Biology subjects

Vrati, S.

Publications and source records attributed to Vrati, S..

12 recordsLinked to original sources

bioRxiv2026

JEV helicase targets host MTOC and participates in the organization of pericentriolar viroplasm

Flaviviruses contribute significantly to the global disease burden and are known to remodel host organelles to their advantage. Centrosomal microtubule-organizing centres (MTOCs) having established role in cell division and signalling are also targeted by viruses. However, it remains uncertain whether they act as bystanders or actively engage in viral processes. Here, we elucidate the centrosome and cytoskeletal involvement during Japanese Encephalitis Virus (JEV) infection. Our virus-free expression studies revealed a centrosome-targeting region within the C-terminal helicase domain that mediates the association of JEV-NS3 with host MTOCs. When expressed exogenously, JEV-NS3 formed pericentriolar aggresomes resembling the helicase-containing viroplasm distribution pattern of infected cells. These pericentriolar viroplasm appears in the non-neuronal cell types with centriolar consequences while the neuronal cell types fail to show such phenotypes. Centriole depletion assays revealed the proviral role of centrosome, where the viroplasm organization depends on centrosomal MTOCs, and vimentin cages. Additionally, microtubule disruption and dynarrestin blockade assays emphasized the roles of microtubules and dynein in concentrating NS3-containing vesicular packets towards centrosomes, highlighting the centrosome-cytoskeleton axis as a potential target for intervention.

cell biology↗

bioRxiv2025

Ewing Sarcoma Breakpoint Region 1 (EWSR1) protein binds to the non-structural protein-2 and the non-coding regions of the Chikungunya virus genome to inhibit the virus replication

Chikungunya virus (CHIKV) is an alphavirus with a single-stranded RNA genome. Conserved sequence elements within the 5'- and 3'-non-coding regions (NCRs) of the CHIKV genome interact with host proteins to regulate viral RNA replication. Electrophoretic mobility shift assays (EMSA) and mass spectrometry identified several host RNA-binding proteins that associate with these conserved NCR elements, among which EWSR1 uniquely bound the 3'-ends of both the plus-sense genomic RNA and the minus-sense replication intermediate RNA. EMSA and biolayer interferometry demonstrated that EWSR1 binds strongly to two RNA elements: a 48-nucleotide region in the plus-strand 3'-NCR (3NCR48) and a 50-nucleotide region at the 3'-end of the minus-strand replication intermediate (5NCR-RC50), which is complementary to the genomes 5'-NCR and its adjacent sequence. RNA immunoprecipitation from CHIKV-infected cells confirmed that EWSR1 binds CHIKV RNA in vivo. Functional analyses revealed that CHIKV infection downregulates EWSR1 expression and causes its cytoplasmic accumulation. Knockdown or knockout of EWSR1 expression increased CHIKV genomic RNA levels and viral titers, whereas its overexpression suppressed both. EWSR1 reduced the synthesis of both plus- and minus-sense CHIKV RNAs in infected cells. Additionally, EWSR1 was found to bind CHIKV nsP2 and inhibit its helicase activity, which is critical for viral genome replication. The antiviral activity of EWSR1 extended to Ross River virus but not to Sindbis virus, consistent with conservation of the 48-nucleotide sequence in their respective 3'-NCRs. Together, these findings identify EWSR1 as a novel host restriction factor that limits CHIKV replication through specific interactions with viral RNA and the nsP2 protein. IMPORTANCEChikungunya virus (CHIKV) poses a significant medical challenge, necessitating the development of novel antiviral strategies. This study demonstrates that the host protein EWSR1 plays a key role in controlling CHIKV replication. By binding to specific regions of viral RNA and interacting with nsP2, a critical viral enzyme, EWSR1 inhibits viral RNA synthesis and reduces viral titers. In the absence of EWSR1, CHIKV replicates more efficiently, underscoring its antiviral function. These findings establish EWSR1 as a novel host restriction factor that limits CHIKV replication. Understanding this interaction enhances our knowledge of host-virus dynamics and may guide the design of new antiviral approaches against CHIKV and related alphaviruses.

microbiology↗

bioRxiv2025

Emetine dihydrochloride inhibits Chikungunya virus nsP2 helicase and shows antiviral activity in the cell culture and mouse model of virus infection

