Biology subjects

Saini, M.

Publications and source records attributed to Saini, M..

At least 19 recordsLinked to original sources

bioRxiv2026

Discovery of non-nucleoside inhibitors of the enterovirus D68 3D polymerase through crystallographic fragment and high-throughput biochemical screening

Enterovirus D68 (EV-D68) is a non-polio picornavirus that has caused increasing rates of severe respiratory illness and acute flaccid myelitis in children worldwide this century. There are no approved vaccines or antivirals for EV-D68. Thus, we conducted a crystallographic fragment screening (CFS) and a high-throughput screening (HTS) biochemical assay against the EV-D68 RNA-dependent RNA polymerase 3D (3Dpol) to identify ligandable sites and non-nucleoside compounds that can spearhead anti-enteroviral drug discovery. The CFS, involving 650 fragments, identified 68 hit compounds (~10% hit rate) distributed across 3Dpol, including the functionally relevant sites RNA template channel, Active site, and RNA primer channel, and the previously unknown "Thumb site II" and "Index-middle finger pocket". Inhibition assays confirmed that compounds binding to each site can inhibit EV-D68 3Dpol activity. The HTS, a fluorescence-based PicoGreen biochemical assay, permitted screening 50,000 compounds of the ChemBridge Premium Library (0.77% hit rate). After a second-round dose-response screening, we identified 5-aminoindazole as a promising scaffold that inhibits EV-D68 3Dpol, including hit-to-lead compound 727590, which displayed an IC50 value of 25 M and preliminary structure-activity relationships. These hits offer amenable starting points for discovery and development of non-nucleoside inhibitors and provide opportunities for structure-based drug design against enteroviruses. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/737532v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@1a7cb78org.highwire.dtl.DTLVardef@11f4bb9org.highwire.dtl.DTLVardef@1a477e0org.highwire.dtl.DTLVardef@ba5391_HPS_FORMAT_FIGEXP M_FIG Created with biorender.com and PyMOL Molecular Graphics System, version 2.5.0. Schrodinger, LLC. C_FIG

biophysics↗

bioRxiv2026

ARL15 promotes inflammatory fibroblast activation and disease severity in rheumatoid arthritis: integrated transcriptomic and collagen-induced arthritis model analyses

BackgroundADP-ribosylation factor-like protein 15 (ARL15) is a rheumatoid arthritis (RA) susceptibility gene identified through GWAS. Previous studies suggested a role for ARL15 in synovial fibroblast (SF) pathogenicity, but its contribution to inflammatory arthritis remains unclear. We investigated the inflammatory role of ARL15 and its therapeutic potential in RA. MethodsARL15 was overexpressed in MH7A cells followed by bulk RNA sequencing and pathway enrichment analyses. Therapeutic relevance was evaluated in collagen-induced arthritis (CIA) mouse model using anti-ARL15 monoclonal antibodies, ARL15-targeting siRNA, or isoquinoline. Arthritis scores, histopathology, micro-CT and serum cytokines were assessed. Publicly available single-cell RNA sequencing (scRNA-seq) datasets were analyzed to determine ARL15 expression in RASF subsets. ResultsARL15 overexpression induced a pro-inflammatory transcriptional program characterized by upregulation of IL1A, IL1B, IL6, IL8, CXCL1, CXCL10, and CCL20. Gene set enrichment analysis revealed activation of IL6-JAK-STAT, TNF, interferon-response, and KRAS signaling pathways, with suppression of oxidative phosphorylation, lipid metabolism, and mTORC1 signaling. In CIA mice, ARL15 inhibition significantly reduced arthritis severity, inflammatory infiltrates, and joint destruction while preserving cartilage and bone integrity. Serum TNF-, IL-6, and IL-1{beta} levels were markedly decreased following ARL15 blockade. Combination monoclonal antibody treatment demonstrated the greatest therapeutic benefit. scRNA-seq analysis showed broad ARL15 expression across RA fibroblast populations, with enrichment in inflammatory lining and SF subsets. ConclusionsARL15 is a pro-inflammatory regulator of SF activation and arthritis progression. Integrated transcriptomic, single-cell, and in vivo analyses identify ARL15 as a therapeutic target for RA and support further translational development of ARL15 based therapies.

immunology↗

bioRxiv2025

Comparative study of Dog and Human Lipid Droplet-associated protein (PLIN2)

