Biology subjects

Eke, L.

Publications and source records attributed to Eke, L..

7 recordsLinked to original sources

bioRxiv2026

Non-cyclic dinucleotide STING agonists abrogate MPXV infection

Mpox has emerged as a global threat to public health following several national and international outbreaks from 2022. Poxviruses deploy multiple strategies to counteract host immune defences including pathways leading to interferon (IFN) production. Here we demonstrate that depleting the viral 23-cGAMP nuclease poxin restores activation of STING and IRF3 during MPXV infection despite the presence of other viral antagonists. We then demonstrate that non-cyclic dinucleotide (non-CDN) STING agonists are resistant to poxin; activate STING and IRF3 during infection; and potently suppress MPXV and orthopoxvirus replication in human primary fibroblasts and differentiated monocytes, where replication is completely abrogated. Mechanistically, non-CDN restriction requires STING, IFNAR and STAT signalling, and induces a unique transcriptional signature over IFN{beta}, enabling expression of additional cytokines. In vivo, non-CDN activity effectively reduces signs of illness and enhances survival in wild-derived castaneous mice inoculated with the virulent clade I MPXV. Our study reveals poxin as an Achilles heel of MPXV, that when bypassed by direct STING agonism, provides a promising novel anti-mpox therapeutic strategy with reduced risk of antiviral resistance.

microbiology↗

bioRxiv2025

Compositional analysis of yellow fever virus induced stress granules reveals a functional connection to mitochondrial homeostasis

The phase separation of biomolecules into so-called stress granules (SGs) allows the cell to tightly regulate translation activity in response to different stimuli, such as oxidative stress, starvation, or the recognition of non-cellular RNA. Recent reports suggest SGs induced during viral infection, may act as a crossroad between the cellular stress response and the activation of the innate immune response. Here, we aimed to dissect the role of SGs in the context of yellow fever virus (YFV) infection. We found that YFV infection resulted in translational shut-off from 24 hpi on followed by the formation of SGs at 48 hpi, a delay potentially associated with the ability of the YFV capsid to inhibit SG formation, through an interaction with the major SG scaffolding protein G3BP1. To elucidate the role of YFV-induced SGs during infection, we inhibited SG assembly using a small-molecule inhibitor and find that SG formation does not influence viral replication. Uncovering the first proteome of virus-induced SGs, our compositional analysis revealed a specific enrichment of proteins associated with mitochondrial processes in YFV-induced SGs. Indeed, we show that YFV infection results in mitochondrial damage and dysfunction. Together, we propose that YFV-induced SGs may be involved not only in the modulation of cellular homeostasis but also in influencing mitochondrial functions. Author SummaryViruses impose a major burden on the infected host - from structural rearrangements needed to assemble replication complexes, to exploiting cellular energy resources and genetic rewiring associated with antiviral responses. The assembly of membrane-less organelles such as stress granules (SGs) enable cells to rapidly tune cellular processes upon sensing of stresses such as viruses. Moreover, the cells innate immune response is proposed to be regulated by SGs and in turn many viruses disrupt or highjack their components. Yet, the molecular basis for SG functions during infection remain ambiguous. Here we investigated the interplay between yellow fever virus (YFV) infection and SGs. We demonstrate that infection with attenuated or pathogenic viruses result in the formation of SGs. Their compositional analysis reveal that they sequester mitochondrial proteins, correlating with altered mitochondrial functions during infection. This highlights a novel complex interplay between membrane-bound and membrane-less organelles which could present novel opportunities for antiviral therapies.

microbiology↗

bioRxiv2025

Attenuation of the 2022 global outbreak monkeypox virus relative to its clade IIb ancestor

