Biology subjects

Sarkar, S.

Publications and source records attributed to Sarkar, S..

At least 109 records · Page 6Linked to original sources

bioRxiv2024

E.PathDash, pathway activation analysis of public cystic fibrosis pathogen gene expression data

E.PathDash facilitates re-analysis of gene expression data from pathogens clinically relevant to chronic respiratory diseases, including a total of 48 studies, 548 samples, and 404 unique treatment comparisons. The application enables users to assess broad biological stress responses at the KEGG pathway or Gene Ontology level and also provides data for individual genes. E.PathDash reduces the time required to gain access to data from multiple hours per dataset to seconds. Users can download high quality images such as volcano plots and boxplots, differential gene expression results and raw count data, making it fully interoperable with other tools. Importantly, users can rapidly toggle between experimental comparisons and different studies of the same phenomenon, enabling them to judge the extent to which observed responses are reproducible. As a proof of principle, we invited two cystic fibrosis scientists to use the application to explore scientific questions relevant to their specific research areas. Reassuringly, pathway activation analysis recapitulated results reported in original publications, but it also yielded new insights into pathogen responses to changes in their environments, validating the utility of the application. All software and data are freely accessible and the application is available at scangeo.dartmouth.edu/EPathDash. ImportanceChronic respiratory illnesses impose a high disease burden on our communities and people with respiratory diseases are susceptible to robust bacterial infections from pathogens, including Pseudomonas aeruginosa and Staphylococcus aureus, that contribute to morbidity and mortality. Public gene expression datasets generated from these and other pathogens are abundantly available and an important resource for synthesizing existing pathogenic research, leading to interventions that improve patient outcomes. However, it can take many hours or weeks to render publicly available datasets usable; significant time and skills are needed to clean, standardize, and apply reproducible and robust bioinformatic pipelines to the data. Through collaboration with two microbiologists we have shown that E.PathDash addresses this problem, enabling them to elucidate pathogen responses to a variety of over 400 experimental conditions and generate mechanistic hypotheses for cell-level behavior in response to disease-relevant exposures, all in a fraction of the time.

bioinformatics↗

bioRxiv2024

Two distinct integrin binding sites on MMP9 drive cancer invasion by mediating integrin membrane trafficking & stabilization

Matrix stiffening has been established to drive cancer progression through increased activity of matrix metalloproteases (MMPs) which degrade the matrix creating paths for migration. However, the non-proteolytic functions of MMPs in cancer invasion remain relatively less understood. Here we have probed the importance of proteolytic and non-proteolytic functions of MMP9, which exhibits robust stiffness dependent expression and secretion in highly invasive cancer cells. We show that while MMP9 sustains spreading and 2D migration non-proteolytically by stabilizing focal adhesions, MMP9 proteolytic activity is essential for 3D invasion. We then establish the function of two distinct integrin {beta}1 (ITG {beta}1) binding sites on MMP9, with the hemopexin domain mediating co-packaging and co-transport of ITG {beta}1/MMP9 to the cell periphery, and the RGD domain stabilizing ITG {beta}1 on the cell membrane prior to matrix degradation. Together, our results illustrate how MMP9 optimizes cancer invasion by spatiotemporally integrating matrix remodeling with adhesion formation.

cell biology↗

bioRxiv2024

Repurposing approved protein kinase inhibitors as potent anti-leishmanials targeting Leishmania MAP kinases

Leishmaniasis is a vast array of chronic diseases caused by the protozoan parasite of the genus Leishmania transmitted by the sandfly belonging to the genus Phlebotomus (Old World) and Lutzomyia (New World). Among the various factors that contribute to the virulence and pathogenesis of the disease, protein kinases play crucial role in modulating the parasites biology in the host system. There are no specific drugs identified to treat the disease specifically. Moreover, resistance against approved anti-leishmanials has made it important to look for a few pre-clinical candidates against visceral leishmaniasis. MAP kinase is one such candidate of protein kinase family that regulates cell proliferation in eukaryotes. In this study, we have identified 23 MAPKs from Leishmania genome and have screened 12 FDA approved protein kinase inhibitors against those MAPKs in search of a potential lead for new drug exploration. Among the inhibitors, sorafenib and imatinib have been identified as potential drug candidates based on multiple criteria including binding affinity, ADME scores, absorption and their ability to cross blood-brain barrier. Furthermore, these drugs showed excellent anti-proliferative effects in Leishmania promastigotes, resulted in change of cell morphology, flagellar length, promoted cell cycle arrest through ROS generation and reduced intra-macrophage parasitic burden. Collectively, these results imply involvement of MAP kinases in infectivity and survival of the parasite and can pave the avenue for repurposing sorafenib and imatinib as anti-leishmanial agents.

