Biology subjects

Bhattacharya, B.

Publications and source records attributed to Bhattacharya, B..

18 recordsLinked to original sources

bioRxiv2026

RTTN moonlights beyond the centrosome to control ribosome biogenesis and tRNA modification in human brain organoids

RTTN (rotatin) is a centrosomal protein mutated in severe malformations of cortical development, yet how its dysfunction disrupts human corticogenesis has remained unclear. Here, we show that RTTN has an unrecognized function at the core of the translation machinery. Using human telencephalic and hippocampal organoids carrying distinct RTTN alleles, together with single-cell and bulk transcriptomics, polysome profiling, and tRNA pseudouridine sequencing, we find that RTTN is enriched in cycling first-trimester neural progenitors and physically associates with ribosome-biogenesis and RNA-processing factors. RTTN mutations impair rRNA biogenesis and polysome assembly, reduce cytoplasmic ribosome density and nascent protein synthesis, and remodel the tRNA pseudouridylation landscape through both a PUS7L-dependent variable-arm signature and a broader RTTN-specific defect. These translational deficits are accompanied by prolonged mitosis, reduced entry into S-phase, and impaired interkinetic nuclear migration in mutant progenitors. Our findings redefine RTTN as a regulator of ribosome homeostasis and mRNA translation and implicate defective translational capacity as a driver of RTTN-associated microcephaly. Graphical AbstractRTTN sustains ribosome and tRNA homeostasis in human neural progenitors; its mutation disrupts mRNA translation, stalling progenitor proliferation and interkinetic nuclear migration, and driving cortical malformation and growth failure. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/744412v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@16124aaorg.highwire.dtl.DTLVardef@ae23f7org.highwire.dtl.DTLVardef@bb588forg.highwire.dtl.DTLVardef@1b35028_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2026

Corilagin attenuates high glucose-induced neurotoxicity and mitochondrial dysfunction through restoration of the AMPK-SIRT1-PGC1α-TFAM signaling axis

Mitochondrial dysfunction and oxidative stress represent two interconnected, primary causes for Diabetic Neuropathy (DN); however, the majority of currently available anti-diabetic therapies have focused on glucose control as opposed to neurodegenerative downstream effects. Corilagin, is an ellagitannin having high anti-oxidant properties; however, it has not been evaluated against hyperglycemia induced neuronal injury. The present study demonstrates the ability of Corilagin to protect against mitochondrial dysfunction via models of diabetic nephropathy and cerebral ischemia. High glucose (50 mM, 24 hr) was utilized to induce diabetes like conditions in the SH-SY5Y human neuroblastoma Cell Line. High glucose induced significant decreases in cell viability, increases in intracellular and mitochondrial reactive oxygen species, depletion of reduced glutathione reserves, induces apoptosis, and causes mitochondrial depolarization and fragmentation. Corilagin pre-treatment attenuated each of these high-glucose induced effects by protecting against mitochondrial membrane potential loss and maintaining mitochondrial network morphology while reducing apoptotic cell fraction relative to glucose alone. Additionally, these protective effects were accompanied by restoration of AMPK phosphorylation and up-regulation of SIRT1, PGC1 and TFAM, components that are part of the principal signaling pathway that regulates mitochondrial biogenesis; therefore, therefore, this pathway may contribute mechanistically to the cyto-protective effect of Corilagin. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=99 SRC="FIGDIR/small/740444v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@1be4a92org.highwire.dtl.DTLVardef@11d6e9org.highwire.dtl.DTLVardef@1346757org.highwire.dtl.DTLVardef@16c9f1e_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstractC_FLOATNO Proposed mechanism underlying the neuroprotective effects of Corilagin against high glucose-induced mitochondrial dysfunction.High glucose suppresses AMPK phosphorylation, leading to downregulation of the SIRT1-PGC-1-TFAM signaling axis, increased intracellular and mitochondrial reactive oxygen species (ROS), glutathione depletion, apoptosis, mitochondrial depolarization, and mitochondrial fragmentation. Corilagin pretreatment restores AMPK activation and the downstream SIRT1-PGC-1-TFAM pathway, thereby reducing oxidative stress, preserving intracellular glutathione, preventing apoptosis, maintaining mitochondrial membrane potential, and protecting mitochondrial network integrity. C_FIG

cell biology↗

bioRxiv2025

Genetically engineered ESC-derived embryos reveal Vinculin-dependent force responses required for mammalian neural tube closure