Monkeypox virus (MPXV) is a zoonotic virus endemic to Africa that has recently re-emerged, becoming the first orthopoxvirus with human-to-human transmission since smallpox eradication. The 2022 global epidemic of MPXV was caused by Clade IIb lineage B.1 virus that derives from the Clade IIb lineage A.1, which is endemic to West Africa1-3. Here we compared an early lineage B.1 virus with its closest earlier A.1 ancestor and show that despite only 46 nucleotide differences, lineage B.1 has attenuating phenotypic changes. Both B.1 and A.1 viruses replicated equivalently in cell culture, but B.1 had defects in long-range spread. MPXV B.1 also displayed defects in innate immune control, inducing higher IFN{beta}, innate immune signalling and MAPK gene expression, and a reduced capacity to suppress interleukin-1{beta}-mediated immune responses. Finally, MPXV B.1 had reduced virulence in a mouse model of MPXV infection relative to the ancestral A.1 endemic strain. Our work demonstrates biological differences between human circulating MPXV lineages that correlate with clinical observations documenting reduced in-host viral dissemination and disease severity for lineage B. Our data also reveal that the APOBEC3-like mutational footprint in MPXV is not only a signature of sustained human transmission but can also drive phenotypic changes.

microbiology↗

bioRxiv2025

Differential time-restricted sensitivity of enveloped viruses to Sec61 translocon blockade

The morphogenesis of enveloped viruses relies on the trafficking of transmembrane proteins through the secretory pathway to sites of virus envelopment. The first step in this pathway, their translocation into the endoplasmic reticulum, is therefore an attractive target for broad-spectrum intervention. Here, we tested if blockade of the Sec61 translocon by the Mycobacterium ulcerans exotoxin mycolactone, a potent inhibitor of Sec61, could block the production of virus glycoproteins and subsequent production of infectious virus from a range of human enveloped viruses: the DNA virus herpes simplex virus 1 (HSV1), and the RNA viruses, respiratory syncytial virus (RSV), influenza A virus (IAV), SARS coronavirus 2 (SARS CoV2) and Zika virus (ZIKV). In line with known translocation mechanisms, mycolactone blocked in vitro translocation and ectopic expression of type I transmembrane proteins but not type III, multipass or cytosolic proteins. Translocation of the type II protein RSV G was also blocked and although ectopically expressed G protein was detected, it was not glycosylated. Pretreatment of cells with mycolactone also blocked the synthesis of type I transmembrane proteins in infected cells and either the synthesis or glycosylation of type II transmembrane proteins, and the production of progeny from all viruses tested, while having no effect on virus entry or downstream synthesis of cytosolic proteins. While mycolactone treatment of HSV1 infected cells at various times after infection resulted in the immediate inhibition of virus production at the point of addition, IAV, RSV and ZIKV became resistant to the action of mycolactone surprisingly early in infection, and before virus glycoprotein synthesis was even detectable or virus production had begun. We therefore conclude that although inhibition of the translocation of virus transmembrane proteins through the Sec61 translocon can in principle block virus production, the morphogenesis of many enveloped RNA viruses requires only limited amounts of envelope proteins for successful propagation, providing novel insight into the biology of these viruses. Author SummaryMany circulating human pathogens are enveloped viruses that all use the cellular secretory pathway to target their envelope proteins to cellular sites of virus particle assembly. The potential to target this pathway could therefore offer a novel broad-spectrum therapy for existing, emerging and as yet unknown human pathogens. Here we have targeted the initial step in this pathway using a highly potent Sec61 inhibitor, mycolactone, to carry out the first comprehensive assessment of translocation disruption on a range of enveloped human viruses from different virus families, including herpes simplex virus, influenza A virus and SARS-CoV2. Our results have shown that Sec61 inhibition blocks the onward trafficking of many virus envelope proteins that are essential to produce infectious virus at assembly sites. However, unexpectedly, we found that several of the viruses were resistant to the effects of this toxin when it was added early in infection, indicating that the synthesis of these essential virus proteins occurs earlier in infection than previously recognised. Hence, while this approach may not be suitable as a broad intervention strategy, it has revealed new information on virus biology and provides us with a novel tool for exploring a wide range of enveloped viruses.