bioinformatics↗

bioRxiv2024

Intermolecular Energy Migration via HomoFRET Captures the Modulation in the Material Property of Phase-Separated Biomolecular Condensates

Biomolecular condensation via phase separation of proteins and nucleic acids has emerged as a crucial mechanism underlying the spatiotemporal organization of cellular components into functional membraneless organelles. However, aberrant maturation of these dynamic, liquid-like assemblies into irreversible gel-like or solid-like aggregates is associated with a wide range of fatal neurodegenerative diseases. New tools are essential to dissect the changes in the internal material properties of these biomolecular condensates that are often modulated by a wide range of factors involving the sequence composition, truncations, mutations, post-translational modifications, and the stoichiometry of nucleic acids and other biomolecules. Here, we employ homo-Forster Resonance Energy Transfer (homoFRET) as a proximity ruler to study intermolecular energy migration that illuminates the molecular packing in the nanometric length-scale within biomolecular condensates. We used the homoFRET efficiency, measured by a loss in the fluorescence anisotropy due to rapid depolarization, as a readout of the molecular packing giving rise to material properties of biomolecular condensates. Using single-droplet anisotropy imaging, we recorded spatially-resolved homoFRET efficiencies of condensates formed by fluorescent protein-tagged Fused in Sarcoma (FUS). By performing single-droplet picosecond time-resolved anisotropy measurements, we were able to discern various energy migration events within the dense network of polypeptide chains in FUS condensates. Our homoFRET studies also captured the modulation of material properties by RNA, ATP, and post-translational modification. Additionally, we utilized mammalian cell lines stably expressing FUS to study nuclear FUS and oxidative stress-induced stress granule formation in the cytoplasm. Our studies demonstrate that spatially-resolved homoFRET methodology offers a potent tool for studying intracellular phase transitions in cell physiology and disease.

biophysics↗

bioRxiv2024

Transcriptional programs mediating neuronal toxicity and altered glial-neuronal signaling in a Drosophila knock-in tauopathy model

Missense mutations in the gene encoding the microtubule-associated protein tau cause autosomal dominant forms of frontotemporal dementia. Multiple models of frontotemporal dementia based on transgenic expression of human tau in experimental model organisms, including Drosophila, have been described. These models replicate key features of the human disease, but do not faithfully recreate the genetic context of the human disorder. Here we use CRISPR-Cas mediated gene editing to model frontotemporal dementia caused by the tau P301L mutation by creating the orthologous mutation, P251L, in the endogenous Drosophila tau gene. Flies heterozygous or homozygous for tau P251L display age-dependent neurodegeneration, metabolic defects and accumulate DNA damage in affected neurons. To understand the molecular events promoting neuronal dysfunction and death in knock-in flies we performed single-cell RNA sequencing on approximately 130,000 cells from brains of tau P251L mutant and control flies. We found that expression of disease-associated mutant tau altered gene expression cell autonomously in all neuronal cell types identified and non-cell autonomously in glial cells. Cell signaling pathways, including glial-neuronal signaling, were broadly dysregulated as were brain region and cell-type specific protein interaction networks and gene regulatory programs. In summary, we present here a genetic model of tauopathy, which faithfully recapitulates the genetic context and phenotypic features of the human disease and use the results of comprehensive single cell sequencing analysis to outline pathways of neurotoxicity and highlight the role of non-cell autonomous changes in glia.

neuroscience↗

bioRxiv2024

Reduction of chemokine CXCL9 expression by omega-3 fatty acids via ADP-ribosylhydrolase ARH3 in MIN6 insulin-producing cells