Intracellular lipid droplets (LDs) are vital organelles that store energy, manage oxidative stress, and coordinate cellular signaling. A key protein family associated with LDs is the perilipins, with perilipin 2 (PLIN2) being prominent. This study focuses on a comparative analysis of canine and human PLIN2 to understand their structural and functional similarities. The genomic data for PLIN2 in both species were curated, revealing location, transcripts, exons, and introns. Sequence analysis demonstrated 85% identity between dog and human PLIN2, with conserved residues essential for structural and functional roles. Amino acid composition analysis revealed similarities in charged residues and in stabilizing and destabilizing residues. Despite their structural similarities (72% common secondary structure elements), a 3D comparison revealed significant differences in conformation. Physicochemical properties, including stability indices, were found to be distinct, possibly influencing their interactions. The study highlights the conservation of PLIN2s functional regions, shedding light on its role in protecting LDs from degradation across species.

bioinformatics↗

bioRxiv2025

Fabrication of a Parali (Rice Straws) Biomass & Herbal Based Filtration System for Sustainable Rural Water Purification

Access to safe drinking water remains a serious challenge in rural India, where traditional chemical and membrane-based filtering systems are often unavailable due to their high cost, energy requirements, and maintenance demands. This work develops and validates a low-cost, eco-friendly herbal filtration system for Mubarakpur hamlet by combining the antibacterial properties of plant extracts with natural filter media. The physical, chemical, and microbiological properties of the water samples collected from ponds, wells, sewage, and tap sources included turbidity, pH, COD, BOD, heavy metals, and bacterial load. Herbal extracts derived from Neem (Azadirachta indica), Bael (Aegle marmelos), Lemon, Amla, Moringa, Garlic, and Ginger had bactericidal effects when tested for antimicrobial activity; however, the peels of Bael and Lemon exhibited the best inhibition of Streptobacillus species. A six-layer prototype filtration device including cotton cloth, charcoal, parali biomass, gravel, sand, and a layer of herbal extract was created as a result of these findings. The extracts of lemon and bael exhibited the greatest inhibition of Streptobacillus species when tested for antibacterial activity. A six-layer prototype filtration device including cotton cloth, charcoal, parali biomass, gravel, sand, and a layer of herbal extract was created as a result of these findings. Laboratory testing of the small prototype revealed significant improvements in water quality: the microbial load dropped from 2,000,000 CFU/mL to 0 CFU/mL, the turbidity went from 300 NTU to 0.8 NTU, the COD decreased from 1000 mg/L to 9 mg/L, and the BOD decreased from 200 mg/L to 3.5 mg/L. Lead levels in tap water (0.02 mg/L) were also reduced to undetectable levels.

bioengineering↗

bioRxiv2025

Slit1 -a MET target gene in the embryonic limbs, prevents premature differentiation during mammalian myogenesis.

Skeletal myogenesis requires precise spatio-temporal regulation of molecular signals during prenatal and postnatal development. Prenatal myogenesis in mouse commences at embryonic day (E) 9.5, characterized by the expression of PAX3 -a key myogenic regulator, and its target MET, in the embryonic muscle progenitor cells (EMPCs). These EMPCs delaminate from dermomyotome in the somites and migrate to designated areas such as the developing embryonic limbs and diaphragm. The trajectory of their migration is directed and limited by spatio-temporal availability of the MET ligand (HGF). Given its periodic expression during embryonic myogenesis and its recent association with familial arthrogryposis, it is important to identify additional non-migratory functions of MET signaling. We find conditional loss of Met in the Pax3/somitic lineage affects survival in early neonatal stages because amuscular diaphragms cause respiratory distress. Impaired progenitor migration in conditional Met knockouts (cMetKO) results in highly dysplastic muscles in neonates compared to muscleless limbs observed in previous mutants. Additionally, using cMetKO embryos (E11.5) we identify Slit1 as a novel target of MET that is downregulated in the mutant limb buds. Pharmacological modulation with SU11274, in vitro, confirms Slit1 as a MET responsive gene, which if knocked down in myoblasts leads to precocious myogenic differentiation. Similarly, cMetKO embryos, having reduced Slit1 expression, show greater myotomal differentiation and compact organization, compared to wildtype embryos. While Slit1 emerges as a MET target that represses precocious switch to myogenic differentiation, molecular intricacies of MET-mediated regulation of Slit1 and their spatio-temporal dynamic in fine-tuning myogenesis in the nascent limbs needs further examination.