microbiology↗

bioRxiv2024

Translational arrest and mRNA decay are independent activities of alphaherpesvirus virion host shutoff proteins

The herpes simplex virus 1 (HSV1) virion host shutoff (vhs) protein is an endoribonuclease that regulates the translational environment of the infected cell, by inducing the degradation of host mRNA via cellular exonuclease activity. To further understand the relationship between translational shutoff and mRNA decay, we have used ectopic expression to compare HSV1 vhs (vhsH) to its homologues from four other alphaherpesviruses - varicella zoster virus (vhsV), bovine herpesvirus 1 (vhsB), equine herpesvirus 1 (vhsE) and Mareks disease virus (vhsM). Only vhsH, vhsB and vhsE induced degradation of a reporter luciferase mRNA, with polyA+ in situ hybridisation indicating a global depletion of cytoplasmic polyA+ RNA and a concomitant increase in nuclear polyA+ RNA and the polyA tail binding protein PABPC1 in cells expressing these variants. By contrast, vhsV and vhsM failed to induce reporter mRNA decay and polyA+ depletion, but rather, induced cytoplasmic G3BP1 and polyA+ mRNA-containing granules and phosphorylation of the stress response proteins eIF2 and protein kinase R. Intriguingly, regardless of their apparent endoribonuclease activity, all vhs homologues induced an equivalent general blockade to translation as measured by single cell puromycin incorporation. Taken together, these data suggest that the activities of translational arrest and mRNA decay induced by vhs are separable and we propose that they represent sequential steps of the vhs host interaction pathway.

microbiology↗

bioRxiv2023

GADD34 mRNA turnover controls the molecular memory of cellular stress experience

The integrated stress response (ISR) is a key cellular signaling pathway activated by environmental alterations that represses protein synthesis to restore homeostasis. To prevent sustained damage, the ISR is counteracted by the upregulation of Growth Arrest and DNA Damage inducible 34 (GADD34), a stress-induced regulatory subunit of protein phosphatase 1 that mediates translation reactivation and stress recovery. Here, we uncover a novel ISR regulatory mechanism that post-transcriptionally controls the stability of PPP1R15A mRNA encoding GADD34. We established that the 3 untranslated region of PPP1R15A mRNA contains an active AU-rich element recognized by proteins of the ZFP36 family, promoting its rapid decay under normal conditions and stabilization for efficient expression of GADD34 in response to stress. We identify the tight temporal control of PPP1R15A mRNA turnover as a key step in establishing the ISR molecular memory, which sets the threshold for cellular responsiveness and mediates adaptation to repeated stress conditions.

cell biology↗

bioRxiv2021

Paracrine granules are cytoplasmic RNP granules distinct from stress granules assembling in response to viral infection.

To rapidly respond and adapt to stresses, such as viral infections, cells have evolved several mechanisms, which include the activation of stress response pathways and the innate immune response. These stress responses result in the rapid inhibition of translation and condensation of stalled mRNAs, together with RNA-binding proteins and signalling components, into cytoplasmic biocondensates called stress granules. Increasing evidence suggests that stress granules contribute to antiviral defense and thus viruses need to evade these response pathways to propagate. In addition, the stress granule pathway is proposed to be dynamic and adaptable to specific stresses. We previously showed that Feline Calicivirus (FCV) impairs SGs assembly by cleaving the scaffolding protein G3BP1. We also observed that uninfected bystander cells assembled G3BP1-granules, suggesting a paracrine response trigged by the infection. We now present evidence that virus-free supernatant generated from infected cells can induce the formation of paracrine granules. They are different from canonical stress granules and exhibit specific kinetics of assembly-disassembly, protein and RNA composition and are linked to antiviral activity. We propose that this paracrine induction reflects a novel cellular defence mechanism to limit viral propagation and promote stress responses in bystander cells. Summary statementWe describe a novel type of paracrine induced RNA granules associated with viruses, highlighting how different stresses results in heterogeneous stress granule-like condensates with specific cellular functions.

cell biology↗