Epithelial sheets build complex structures by converting mechanical forces into changes in cell and tissue organization. During neural tube closure, the neural plate dynamically remodels to produce a closed tube that provides the structural foundation for the developing brain and spinal cord. How cells maintain epithelial integrity despite the forces required for tissue morphogenesis during neural tube closure is not understood. We show that mechanical forces are upregulated during cranial neural tube closure in the mouse embryo and recruit the force-sensitive protein Vinculin to adherens junctions. Leveraging a genetically engineered embryonic stem cell-based pipeline to efficiently generate mutant embryos, we show that Vinculin mutants produce mechanical forces correctly but fail to maintain cell adhesion under tension, resulting in a failure of cranial neural fold elevation. Live imaging of cell behavior in the developing midbrain reveals that apical constriction, cell rearrangement, and cell division initiate correctly in Vinculin mutants, but their progression is impeded by disruption of adherens junctions at sites of increased tension. These results demonstrate that Vinculin is required to reinforce cell adhesion in response to increasing physiological forces during cranial neural tube closure, and that this activity is necessary to translate these forces into changes in tissue structure.

developmental biology↗

bioRxiv2025

Neural Progenitors as a Novel Pathogenic Mechanism in Microcephaly

Despite their significance, the genetic and molecular bases of neurodevelopmental disorders remain poorly understood. In this study, using human brain organoids and mouse models, we show that loss of NDE1, a gene closely associated with microcephaly, disrupts progenitor identity, prolongs mitosis, and alters regional patterning in the forebrain. NDE1 knockout leads to a caudal identity shift of neural progenitor cells in the organoids and mouse brains, coinciding with aberrant ERK signaling. Notably, downstream activation of the ERK pathway restored rostral PAX6 expression in human brain organoids. Parallel analyses of Nde1 knockout mice confirmed disrupted regional patterning of the forebrain. Together, our data establish NDE1 as a critical regulator of early human brain regionalization and elucidate molecular mechanisms underlying the structural abnormalities observed in NDE1-associated microcephaly.

developmental biology↗

bioRxiv2024

A single-cell atlas of spatial and temporal gene expression in the mouse cranial neural plate

The formation of the mammalian brain requires regionalization and morphogenesis of the cranial neural plate, which transforms from an epithelial sheet into a closed tube that provides the structural foundation for neural patterning and circuit formation. Sonic hedgehog (SHH) signaling is important for cranial neural plate patterning and closure, but the transcriptional changes that give rise to the spatially regulated cell fates and behaviors that build the cranial neural tube have not been systematically analyzed. Here we used single-cell RNA sequencing to generate an atlas of gene expression at six consecutive stages of cranial neural tube closure in the mouse embryo. Ordering transcriptional profiles relative to the major axes of gene expression predicted spatially regulated expression of 870 genes along the anterior-posterior and mediolateral axes of the cranial neural plate and reproduced known expression patterns with over 85% accuracy. Single-cell RNA sequencing of embryos with activated SHH signaling revealed distinct SHH-regulated transcriptional programs in the developing forebrain, midbrain, and hindbrain, suggesting a complex interplay between anterior-posterior and mediolateral patterning systems. These results define a spatiotemporally resolved map of gene expression during cranial neural tube closure and provide a resource for investigating the transcriptional events that drive early mammalian brain development.