developmental biology↗

bioRxiv2025

Targeting Leishmania donovani Sphingosine Kinase 1 using PF-543 enhances immune response and limits parasite load

BackgroundSphingosine-1-phosphate (S1P) is a bioactive lipid mediator regulating apoptosis, proliferation, and immune responses. While S1Ps presence in Leishmania donovani phagolysosomes has been reported, the role of sphingosine kinases, especially SphK1, in parasite survival and host immune modulation remains underexplored. This study investigates the molecular and functional role of L. donovani SphK1 (LdSphK1) and evaluates the antileishmanial potential of PF-543, a specific SphK1 inhibitor. MethodsLdSphK1 and human SphK1 (rhSphK1) were cloned, expressed in E. coli, purified, and analyzed by SDS-PAGE. Enzymatic activity and inhibition by PF543 were assessed using NBD-S1P-based fluorometric assays. Protein-ligand interactions were analyzed using Microscale Thermophoresis (MST). Leishmania promastigotes overexpressing LdSphK1 were studied via confocal microscopy, and their viability and infectivity were assessed in vitro. THP-1 macrophages infected with L. donovani were treated with PF543 alone or with Amphotericin B and analyzed by MTT assay, RT-PCR, Giemsa staining, ELISA and immunoblotting. In vivo efficacy was tested in L. donovani-infected Swiss mice. ResultsrLdSphK1 ([~]102 kDa) and rhSphK1 ([~]50 kDa) were enzymatically active and significantly inhibited by PF-543. MST confirmed high-affinity binding of PF-543 (KD [~]29 microMolar). In L. donovani SphK1 overexpressor (LdSphKa) promastigotes, PF543 inhibited SphK1 activity and reduced parasite infectivity, more than in wildtype L. donovani promastigotes. Notably, PF543 treatment reduced parasite infectivity in vitro, lowered amastigote load by [~]40%, and promoted a pro-inflammatory cytokine shift ({uparrow}IL-12, {uparrow}TNF-, {downarrow}IL-10). Inhibition of ceramide synthesis and S1P supplementation revealed that S1P rescues ceramide-induced parasite death, implicating SphK1 in parasite survival. PF543 and Amphotericin B demonstrated synergistic anti-parasitic effects both in vitro and in vivo, with >90% reduction in parasite burden in mice. ConclusionPF543 is a potent inhibitor of SphK1, impairing parasite survival and modulating host immune responses. When combined with Amphotericin B, it offers a synergistic therapeutic strategy against visceral leishmaniasis, warranting further clinical exploration. Author SummaryLeishmaniasis, a neglected tropical disease, has limited available treatments and is becoming more resistant to medications. In this study, we explored the therapeutic potential of PF-543, a potent sphingosine kinase 1 (SphK1) inhibitor (demonstrated anticancer effects in various preclinical models) against Leishmania donovani. We successfully cloned and purified both Leishmania and human SphK1 proteins and confirmed PF-543 binding through biochemical and biophysical assays. Overexpression of LdSphK1 in parasites enhanced their survival and infectivity. In vitro, PF-543 treatment of infected macrophages decreased amastigote burden, shifted cytokine profiles towards a pro-inflammatory state, and enhanced host cell apoptosis. Notably, PF-543 acted synergistically with Amphotericin B, the current clinical drug, both in vitro and in vivo in Swiss mice, drastically lowering parasite burden. This study highlights the possibility of combination therapy and finds PF-543 to be a promising irresistible host-targeted antileishmanial drug. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/652326v2_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@1926575org.highwire.dtl.DTLVardef@4305f4org.highwire.dtl.DTLVardef@3c10c7org.highwire.dtl.DTLVardef@171801e_HPS_FORMAT_FIGEXP M_FIG C_FIG

pathology↗

bioRxiv2025

Crystallographic fragment screening of the dengue virus polymerase reveals multiple binding sites for the development of non-nucleoside antiflavivirals

Dengue viruses (DENV) infect approximately 400 million people each year, and there are currently no effective therapeutics available. To explore potential starting points for antiviral drug development, we conducted a large-scale crystallographic fragment screen targeting the RNA-dependent RNA polymerase (RdRp) domain of the non-structural protein 5 (NS5) from DENV serotype 2. Our screening, which involved 1,108 fragments, identified 60 hit compounds across various known binding sites, including the active site, N pocket, and RNA tunnel. Additionally, we discovered a novel binding site and a fragment-binding hotspot in thumb site II. These structural findings open amenable avenues for developing non-nucleoside inhibitors and offer valuable insights for future structure-based drug design aimed at DENV and other flaviviral RdRps.

