Genomics-guided targeting of stress granule proteins G3BP1/2 to inhibit SARS-CoV-2 propagation.
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ABSTRACT:
SUBMITTER: Ali N
PROVIDER: S-EPMC8431879 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Stress granules (SGs) are cytoplasmic condensates that often form as part of the cellular antiviral response. Despite the growing interest in understanding the interplay between SGs and other biological condensates and viral replication, the role of SG formation during coronavirus infection remains poorly understood. Several proteins from different coronaviruses have been shown to suppress SG formation upon overexpression, but there are only a handful of studies analyzing SG formation in coronavirus-infected cells. To better understand SG inhibition by coronaviruses, we analyzed SG formation during infection with the human common cold coronavirus OC43 (HCoV-OC43) and the pandemic SARS-CoV2. We did not observe SG induction in infected cells and both viruses inhibited eukaryotic translation initiation factor 2α (eIF2α) phosphorylation and SG formation induced by exogenous stress. Furthermore, in SARS-CoV2 infected cells we observed a sharp decrease in the levels of SG-nucleating protein G3BP1. Ectopic overexpression of nucleocapsid (N) and non-structural protein 1 (Nsp1) from both HCoV-OC43 and SARS-CoV2 inhibited SG formation. The Nsp1 proteins of both viruses inhibited arsenite-induced eIF2α phosphorylation, and the Nsp1 of SARS-CoV2 alone was sufficient to cause a decrease in G3BP1 levels. This phenotype was dependent on the depletion of cytoplasmic mRNA mediated by Nsp1 and associated with nuclear accumulation of the SG-nucleating protein TIAR. To test the role of G3BP1 in coronavirus replication, we infected cells overexpressing EGFP-tagged G3BP1 with HCoV-OC43 and observed a significant decrease in virus replication compared to control cells expressing EGFP. The antiviral role of G3BP1 and the existence of multiple SG suppression mechanisms that are conserved between HCoV-OC43 and SARS-CoV2 suggest that SG formation may represent an important antiviral host defense that coronaviruses target to ensure efficient replication.
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Project description:Novel coronavirus disease 2019 (COVID-19), a respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has brought an unprecedented public health crisis and continues to threaten humanity due to the persistent emergence of new variants. Therefore, developing more effective and broad-spectrum therapeutic and prophylactic drugs against infection by SARS-CoV-2 and its variants, as well as future emerging CoVs, is urgently needed. In this study, we screened several US FDA-approved drugs and identified phenothiazine derivatives with the ability to potently inhibit the infection of pseudotyped SARS-CoV-2 and distinct variants of concern (VOCs), including B.1.617.2 (Delta) and currently circulating Omicron sublineages XBB and BQ.1.1, as well as pseudotyped SARS-CoV and MERS-CoV. Mechanistic studies suggested that phenothiazines predominantly inhibited SARS-CoV-2 pseudovirus (PsV) infection at the early stage and potentially bound to the spike (S) protein of SARS-CoV-2, which may prevent the proteolytic cleavage of the S protein, thereby exhibiting inhibitory activity against SARS-CoV-2 infection. In summary, our findings suggest that phenothiazines can serve as a potential broad-spectrum therapeutic drug for the treatment of SARS-CoV-2 infection as well as the infection of future emerging human coronaviruses (HCoVs).
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Project description:The unprecedented emergence and spread of SARS-CoV-2, the coronavirus responsible for the COVID-19 pandemic, underscores the need for diagnostic and therapeutic technologies that can be rapidly tailored to novel threats. Here, we show that site-specific RNA endonuclease XNAzymes - artificial catalysts composed of single-stranded synthetic xeno-nucleic acid oligonucleotides (in this case 2'-deoxy-2'-fluoro-β-D-arabino nucleic acid) - may be designed, synthesised and screened within days, enabling the discovery of a range of enzymes targeting SARS-CoV-2 ORF1ab, ORF7b, spike- and nucleocapsid-encoding RNA. Three of these are further engineered to self-assemble into a catalytic nanostructure with enhanced biostability. This XNA nanostructure is capable of cleaving genomic SARS-CoV-2 RNA under physiological conditions, and when transfected into cells inhibits infection with authentic SARS-CoV-2 virus by RNA knockdown. These results demonstrate the potential of XNAzymes to provide a platform for the rapid generation of antiviral reagents.