Chikungunya virus (CHIKV), a mosquito-borne alphavirus, causes frequent epidemics of chikungunya fever across the world and has become a significant medical challenge, warranting the development of novel antivirals. A cell imaging-based high-content screening of the Spectrum collection of small molecules, containing all the US and international drug molecules, identified Emetine dihydrochloride (ED) as a potent antiviral against CHIKV. ED inhibited CHIKV replication in the C57BL/6 mouse model of chikungunya disease, resulting in significantly lower viremia. Importantly, clinical symptoms of joint swelling were altogether absent in the CHIKV-infected mice treated with ED. In the ERMS cells, ED inhibited the CHIKV uptake, and the virus replication early during the virus life cycle by inhibiting the viral RNA synthesis, resulting in the inhibition of the viral protein synthesis. ED was predicted to bind the helicase domain of the CHIKV non-structural protein nsP2 by in silico methods. The ED binding to the nsP2 protein and its helicase domain was validated in vitro by microscale thermophoresis and isothermal titration calorimetry. Importantly, ED inhibited the CHIKV nsP2 helicase activity in vitro in a dose-dependent manner. These data demonstrate the potential of ED to be repurposed as a novel CHIKV antiviral, warranting clinical development. AUTHOR SUMMARYChikungunya virus (CHIKV) spreads through the bites of the virus-infected Aedes mosquitoes. The virus causes frequent epidemics of chikungunya fever involving severe joint edema and muscle pain. The virus activity has been recorded in more than 100 countries in Asia, Africa, South and Central America, and Europe, and it has become endemic in several regions of the world. In 2024, around 480,000 CHIKV cases and over 200 deaths were reported worldwide. While a CHIKV vaccine was recently approved, no virus-specific antiviral therapy is available. Considering the global medical significance of the virus, the development of effective CHIKV antivirals is a priority. With a view to repurposing an existing drug, we screened a collection of all the approved US and international drug molecules and identified Emetine dihydrochloride (ED) as a potent inhibitor of CHIKV replication in the cell culture model. The CHIKV-infected mice treated with ED showed reduced virus replication and no joint swelling, which is a typical clinical symptom of CHIKV disease. Our studies show that ED binds the CHIKV nsP2, inhibiting its helicase action, which is required for replicating the viral genomic RNA and producing the viral proteins. In the past, emetine has been used in humans to treat amoebiasis. Our work thus shows the potential of the drug emetine to be repurposed for treating CHIKV patients.

microbiology↗

bioRxiv2025

AGPAT1 is a novel Chikungunya virus receptor on human cells

Chikungunya virus (CHIKV) is a medically important alphavirus whose host receptor is not fully understood. We identified AGPAT1 from the human Huh7 cell plasma membrane binding with CHIKV particles in vitro. The CHIKV binding with AGPAT1 was demonstrated on Huh7, HAP1, and ERMS plasma membrane by confocal microscopy. The AGPAT1 antibody inhibited CHIKV binding to cells, reducing the virus uptake in Huh7 and ERMS cells. CHIKV binding, uptake, and replication were significantly reduced in the AGPAT1 knockout HAP1 cells, and the ectopic expression of AGPAT1 rescued the reduced virus binding, uptake, and replication. AGPAT1 interacted with the E1 surface on the E1-E2 dimer of CHIKV envelope proteins in silico. The E1-AGPAT1 interacting amino acid residues identified in the computational study were experimentally verified. AGPAT1 was also shown to have a role in the binding and uptake of another alphavirus, Ross River virus. These data demonstrate an important role for AGPAT1 as a novel host receptor involved in CHIKV binding and uptake in human cells. AUTHOR SUMMARYChikungunya virus (CHIKV) is a medically important alphavirus. Identifying its receptor on human cells will aid the development of novel antivirals. We have identified AGPAT1 as a novel CHIKV receptor on several human cells. We provide data showing the interaction of AGPAT1 with the E1 protein of CHIKV E1-E2 dimer present on the virion surface and identify the amino acid residues involved in the interaction. AGPAT1 was also shown to have a role in the binding and uptake of Ross River virus, another alphavirus. AGPAT1 is a protein involved in lipid metabolism and has not been reported to have a direct role in any virus infection, or as a virus receptor. Thus, this work identifies AGPAT1 as a novel receptor for CHIKV on human cells, and has implications for understanding the virus pathogenesis and designing the receptor-blocking CHIKV antivirals.

microbiology↗

bioRxiv2025

Identification and In Silico Characterization of Novel lncRNAs Associated with Dengue Infection

