage of the AlphaFold-Multimer software, which succeeded in predicting the structure of many protein complexes. We designed a relatively simple algorithm based on assessing the physical proximity of a test protein with other AlphaFold structures. Using this method, named AlphaFold-pairs, we have successfully defined the probability of a protein-protein interaction forming. AlphaFold-pairs was validated using well-defined protein-protein interactions found in the literature and specialized databases. All pairwise interactions forming within the 12-subunit transcription machinery RNA Polymerase II, according to available structures, have been identified. Out of 66 possible interactions (excluding homodimers), 19 specific interactions have been found, and an additional previously unknown interaction has been unveiled. The SARS-CoV-2 surface glycoprotein Spike (or S) was confirmed to interact with high preference with the human ACE2 receptor when compared to other human receptors. Notably, two additional receptors, INSR and FLT4, were found to interact with S. For the first time, we have successfully identified protein-protein interactions that are likely to form within the reassortant Eurasian avian-like (EA) H1N1 swine G4 genotype Influenza A virus, which poses a potential zoonotic threat. Testing G4 proteins against human transcription factors and molecular chaperones (a total of 100 proteins) revealed strong specific interactions between the G4 HA and HSP90B1, the G4 NS and the PAQosome subunit RPAP3, as well as the G4 PA and the POLR2A subunit. We predict that AlphaFold-pairs will revolutionize the study of protein-protein interactions in a large number of healthy and diseased systems in the years to come.

bioinformatics↗
bioRxiv2020

Pinpointing of cysteine oxidation sites in vivo by high-resolution proteomics reveals mechanism of redox-dependent inhibition of STING

Protein function is regulated by post-translational modifications, among which reversible oxidation of Cys (Cys ox-PTM) emerged as a key regulatory mechanism of cellular responses. The redox regulation of virus-host interactions is well documented, but in most cases, proteins subjected to Cys ox-PTM remain unknown. The identification of Cys ox-PTM sites in vivo is essential to underpin our understanding of the mechanisms of the redox regulation. In this study, we present a proteome-wide identification of reversible Cys ox-PTM sites in vivo during stimulation by oxidants using a maleimide-based bioswitch method coupled to mass spectrometry. We identified 2720 unique Cys ox-PTM sites encompassing 1473 proteins with distinct abundance, location and functions. Label-free quantification (LFQ)-based analysis revealed the enrichment of ox-PTM in numerous pathways, many relevant to virus-host interaction. Here, we focused on the oxidation of STING, the central adaptor of the innate immune type I interferon pathway induced upon detection of cytosolic DNA. We provide the first in vivo demonstration of reversible oxidation of Cys148 and Cys206 of STING. Molecular analyses led us to establish a new model in which Cys148 oxidation is constitutive, while Cys206 oxidation is inducible by oxidative stress or by the natural ligand 23-cGAMP. We show that oxidation of Cys206 has an inhibitory function to prevent STING hyperactivation through the constraint of a conformational change associated with the formation of inactive polymers containing intermolecular disulfide bonds. This provides new ground for the design of therapies targeting STING relevant to autoinflammatory disorders, immunotherapies and vaccines. Brief summary of the main resultsThe function of proteins is regulated by post-translational modifications, among which reversible oxidation of Cys recently emerged as a key component. Comprehension of redox regulation of cellular responses requires identification of specific oxidation sites in vivo. Using a bioswitch method to specifically label Cys subjected to reversible oxidation coupled to mass spectrometry, we identified thousands of novel oxidation sites. Many are relevant to virus-host interaction pathways. Here, we focused on the oxidation of STING, an adaptor critical for activating the innate immune type I interferon pathway engaged upon cytosolic DNA sensing. Molecular studies led us to establish a new model in which STING Cys148 is oxidized at basal levels, while Cys206 oxidation is induced by oxidative stress and ligand binding. We show that oxidation of Cys206 has an inhibitory function to prevent STING hyperactivation. This study provides ground for novel research avenues aimed at designing therapeutics that target this pathway.

immunology↗
bioRxiv2020

Defective influenza A virus RNA products mediate MAVS-dependent upregulation of human leukocyte antigen class I proteins