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Project description:The continuing emergence of SARS-CoV-2 variants has highlighted the need to identify additional points for viral inhibition. Ribosome inactivating proteins (RIPs), such as MAP30 and Momordin which are derived from bitter melon (Momordica charantia), have been found to inhibit a broad range of viruses. MAP30 has been shown to potently inhibit HIV-1 with minimal cytotoxicity. Here we show that MAP30 and Momordin potently inhibit SARS-CoV-2 replication in A549 human lung cells (IC50 ~ 0.2 μM) with little concomitant cytotoxicity (CC50 ~ 2 μM). Both viral inhibition and cytotoxicity remain unaltered by appending a C-terminal Tat cell-penetration peptide to either protein. Mutation of tyrosine 70, a key residue in the active site of MAP30, to alanine completely abrogates both viral inhibition and cytotoxicity, indicating the involvement of its RNA N-glycosylase activity. Mutation of lysine 171 and lysine 215, residues corresponding to those in Ricin which when mutated prevented ribosome binding and inactivation, to alanine in MAP30 decreased cytotoxicity (CC50 ~ 10 μM) but also the viral inhibition (IC50 ~ 1 μM). Unlike with HIV-1, neither Dexamethasone nor Indomethacin exhibited synergy with MAP30 in the inhibition of SARS-CoV-2. From a structural comparison of the two proteins, one can explain their similar activities despite differences in both their active-sites and ribosome-binding regions. We also note points on the viral genome for potential inhibition by these proteins.
| S-EPMC10310010 | biostudies-literature
Project description:Stress granules (SGs) are cytoplasmic condensates of stalled messenger ribonucleoprotein complexes (mRNPs) that form when eukaryotic cells encounter environmental stress. RNA-binding proteins are enriched for arginine methylation and facilitate SG assembly through interactions involving regions of low amino acid complexity. How methylation of specific RNA-binding proteins regulates RNA granule assembly has not been characterized. Here, we examined the potent SG-nucleating protein Ras-GAP SH3-binding protein 1 (G3BP1), and found that G3BP1 is differentially methylated on specific arginine residues by protein arginine methyltransferase (PRMT) 1 and PRMT5 in its RGG domain. Several genetic and biochemical interventions that increased methylation repressed SG assembly, whereas interventions that decreased methylation promoted SG assembly. Arsenite stress quickly and reversibly decreased asymmetric arginine methylation on G3BP1. These data indicate that arginine methylation in the RGG domain prevents large SG assembly and rapid demethylation is a novel signal that regulates SG formation.
| S-EPMC5077203 | biostudies-literature
Project description:BackgroundA role for neutrophils in the pathogenesis of Alzheimer's disease (AD) is emerging. We previously showed that the neutrophil granule proteins cationic antimicrobial protein of 37 kDa (CAP37), cathepsin G (CG), and neutrophil elastase (NE) directly bind the amyloid-beta peptide Aβ1-42, a central player in AD pathogenesis. CAP37, CG, and NE are serine proteases that can cleave Aβ1-42 at different sites and with different catalytic activities.ObjectiveIn this study, we compared the effects of these three proteins on Aβ1-42 fibrillation and neurotoxicity.MethodsUsing mass spectrometry and in vitro aggregation assay, we found that NE and CG efficiently cleave Aβ1-42. This cleavage correlates well with the inhibition of Aβ1-42 aggregation into fibrils. In contrast, CAP37 did not efficiently cleave Aβ1-42, but was still able to inhibit its fibrillation, most likely through a quenching effect. Inhibition of Aβ1-42 aggregation by NE and CG neutralized its toxicity measured in cultured neurons. In contrast, inhibition of Aβ1-42 aggregation by CAP37 did not inhibit its neurotoxicity.ResultsWe found that a peptide derived from CAP37 could mimic the quenching and inhibition of Aβ1-42 aggregation effects of the full-length protein. Additionally, this peptide was able to inhibit the neurotoxicity of the most toxic Aβ1-42 aggregate, an effect that was not found with the full-length CAP37.ConclusionThese results shed light on the mechanisms of action of neutrophil granule proteins with regard to inhibition of Aβ1-42 aggregation and neurotoxicity and open up a possible strategy for the discovery of new disease-modifying drugs for AD.
