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Das, B.

Publications and source records attributed to Das, B..

At least 37 records · Page 2Linked to original sources
bioRxiv2024

(p)ppGpp and DksA play crucial role in reducing the efficacy of b-lactam antibiotics by modulating bacterial membrane permeability

The key signaling molecules in the bacterial stress sensing pathway, the alarmone (p)ppGpp and transcription factor DksA, help in survival during nutritional deprivation and exposure to xenobiotics by modulating cellular metabolic pathways. In Vibrio cholerae, (p)ppGpp metabolism is solely linked with the functions of three proteins: RelA, SpoT, and RelV. At threshold or elevated concentrations of (p)ppGpp, the level of cellular metabolites and proteins in the presence and absence of DksA in V. cholerae and other bacteria has not yet been comprehensively studied. We engineered the genome of V. cholerae to develop DksA null mutants in the presence and absence of (p)ppGpp biosynthetic enzymes. We observed a higher sensitivity of the (p)ppGpp0{Delta}dksA V. cholerae mutant to different -lactam antibiotics compared to the wild-type (WT) strain. Our whole-cell metabolomic and proteome analysis revealed that the cell membrane and peptidoglycan biosynthesis pathways are significantly altered in the (p)ppGpp0, {Delta}dksA, and (p)ppGpp0{Delta}dksA V. cholerae strains. Further, the mutant strains displayed enhanced inner and outer membrane permeability in comparison to the WT strains. These results directly correlate with the tolerance and survival of V. cholerae to -lactam antibiotics. These findings may help in the development of adjuvants for -lactam antibiotics by inhibiting the functions of stringent response modulators. ImportanceThe (p)ppGpp biosynthetic pathway is widely conserved in bacteria. Intracellular levels of (p)ppGpp and the transcription factor DksA play crucial roles in bacterial multiplication and viability in the presence of antibiotics and/or other xenobiotics. The present findings have shown that (p)ppGpp and DksA significantly reduces the efficacy of -lactam and other antibiotics by modulating the availability of peptidoglycan and cell membrane-associated metabolites by reducing membrane permeability. Nevertheless, the whole-cell proteome analysis of (p)ppGpp0, {Delta}dksA, and (p)ppGpp0{Delta}dksA strains identified the biosynthetic pathways and associated enzymes that are directly modulated by the stringent response effector molecules. Thus, the (p)ppGpp metabolic pathways and DksA could be a potential target for increasing the efficacy of antibiotics and developing antibiotic adjuvants.

microbiology↗
bioRxiv2024

Preclinical assessment of MAGMAS inhibitor as a potential therapy for pediatric medulloblastoma

Medulloblastoma, the most common pediatric brain malignancy, has Sonic Hedgehog (SHH) and non-SHH group3 subtypes. MAGMAS (Mitochondrial Associated Granulocyte Macrophage colony-stimulating factor Signaling molecules) encode for mitochondrial import inner membrane translocase subunit and is responsible for translocation of matrix proteins across the inner membrane. We previously reported that a small molecule MAGMAS inhibitor, BT9, decreases cell proliferation, migration, and oxidative phosphorylation in adult glioblastoma cell lines. The aim of our study was to investigate whether the chemotherapeutic effect of BT9 can be extended to pediatric medulloblastoma. MethodsMultiple in vitro assays were performed using human DAOY (SHH activated tp53 mutant) and D425 (non-SHH group 3) cells. The impact of BT9 on cellular growth, death, migration, invasion, and metabolic activity were quantified using MTT assay, TUNEL staining, scratch wound assay, Matrigel invasion chambers, and seahorse assay, respectively. Survival following 50mg/kg BT9 treatment was assessed in vivo in immunodeficient mice intracranially implanted with D425 cells. ResultsCompared to control, BT9 treatment led to a significant reduction in medulloblastoma cell growth (DAOY, 24hrs IC50: 3.6uM, 48hrs IC50: 2.3uM, 72hrs IC50: 2.1uM; D425 24hrs IC50: 3.4uM, 48hrs IC50: 2.2uM, 72hrs IC50: 2.1uM) and a significant increase in cell death (DAOY, 24hrs p=0.0004, 48hrs p<0.0001; D425, 24hrs p=0.0001, 48hrs p=0.02). In DAOY cells, 3uM BT9 delayed migration, and significantly decreased DAOY and D425 cells invasion (p < 0.0001). Our in vivo study, however, did not extend survival in xenograft mouse model of group3 medulloblastoma compared to vehicle-treated controls. ConclusionsOur in vitro data showed BT9 antitumor efficacy in DAOY and D425 cell lines suggesting that BT9 may represent a promising targeted therapeutic in pediatric medulloblastoma. These data, however, need to be further validated in animal models.