biophysics↗

bioRxiv2025

Screening of Natural Plant Extracts for Antimicrobial Activity Against Streptobacillus moniliformis

The rise of antimicrobial resistance has driven the search for alternative antibacterial agents, including plant-based compounds. This study evaluates the antimicrobial potential of selected herbal extracts against Streptobacillus moniliformis using the agar well diffusion method. The tested extracts included Tulsi leaves (Ocimum sanctum), Neem leaves (Azadirachta indica), Bael leaves (Aegle marmelos), Adarak peels (Zingiber officinalef), Moringa seeds and leaves (Moringa oleifera), Dalchini (Cinnamomum verum), Lemon/Orange peels (Citrus limon and Citrus sinensis), and Ginger peels (Zingiber officinale). Among these, Bael leaves and Lemon peels demonstrated significant antibacterial activity, forming distinct zones of inhibition. In contrast, Neem and Moringa extracts did not inhibit bacterial growth. The observed antimicrobial activity is likely due to the presence of bioactive compounds such as flavonoids, tannins, and essential oils, which may disrupt bacterial cell walls and metabolic processes. Notably, S. moniliformis exhibited limited survival in culture, while other bacterial strains showed minimal resistance. These findings suggest that certain herbal extracts, particularly Bael leaves and Lemon peels, may serve as natural antimicrobial agents against S. moniliformis. Further studies are required to isolate and characterize the active compounds responsible for this antibacterial activity to explore their potential in developing alternative antimicrobial therapies.

microbiology↗

bioRxiv2025

THE CORRELATION BETWEEN REDOX ACTIVITY AND ANTIMICROBIAL PROPERTIES OF PYOCYANIN FROM Pseudomonas aeruginosa

Pseudomonas aeruginosa, a metabolically versatile gram-negative bacterium, has garnered attention for its ability to thrive in diverse environments and its capacity to produce pyocyanin, a secondary metabolite with multifunctional properties. Pyocyanin, a redox-active phenazine compound, plays a critical role in mediating the ecological competitiveness of P. aeruginosa through its antimicrobial, biofilm-modulating, and reactive oxygen species (ROS)-generating activities. Beyond its contributions to bacterial virulence, pyocyanin demonstrates significant potential in various industrial and biomedical applications due to its redox properties and ability to function under diverse environmental conditions. This study investigates the electrochemical behaviour and pH-dependent antimicrobial activity of pyocyanin to evaluate its applicability in environmental and medical fields. Soil-derived P. aeruginosa isolates were cultured for pyocyanin (PYO) production, and the pigment was characterized using UV-visible spectroscopy to get its spectral integrity. Electrochemical analysis through cyclic voltammetry revealed enhanced redox activity in acidic environments and stable functionality in alkaline conditions. Antimicrobial assays demonstrated that pyocyanin exhibited optimal activity at neutral to slightly alkaline pH, effectively inhibiting bacterial and fungal growth, while extreme acidic conditions reduced its efficacy. The findings highlight pyocyanins versatility as both a redox mediator and an antimicrobial agent. In medical contexts, its pH-sensitive activity aligns well with physiological conditions, offering promise for combating multidrug-resistant pathogens. Future optimization of pyocyanin biosynthesis, particularly through cost-effective and scalable methods, could unlock its full potential in biotechnological and therapeutic innovations.

microbiology↗

bioRxiv2024

Quantitative analyses of structure-function heterogeneity of individual mitochondrial components reveal an early role of small-mitochondrial-networks in priming neoplastic transformation

Lack of quantitative understanding of the marked heterogeneity of multifaceted mitochondria poses challenges in unraveling their translatable role. Here, we hierarchically untangled multilevel heterogeneity of mitochondrial networks and non-networks by simultaneously analysing their structure-function within single components and their units, in cells and tissues. Such mito-SinComp quantitative analyses revealed that redox levels of mitochondrial networks and their dramatic intra-network heterogeneity can be predicted by structural features through a translatable machine-learning approach. Mito-SinComp identified and quantitatively characterized a redox-tuned subpopulation of Small-Mitochondrial-Networks(SMNs) that specifies stemness. These SMNs are generated by severing of nodes of oxidized Hyperfused-Mitochondrial-Networks(HMNs), are ten-folds smaller with specific network complexity and elevated mt-DNA nucleoid abundance. Thus, HMN to SMN conversion supports elevated expression of mtDNA genes in establishing MT-ND1(redox)-KRT15(stemness) transcriptomic interaction, as revealed by coupled scRNA-seq. This stemness priming of non-transformed cells is sustained after neoplastic transformation and is detected in patient transcriptome, demonstrating translational relevance of SMNs.