Influenza A virus (IAV) increases presentation of class I human leukocyte antigen (HLA) proteins that limit antiviral responses mediated by natural killer (NK) cells, but molecular mechanisms have not yet been fully elucidated. We observed that infection with A/Fort Monmouth/1/1947 (H1N1) IAV significantly increased presentation of HLA-B, -C and -E on lung epithelial cells. Virus entry was not sufficient to induce HLA upregulation, because UV-inactivated virus had no effect. We found that HLA upregulation was elicited by aberrant internally-deleted viral RNAs (vRNAs) known as mini viral RNAs (mvRNAs) and defective interfering RNAs (DI RNAs), which bind to retinoic acid-inducible gene-I (RIG-I) and initiate mitochondrial antiviral signaling (MAVS) protein-dependent antiviral interferon (IFN) responses. Indeed, MAVS was required for HLA upregulation in response to IAV infection or ectopic mvRNA/DI RNA expression. The effect was partially due to paracrine signalling, as we observed that IAV infection or mvRNA/DI RNA-expression stimulated production of IFN-{beta} and IFN-{lambda}1, and conditioned media from these cells elicited a modest increase in HLA surface levels in naive epithelial cells. HLA upregulation in response to aberrant viral RNAs could be prevented by chemical blockade of IFN receptor signal transduction. While HLA upregulation would seem to be advantageous to the virus, it is kept in check by the viral non-structural 1 (NS1) protein; we determined that NS1 limits cell-intrinsic and paracrine mechanisms of HLA upregulation. Taken together, our findings indicate that aberrant IAV RNAs stimulate HLA presentation, which may aid viral evasion of innate immunity. IMPORTANCEHuman leukocyte antigens (HLA) are cell surface proteins that regulate innate and adaptive immune responses to viral infection by engaging with receptors on immune cells. Many viruses have evolved ways to evade host immune responses by modulating HLA expression and/or processing. Here, we provide evidence that aberrant RNA products of influenza virus genome replication can trigger RIG-I/MAVS-dependent remodeling of the cell surface, increasing surface presentation of HLA proteins known to inhibit the activation of an immune cell known as a natural killer (NK) cell. While this HLA upregulation would seem to be advantageous to the virus, it is kept in check by the viral non-structural 1 (NS1) protein, which limits RIG-I activation and interferon production by the infected cell.

microbiology↗
bioRxiv2019

The E3 ubiquitin ligase TRAF6 is a novel interacting protein of amyotrophic lateral sclerosis-linked misfolded SOD1

Amyotrophic lateral sclerosis (ALS) is a fatal disease, characterized by the selective loss of motor neurons leading to paralysis. Mutations in the gene encoding superoxide dismutase 1 (SOD1) are the second most common cause of familial ALS, and considerable evidence suggests that these mutations result in an increase in toxicity due to protein misfolding. We previously demonstrated in the SOD1G93A rat model that misfolded SOD1 exists as distinct conformers and forms deposits on mitochondrial subpopulations. Here, using SOD1G93A rats and conformation-restricted antibodies specific for misfolded SOD1 (B8H10 and AMF7-63), we identified the interactomes of the mitochondrial pools of misfolded SOD1. This strategy identified binding proteins that uniquely interacted with either AMF7-63 or B8H10-reactive SOD1 conformers as well as with a high proportion of interactors common to both conformers. Of this latter set, we identified the E3 ubiquitin ligase TNF receptor-associated factor 6 (TRAF6) as a SOD1 interactor and determined that exposure of the SOD1 functional loops facilitates this interaction. Of note, this conformational change was not universally fulfilled by all SOD1 variants and differentiated TRAF6-interacting from TRAF6 non-interacting SOD1 variants. Functionally, TRAF6 stimulated polyubiquitination and aggregation of the interacting SOD1 variants. TRAF6 E3 ubiquitin ligase activity was required for the former, but was dispensable for the latter, indicating that TRAF6-mediated polyubiquitination and aggregation of the SOD1 variants are independent events. We propose that the interaction between misfolded SOD1 and TRAF6 may be relevant to the etiology of ALS.