Type 1 diabetes (T1D) results from the autoimmune destruction of the insulin producing {beta} cells of the pancreas. Omega-3 fatty acids protect {beta} cells and reduce the incident of T1D. However, how omega-3 fatty acids act on {beta} cells is not well understood. We have shown that omega-3 fatty acids reduce pro-inflammatory cytokine-mediated {beta}-cell apoptosis by upregulating the expression of the ADP-ribosylhydrolase ARH3. Here, we further investigate the {beta}-cell protection mechanism by ARH3 by performing siRNA of its gene Adprhl2 in MIN6 insulin-producing cells followed by treatment with a cocktail of the pro-inflammatory cytokines IL-1{beta} + IFN-{gamma} + TNF-, and proteomics analysis. ARH3 regulated proteins from several pathways related to the nucleus (splicing, RNA surveillance and nucleocytoplasmic transport), mitochondria (metabolic pathways) and endoplasmic reticulum (protein folding). ARH3 also regulated the levels of cytokine-signaling proteins related to the antigen processing and presentation, and chemokine-signaling pathway. We further studied the role of ARH in regulating the chemokine CXCL9. We confirmed that ARH3 reduces the cytokine-induced expression of CXCL9 by ELISA. We also found that CXCL9 expression is regulated by omega-3 fatty acids. In conclusion, we showed that omega-3 fatty acids regulate CXCL9 expression via ARH3, which might have a role in protecting {beta} cells from immune attack and preventing T1D development.

cell biology↗

bioRxiv2024

Epitranscriptomic Reader YTHDF2 Regulates SEK1(MAP2K4)-JNK-cJUN Inflammatory Signaling in Astrocytes during Neurotoxic Stress

As the most abundant glial cells in the CNS, astrocytes dynamically respond to neurotoxic stress, however, the key molecular regulators controlling the inflammatory status of these sentinels during neurotoxic stress have remained elusive. Herein, we demonstrate that the m6A epitranscriptomic mRNA modification tightly regulates the pro-inflammatory functions of astrocytes. Specifically, the astrocytic neurotoxic stresser, manganese (Mn), downregulated the m6A reader YTHDF2 in human and mouse astrocyte cultures and in the mouse brain. Functionally, YTHDF2 knockdown augmented, while its overexpression dampened, neurotoxic stress induced proinflammatory response, suggesting YTHDF2 serves as a key upstream regulator of inflammatory responses in astrocytes. Mechnistically, YTHDF2 RIP-sequencing identified MAP2K4 (MKK4; SEK1) mRNA as a YTHDF2 target influencing inflammatory signaling. Our target validation revealed Mn-exposed astrocytes mediates proinflammatory response by activating the phosphorylation of SEK1, JNK, and cJUN signaling. Collectively, YTHDF2 serves a key upstream molecular switch controlling SEK1(MAP2K4)-JNK-cJUN proinflammatory signaling in astrocytes.

neuroscience↗

bioRxiv2024

A fast and sensitive size-exclusion chromatography method for plasma extracellular vesicle proteomic analysis

Extracellular vesicles (EVs) carry diverse biomolecules derived from their parental cells, making their components excellent biomarker candidates. However, purifying EVs is a major hurdle in biomarker discovery since current methods require large amounts of samples, are time-consuming and typically have poor reproducibility. Here we describe a simple, fast, and sensitive EV fractionation method using size exclusion chromatography (SEC) on a fast protein liquid chromatography (FPLC) system. Our method uses a Superose 6 Increase 5/150, which has a bed volume of 2.9 mL. The FPLC system and small column size enable reproducible separation of only 50 {micro}L of human plasma in 15 minutes. To demonstrate the utility of our method, we used longitudinal samples from a group of individuals that underwent intense exercise. A total of 838 proteins were identified, of which, 261 were previously characterized as EV proteins, including classical markers, such as cluster of differentiation (CD)9 and CD81. Quantitative analysis showed low technical variability with correlation coefficients greater than 0.9 between replicates. The analysis captured differences in relevant EV-proteins involved in response to physical activity. Our method enables fast and sensitive fractionation of plasma EVs with low variability, which will facilitate biomarker studies in large clinical cohorts.