cancer biology↗
bioRxiv2023

Non-canonical NF-κB signaling in dendritic cells promotes intestinal inflammation by restraining the tolerogenic β-catenin-Raldh2 axis

Dendritic cell (DC) dysfunctions exacerbate intestinal pathologies. However, the mechanisms compromising DC-mediated immune controls remain unclear. We found that intestinal DCs from mice subjected to experimental colitis possessed heightened non-canonical NF-{kappa}B signaling, which activates the RelB:p52 heterodimer. Genetic inactivation of this pathway in DCs alleviated inflammation in colitogenic mice. Unexpectedly, RelB:p52 deficiency diminished the transcription of Axin1, a critical component of the {beta}-catenin destruction complex. This reinforced {beta}-catenin-driven expression of Raldh2, which imparts tolerogenic DC attributes by promoting retinoic acid (RA) synthesis. Indeed, DC-specific non-canonical NF-{kappa}B impairment improved the colonic frequency of Tregs and IgA+ B cells, which fostered luminal IgA and eubiosis. Introducing {beta}-catenin haploinsufficiency in non-canonical NF-{kappa}B-deficient DCs moderated Raldh2 activity, reinstating colitogenic sensitivity in mice. Finally, IBD patients displayed a deleterious non-canonical NF-{kappa}B signature in intestinal DCs. In sum, we establish a DC network that integrates non-canonical NF-{kappa}B signaling to subvert RA metabolic pathway in fueling intestinal inflammation. Significance (100)Distorted dendritic cell (DC) functions have been implicated in aberrant intestinal inflammation; however, the underlying mechanism remains obscure. We discovered that the non-canonical NF-{kappa}B pathway exacerbates inflammation in the colitogenic gut by downmodulating {beta}-catenin-driven synthesis of Raldh2 in DCs. Raldh2 represents a key enzyme involved in the production of tolerogenic retinoic acid in intestinal DCs. Beyond regulating immune genes, therefore, non-canonical NF-{kappa}B signaling appears to instruct retinoic acid-mediated control of gut health. While we illustrate a DC network integrating immune signaling and micronutrient metabolic pathways in the intestine, our finding may have broad relevance for nutritional interventions in inflammatory ailments. eToCDeka and Kumar et al. illustrate a DC-circuitry that exacerbates intestinal inflammation in IBD patients and colitogenic mice. Non-canonical NF-{kappa}B signaling restrains {beta}-catenin in DCs to downmodulate Raldh2, which promotes tolerogenic RA synthesis, leading to diminished Treg and IgA+ cell frequencies in the gut. HighlightsO_LIAberrant intestinal inflammation is associated with and exacerbated by non-canonical NF-{kappa}B signaling in DCs. C_LIO_LINon-canonical signaling restrains the tolerogenic {beta}-catenin-Raldh2 axis in DCs by upregulating Axin1. C_LIO_LIDC-specific RelB:p52 impairment promotes {beta}-catenin-dependent Treg accumulation in the gut. C_LIO_LIA DC defect of non-canonical signaling causes {beta}-catenin-dependent increase in luminal sIgA, fostering the gut microbiome. C_LI One sentenceThe non-canonical NF-{kappa}B pathway fuels intestinal inflammation by waning the tolerogenic {beta}-catenin-Raldh2-retinoic acid axis in DCs.