developmental biology↗

bioRxiv2024

Oxysterol accumulation in aging cells alters GPCR signalling

Organismal aging is accompanied by the accumulation of senescent cells in the body, which drives tissue dysfunction. Senescent cells have a distinctive profile, including proliferation arrest, resistance to apoptosis, altered gene expression, and high inflammation. Despite global signalling and metabolic dysregulation during senescence, the underlying reasons for changes in signalling remain unclear. GPCRs are pivotal in cellular signalling, dynamically mediating the complex interplay between cells and their surrounding environment to maintain cellular homeostasis. The chemokine receptor CXCR4 plays a crucial role in modulating immune responses and inflammation. It has been shown that expression of CXCR4 increases in cells undergoing senescence, which enhances inflammation post-activation. Here we examine CXCR4 signalling in deeply senescent cells, where cholesterol and its oxidized derivatives, oxysterols, affect receptor function. We report elevated oxysterol levels in senescent cells, which altered classical CXCL12-mediated CXCR4 signalling. Tail-oxidized sterols disrupted signalling more than ring-oxidized counterparts. Molecular dynamics simulations revealed that 27-hydroxycholesterol displaces cholesterol and binds strongly to alter the conformation of critical signalling residues to modify the sterol-CXCR4 interaction landscape. Our study provides a molecular view of the observed mitigated GPCR signalling in the presence of oxysterols, which switched G-protein signalling from Gi/o to Gs class. Overall, we present an altered paradigm of GPCR signalling where cholesterol oxidation alters the signalling outcome in aged cells. Significance StatementOur study brings to light a novel and significant discovery in aged cells: the accumulation of oxysterols, oxidized forms of cholesterol, critically impairs CXCR4-dependent signalling and alters G-protein coupling specificity. This effect of oxysterols is demonstrated for the first time in aged cellular models, providing a molecular basis for a multitude of observed alterations in senescence, such as compromised immune functions and a decline in cellular responsiveness with age. Our research not only fills a crucial gap in understanding the aging process at the molecular level but also identifies potential targets for therapeutic interventions aimed at mitigating age-related cellular dysfunctions and diseases.

cell biology↗

bioRxiv2024

Altered Extracellular Matrix Structure and Elevated Stiffness in a Brain Organoid Model for Disease

The viscoelasticity of tissues impacts their shape, as well as the growth and differentiation of their cells. Nevertheless, little is known about changes in viscoelastic properties during brain malformations. Lissencephaly is a severe malformation of cortical development caused by LIS1 mutations, which results in a lack of cortical convolutions. Here, we show that human-derived brain organoids with LIS1 mutation are stiffer than control ones at multiple developmental times. This stiffening is accompanied by abnormal ECM expression and organization, as well as elevated water content, as measured by diffusion-weighted MRI. Proteolytic cleavage of ECM components by short-term treatment with the catalytic subunit of MMP9 reduced the stiffening and water diffusion levels of mutated organoids to control levels. Finally, based on the molecular and rheological properties obtained, we generated a computational microstructure mechanical model that can successfully predict mechanical changes that follow differential ECM localization and integrity in the developing brain. Overall, our study reveals that LIS1 is essential for the expression and organization of ECM proteins during brain development, and its mutation leads to a substantial viscoelastic change. To our knowledge, this is the first study to elucidate how tissue mechanics change in disease states using human brain organoids.