biochemistry↗

bioRxiv2024

ATP Prevents Aggregation of Protein via Modulating its Monomeric Conformation

Proteins occurring in significantly high concentrations in cellular environments (over 100 mg/mL) and functioning in crowded cytoplasm, often face the prodigious challenges of aggregation which are the pathological hallmark of aging and are critically responsible for a wide spectrum of rising human diseases. Here we combine a joint-venture of complementary wet-lab experiment and molecular simulation to discern the potential ability of adenosine triphosphate (ATP) as solubilizer of protein aggregates. We show that ATP prevents both condensation of aggregation-prone intrinsically disordered protein A{beta}40 and promotes dissolution of pre-formed aggregates. Computer simulation links ATPs solubilizing role to its ability to modulate proteins structural plasticity by unwinding protein conformation. We show that ATP is positioned as a superior biological solubilizer of protein aggregates over traditional chemical hydrotropes, potentially holding promises in therapeutic interventions in protein-aggregation related diseases. Going beyond its conventional activity as energy currency, the amphiphilic nature of ATP enables its protein-specific interaction that would enhance ATPs efficiency in cellular processes.

biochemistry↗

bioRxiv2024

Pathways controlling neurotoxicity and proteostasis in mitochondrial complex I deficiency

Neuromuscular disorders caused by dysfunction of the mitochondrial respiratory chain are common, severe and untreatable. We recovered a number of mitochondrial genes, including electron transport chain components, in a large forward genetic screen for mutations causing age-related neurodegeneration in the context of proteostasis dysfunction. We created a model of complex I deficiency in the Drosophila retina to probe the role of protein degradation abnormalities in mitochondrial encephalomyopathies. Using our genetic model, we found that complex I deficiency regulates both the ubiquitin/proteasome and autophagy/lysosome arms of the proteostasis machinery. We further performed an in vivo kinome screen to uncover new and potentially druggable mechanisms contributing to complex I related neurodegeneration and proteostasis failure. Reduction of RIOK kinases and the innate immune signaling kinase pelle prevented neurodegeneration in complex I deficiency animals. Genetically targeting oxidative stress, but not RIOK1 or pelle knockdown, normalized proteostasis markers. Our findings outline distinct pathways controlling neurodegeneration and protein degradation in complex I deficiency and introduce an experimentally facile model in which to study these debilitating and currently treatment-refractory disorders.

neuroscience↗

bioRxiv2024

Leveraging Soil Mapping and Machine Learning to Improve Spatial Adjustments in Plant Breeding Trials

Spatial adjustments are used to improve the estimate of plot seed yield across crops and geographies. Moving mean and P-Spline are examples of spatial adjustment methods used in plant breeding trials to deal with field heterogeneity. Within trial spatial variability primarily comes from soil feature gradients, such as nutrients, but study of the importance of various soil factors including nutrients is lacking. We analyzed plant breeding progeny row and preliminary yield trial data of a public soybean breeding program across three years consisting of 43,545 plots. We compared several spatial adjustment methods: unadjusted (as a control), moving means adjustment, P-spline adjustment, and a machine learning based method called XGBoost. XGBoost modeled soil features at (a) local field scale for each generation and per year, and (b) all inclusive field scale spanning all generations and years. We report the usefulness of spatial adjustments at both progeny row and preliminary yield trial stages of field testing, and additionally provide ways to utilize interpretability insights of soil features in spatial adjustments. These results empower breeders to further refine selection criteria to make more accurate selections, and furthermore include soil variables to select for macro- and micro-nutrients stress tolerance.

plant biology↗

bioRxiv2023

Age-dependent Powassan Virus Lethality is Directed by Glial Cell Activation and Divergent Neuroinflammatory Cytokine Responses in a Murine Model