immunology↗
bioRxiv2023

From the Wild to the City: How Domestication and Urbanization Reshape Animal Gut Microbiome

This review explores the profound effects of domestication and urbanization on the gut microbiota of animals. It delves into the complex interplay between these two processes and their transformative impact on the microorganisms residing in the gastrointestinal tracts of a wide range of species. Domestication, the centuries-old practice of taming and breeding animals for human use, has led to significant shifts in the gut microbiomes of domesticated animals. This shift is a result of altered diets, living conditions, and reduced exposure to natural environments. The paper examines the consequences of these changes on animal health, behavior, and their adaptation to domestic life. Conversely, urbanization, characterized by the rapid expansion of cities and human habitats, has driven wild animals to adapt to urban environments. This review investigates how the urban landscape, pollution, and dietary changes reshape the gut microbiomes of urban wildlife. It explores the potential implications of these alterations on the animals resilience to urban stressors and disease. Drawing parallels between domestication and urbanization, the paper reveals intriguing similarities and differences in gut microbiome transformations across various species. It also assesses the broader implications of these shifts on ecological dynamics, zoonotic disease transmission, and the potential for microbial interactions between domesticated animals, urban wildlife, and humans. Ultimately, this review consolidates current knowledge on the topic, shedding light on the shared mechanisms and unique adaptations that drive microbial changes in animals undergoing domestication and those adapting to urban environments. It concludes with a discussion of the implications for animal conservation, animal-human interactions, and the One Health perspective, emphasizing the importance of understanding these intricate icrobial relationships in our ever-changing world. By enhancing our comprehension of these complex dynamics, this paper contributes to the growing body of knowledge that informs our coexistence with the animals we share our lives and cities with, highlighting the critical role of gut microbiota in these processes.

ecology↗
bioRxiv2023

Fusobacterium nucleatum present in the saliva of oral cancer subjects can activate niche defense of oral squamous cell carcinoma

Oral cancer is a subset of head and neck cancer (HNC), has a high incidence rate in this malignancy group. Cancer Stem Cells (CSCs) are population of the heterogeneous malignant cells present within oral tumor microenvironment. CSCs stemness permits them to control several signaling pathways and so play a role in cancer progression and relapse. A number of studies have recently demonstrated the presence of specific oral bacteria populations and their lipopolysaccharides (LPS) in the tumor microenvironment. The precise mechanism of action in the initiation, progression, and relapse of oral cancer by the oral bacteria are yet to be determined. We previously reported pathogenic bacterial internalization in CSCs. Based on the findings; we have developed an in-vitro model to investigate how oral microbiota may integrate into the tumor microenvironments CSC population and control its activity. Notably, we found that live bacteria and their LPS, mostly Fusobacterium nucleatum isolated from clinical subjects, were capable of invading CSCs in the in-vitro experimental design setup. Post the host-pathogen interaction; it enabled the activation of a niche modulatory tumor stemness defense (TSD) phenotype in the CSCs. These aggressive CSCs with the TSD phenotype have been found to have a critical role in the progression and relapse of oral cancer.

cancer biology↗
bioRxiv2023

Antisense RNA C9orf72 Hexanucleotide Repeat Associated With Amyotrophic Lateral Sclerosis and Frontotemporal Dementia Forms A Triplex-Like Structure and Binds Small Synthetic Ligand

The abnormal expansion of GGGGCC/CCCCGG hexanucleotide repeats (HR) in C9orf72 is associated with familial amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Structural polymorphisms of HR result in the multifactorial pathomechanism of ALS/FTD. Consequently, many ongoing studies are focused at developing therapies targeting pathogenic HR RNA. One of them involves small molecules blocking the sequestration of important proteins, preventing the formation of toxic nuclear foci. However, rational design of potential therapeutics is hindered by limited number of structural studies of RNA-ligand complexes. We determined the crystal structure of antisense HR RNA in complex with ANP77 ligand and in the free form. HR RNA folds into a triplex structure composed of four RNA chains. ANP77 interacted with two neighboring single-stranded cytosines to form pseudo-canonical base pairs by adopting sandwich-like conformation and adjusting the position of its naphthyridine units to the helical twist of the RNA. In the unliganded structure, the cytosines formed a peculiar triplex i-motif, assembled by trans C*C+ pair and a third cytosine located at the Hoogsteen edge of the C*C+ pair. These results extend our knowledge of the structural polymorphisms of HR and can be used for the rational design of small molecules targeting disease-related RNAs.