developmental biology↗

bioRxiv2023

A mechanistic study on the tolerance of PAM distal end mismatch by SpCas9

CRISPR-Cas9 is the newest technology available for targeted genome editing. It is very efficient and cheap compared to other genome editing techniques. However, its therapeutic application is limited due to its off-target activity. To have a better understanding of this off-target effect, we concentrated our efforts on its mismatch-prone PAM distal end. Current off-target prediction algorithms use RNA-DNA complementation derived energy as a major factor in predicting off-target effect. RNA-DNA complementation derived energy drives Cas9 conformational change, which in turn drives its functional activity. In the case of lower RNA-DNA complementarity, a partial conformational change occurs resulting in a slower reaction rate and partial activity. However, extensive mismatches are often tolerated despite lower complementation derived energy available from RNA: DNA duplex formation. Thus, the off-target activity of Cas9 depends directly on the nature of mismatches which in turn result in deviation of the active site of the enzyme due to structural instability in the duplex strand. In order to test the hypothesis, we have designed an array of mismatched target sites and performed in vitro and cell line-based experiments to assess the effects of PAM distal mismatches in Cas9 activity. For further mechanistic validation, Molecular dynamics simulation was performed and it revealed that certain mismatch mutations induced pronounced conformational instability within the RNA-DNA duplex, leading to elevated root mean square deviation (RMSD) values. We found that, target sites having mismatches in the 18th to 16th position upstream of the PAM showed no to little activity.

genomics↗

bioRxiv2023

Differential Carbonic Anhydrase Activities Control EBV-Induced B-Cell Transformation and Lytic Cycle Reactivation

Epstein-Barr virus (EBV) contributes to [~]1% of all human cancers including several B-cell neoplasms. A characteristic feature of EBV life cycle is its ability to transform metabolically quiescent B-lymphocytes into hyperproliferating B-cell blasts with the establishment of viral latency, while intermittent lytic cycle induction is necessary for the production of progeny virus. Our RNA-Seq analyses of both latently infected naive B-lymphocytes and transformed B-lymphocytes upon lytic cycle replication indicate a contrasting expression pattern of a membrane-associated carbonic anhydrase isoform CA9, an essential component for maintaining cell acid-base homeostasis. We show that while CA9 expression is transcriptionally activated during latent infection model, lytic cycle replication restrains its expression. Pharmacological inhibition of CA-activity using specific inhibitors retards EBV induced B-cell transformation, inhibits B-cells outgrowth and colony formation ability of transformed B-lymphocytes through lowering the intracellular pH, induction of cell apoptosis and facilitating degradation of CA9 transcripts. Reanalyses of ChIP-Seq data along with utilization of EBNA2 knockout virus and sh-RNA mediated knockdown of CA9 expression we further demonstrate that EBNA2 mediated CA9 transcriptional activation is essential for EBV latently infected B-cell survival. In contrast, during lytic cycle reactivation CA9 expression is transcriptionally suppressed by the key EBV lytic cycle transactivator, BZLF1 through its transactivation domain. Overall, our study highlights the dynamic alterations of CA9 expression and its activity in regulating pH homeostasis act as one of the major drivers for EBV induced B-cell transformation and subsequent B-cell lymphomagenesis.

microbiology↗

bioRxiv2023

PRDM16 co-operates with LHX2 to shape the human brain

PRDM16 is a dynamic transcriptional regulator of various stem cell niches, including adipocytic, hematopoietic, cardiac progenitors, and neural stem cells. PRDM16 has been suggested to contribute to 1p36 deletion syndrome, one of the most prevalent subtelomeric microdeletion syndromes. We report a patient with a de novo nonsense mutation in the PRDM16 coding sequence, accompanied by lissencephaly and microcephaly features. Human stem cells were genetically modified to mimic this mutation, generating cortical organoids that exhibited altered cell cycle dynamics. RNA sequencing of cortical organoids at day 32 unveiled changes in cell adhesion and WNT-signaling pathways. ChIP-seq of PRDM16 identified binding sites in postmortem human fetal cortex, indicating the conservation of PRDM16 binding to developmental genes in mice and humans, potentially at enhancer sites. A shared motif between PRDM16 and LHX2 was identified and further examined through comparison with LHX2 ChIP-seq data from mice. These results suggested a collaborative partnership between PRDM16 and LHX2 in regulating a common set of genes and pathways in cortical radial glia cells, possibly via their synergistic involvement in cortical development.

developmental biology↗

bioRxiv2023

Cell state transition analysis identifies interventions that improve control of M. tuberculosis infection by susceptible macrophages

