Biology subjects

Sah, R. K.

Publications and source records attributed to Sah, R. K..

6 recordsLinked to original sources

bioRxiv2026

RBFOX2 restrains oncogenic cell plasticity in Group 3 medulloblastoma

Cancer cell plasticity underlies tumor progression, metastasis and therapeutic resistance, yet how RNA-binding proteins regulate malignant state transitions remains poorly defined. Here, we identify the splicing regulator RBFOX2 as a suppressor of oncogenic cell plasticity in Group 3 medulloblastoma (MB). OTX2 antagonizes RBFOX2 by directing an opposing alternative splicing program that mirrors developmental origins and controls cytoskeletal dynamics and cell state transitions. Mechanistically, OTX2 alters the RBFOX2 RNA-binding landscape, limiting RBFOX2 engagement at cytoskeletal loci and suppressing exon inclusion. RBFOX2 loss rewires splicing and transcriptional outputs to promote highly plastic proliferative, mesenchymal-like and undifferentiated cellular states associated with enhanced oncogenic properties. Consistent with these findings, RBFOX2low states mark highly plastic cell populations in patient tumors and xenografts, positioning RBFOX2 as a determinant of malignant cell stability. Together, these findings establish RBFOX2 as a developmental gatekeeper that restrains malignant cell plasticity through coordinated control of cytoskeletal gene programs.

cancer 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

'Erythritol, a safe natural sweetener exhibits multi-stage anti-malarial activity by blocking Plasmodium falciparum membrane transporter 'aquaporin

The increased resistance of human malaria parasite Plasmodium falciparum to currently used drugs necessities the development of novel anti-malarials. In the present study, we examine the potential of erythritol, a sugar substitute, for therapeutic intervention that target a multifunctional transporter protein Plasmodium aquaglyceroporin (PfAQP) responsible for maintaining hydro-homeostasis. We show that erythritol effectively inhibited growth and progression of asexual blood stage malaria parasite by suppressing invasion and egress processes. It inhibited the liver stage (sporozoites) and transmission stage parasite (gametocytes) development that suggest its multi-stage, transmission-blocking potential. Interestingly, erythritol inhibited in vivo growth of malaria parasite in mouse experimental model. It was more effective in inhibiting parasite growth both in vivo and in vitro when tested together with a known anti-malarial artesunate. No Evans blue staining in treated mice indicated erythritol mediated protection of blood-brain barrier integrity in mice infected with P. berghei. Additionally, erythritol showed cytokine-modulating effect which suggest its direct effect on the host immune system. Our results of cellular thermal shift assay and ammonia detection assay demonstrate that erythritol binds with PfAQP and reduce the amount of ammonia release across the parasite respectively. We performed functional complementation assays which suggest that PfAQP expression in yeast mutant restores its growth in hyperosmotic conditions but showed reduced growth in the presence of erythritol, suggesting erythritol as an inhibitor of PfAQP. Overall, our data bestow erythritol as a promising new lead compound with an attractive antimalarial profile and could possibly be combined with known drugs without losing its efficacy.

molecular biology↗

bioRxiv2022

Multistage and transmission-blocking tubulin targeting potent antimalarial discovered from the open access MMV Pathogen Box

Development of resistance to current antimalarial therapies remains a significant source of concern. To address this risk, new drugs with novel targets in distinct developmental stages of Plasmodium parasites are required. In our current work, we have targeted P. falciparum Tubulin (PfTubulin) proteins which represent some of the potential drug targets for malaria chemotherapy. Plasmodial Microtubules play a crucial role during parasite proliferation, growth, and transmission, which render them highly desirable targets for the development of next-generation chemotherapeutics. Towards this, we have evaluated the antimalarial activity of Tubulin targeting compounds received from the Medicines for Malaria Venture (MMV) "Pathogen Box" against the human malaria parasite, P. falciparum (including 3D7, RKL-9 (Chloroquine resistant) and R539T (Artemisinin resistant) strains). At nanomolar concentrations, filtered out compounds exhibited pronounced multistage antimalarial effects across the parasite life cycle, including intra-erythrocytic blood stages, liver stage parasites, gametocytes and ookinetes. Concomitantly, these compounds were found to impede male gamete ex-flagellation, thus showing transmission-blocking potential of these compounds. Target mining of these potent compounds, by combining in silico, biochemical and biophysical assays, implicated PfTubulin as their molecular target, which may possibly act by disrupting microtubule assembly dynamics by binding at the interface of -{beta}Tubulin-dimer. Further, promising ADME profile of the parent scaffold supported its consideration as a lead compound for further development. Thus, our work highlights the potential of targeting PfTubulin proteins in discovering and developing next-generation, multistage antimalarial agents for treating Multi-Drug Resistant (MDR) malaria parasites. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/488926v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@ae9713org.highwire.dtl.DTLVardef@40950forg.highwire.dtl.DTLVardef@1fa34f2org.highwire.dtl.DTLVardef@1aa1cae_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2019