molecular biology↗
bioRxiv2023

Differential expression of miRNAs between Young-Onset and Late-Onset Indian colorectal carcinoma patients

Early-Onset Colorectal Carcinoma (EOCRC) is a growing concern as reports indicate a worldwide increase in the incidence of CRC among young adults (<50 years old). In an effort to understand the different mode of pathogenesis in young-onset CRC, we performed a pilot study wherein we looked at colorectal tumors from both young (< 50 years old) and old patients (>55 years old) and screened them to eliminate tumors positive for Microsatellite Instability (MSI) and showing activation of the Wnt pathway, known canonical factors in CRC pathogenesis. RNA isolated from EOCRC and Late-Onset (LOCRC) tumors and paired normal tissues without MSI, nuclear {beta}-catenin and APC mutations were sent for small RNA seq to identify miRNA alterations between the two subsets. Comparative analysis revealed differential expression of 23 miRNAs specific to EOCRC and 11 miRNAs specific to LOCRC. We validated the top 10 EOCRC DEMs in TCGA-COAD cohorts followed by validation in additional EOCRC and LOCRC cohorts. Our integrated analysis revealed upregulation of hsa-miR-1247-3p, hsa-miR-148a-3p and hsa-miR-27a-5p and downregulation of hsa-miR-326 between the two subsets. Experimentally validated targets of the above miRNAs were compared with differentially expressed genes in the TCGA dataset to identify targets with physiological significance in EOCRC development. Our analysis revealed downregulation of epithelial gene expression and intercellular junction proteins potentially leading to dissolution of epithelial intercellular junctions in EOCRC development and EMT progression. Upregulated targets included genes whose expression have been reported to correlate with CRC tumor invasion, liver metastasis, disease recurrence and poor prognosis.

cancer biology↗
bioRxiv2023

A signalling rheostat controls chromosome segregation fidelity during early lineage specification and neurogenesis by modulating DNA replication stress

The development and homeostasis of organisms rely on the correct replication, maintenance and segregation of their genetic blueprints. How these intracellular processes are monitored across generations of different human cellular lineages, and why the spatio-temporal distribution of mosaicism varies during development remain unknown. Here, we identify several lineage specification signals that regulate chromosome segregation fidelity in both human and mouse pluripotent stem cells. Through epistatic analyses, we find that that WNT, BMP and FGF form a signalling "rheostat" upstream of ATM that monitors replication fork velocity, origin firing and DNA damage during S-phase in pluripotency, which in turn controls spindle polymerisation dynamics and faithful chromosome segregation in the following mitosis. Cell signalling control of chromosome segregation fidelity declines together with ATM activity after pluripotency exit and specification into the three human germ layers, or further differentiation into meso- and endoderm lineages, but re-emerges during neuronal lineage specification. In particular, we reveal that a tug-of-war between FGF and WNT signalling in neural progenitor cells results in DNA damage and chromosome missegregation during cortical neurogenesis, which could provide a rationale for the high levels of mosaicism in the human brain. Our results highlight a moonlighting role of morphogens, patterning signals and growth factors in genome maintenance during pluripotency and lineage specification, which could have important implications for our understanding on how mutations and aneuploidy arise during human development and disease. One sentence summaryDevelopmental signals link genome maintenance to cell fate

cell biology↗
bioRxiv2023

Uip4 governs growth phase-dependent organelle remodeling by modulating Saccharomyces cerevisiae lipidome