cell biology↗

bioRxiv2024

Insights from Molecular Docking and Dynamics Simulations of P2RX7-????Syn Complex

Alpha-synucleinopathies, characterized by extracellular alpha-synuclein (Syn) accumulation and aggregation, have been linked to neurological disorders including Parkinsons disease (PD) and multiple system atrophy (MSA). Syn interacts with membrane proteins, phospholipids, and cholesterol, leading to membrane damage and inflammation. This interaction heightens the likelihood of Syn engaging with P2RX7, a non-selective cationic transmembrane receptor that is primarily overexpressed in immune and neural cells. Activation of P2RX7 by Syn is implicated in neuronal degeneration, potentially causing pore dilation and increased inflammation. However, the precise molecular mechanisms and binding sites for this interaction, as well as the conformational dynamics of P2RX7 in response to Syn, remain unclear. We attempted to elucidate the molecular mechanisms and binding sites for P2RX7-Syn interaction, by integrating the data curation, molecular docking, and molecular dynamics (MD) simulations coupled with structural analyses. We elucidated interactions between P2RX7 and the N-terminal domain (NTD) of Syn using cryo-EM structures of P2RX7 in both ATP-bound and unbound states and assessed how Syn influences P2RX7structural and functional dynamics. Initially, the analyses revealed that Syn interactomes are mainly involved in regulating mitochondrial homeostasis, while P2RX7 interactors are linked to receptor internalization and calcium transport. Molecular docking with six tools identified that Syn-NTD fragments preferentially bind to the proximal region of P2RX7 transmembrane domain. Microsecond all atom MD simulations in a POPS lipid bilayer showed significant atomic fluctuations, particularly in the head region, lower body, and large loop of P2RX7 cytoplasmic domain. Secondary structure analysis indicated unfolding in regions related to pore dilation and receptor desensitization. Further by contact-based and solvent accessibility analyses, along with protein structure network (PSN) studies, we identified crucial residues involved in Syn-P2RX7 interactions. This insight deepens our understanding of how Syn and P2RX7 interact, offering a detailed atomic view of the structural and functional changes that occur during these interactions. This understanding could advance our grasp of neurodegenerative diseases and be vital for devising future preventive and therapeutic strategies. Author summaryNeural homeostasis is crucial for neuron survival and function, with protein-protein interactions, particularly between Syn and P2RX7, playing a vital role. Accumulation of Syn can worsen neuronal damage through its interaction with P2RX7. Traditional biological experiments struggle with time-scale limitations, but advances in computational methods--like molecular dynamics (MD) simulations and protein structure network (PSN) analysis--allow detailed atomic-level study of these interactions. This study used these computational tools to explore the dynamics between Syn and P2RX7, aiming to uncover structural and functional changes relevant to protein interactions and neural damage. The findings contribute to understanding the dynamics of P2RX7-Syn interactions.

bioinformatics↗

bioRxiv2023

Cognitive outcome and its neural correlates after cardiorespiratory arrest in childhood

Hypoxia-ischaemia (HI) can result in structural brain abnormalities, which in turn can lead to behavioural deficits in various cognitive and motor domains, in both adult and paediatric populations. Cardiorespiratory arrest (CA) is a major cause of hypoxia-ischaemia in adults, but it is relatively rare in infants and children. While the effects of adult CA on brain and cognition have been widely studied, to date, there are no studies examining the neurodevelopmental outcome of children who suffered CA early in life. Here, we studied the long-term outcome of 28 children who suffered CA during infancy or childhood (i.e., before age 16). They were compared to a group of control participants (n = 28) matched for age, gender and socio-economic status. The patient group had impairments in the domains of memory, language and academic attainment (measured using standardised tests; impairment defined as a score > 1.5 standard deviations below the control group mean). Individual scores within the impaired range were most commonly found within the memory domain (79%), followed by attainment (50%), and language (36%). The patient group also had reduced whole brain grey matter volume, and reduced volume and fractional anisotropy of the white matter. In addition, lower performance on memory tests was correlated with bilaterally reduced volume of the hippocampi, thalami, and striatum, while lower attainment scores were correlated with bilateral reduction of fractional anisotropy in the superior cerebellar peduncle, the main output tract of the cerebellum. We conclude that patients who suffered early CA are at risk of developing specific cognitive deficits associated with structural brain abnormalities.