Powassan virus (POWV) is an emergent tick-borne flavivirus that causes fatal encephalitis in the elderly and long-term neurologic sequelae in survivors. How age contributes to severe POWV encephalitis remains an enigma and there are currently no animal models that reflect age-dependent POWV neuropathology. Inoculating C57BL/6 mice with a POWV strain (LI9) currently circulating in Ixodes ticks, resulted in age-dependent POWV lethality with overt spongiform brain damage 10-15 dpi. Infection of 50 week old mice resulted in 82% lethality 10-15 dpi that was sequentially reduced by age to 7.1% in 10 week old mice. LI9 encephalitis resulted in early neuronal depletion, with severe CNS damage, persistent inflammatory gliosis and long-term spongiform pathology in survivors (30 dpi). In all mice POWV LI9 was neuroinvasive and reached maximum POWV loads in the CNS 10 dpi. Coincident with murine lethality, in 50 week old mice maximum POWV CNS levels persisted 15 dpi, while instead decreasing by 2-4 logs in 10-30 week old mice. Although glial cells were highly activated in all POWV infected mice, differences in age-dependent CNS cytokine responses were striking 15 dpi. In 50 week old mice POWV induced Th1-type cytokines (IFN{gamma}, IL-2, IL-12, IL-4, TNF, IL-6), suggesting a pro-inflammatory M1 microglial activation cascade. In contrast, POWV induced Th2-type cytokines (IL-10, TGF{beta}, IL-4) in 10 week old mice consistent with a neuroprotective M2 microglial phenotype. These findings reflect differences in neurodegenerative versus neuroprotective glial cell responses that correlate with divergent CNS viral clearance and age-dependent POWV LI9 lethality. Discrete age-dependent CNS cytokine responses suggest neuroinflammatory targets as potential POWV therapeutics. These studies establish a highly lethal POWV murine model and reveal a hyperinflammatory mechanism of age-dependent POWV lethality that mirrors human POWV severity and long-term CNS sequelae in the elderly. ImportancePowassan virus is an emerging tick-borne flavivirus causing lethal encephalitis in aged individuals. We reveal an age-dependent POWV murine model that mirrors human POWV encephalitis and long-term CNS damage in the elderly. Findings demonstrate that POWV load and discrete glial cell cytokine responses in the CNS are critical determinants of age-dependent POWV lethality. POWV age-independently activates microglia and astrocytes, but directs neuroprotective Th2 cytokine responses in 10 week old mice and distinct pro-inflammatory Th1 cytokine responses in the CNS of 50 week old mice. This reveals roles for a hyperinflammatory CNS cytokine cascade in age-dependent POWV lethality, and protective anti-inflammatory cytokines in murine survival. Notably, results define potential therapeutic targets and rationalize approaches for preventing severe POWV encephalitis that may be broadly applicable to neurodegenerative diseases. This age-dependent murine POWV model permits analysis of vaccines, and therapeutics that prevent POWV neuroinvasion or resolve severe POWV encephalitis in the elderly.

microbiology↗

bioRxiv2023

Chandipura Virus forms cytoplasmic inclusion bodies through phase separation and proviral association of cellular protein Kinase R and stress granules protein TIA-1

Negative-strand RNA viruses form cytoplasmic inclusion bodies (IBs) representing virus replication foci through phase separation or bio-molecular condensation of viral and cellular proteins, as a hallmark of their infection. Alternatively, mammalian cells form stalled-mRNA containing antiviral stress granules (SGs), as a consequence of phosphorylation of eukaryotic initiation factor 2 (eIF2) through condensation of several RNA-binding proteins including TIA-1. Whether and how Chandipura virus (CHPV), an emerging human pathogen causing influenza-like illness, coma and death; forms IBs and evades antiviral SGs, remains unknown. By confocal imaging on CHPV-infected Vero-E6 cells, we found that CHPV infection doesnt induce formation of distinct canonical SGs. Instead, CHPV proteins condense and co-localize together with SG-proteins to form heterogeneous IBs, which ensued independent of the activation of eIF2 and eIF2 Kinase, Protein Kinase R (PKR). Interestingly, siRNA-mediated depletion of PKR or TIA-1 significantly decreased viral transcription and virion production. Moreover, CHPV infection also caused condensation and recruitment of PKR to IBs. Compared to SGs, IBs exhibited significant rapidity in disassembly dynamics. Altogether, our study demonstrates that CHPV-replication co-optimizing with SG-proteins and revealing unprecedented proviral role of TIA-1/PKR, may have implication in understanding the mechanisms regulating CHPV-IB formation, and designing antiviral therapeutic. ImportanceCHPV is an emerging tropical pathogen reported to cause acute influenza-like-illness and encephalitis in children with very high mortality rate of [~]70%. Lack of a vaccines and an effective therapy against CHPV makes it a potent pathogen for causing an epidemic in tropical parts of globe. Given these forewarnings, it is of paramount importance that CHPV biology must be understood comprehensively. Targeting of host factors offers several advantages over targeting the viral components due to in general higher mutation rate in viral genome. In this study, we aimed at understanding the role of those cellular RNA binding proteins in CHPV replication, which form SGs. Our study helps understand participation of cellular factors in CHPV replication and could help develop effective therapeutics against the virus.