Understanding cell state transitions and purposefully controlling them to improve therapies is a longstanding challenge in biological research and medicine. Here, we identify a transcriptional signature that distinguishes activated macrophages from TB-susceptible and TB-resistant mice. We then apply the cSTAR (cell State Transition Assessment and Regulation) approach to data from screening-by-RNA sequencing to identify chemical perturbations that shift the. transcriptional state of the TB-susceptible macrophages towards that of TB-resistant cells. Finally, we demonstrate that the compounds identified with this approach enhance resistance of the TB-susceptible mouse macrophages to virulent M. tuberculosis.

immunology↗

bioRxiv2022

Supervised Machine Learning Enables Geospatial Microbial Provenance

The recent increase in publicly available metagenomic datasets with geospatial metadata has made it possible to determine location-specific, microbial fingerprints from around the world. Such fingerprints can be useful for comparing microbial niches for environmental research, as well as for applications within forensic science and public health. To determine the regional specificity for environmental metagenomes, we examined 4305 shotgun-sequenced samples from the MetaSUB Consortium dataset - the most extensive public collection of urban microbiomes, spanning 60 different cities, 30 countries, and 6 continents. We were able to identify city-specific microbial fingerprints using supervised machine learning (SML) on the taxonomic classifications, and we also compared the performance of ten SML classifiers. We then further evaluated the five algorithms with the highest accuracy, with the city and continental accuracy ranging from 85-89% to 90-94%, respectively. We then used these results to develop Cassandra, a random-forest-based classifier that identifies indicator species to aid in fingerprinting and can infer higher-order microbial interactions at each site. We further tested the Cassandra algorithm on the Tara Oceans dataset, the largest collection of marine-based microbial genomes, where it classified the oceanic sample locations with 83% accuracy. These results and code show the utility of SML methods and Cassandra to identify bioindicator species across both oceanic and urban environments, which can help guide ongoing efforts in biotracing, environmental monitoring, and microbial forensics (MF).

microbiology↗

bioRxiv2020

Maladaptive oxidative stress cascade drives type I interferon hyperactivity in TNF activated macrophages promoting necrosis in murine tuberculosis granulomas

Tuberculosis remains a critical infectious disease world-wide. The development of novel therapeutic strategies requires greater understanding of host factors that contribute to disease susceptibility. A major unknown in TB pathogenesis is the mechanism of necrosis in TB granulomas that leads to the massive lung tissue damage and cavity formation necessary for the pathogen transmission. In humans, TB progression has been linked to hyperactivity of type I IFN (IFN-I) pathway, the primary cause of which remains elusive. We studied the mechanistic drivers of pulmonary TB progression using a unique model B6J.C3-Sst1C3HeB/Fej Krmn mice that develop human-like necrotic TB granulomas and IFN-I hyperactivity. We established that IFN{beta} super-induction occurred in the susceptible macrophages in response to continuous TNF stimulation in the context of a dysregulated antioxidant defense. We observed that unresolving oxidative stress amplified the induction of IFN{beta} through JNK activation and induced the Integrated Stress Response via PKR activation as a compensatory pathway. Subsequently, PKR amplifies IFN{beta} upregulation, forming a positive feedback loop, maintaining the hyperinflammatory state in susceptible macrophages and leading to mitochondrial dysfunction. Thus, within the inflammatory milieu, a cell-intrinsic mechanism of chronic regulatory dysfunction and unresolved stress gradually weakens the macrophage and ultimately promotes the necrotization of TB granulomas. The aberrant macrophage response to TNF can be prevented by an iron chelator and inhibitor of lipid peroxidation, ferrostatin-1. Moreover, ferrostatin treatment increased macrophage survival and boosted bacterial control in the TNF-stimulated macrophages infected with virulent Mtb. These findings identify targets for host-directed therapeutics to interrupt necrotization in TB granulomas.