BackgroundLong noncoding RNAs (lncRNAs) are essential regulators of various biological processes in viral infections. In our previous study, we described the association of known lncRNAs with dengue disease progression. However, little is known about novel lncRNAs in the context of dengue infection. In this study, we aimed to identify novel lncRNAs and characterize their interaction with mRNAs during different stages of dengue infection using RNA sequencing (RNA-seq) technology to better understand their role in dengue pathogenesis. MethodsWe analyzed RNA-seq data (GSE94892) obtained from peripheral blood mononuclear cells (PBMCs) of 39 dengue-infected patients. RNA-seq data analysis was performed using the Tuxedo protocol, and the coding potential of novel transcripts was examined using CPC and CPAT tools. LncRNAs and cis-regulated mRNAs were identified through location-expression analysis within a 20 kbp genomic region surrounding the identified lncRNAs. ResultsWe identified and characterized a total of 65 novel lncRNAs differentially expressed during dengue disease progression. These included 34 long intergenic lncRNAs, 2 antisense lncRNAs, and 25 alternatively spliced lncRNAs classified based on their localization. Bioinformatics analysis predicted potential cis-regulated target genes. Co-expression analysis revealed a strong correlation between lncRNAs and genes enriched in pathways related to megakaryocyte development and platelet production, suggesting a potential role in dengue pathogenesis. Furthermore, comparison with miRBase-21 indicated that some of the identified lncRNAs could act as miRNA precursors, highlighting a novel function of lncRNAs in gene regulation. ConclusionWe developed an analytical pipeline to identify novel lncRNAs from RNA-seq data. Our analyses led to the identification of novel lncRNAs and their associated genes involved in dengue disease progression. These findings provide insights into the functional role of lncRNAs in dengue pathogenesis.

bioinformatics↗

bioRxiv2025

Endophilin mediated endocytosis and Epidermal growth factor receptor govern Japanese encephalitis virus entry and infection in neuronal cells

Several trafficking pathways are operational at the plasma membrane, and both clathrin-dependent, and clathrin-independent endocytosis (CIE), can serve as virus entry portals. Our research has shown that the neurotropic flavivirus: Japanese encephalitis virus (JEV), infects neuronal cells via CIE. Here we have identified and characterized two essential host-factors for JEV trafficking in neuronal cells: Endophilin & Epidermal Growth Factor Receptor (EGFR). Through quantitative estimation of viral RNA copy number, we demonstrate that JEV entry in neuronal cells, was blocked by knock-down of Endophilin A isoforms, while activation of Endophilin-mediated endocytosis using a specific inhibitor of GSK-3{beta} enhanced virus entry. Deletion mutants of Endophilin showed an essential role of SH3, BAR, H0 domains for virus entry. High resolution fluorescence imaging of virions showed overlap with Endophilin A2 puncta. Virus entry led to rearrangements of the actin cytoskeleton, and was highly sensitive to any pharmacological actin perturbation. Virus endocytosis activated EGFR, and the specific kinase inhibitors Erlotinib, and Gefitinib, reduced virus entry and replication in cultured cells and mouse primary cortical neurons. Silencing of EGFR, competitive inhibition with receptor ligand EGF, and EGFR specific antibodies significantly impaired JEV binding and entry, indicating the crucial role of its ligand binding domain for virus attachment/receptor interaction. EGFR colocalized with virions at early time-points of infection, and the ED3 domain of the JEV-envelope protein showed specific interaction with EGFR through BLI. Our study provides evidence for JEV entry in neuronal cells through an endocytic pathway involving Endophilin and EGFR.

microbiology↗

bioRxiv2024

Identification and Characterization of Novel Metagenome Assembled Uncultivated Virus Genomes from Human Gut

Metagenomics has revealed an unprecedented viral diversity in human gut although, most of the sequence data remains to be characterized. In this study, we mined a collection of 1090 metagenome assembled "high quality" genomes of human gut viruses. Sequence analysis has revealed eight new species from seven genera of the class, Caudoviricetes and nineteen new species from fourteen genera of the ssDNA virus family, Microviridae. In addition, four "high quality" genomes were identified, which do not show similarity to sequences present in any of the four major viral databases, NCBI viral RefSeq, IMG-VR, Gut Phage Database (GPD) and Gut Virome Database (GVD). Further, annotation of the "high-quality" genomes and KEGG pathway analysis has identified antB, dnaB, DNMT1, DUT, xlyAB, xtmB and xtmA as the most widespread viral and Auxiliary Metabolic Genes (AMGs). Genes for virulence, host-takeover, drug resistance, tRNA, tmRNA and CRISPR elements were also found. Bacterial hosts are predicted for around 40% of the analyzed genomes. Overall, we report identification of new viral genomes and genome analyses of human gut viruses, which will be useful for biological characterization to establish their significance in physiology. IMPORTANCEMultiple studies have found that dysbiosis of gut virome is associated with conditions such as metabolic syndromes, autoimmune disorders and infectious diseases. In the interest of its therapeutic and diagnostic potential, intestinal virome warrants detailed investigation. However, limited ability to culture gut viruses becomes one of the challenges for their biological characterization and fully understanding their role in physiology. Sequence analysis and host prediction methods provide opportunities to understand gut viruses, their functional potential and devise ways for further characterization.