When yeast cells are exposed to nutrient-limiting conditions, they undergo transcriptional and translational reprogramming that results in the remodelling of metabolite utilization and organelle architecture. Organelle membranes and contacts also undergo structural and functional alterations. In the budding yeast Saccharomyces cerevisiae, regulated expression of Uip4 is shown to be a critical effector of nuclear shape and function, particularly during the stationary phase. In this work, we demonstrate that the absence of UIP4 affects the morphology of multiple other organelles including mitochondria, endoplasmic reticulum, vacuole and the distribution of lipid droplets. The results show that modulating carbon source, nitrogen availability and cellular energy state impact Uip4 expression. This expression of Uip4 is controlled by the transcription factor Msn2, downstream of Sch9 signaling pathway. Cells lacking Uip4 have poor survival in the stationary phase of the growth cycle. These cellular changes are concomitant with dysregulation of the global lipidome profile and aberrant organelle interaction. We propose that the dynamic and regulated expression of Uip4 is required to maintain lipid homeostasis and organelle architecture which is ultimately required to survive in nutrient limiting conditions such as stationary phase.

cell biology↗
bioRxiv2023

Both behavior-manipulating and non-manipulating entomopathogenic fungi affect rhythmic gene expression in carpenter ant foragers upon infection

BackgroundBehavioral plasticity in the nocturnal ant Camponotus floridanus is associated with changes in daily rhythms of core clock and clock-controlled genes in the brain. Plasticity in clock-controlled output, although adaptive, has been hypothesized to be a target for parasites that change host behavior in a timely manner to complete their life cycle. This study aims to explore this hypothesis by characterizing how the transcriptomic rhythms of the ant host change upon infection by a behavior manipulating parasite. We compared and contrasted the daily gene expression profile of uninfected C. floridanus ant heads to ants infected by a manipulating fungal parasite Ophiocordyceps camponoti-floridani and a non-manipulating fungus Beauveria bassiana, to test if changes to host clock and clock-controlled gene expression are specific to behavioral modifying diseases, or if such changes are a general hallmark of infectious diseases. ResultsThe repertoire of genes oscillating every 24h in the ant heads showed almost three-fold reduction during O. camponoti-floridani infections, as compared to uninfected controls. Control-like nocturnal activity of 24h-rhythmic genes was maintained during O. camponoti-floridani infections, but not in B. bassiana infected ant heads. Half of all genes that showed 24h rhythms in the heads and brains of uninfected ants displayed highly synchronized changes in their rhythmic expression during both diseases, but in a species-specific manner. Network analyses revealed that both fungal parasites affected the same links between behavioral plasticity and clock output, albeit in a different manner. ConclusionChanges to clock-controlled transcriptomic rhythms of hosts might be a general hallmark of infectious diseases. However, the infection-associated changes to clock-controlled rhythms of the host are species-specific, and likely depends on the life history strategies used by the parasite.

animal behavior and cognition↗
bioRxiv2023

Using RNASeq to investigate the involvement of the Ophiocordyceps clock in ant host infection and behavioral manipulation