immunology↗

bioRxiv2019

Atypical Protein Kinase C iota (PKC{lambda}/{iota}) Ensures Mammalian Development by Establishing the Maternal-Fetal Exchange Interface

In utero mammalian development relies on the establishment of the maternal-fetal exchange interface, which ensures transportation of nutrients and gases between the mother and the fetus. This exchange interface is established via development of multinucleated syncytiotrophoblast cells (SynTs) during placentation. In mouse, SynTs develop via differentiation of the trophoblast progenitor cells (TSPCs) of the placenta primordium and in human, SynTs are developed via differentiation of villous cytotrophoblast (CTB) progenitors. Despite the critical need in pregnancy progression, conserved signaling mechanisms that ensure SynT development are poorly understood. Herein, we show that Atypical Protein Kinase C iota (PKC{lambda}/I) plays an essential role in establishing the SynT differentiation program in trophoblast progenitors. Loss of PKC{lambda}/I in the mouse TSPCs abrogates SynT development leading to embryonic death at ~E9.0. We also show that PKC{lambda}/I-mediated priming of trophoblast progenitors for SynT differentiation is a conserved event during human placentation. PKC{lambda}/I is selectively expressed in the first-trimester CTBs of a developing human placenta. Furthermore, loss of PKC{lambda}/I in CTB-derived human trophoblast stem cells (Human TSCs) impairs their SynT differentiation potential both in vitro and after transplantation in immunocompromised mice. Our mechanistic analyses indicate that PKC{lambda}/I signaling maintains expression of GCM1, GATA2, and PPAR{gamma}, which are key transcription factors to instigate SynT differentiation programs in both mouse and human trophoblast progenitors. Our study uncovers a conserved molecular mechanism, in which PKC{lambda}/I signaling regulates establishment of the maternal-fetal exchange surface by promoting trophoblast progenitor to SynT transition during placentation.

developmental biology↗

bioRxiv2019

Trophoblast paracrine signaling regulates placental hematoendothelial niche

The placenta acts as a major organ for hematopoiesis. It is believed that placental hematopoietic stem and progenitor cells (HSPCs) migrate to the fetal liver to ensure optimum hematopoiesis in the developing embryo. The labyrinth vasculature in a mid-gestation mouse placenta provides a niche for the definitive hematopoietic stem cell (HSC) generation and expansion. It has been proposed that these processes are regulated by a host of paracrine factors secreted by trophoblast giant cells (TGCs) at the maternal-fetal interface. However, the molecular mechanism by which the TGCs regulate the hematoendothelial niche in a developing placenta is yet to be defined. Using a TGC-specific Gata2 and Gata3 double knockout mouse model, we show that the loss of GATA2 and GATA3 at the TGC layer leads to fetal growth retardation and embryonic death due to disruptions in the delicate hematopoietic-angiogenic balance in the developing placenta. Using single-cell RNA-Seq analyses, we also show that the loss of GATA factors in the TGCs results in the loss of HSC population within the placental labyrinth and is associated with defective placental angiogenesis. Interestingly, we also found that this TGC-specific GATA factor-loss leads to impaired differentiation and distribution of trophoblast progenitor cells. Our study helps to define the GATA-dependent non-autonomous signaling mechanisms of the primary parietal trophoblast giant cells by which it regulates the delicate hematopoietic-angiogenic balance in the developing placenta.

developmental biology↗

bioRxiv2019

Channeling macrophage polarization by using a selective translation inhibitor

Macrophages contribute to host immunity and tissue homeostasis via alternative activation programs. M1-like macrophages control intracellular bacterial pathogens and tumor progression. In contrast, M2-like macrophages shape reparative microenvironments that can be conducive for pathogen survival or tumor growth. An imbalance of these macrophages phenotypes may perpetuate sites of chronic unresolved inflammation, such as infectious granulomas and solid tumors. We have found that plant-derived and synthetic rocaglates sensitize macrophages to low concentrations of the M1-inducing cytokine IFN-gamma and inhibit their responsiveness to IL-4, a prototypical activator of the M2-like phenotype. Treatement of primary macrophages with rocaglates increased their resilience to oxidative stress, stimulated autophagy and killing of intracellular mycobacteria. Thus, rocaglates represent a novel class of immunomodulators that can direct macrophage polarization towards the M1-like phenotype in complex microenvironments associated with hypofunction of type 1 and/or hyperactivation of type 2 immunity, e.g. chronic bacterial infections, allergies and, possibly, certain tumors.