neuroscience↗
bioRxiv2018

RNASeq analysis identifies non-canonical role of STAT2 and IRF9 in the regulation of a STAT1-independent antiviral and immunoregulatory transcriptional program induced by IFNβ and TNFα

IFN{beta} typically induces an antiviral and immunoregulatory transcriptional program through the activation of ISGF3 (STAT1, STAT2 and IRF9) transcriptional complexes. The response to IFN{beta} is context-dependent and is prone to crosstalk with other cytokines, such as TNF IFN{beta} and TNF synergize to drive a specific delayed transcriptional program. Previous observation led to the hypothesis that an alternative STAT1-independent pathway involving STAT2 and IRF9 might be involved in gene induction by the combination of IFN{beta} and TNF. Using genome wide transcriptional profiling by RNASeq, we found that the costimulation with IFN{beta} and TNF induces a broad antiviral and immunoregulatory transcriptional program independently of STAT1. Additionally, STAT2 and IRF9 are involved in the regulation of only a subset of these STAT1-independent genes. Consistent with the growing literature, STAT2 and IRF9 act in concert to regulate a subgroup of these genes. Unexpectedly, STAT2 and IRF9 were also engaged in specific independent pathways to regulate distinct sets of IFN{beta} and TNF-induced genes. Altogether these observations highlight the existence of distinct previously unrecognized non-canonical STAT1-independent, but STAT2 and/or IRF9-dependent pathways in the establishment of a delayed antiviral and immunoregulatory transcriptional program in conditions where elevated levels of both IFN{beta} and TNF are present.

immunology↗
bioRxiv2017

DUSP1 promotes apoptosis and suppresses cell migration, while leaving the JIP1-protected cytokine production intact, during paramyxovirus infection.

The host antiviral response involves the induction of interferons and proinflammatory cytokines, but also the activation of cell death pathways, including apoptosis, to limit viral replication and spreading. This host defense is strictly regulated to eliminate the infection while limiting tissue damage that is associated with virus pathogenesis. Post-translational modifications, most notably phosphorylation, are key regulators of the antiviral defense implying an important role of protein phosphatases. Here, we investigated the role of the dual-specificity phosphatase 1 (DUSP1) in the host defense against human respiratory syncytial virus (RSV), a pathogenic virus of the Pneumoviridae family, and Sendai virus (SeV), a model virus being developed as a vector for anti-RSV vaccine. We found that DUSP1 is upregulated before being subjected to proteasomal degradation. DUSP1 does not inhibit the antiviral response, but negatively regulates virus-induced JNK/p38 MAPK phosphorylation. Interaction with the JNK-interacting protein 1 scaffold protein prevents dephosphorylation of JNK by DUSP1, likely explaining that AP-1 activation and downstream cytokine production are protected from DUSP1 inhibition. Importantly, DUSP1 promotes SeV-induced apoptosis and suppresses cell migration in RSV-infected cells. Collectively, our data unveil a previously unrecognized selective role of DUSP1 in the regulation of tissue damage and repair during infections by RSV and SeV.

microbiology↗
bioRxiv2017

Structural Basis Of STAT2 Recognition By IRF9 Reveals Molecular Insights Into ISGF3 Function

Cytokine signalling is mediated by the activation of distinct sets of structurally homologous JAK and STAT signalling molecules, which control nuclear gene expression and cell fate. A significant expansion in the gene regulatory repertoire controlled by JAK/STAT signalling has arisen by the selective interaction of STATs with IRF transcription factors. Type I interferons (IFN), the major antiviral cytokines, trigger the formation of the ISGF3 complex containing STAT1, STAT2 and IRF9. ISGF3 regulates the expression of IFN-stimulated genes (ISGs). ISGF3 assembly depends on selective interaction between IRF9, through its IRF-association domain (IAD), with the coiled-coil domain (CCD) of STAT2. Here, we report the crystal structures of the IRF9-IAD alone and in a complex with STAT2-CCD. Despite similarity in the overall structure among respective paralogs, the surface features of the IRF9-IAD and STAT2- CCD have diverged to enable specific interaction between these family members, thus enabling ISGF3 formation and expression of ISGs.

biophysics↗