IntroductionParasites can modify host behavior to ensure their own growth and transmission. Multiple species of the fungi Ophiocordyceps infect ants, but in a species-specific manner; one fungal species co-evolved to successfully modify the behavior of one ant species. However, several characteristics of the behavioral modification seem to be similar across different Ophiocordyceps-ant systems, including a preference for the time of the day for manipulating host behavior. In this study, we explored the various mechanisms via which the circadian clock of Ophiocordyceps might be playing a role in modifying host behavior. We studied O. camponoti-floridani that modifies the behavior of its ant host Camponotus floridanus. To separate the role of the clock in behavior manipulation, from its role in growth and survival, we compared the daily gene expression profile of O. camponoti-floridani to a generalist, non-manipulating fungal parasite, Beauveria bassiana, which also successfully infects the same ant host. ResultsMajority of the 24h rhythmic O. camponoti-floridani genes show peak expression before or at the transitions between light and dark. Rhythmic genes in O. camponoti-floridani, for which B. bassiana lacks an ortholog, were overrepresented for enterotoxin genes. Around half of all genes that show 24h rhythms in either O. camponoti-floridani or B. bassiana showed a consistent difference in their temporal pattern of daily expression. At the halfway mark in O. camponoti-floridani infections, when diseased ants show a loss of 24h rhythms in daily foraging, several fungal clock genes, including Frequency, showed differential expression. Network analyses revealed a single gene cluster, containing White Collar 1 and 2, that showed overrepresentation for genes oscillating every 24h in liquid culture as well as genes differentially expressed while growing inside the ant head. ConclusionThis study identifies several sets of putatively clock-controlled genes and biological processes in O. camponoti-floridani that likely plays a role in modifying the behavior of its ant host. Differential expression of O. camponoti-floridani clock genes or 24h-rhythmic genes during infection is suggestive of either a loss of daily rhythm or a change in the amplitude of rhythmic gene expression. Both possibilities would suggest that a disease-associated change occurs to the functioning of the O. camponoti-floridani clock, and its output, while the fungi grows inside the ant head.

molecular biology↗
bioRxiv2022

Ancestral SARS-CoV-2 driven antibody repertoire diversity in an unvaccinated individual correlates with expanded neutralization breadth

Understanding the quality of immune repertoire triggered during natural infection can provide vital clues that form the basis for development of humoral immune response in some individuals capable of broadly neutralizing pan SARS-CoV-2 variants. We assessed the diversity of neutralizing antibody responses developed in an unvaccinated individual infected with ancestral SARS-CoV-2 by examining the ability of the distinct B cell germline-derived monoclonal antibodies (mAbs) in neutralizing known and currently circulating Omicron variants by pseudovirus and authentic virus neutralization assays. The ability of the antibodies developed post vaccination in neutralizing Omicron variants was compared to that obtained at baseline of the same individual and to those obtained from Omicron breakthrough infected individuals by pseudovirus neutralization assay. Broadly SARS-CoV-2 neutralizing mAbs representing unique B cell lineages with non-overlapping epitope specificities isolated from a single donor varied in their ability to neutralize Omicron variants. Plasma antibodies developed post vaccination from this individual demonstrated neutralization of Omicron BA.1, BA.2 and BA.4 with increased magnitude and found to be comparable with those obtained from other vaccinated individuals who were infected with ancestral SARS-CoV-2. Development of B cell repertoire capable of producing antibodies with distinct affinity and specificities for the antigen immediately after infection capable of eliciting broadly neutralizing antibodies offers highest probability in protecting against evolving SARS-CoV-2 variants. ImportanceDevelopment of robust neutralizing antibodies in SARS-CoV-2 convalescent individuals is known, however varies at population level. We isolated monoclonal antibodies from an individual infected with ancestral SARS-CoV-2 in early 2020 that not only varied in their B cell lineage origin but also varied in their capability and potency to neutralize all the known VOC and currently circulating Omicron variants. This indicated establishment of unique lineages that contributed in forming B cell repertoire in this particular individual immediately following infection giving rise to diverse antibody responses that could compensate each other in providing broadly neutralizing polyclonal antibody response. Individuals who were able to produce such potent polyclonal antibody responses after infection have a higher chance of being protected from evolving SARS-CoV-2 variants.

immunology↗
bioRxiv2022

The Rab GTPase Ypt1p governs the activation of Unfolded Protein Response (UPR) in Saccharomyces cerevisiae by promoting the preferential nuclear degradation of pre-HAC1 mRNA