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Project description:The SARS-CoV-2 pandemic, and the likelihood of future coronavirus pandemics, emphasized the urgent need for development of novel antivirals. Small-molecule chemical probes offer both to reveal aspects of virus replication and to serve as leads for antiviral therapeutic development. Here, we report on the identification of amiloride-based small molecules that potently inhibit OC43 and SARS-CoV-2 replication through targeting of conserved structured elements within the viral 5′-end. Nuclear magnetic resonance–based structural studies revealed specific amiloride interactions with stem loops containing bulge like structures and were predicted to be strongly bound by the lead amilorides in retrospective docking studies. Amilorides represent the first antiviral small molecules that target RNA structures within the 5′ untranslated regions and proximal region of the CoV genomes. These molecules will serve as chemical probes to further understand CoV RNA biology and can pave the way for the development of specific CoV RNA–targeted antivirals.
| S-EPMC8626076 | biostudies-literature
Project description:The SARS-CoV-2 pandemic, and the likelihood of future coronavirus pandemics, has rendered our understanding of coronavirus biology more essential than ever. Small molecule chemical probes offer to both reveal novel aspects of virus replication and to serve as leads for antiviral therapeutic development. The RNA-biased amiloride scaffold was recently tuned to target a viral RNA structure critical for translation in enterovirus 71, ultimately uncovering a novel mechanism to modulate positive-sense RNA viral translation and replication. Analysis of CoV RNA genomes reveal many conserved RNA structures in the 5'-UTR and proximal region critical for viral translation and replication, including several containing bulge-like secondary structures suitable for small molecule targeting. Following phylogenetic conservation analysis of this region, we screened an amiloride-based small molecule library against a less virulent human coronavirus, OC43, to identify lead ligands. Amilorides inhibited OC43 replication as seen in viral plaque assays. Select amilorides also potently inhibited replication competent SARS-CoV-2 as evident in the decreased levels of cell free virions in cell culture supernatants of treated cells. Reporter screens confirmed the importance of RNA structures in the 5'-end of the viral genome for small molecule activity. Finally, NMR chemical shift perturbation studies of the first six stem loops of the 5'-end revealed specific amiloride interactions with stem loops 4, 5a, and 6, all of which contain bulge like structures and were predicted to be strongly bound by the lead amilorides in retrospective docking studies. Taken together, the use of multiple orthogonal approaches allowed us to identify the first small molecules aimed at targeting RNA structures within the 5'-UTR and proximal region of the CoV genome. These molecules will serve as chemical probes to further understand CoV RNA biology and can pave the way for the development of specific CoV RNA-targeted antivirals.
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Project description:In early 2020, the COVID-19 pandemic sparked a global crisis that continues to pose a serious threat to human health and the economy. Further advancement in research is necessary and requires the availability of quality molecular tools, including monoclonal antibodies. Here, we present the development and characterization of a collection of over 40 new monoclonal antibodies directed against different SARS-CoV-2 proteins. Recombinant SARS-CoV-2 proteins were expressed, purified, and used as immunogens. Upon development of specific hybridomas, the obtained monoclonal antibody (mAb) clones were tested for binding to recombinant proteins and infected cells. We generated mAbs against structural proteins, the Spike and Nucleocapsid protein, several non-structural proteins (nsp1, nsp7, nsp8, nsp9, nsp10, nsp16) and accessory factors (ORF3a, ORF9b) applicable in flow cytometry, immunofluorescence, or Western blot. Our collection of mAbs provides a set of novel, highly specific tools that will allow a comprehensive analysis of the viral proteome, which will allow further understanding of SARS-CoV-2 pathogenesis and the design of therapeutic strategies.
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Project description:COVID-19 is a disease with unique characteristics that include lung thrombosis1, frequent diarrhoea2, abnormal activation of the inflammatory response3 and rapid deterioration of lung function consistent with alveolar oedema4. The pathological substrate for these findings remains unknown. Here we show that the lungs of patients with COVID-19 contain infected pneumocytes with abnormal morphology and frequent multinucleation. The generation of these syncytia results from activation of the SARS-CoV-2 spike protein at the cell plasma membrane level. On the basis of these observations, we performed two high-content microscopy-based screenings with more than 3,000 approved drugs to search for inhibitors of spike-driven syncytia. We converged on the identification of 83 drugs that inhibited spike-mediated cell fusion, several of which belonged to defined pharmacological classes. We focused our attention on effective drugs that also protected against virus replication and associated cytopathicity. One of the most effective molecules was the antihelminthic drug niclosamide, which markedly blunted calcium oscillations and membrane conductance in spike-expressing cells by suppressing the activity of TMEM16F (also known as anoctamin 6), a calcium-activated ion channel and scramblase that is responsible for exposure of phosphatidylserine on the cell surface. These findings suggest a potential mechanism for COVID-19 disease pathogenesis and support the repurposing of niclosamide for therapy.
| S-EPMC7611055 | biostudies-literature