neuroscience↗

bioRxiv2022

Chaperonin activity of Plasmodium prefoldin complex is essential to guard proteotoxic stress response and presents a new target for drug discovery

The intraerythrocytic growth of malaria parasite is challenged by the presence of proteotoxic stress and intrinsically unstructured proteins in the cytoplasm due to formation of toxic heme during haemoglobin digestion. To overcome the unavoidable stress and maintain the cellular protein homeostasis, parasite encodes for a number of chaperones and co-chaperones. Here, we functionally characterize the Plasmodium falciparum prefoldins (PfPFD1-6), a hexameric co-chaperone complex, for their role in protein homeostasis. We demonstrate that PfPFD1-6 localise to cytosol of the parasite and the subunits perform an orchestrated interaction (-PFD3-PFD2-PFD1-PFD5-PFD6-PFD4-) to form an active jelly-fish like complex. Biperiden, an N-propylpiperidine analogue identified by chemotype search from FDA, strongly binds and restricts the formation of prefoldin complex and inhibited its interaction with the substrates, PfMSP-1 and -tubulin-I. Biperiden treatment potently inhibited the in vitro (IC50: 1M) and in vivo growth of malaria parasite. Thus, this study provides novel virtues towards understanding the role of PfPFDs in regulating protein homeostasis and opens new avenues for drug discovery against malaria.

molecular biology↗

bioRxiv2022

Human malaria parasite cold shock protein plays an essential role in asexual and sexual stage development and presents an excellent druggable target

Cold shock proteins are well characterized in bacteria, plants and humans, however there is no information on their existence and role in malaria parasite. Here, we have delineated the function of a novel cold shock protein of Plasmodium falciparum (Pf) which we have annotated PfCoSP. Our results show that recombinant PfCoSP has both DNA and RNA binding activity, and also interacts with alpha and beta tubulin of Pf. PfCoSP binds with RNA and alpha tubulin simultaneously to form a complex. Expression of PfCoSP was found during asexual blood stages and gametocyte stages of malaria parasite. PfCoSP expression up-regulates many folds upon cold treatment, suggesting its role during hypothermic cold shock. Interestingly, PfCoSP showed binding with human cold shock protein LIN28A inhibitor LI71 that also inhibits PfCSP -alpha/beta tubulin interactions. LI71 showed antimalarial activity against asexual blood stage and gametocyte stage suggesting its multi-stage, transmission-blocking potential. We propose that PfCoSP may form a workbench for translation during cold stress via its interactions with target mRNAs and the cytoskeleton protein tubulin.

molecular biology↗

bioRxiv2022

Sphingosine-1-phosphate regulates Plasmodium histone deacetylase activity and exhibits epigenetic control over cell death and differentiation

Histone deacetylases (HDACs) play a key role in cellular processes by the regulation of gene transcription. This study contributes a novel insight how Plasmodium falciparum HDAC (PfHDAC-1) is regulated by S1P produced by host erythrocyte SphK-1. The binding of S1P with endogenous nuclear extract PfHDAC-1 and recombinant PfHDAC-1 blocks their activity. A significant modulation in transcriptional regulation of P. falciparum HDAC regulated genes resulted upon inhibition of S1P production through blocking of hSphK-1 by clinical SphK-1 inhibitor PF-543. PF-543 led to profound decrease in S1P in the parasites nuclear fraction. The significant modulation of PfHDAC-1 regulated specific candidate genes related to gametocytogenesis, virulence and proliferation was observed in parasite treated with SphK-1 inhibitor, suggesting S1P targets PfHDAC-1 and participates in epigenetic regulation of these key cellular processes. The epigenetic modulation of parasite cell growth and differentiation by host provides a novel approach for the developmenthost-targeted therapeutics.

molecular biology↗

bioRxiv2022

Characterization of prohibitins as novel target to block asexual and sexual stage growth of Plasmodium falciparum