Induction of unfolded protein response (UPR) involves activation of transcription factor Hac1p that facilitates the transactivation of genes encoding ER-chaperones. Hac1p is encoded by HAC1 pre-mRNA harboring an intron and a bipartite element (BE) at its 3'-UTR. This precursor RNA undergoes a reversible and differential intra-nuclear mRNA decay by the nuclear exosome/CTEXT at various phases of UPR. In this investigation, using a combination of genetic, and biochemical approach, the Rab-GTPase Ypt1p is demonstrated to control UPR signaling dynamics. Regulation of UPR by Ypt1p relies on its characteristic nuclear localization in absence of ER-stress resulting in its strong association with pre-HAC1 mRNA at its 3'-UTR that promotes sequential recruitments of Nrd1-Nab3p-Sen1p (NNS) complex [->] CTEXT [->] the nuclear exosome onto the pre-HAC1 mRNA that is accompanied by its rapid and selective nuclear decay. This accelerated 3'[->]5' mRNA decay produces a pre-HAC1 mRNA pool lacking the functional BE thus causing its inefficient targeting to Ire1p foci leading to their diminished splicing and translation. ER stress triggers a rapid relocalization of Ypt1p to the cytoplasm with its consequent dissociation from pre-HAC1 mRNA thereby causing a decreased recruitment of NNS/exosome/CTEXT to precursor HAC1 RNA leading to its diminished 3'[->]5' degradation by the exosome. This diminished decay produces an increased abundance of pre-HAC1 mRNA population with intact functional BE leading to its enhanced recruitment to Ire1p foci that is followed by its increased splicing and translation. This enhanced translation produces a huge burst of Hac1p that rapidly transactivates the genes encoding ER-chaperones.

molecular biology↗
bioRxiv2022

Targeting tumor stemness switch phenotype by activating pathogen induced stem cell niche defense

Cancer stem cells (CSCs) reside in their tumor microenvironment (TME) niches, which are often hypoxic. Previously, we found that hypoxia and oxidative stress prevalent in TME may reprogram CSCs to a highly aggressive and inflammatory phenotype, the tumor stemness switch (TSS) phenotype. We previously reported a "stem cell niche defense" mechanism in bone marrow and lung mesenchymal stem cell niche against pathogen. Pathogen induced bystander apoptosis (PIBA) of stem cells harboring intracellular pathogen may be part of this defense mechanism. We speculate that the TSS phenotype may also activate this niche defense mechanism to defend their TME niche against pathogen and therefore could be exploited to target CSCs. Here we report that CSCs of TSS phenotype enriched in post-hypoxia ABCG2+ CSCs of several cell lines of diverse tumors including oral squamous cell carcinoma cell line SCC-25 exhibited bystander apoptosis when infected with either Bacillus Calmette Guerin (BCG) or mutant Mycobacterium tuberculosis (Mtb) strain 18b. The conditioned media (CM) of the infected cells not only exhibited marked anti-tumor activity in vivo, but also showed significant anti-microbial activity. A detailed mechanisms study revealed that some of the infected ABCG2+ CSCs underwent pyroptosis and released a high mobility group box protein 1 (HMGB1)/p53 death signal that can induce a toll like receptor (TLR) 2/4 mediated bystander apoptosis. Thus, our findings suggest that PIBA can be utilized to activate the "niche defense" mechanism in TSS phenotype, which not only target the TSS, but also exhibit marked anti-tumor activity in vivo.

cancer biology↗
bioRxiv2022

Zn-dependent structural transition of SOD1 modulates its ability to undergo liquid-liquid phase separation.