genomics↗

bioRxiv2023

Methotrimeprazine exerts antiviral and neuroprotective effects in Japanese encephalitis virus infection through activation of adaptive ER stress and autophagy

Japanese encephalitis virus (JEV) is the leading global cause of virus-induced encephalitis. Its pathogenesis is driven by a combination of neuronal cell death and neuroinflammation. We hypothesized that pharmacological upregulation of autophagy could exert a neuroprotective antiviral effect, and tested a panel of forty-two FDA-approved drugs that were shown to induce autophagy. Four drugs were tested in the JE mouse model based on in vitro protective effects on neuronal cell death, inhibition of viral replication, and anti-inflammatory effects in microglial cells. The antipsychotic phenothiazines Methotrimeprazine (MTP) and Trifluoperazine (TFP) showed a significant survival benefit with reduced virus titers in the brain, prevention of blood-brain barrier (BBB) breach, and inhibition of neuroinflammation. Both drugs were potent mTOR-independent autophagy flux inducers. Mechanistically MTP inhibited SERCA channel functioning, thereby resulting in rise in cytosolic calcium levels, and induction of a unique adaptive ER stress response. In virus infected drug treated cells, there was a strong transcriptional downregulation of type I interferon and interferon-stimulated genes and upregulation of cholesterol metabolic pathway genes. The drugs exerted an autophagy-dependent antiviral effect at the level of JEV protein translation/replication complex formation in diverse cell types. Inhibition of inflammatory cytokine/chemokine release from mouse microglial cells was partly autophagy-dependent. Our study suggests that MTP exerts a combined antiviral and anti-inflammatory effect in JEV infection, and has therapeutic potential to be repurposed for JE treatment.

microbiology↗

bioRxiv2022

Dietary αKG inhibits SARS CoV-2 infection and rescues inflamed lungs to restore normal O2 saturation in animals

Our recent works described the rescue effect of -ketoglutarate (KG, a metabolite of Krebs cycle) on thrombosis and inflammation in animals. KG augments activity of prolyl hydroxylase 2 (PHD2), which in turn degrades proline residues of substrates like phosphorylated Akt (pAkt) and hypoxia inducible factor (HIF). Here we describe the inhibitory effect of octyl KG on pAkt as well as on HIF1/HIF2, and in turn decreasing SARS CoV-2 replication in Vero E6 cells. KG failed to inhibit the viral replication and Akt phosphorylation in PHD2-knockdown U937 cells transiently expressing ACE2. Contrastingly, triciribine (TCN, an Akt-inhibitor) inhibited viral replication alongside a downmodulation of pAkt in PHD2-KD cells. Dietary KG significantly inhibited viral infection and rescued hamsters from thrombus formation and inflammation in lungs, the known causes of acute respiratory distress syndrome (ARDS) in COVID-19. KG supplementation also reduced the apoptotic death of lung tissues in infected animals, alongside a downmodulation of pAkt and HIF2. KG supplementation neither affected IgG levels against SARS CoV-2 RBD protein nor altered the neutralization antibody response against SARS CoV-2. It did not interfere with the percentage of interferon-{gamma} positive (IFN{gamma}+) CD4+ and IFN{gamma}+CD8+ T cells in infected animals. The extended work in balb/c mice transiently expressing ACE2 showed a similar effect of KG in reducing accumulation of inflammatory immune cells and cytokines, including IL6, IL1{beta} and TNF, in lungs as well as in circulation of infected animals. Pro-thrombotic markers like platelet microparticles and platelet-leukocyte aggregates were reduced significantly in infected mice after KG supplementation. Importantly, KG supplementation restored the O2 saturation (SpO2) in circulation of SARS CoV-2 infected hamsters and mice, suggesting a potential therapeutic role of this metabolite in COVID-19 treatment.

pathology↗

bioRxiv2022

Insights into the Human Gut Virome by Sampling a Population from the Indian Subcontinent