microbiology↗

bioRxiv2023

Multivalent DNA-encoded lectins on phage enable detecting compositional glycocalyx differences

Selective detection of disease-associated changes in the cellular glycocalyx is a foundation of modern targeted therapies. Detecting minor changes in the density and identity of glycans on the cell surface is a technological challenge exacerbated by lack of 1:1 correspondence between cellular DNA/RNA and glycan structures on cell surface. We demonstrate that multivalent displays of up to 300 lectins on DNA-barcoded M13 phage on a liquid lectin array (LiLA), detects subtle differences in composition and density of glycans on cells ex vivo and in immune cells or organs in animals. For example, constructs displaying 73 copies of diCBM40 lectin per 700x5 nm virion ({varphi}-CBM73) exhibit non-linear ON/OFF-like recognition of sialoglycans on the surface of normal and cancer cells. In contrast, a high-valency {varphi}-CBM290 display, or soluble diCBM40, exhibit canonical progressive scaling in binding with increased epitope density; these constructs cannot amplify the subtle differences detected by {varphi}-CBM73. Similarly, multivalent displays of diCBM40 and Siglec-7 detect differences in the glycocalyx between stem-like and non-stem populations in cancer cells that are not detected with soluble lectins. Multivalent display of lectins on M13 scaffold with protected DNA inside the phage offer non-destructive detection of minor differences in glycocalyx in cells in vitro and in vivo not feasible to currently available technologies.

biochemistry↗

bioRxiv2023

Spatially resolved single-cell analysis uncovers protein kinase C-& expressing microglia with anti-tumor activity in glioblastoma

Glioblastoma (GBM) is a brain tumor that poses a formidable challenge to treatment options available. The tumor microenvironment (TME) in GBM is highly complex, marked by immunosuppression and cellular heterogeneity. Understanding the cellular interactions and their spatial organization within the TME is crucial for developing effective therapeutic strategies. In this study, we integrated single-cell RNA sequencing and spatial transcriptomics in a GBM mouse model to unravel the spatial landscape of the brain TME. We identified a previously unrecognized microglia subtype expressing protein kinase C{delta} (PKC{delta}) associated with potent anti-tumor functions. The presence of PKC{delta}-expressing microglia was confirmed in resected human GBM specimens. Elevating tumoral PKC{delta} expression using niacin or adeno-associated virus in mice enhanced the phagocytosis of GBM cells by microglia in culture and increased the lifespan of mice with intracranial GBM. These findings were corroborated in analyses of the TCGA GBM datasets where low PKC{delta} samples showed negative pathway enrichment for apoptosis, phagocytosis, and immune signaling pathways, as well as lower levels of immune cell infiltration overall. Our study underscores the importance of integrating spatial context to unravel the TME, resulting in the identification of previously unrecognized subsets of microglia with anti-tumor functions. These findings provide valuable insights for advancing innovative immunotherapeutic strategies in GBM.

immunology↗

bioRxiv2023

A mitochondrial quality control mechanism reverses the phagosome maturation arrest caused by Mycobacterium tuberculosis

Phagosome maturation arrest (PMA) imposed by Mycobacterium tuberculosis (Mtb) is a classic tool that helps Mtb evade macrophage anti-bacterial responses. The exclusion of RAB7, a small GTPase, from Mtb-phagosomes causes PMA. Here, we report an unexpected mechanism that triggers crosstalk between the mitochondrial quality control (MQC) and the phagosome maturation pathways that reverses the PMA. CRISPR-mediated p62/SQSTM1 depletion (p62KD) does not appear to impact mitochondrial quality. The p62KD cells are restrictive to Mtb growth, triggered by an increasingly oxidative environment and increased lysosomal targeting. The lysosomal targeting of Mtb is facilitated by enhanced TOM20+ mitochondria-derived vesicles (MDVs) biogenesis, a key MQC mechanism. In p62KD cells, TOM20+-MDVs biogenesis is MIRO1/MIRO2-dependent and gets delivered to lysosomes for degradation in a RAB7-dependent manner. Upon infection in p62KD cells, TOM20+-MDVs get extensively targeted to Mtb-phagosomes, inadvertently facilitating RAB7 recruitment, PMA reversal and lysosomal targeting of Mtb; the phenotype also replicated in p62/SQSTM1 knockout cells. Triggering MQC collapse in p62KDcells further diminishes Mtb survival, signifying cooperation between redox- and lysosome-mediated mechanisms. The MQC-anti-bacterial pathway crosstalk could be exploited for host-directed anti-tuberculosis therapies.