Prohibitins (PHBs) are highly conserved pleiotropic proteins as they have been shown to mediate key cellular functions. Here, we characterize PHBs encoding putative genes of Plasmodium falciparum by exploiting different orthologous models. We demonstrated that PfPHB1 (PF3D7_0829200) and PfPHB2 (PF3D7_1014700) are expressed in asexual and sexual blood stages of the parasite. Immunostaining indicated these proteins as mitochondrial residents as they were found to be localized as punctate foci. We further validated PfPHBs as organellar proteins residing in the Plasmodium mitochondria, where they interact with each other. Functional characterization was done in Saccharomyces cerevisiae orthologous model by expressing PfPHB1 and PfPHB2 in cells harboring respective mutants. The PfPHBs functionally complemented the yeast PHB1 and PHB2 mutants, where the proteins were found to be involved in stabilizing the mitochondrial DNA, retaining mitochondrial integrity and rescuing yeast cell growth. Further, Rocaglamide (Roc-A), a known inhibitor of PHBs and anti-cancerous agent, was tested against PfPHBs and as an antimalarial. Roc-A treatment retarded the growth of PHB1, PHB2, and ethidium bromide petite yeast mutants. Moreover, Roc-A inhibited growth of yeast PHBs mutants that were functionally complemented with PfPHBs, validating P. falciparum PHBs as one of the molecular targets for Roc-A. Roc-A treatment led to growth inhibition of artemisinin-sensitive (3D7), artemisinin-resistant (R539T) and chloroquine-resistant (RKL-9) parasites in nanomolar ranges. The compound was able to retard gametocyte growth with significant morphological aberrations. Based on our findings, we propose the presence of functional mitochondrial PfPHB1 and PfPHB2 in P. falciparum and their druggability to block parasite growth.

molecular biology↗

bioRxiv2020

Antimalarial and Plasmodium falciparum serpentine receptor 12 targeting effect of a purinergic receptor antagonist FDA approved drug

Intraerythrocytic stages of Plasmodium falciparum responsible for all clinical manifestations of malaria are regulated by array of signaling cascades and effector molecules that represents attractive targets for antimalarial therapy. G-protein coupled receptors (GPCRs) are druggable targets in treatment of various pathological conditions however there is limited understanding about the role of GPCRs in malaria pathogenesis. In Plasmodium, serpentine receptors (PfSR1, PfSR10, PfSR12 and PfSR25) with GPCR like membrane topology have been reported with the finite knowledge about their potential as antimalarial targets. Herein we evaluated the druggability of PfSR12 using FDA approved P2Y type of purinergic signaling antagonist, Prasugrel. Blocking of purinergic receptor signaling resulted in inhibition of growth and development of P. falciparum. Progression studies indicated the inhibitory effect of purinergic signalling inhibitor begins in late erythrocyte stages predominantly in the schizonts. Furthermore, purinoreceptor inhibitor blocked in vivo growth of malaria parasite in mouse experimental model. The localization of PfSR1, PfSR10, PfSR12 and PfSR25 was analyzed by immunofluorescence assays. The putative purinergic receptor PfSR12 is found to be expressed in late intraerythrocytic stages. Prasugrel, a generic purinoreceptor inhibitor and agonist ATP showed specific binding to recombinant PfSR12 confirming it as purinergic receptor. This study indicates the presence of P2Y type of purinergic signaling in growth and development of malaria parasite and suggests PfSR12 as putative purinergic receptor.

microbiology↗

bioRxiv2020

PRAK-03202: A triple antigen VLP vaccine candidate against SARS CoV-2

The rapid development of safe and effective vaccines against SARS CoV-2 is the need of the hour for the coronavirus outbreak. Here, we have developed PRAK-03202, the worlds first triple antigen VLP vaccine candidate in a highly characterized S. cerevisiae-based D-CryptTM platform, which induced SARS CoV-2 specific neutralizing antibodies in BALB/c mice. Immunizations using three different doses of PRAK-03202 induces antigen specific (Spike, envelope and membrane proteins) humoral response and neutralizing potential. PBMCs from convalescent patients, when exposed to PRAK-03202, showed lymphocyte proliferation and elevated IFN-{gamma} levels suggestive of conservation of epitopes and induction of T helper 1 (Th1)-biased cellular immune responses. These data support the clinical development and testing of PRAK-03202 for use in humans.

immunology↗