immunology↗

bioRxiv2018

The integrated stress response mediates type I interferon driven necrosis in Mycobacterium tuberculosis granulomas

Necrosis in the tuberculous granuloma is a hallmark of tuberculosis that enables pathogen survival and transmission. Susceptibility to tuberculosis and several other intracellular bacteria is controlled by a mouse genetic locus, sst1, and mice carrying the sst1-suscepible (sst1S) genotype develop necrotic inflammatory lung lesions, similar to human TB granulomas. Our previous work established that increased disease severity in sst1S mice reflects dysfunctional macrophage effector or tolerance mechanisms, but the molecular mechanisms have remained unclear. Here we demonstrate that sst1S macrophages develop aberrant, biphasic responses to TNF characterized by super-induction of stress and type I interferon pathways after prolonged TNF stimulation with this late-stage response being initiated by oxidative stress and Myc activation and driven via a JNK - IFN{beta} - PKR circuit. This circuit leads to induction of the integrated stress response (ISR) mediated by eIF2 phosphorylation and the subsequent hyper-induction of ATF3 and ISR-target genes Chac1, Trib3, Ddit4. The administration of ISRIB, a small molecule inhibitor of the ISR, blocked the development of necrosis in lung granulomas of M. tuberculosis-infected sst1S mice and concomitantly reduced the bacterial burden revealing that induction of the ISR and the locked-in state of escalating stress driven by type I IFN pathway in sst1S macrophages plays a causal role in the development of necrosis. Our data support a generalizable paradigm in intracellular pathogen-host interactions wherein host susceptibility emerges within inflammatory tissue due to imbalanced macrophage responses to growth, differentiation, activation and stress stimuli. Successful pathogens such as M. tuberculosis may exploit this aberrant response in susceptible hosts to induce necrotic lesions that favor long-term pathogen survival and transmission. Interruption of the aberrant stress response with inhibitors such as ISRIB may offer novel therapeutic strategies.

immunology↗

bioRxiv2017

Macrophage resilience and control of intracellular bacteria requires sst1-dependent integration of c-Myc, stress response and type I IFN pathways

Host susceptibility to tuberculosis and several other intracellular bacteria is controlled by a mouse genetic locus, sst1. Necrotic inflammatory lesions, similar to human TB granulomas, are a hallmark of the sst1 susceptible phenotype. Our previous work established that increased disease severity in sst1 susceptible mice reflects dysfunctional macrophage effector or tolerance mechanisms, but the molecular mechanisms have been unclear.\n\nWe demonstrate that sst1-deficient macrophages develop aberrant, biphasic responses to TNF, characterized by super-induction of stress and type I interferon pathways after prolonged TNF stimulation. This late stage response was initiated by oxidative stress and Myc. It was driven via a JNK - IFN{beta} - PKR feed-forward circuit locking the susceptible macrophages in a state of escalating stress. Consequently, prolonged TNF stimulation of the susceptible macrophages reduced their resilience to subsequent infection with intracellular bacteria.\n\nThe data support a generalizable paradigm in host - pathogen interactions, where susceptibility emerges gradually within inflammatory tissue due to imbalanced macrophage responses to growth, differentiation, activation and stress stimuli prior to encountering pathogens. This explains how successful pathogens may locally bypass mechanisms of resistance in otherwise immunocompetent hosts and suggests novel therapeutic strategies.

immunology↗