microbiology↗

bioRxiv2023

Biotin rescues manganese-induced Parkinson's disease phenotypes and neurotoxicity

Occupational exposure to manganese (Mn) induces manganism and has been widely linked as a contributing environmental factor to Parkinsons disease (PD), featuring dramatic signature overlaps between the two in motor symptoms and clinical hallmarks. However, the molecular mechanism underlying such link remains elusive, and for combating PD, effective mechanism-based therapies are lacking. Here, we developed an adult Drosophila model of Mn toxicity to recapitulate key parkinsonian features, spanning behavioral deficits, neuronal loss, and dysfunctions in lysosome and mitochondria. We performed global metabolomics on flies at an early stage of toxicity and identified metabolism of the B vitamin, biotin (vitamin B7), as a master pathway underpinning Mn toxicity with systemic, body-brain increases in Mn-treated groups compared to the controls. Using BtndRNAi mutant flies, we show that biotin depletion exacerbates Mn-induced neurotoxicity, parkinsonism, and mitochondrial dysfunction; while in Mn-exposed wild-type flies, biotin feeding dramatically ameliorates these pathophenotypes. We further show in human induced stem cells (iPSCs)- differentiated midbrain dopaminergic neurons that the supplemented biotin protects against Mn-induced neuronal loss, cytotoxicity, and mitochondrial dysregulation. Finally, human data profiling biotin-related proteins show for PD cases elevated circulating levels of biotin transporters but not of metabolic enzymes compared to healthy controls, suggesting humoral biotin transport as a key event involved in PD. Taken together, our findings identified compensatory biotin pathway as a convergent, systemic driver of Mn toxicity and parkinsonian pathology, providing new basis for devising effective countermeasures against manganism and PD. Significance StatementEnvironmental exposure to manganese (Mn) may increase the risk for Parkinsons disease (PD); however, the mechanistic basis linking the two remains unclear. Our adult fruit fly (Drosophila) model of Mn toxicity recapitulated key Parkinsons hallmarks in vivo spanning behavioral deficits, neuronal loss, and mitochondrial dysfunction. Metabolomics identified the biotin (vitamin B7) pathway as a key mediator, featuring systemic biotin increases in the flies. Rescue trials leveraging biotin-deficient flies, wild-type flies, and human iPSC-derived dopaminergic neurons determined biotin as a driver of manganism, with the parkinsonian phenotypes dramatically reversed through biotin supplementation. Our findings, in line with overexpressed circulating biotin transporters observed in PD patients, suggest compensatory biotin pathway as a key to untangle the Mn-PD link for combating neurodegenerative disease.

neuroscience↗

bioRxiv2023

Ammonia-oxidizing archaea and bacteria differentially contribute to ammonia oxidation in soil under precipitation gradients and land legacy

BackgroundGlobal change has accelerated the nitrogen cycle. Soil nitrogen stock degradation by microbes leads to the release of various gases, including nitrous oxide (N2O), a potent greenhouse gas. Ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) participate in the soil nitrogen cycle, producing N2O. There are outstanding questions regarding the impact of environmental processes such as precipitation and land use legacy on AOA and AOB structurally, compositionally, and functionally. To answer these questions, we analyzed field soil cores and soil monoliths under varying precipitation profiles and land legacies. ResultsWe resolved 28 AOA and AOB metagenome assembled genomes (MAGs) and found that they were significantly higher in drier environments and differentially abundant in different land use legacies. We further dissected AOA and AOB functional potentials to understand their contribution to nitrogen transformation capabilities. We identified the involvement of stress response genes, differential metabolic functional potentials, and subtle population dynamics under different environmental parameters for AOA and AOB. We observed that AOA MAGs lacked a canonical membrane-bound electron transport chain and F-type ATPase but possessed A/A-type ATPase, while AOB MAGs had a complete complex III module and F-type ATPase, suggesting differential survival strategies of AOA and AOB. ConclusionsThe outcomes from this study will enable us to comprehend how drought-like environments and land use legacies could impact AOA- and AOB-driven nitrogen transformations in soil.

bioinformatics↗