Plasmodium falciparum growth is regulated by Sphingosine 1 phosphate produced by Host Erythrocyte Membrane Sphingosine kinase 1

Sphingosine-1-phosphate (S1P) a bioactive lipid is produced in its primary reservoir, erythrocytes by an enzyme Sphingosine kinase-1 (SphK-1). The activation of such kinases and the subsequent S1P generation and secretion in the blood serum represent a major regulator of many cellular signaling cascades. Orthologue of sphingosine kinases 1 and 2 (SphK-1 and 2) that catalyze the phosphorylation of sphingosine generating S1P are not present in malaria parasite. The malaria parasite, Plasmodium falciparum, is an intracellular obligatory organism that reside in the human erythrocyte during its blood stage life cycle and orchestrates many metabolic interactions with host for its survival. Given the regulatory role of S1P, we targeted host SphK-1 by a generic pharmacological inhibitor N,N-Dimethyl-sphingosine (DMS) and analyzed growth of intra-erythrocytic parasite. We found that reducing S1P levels by inhibiting host SphK-1 activity led to halted parasite growth and ultimately cell death. Reduced intracellular S1P levels were attributed to decreased glycolysis marked by the low uptake of glucose by parasite and by less production of lactate, a byproduct of glycolysis. Reduced glycolysis was mediated by decrease translocation of the glycolytic enzyme, Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) to the cytosol of infected erythrocytes and cell death. Knocking down of erythrocyte SphK-1 is not lethal to the host and being a host encoded enzyme, targeting it with safe and specific drugs will not lead to the problem of resistance; thus, SphK-1 represents a potent target for the development of therapeutics against intra-erythrocytic P. falciparum.\n\nAuthor SummaryErythrocytes membrane enzyme Sphingosine kinase-1 (SphK-1) produces Sphingosine-1-phosphate (S1P) a bioactive lipid by phosphorylation of Sphingosine (Sph). S1P generated by activation of SphK is prosurvival signal and regulate cell growth. The malaria parasite, Plasmodium falciparum, is an intracellular obligatory pathogen that reside in erythrocyte during its blood stage life cycle and orchestrates many metabolic interactions with its host erythrocytes for survival. Orthologue of SphK-1/ 2 are not present in malaria parasite, therefore treatment with SphK inhibitor targeted host SphK-1 and led to reduced S1P level. The reduction in host S1P led to halted parasite growth and cell death. Furthermore, reduced erythrocyte S1P levels led to decreased glycolysis marked by the low uptake of glucose by parasite and by less production of lactate. Erythrocyte SphK-1 being a host encoded enzyme, is resistance safe and represents a potent target for the development of therapeutics against intra-erythrocytic P. falciparum.

cell biology↗

bioRxiv2019

Transcriptome Profiling of Mouse Brain and Lung under Dip2A Regulation Using RNA-Sequencing

Disconnected interacting 2 homolog A (DIP2A) gene is highly expressed in nervous system and respiratory system of developing embryos. However, genes regulated by Dip2a in developing brain and lung have not been systemically studied. Transcriptome of brain and lung in embryonic 19.5 day (E19.5) were compared between wild type and Dip2a-/- mice. Total RNAs were extracted from brain and lung of E19.5 embryos for RNA-Seq. Clean reads were mapped to mouse reference sequence (mm9) using Tophat and assembled into transcripts by Cufflinks. Edge R and DESeq were applied to identify differentially expressed genes (DEGs) and annotated under GO, COG, KEGG and TF. An average of 50 million reads per sample was mapped to the reference sequence. A total of 214 DEGs were detected in brain (82 up and 132 down) and 1900 DEGs in lung (1259 up and 641 down). GO enrichment analysis indicated that DEGs in both Brain and Lung were mainly enriched in biological processes DNA-templated transcription and Transcription from RNA polymerase II promoter, multicellular organism development, cell differentiation and apoptotic process. In addition, COG classification showed that both were mostly involved in Replication, Recombination and Repair, Signal transduction and mechanism, Translation, Ribosomal structure and Biogenesis and Transcription. KEGG enrichment analysis showed that brain was mainly enriched in Thryoid cancer pathway whereas lung in Complement and Coagulation Cascades pathway. Transcription factor (TF) annotation analysis identified Zinc finger domain containing (ZF) proteins were mostly regulated in lung and brain. Interestingly, study identified genes Skor2, Gpr3711, Runx1, Erbb3, Frmd7, Fut10, Sox11, Hapln1, Tfap2c and Plxnb3 from brain that play important roles in neuronal cell maturation, differentiation and survival; genes Hoxa5, Eya1, Ctsh, Erff1, Lama1, Lama2, Rspo2, Sox11, Spry4, Shh, Igf1 and Wnt7a from lung are important in lung development and morphogenesis. Expression levels of the candidate genes were validated by qRT-PCR. Genome wide transcriptional analysis using wild type and Dip2a knockout mice in brain and lung at embryonic day 19.5 (E19.5) provided a genetic basis of molecular function of these genes.

genetics↗