The toxic gain of function of Cu/Zn superoxide dismutase (SOD1) associated with the neurodegenerative disease - Amyotrophic lateral sclerosis (ALS), is believed to occur via misfolding and/or aggregation. SOD1 is also associated with stress granules (SGs) which are a type of membraneless organelle believed to form via liquid-liquid phase separation (LLPS) of several proteins containing low-complexity, disordered regions. Using a combination of experiments and computer simulations, we report here that structural disorder in two loop regions of SOD1 induced by the absence of metal cofactor - Zn, triggers its LLPS. The phase-separated droplets give rise to aggregates which eventually form toxic amyloids upon prolonged incubation. The addition of exogenous Zn to immature, metal-free SOD1 and the severe ALS mutant - I113T, stabilized the loops and restored the folded structure, thereby inhibiting LLPS and subsequent aggregation. In contrast, the Zn-induced inhibition of LLPS and aggregation was found to be partial in the case of another severe ALS-associated mutant - G85R, which exhibits reduced Zn-binding. Moreover, a less-severe ALS mutant - G37R with perturbed Cu binding does not undergo LLPS. In conclusion, our work establishes a role for Zn-dependent modulation of SOD1 disorder and LLPS as a precursor phenomenon which may lead to the formation of toxic amyloids associated with ALS. Significance StatementThe formation of membraneless organelles such as stress granules (SGs) is believed to occur through the process of liquid-liquid phase separation (LLPS) and involves numerous proteins containing intrinsically disordered regions. Whether SOD1, which is also associated with SGs and whose aggregation is associated with Amyotrophic lateral sclerosis (ALS), can independently undergo LLPS, is not known. SOD1 is a metalloenzyme which is stabilized by the metal co-factor - Zn. In this work, we utilize experimental and simulation techniques to highlight the modulation of SOD1 LLPS propensity in a Zn-dependent manner due to underlying conformational transitions between folded and partially disordered states. Our work establishes a link between SOD1 LLPS and aggregation, which is relevant to ALS pathogenesis.

biophysics↗
bioRxiv2022

Chlorpyrifos degradation by combined solar photo-Fenton and bacterial metabolism and simultaneous toxicity analysis in zebrafish (Danio rerio)

Chlorpyrifos (CP) is a widely used insecticide that has been used extensively, contributing towards a negative impact on public health concerns and associated ecosystems. Bioremediation is one of the key biological methods used for reducing these environmental toxicants. The present study examined the effectiveness of a combined process including solar photo-Fenton process followed by bacterial degradation using Ochrobactrum sp. CPD-03 for effective CP degradation in wastewater. Results showed that solar photo-Fenton treatment had CP degradation efficiency of ~42% in 4 h with a final degradation efficiency of ~92% in 96 h upon combined bacterial degradation. Simultaneous survivability of zebrafish (Danio rerio) was also studied during CP degradation. Compared to control, adult zebrafishes showed increased survivability following the addition of CPD-03 in water resulting a reduced CP concentration. CP toxicity in wastewater had caused acetylcholinesterase inhibition in zebrafish; however, this inhibition is due to absence of CP degrading bacteria. Therefore, a combined approach would influence for regulating CP degradation in wastewater along with simultaneous survival of Danio rerio.

microbiology↗
bioRxiv2021

The Effect of a Fennel Extract on the STAT Signaling and Intestinal Barrier Function

BackgroundFoeniculum vulgare, F. vulgare, commonly known as fennel, is believed to be one of the worlds oldest medicinal herbs and has been exploited by people for centuries as a nutritional aid for digestive disorders. In many southeast Asian countries it is ingested as an after-meal snack, mukhvas, due to its breath-freshening and digestive aid properties. F. vulgare is used in some countries, such as Iran, as a complementary and alternative treatment for inflammatory bowel disease (IBD). MethodsThis study investigated the effects of F. vulgare on the barrier function of the intestinal epithelium Signal Transducer and Activator of Transcription (STAT) pathway, which is active in inflammatory bowel disease. To study the protective effects of F. vulgare extract in vitro, monolayers derived from the T84 colonic cell line were challenged with interferon-gamma (IFN-{gamma}) and monitored with and without F. vulgare extract. To complement our in vitro studies, the dextran sodium sulfate induced murine colitis model was employed to ascertain whether the protective effect of F. vulgare extract can be recapitulated in vivo. ResultsF. vulgare extract was shown to exert a protective effect on TEER in both T84 and murine models and showed increases in tight junction-associated mRNA in T84 cell monolayers. Both models demonstrated significant decreases in phosphorylated STAT1 (pSTAT1), indicating reduced activation of the STAT pathway. Additionally, mice treated with F. vulgare showed significantly lower ulcer indices than control mice. ConclusionsWe conclude barrier function of the gastrointestinal tract is improved by F. vulgare, suggesting the potential utility of this agent as an alternative or adjunctive therapy in IBD.

pharmacology and toxicology↗