Gut virome plays an important role in human physiology but remains poorly understood. This study reports an investigation of the human gut DNA-virome of a previously unexplored ethnic population through metagenomics of faecal samples collected from individuals residing in Northern India. Analysis shows that, similar to the populations investigated earlier, majority of the identified virome belongs to bacteriophages and a smaller fraction (< 20%) consists of viruses that infect animals, archaea, protists, multiple domains or plants. However, crAss-like phages, in this population, are dominated by the genera VII, VIII and VI. Interestingly, it also reveals the presence of a virus family, Sphaerolipoviridae, which has not been detected in the human gut earlier. Viral families, Siphoviridae, Myoviridae, Podoviridae, Microviridae, Herelleviridae and Phycodnaviridae are detected in all of the analyzed individuals, which supports the existence of a core virome. Lysogeny-associated genes were found in less than 10% of the assembled genomes and a negative correlation was observed in the richness of bacterial and free-viral species, suggesting that the dominant lifestyle of gut phage is not lysogenic. This is in contrast to some of the earlier studies. Further, several hundred high-quality viral genomes were recovered. Detailed characterization of these genomes would be useful for understanding the biology of these viruses and their significance in human physiology. ImportanceViruses are important constituents of the human gut microbiome but it remains poorly understood. The Indian subcontinent is a unique biogeographic region and the Indian population is known to harbour a distinct bacterial microbiome. However, the gut virome in this population has not been investigated earlier. Therefore, in this study, we investigated fecal samples of 12 healthy individuals to analyze their gut virome, through metagenomics.

microbiology↗

bioRxiv2022

Avobenzone, Guaiazulene and Tioxolone identified as potent autophagy inducers in a high-throughput image based screen for autophagy flux

Autophagy is a conserved intracellular degradation pathway that is essential for maintaining cellular homeostasis. Given its critical role in several disease conditions, recent studies are focussed on identifying drugs/small molecules with autophagy modulating capacity for potential clinical applications. Here, we describe the development and characterisation of a quantitative image-based high content screening platform for autophagy flux measurements using the human melanoma A375 cell line that stably expresses the GFP-LC3-RFP probe. The GFP-LC3 is incorporated into autophagosomes, while RFP serves an internal control. The GFP/RFP fluorescence intensity ratio gives an accurate indication of autophagy induction (low ratio) vs blockage of autophagy flux (high ratio), and was validated with the autophagy inducer Torin1 and inhibitor Bafilomycin A1. This assay was used to screen the Spectrum collection library comprising of 2560 compounds, to identify autophagy modulators. In addition to known autophagy effectors, several novel autophagy inducers and inhibitors were identified in our study. Further three FDA approved drugs that are widely used in skin-care products: Avobenzone, Guaiazulene and Tioxolone, were validated as potent autophagy inducers that function in an mTOR independent manner.

cell biology↗

bioRxiv2018

Japanese Encephalitis Virus Infected Microglial Cells Secrete Exosomes Containing let-7a/b that Facilitate Neuronal Damage via Caspase Activation

Extracellular microRNAs (miRNAs) are essential for the cell to cell communication in the healthy and diseased brain. MicroRNAs released from the activated microglia upon neurotropic virus infection may exacerbate CNS damage. Here, we identified let-7a and let-7b (let-7a/b) as the overexpressed miRNAs in Japanese Encephalitis virus (JEV) infected microglia and assessed their role in JEV pathogenesis. We measured the let-7a/b expressions in JEV infected post-mortem human brains, mice brains and in mouse microglial N9 cells by the qRT-PCR and in situ hybridization assay. The interaction between let-7a/b and NOTCH signaling pathway further examined in Toll-like receptor 7 knockdown (TLR7 KD) mice to assess the functions. Exosomes released from JEV infected or let-7a/b mimic transfected N9, and HEK-293 cells were isolated and evaluated their function. We observed an upregulation of let-7a/b in the infected brains as well as in microglia. Knockdown of TLR7 or Inhibition of let-7a/b suppressed the JEV induced NOTCH activation possibly via NF-{kappa}B dependent manner and subsequently, attenuated JEV induced TNF production in microglial cells. Further, exosomes secreted from JEV-infected microglial cells specifically contained let-7a/b. Exosomes overexpressed with let-7a/b were injected into BALB/c mice as well as co-incubated with mouse neuronal (Neuro2a) cells, or primary cortical neuron resulted in caspase activation leading to neuronal damage in the brain. Thus, our results provide evidence for the multifaceted role of let-7a/b miRNAs and unravel the exosomes mediated mechanism for JEV induced pathogenesis.

neuroscience↗