Although cells of the immune system experience force and pressure throughout their lifecycle, almost nothing is known about how these mechanical processes regulate the immune response 1. Both tissue-resident and tissue-infiltrating immune cells in highly mechanical organs, such as the lung, are constantly exposed to tonic and dynamically changing mechanical cues 2. Here using reverse genetics, we show that myeloid cells respond to force and alterations in cyclical hydrostatic pressure via the mechanosensory ion channel PIEZO1 3. Unbiased RNA sequencing from macrophages subjected to cyclical hydrostatic pressure reveals a striking state of proinflammatory reprogramming. We report a novel mechanosensory-immune signaling circuit which PIEZO1 initiates in response to cyclical hydrostatic pressure, driving c-JUN activation and transcriptional upregulation of Endothelin-1 (EDN1). EDN1 in turn stabilizes HIF1α, which facilitates transcription of a potent and prolonged program of proinflammatory mediators. Using mice conditionally deficient of PIEZO1 in myeloid cells, and cellular depletion assays, we show 10

Influenza A virus (IAV) causes up to half a million deaths worldwide annually, 90% of which occur in older adults. We show that IAV-infected monocytes from older humans have impaired antiviral interferon production but retain intact inflammasome responses. To understand the in vivo consequence, we used mice expressing a functional Mx gene encoding a major interferon-induced effector against IAV in humans. In Mx1-intact mice with weakened resistance due to deficiencies in Mavs and Tlr7, we found an elevated respiratory bacterial burden. Notably, mortality in the absence of Mavs and Tlr7 was independent of viral load or MyD88-dependent signaling but dependent on bacterial burden, caspase-1/11, and neutrophil-dependent tissue damage. Therefore, in the context of weakened antiviral resistance, vulnerability to IAV disease is a function of caspase-dependent pathology.

The initiation of an intestinal tumour is a probabilistic process that depends on the competition between mutant and normal epithelial stem cells in crypts 1 . Intestinal stem cells are closely associated with a diverse but poorly characterized network of mesenchymal cell types 2 , 3 . However, whether the physiological mesenchymal microenvironment of mutant stem cells affects tumour initiation remains unknown. Here we provide in vivo evidence that the mesenchymal niche controls tumour initiation in trans . By characterizing the heterogeneity of the intestinal mesenchyme using single-cell RNA-sequencing analysis, we identified a population of rare pericryptal Ptgs2 -expressing fibroblasts that constitutively process arachidonic acid into highly labile prostaglandin E 2 (PGE 2 ). Specific ablation of Ptgs2 in fibroblasts was sufficient to prevent tumour initiation in two different models of sporadic, autochthonous tumorigenesis. Mechanistically, single-cell RNA-sequencing analyses of a mesenchymal niche model showed that fibroblast-derived PGE 2 drives the expansion οf a population of Sca-1 + reserve-like stem cells. These express a strong regenerative/tumorigenic program, driven by the Hippo pathway effector Yap. In vivo, Yap is indispensable for Sca-1 + cell expansion and early tumour initiation and displays a nuclear localization in both mouse and human adenomas. Using organoid experiments, we identified a molecular mechanism whereby PGE 2 promotes Yap dephosphorylation, nuclear translocation and transcriptional activity by signalling through the receptor Ptger4. Epithelial-specific ablation of Ptger4 misdirected the regenerative reprogramming of stem cells and prevented Sca-1 + cell expansion and sporadic tumour initiation in mutant mice, thereby demonstrating the robust paracrine control of tumour-initiating stem cells by PGE 2 –Ptger4. Analyses of patient-derived organoids established that PGE 2 –PTGER4 also regulates stem cell function in humans. Our study demonstrates that initiation of colorectal cancer is orchestrated by the mesenchymal niche and reveals a mechanism by which rare pericryptal Ptgs2 -expressing fibroblasts exert paracrine control over tumour-initiating stem cells via the druggable PGE 2 –Ptger4–Yap signalling axis.

The annotation of the mammalian protein coding genome is incomplete. Arbitrary open reading frame (ORF) size restriction and the absolute requirement for a methionine codon as the sole initiator of translation, have constrained identification of potentially important transcripts with non-canonical protein coding potential1,2. Using unbiased transcriptomic approaches in macrophages responding to bacterial infection, we show widespread ribosome association with a large number of RNAs that were previously annotated as “non-protein coding”. Although the ability of such non-canonical ORFs to encode functional protein is controversial3,4, we identify a plethora of novel short and non-ATG initiated ORFs with the ability to generate stable and spatially distinct proteins. Importantly, we show that the translation of a novel ORF ‘hidden’ within the long non-coding RNA Aw112010 is essential for the orchestration of mucosal immunity during both bacterial infection and colitis. Together this work expands our interpretation of the protein coding genome and demonstrates the critical nature of proteinaceous products generated from non-canonical ORFs to the immune response in vivo. We therefore propose that the misannotation of non-canonical ORF-containing genes as non-coding RNAs may obscure the essential role of a multitude of previously undiscovered protein coding genes in immunity and disease.

Activated CD4 T cells proliferate rapidly and remodel epigenetically before exiting the cell cycle and engaging their acquired effector function. Metabolic reprograming from the naïve-state is required throughout these phases of activation1. In CD4 T cells, T cell receptor (TCR) ligation, along with co-stimulatory and cytokine signals induce a glycolytic anabolic program required for biomass generation, rapid proliferation, and effector function2. CD4 T cell differentiation (proliferation and epigenetic remodeling) and function are coordinately orchestrated by signal transduction and transcriptional remodeling; however, it remains unclear whether these processes are independently regulated by cellular biochemical composition. Here we demonstrate that distinct modes of mitochondrial metabolism support T helper 1 (Th1) cell differentiation and effector function, biochemically uncoupling these processes. We find that the TCA cycle is required for terminal Th1 cell effector function through succinate dehydrogenase (SDH; Complex II), yet the activity of SDH suppresses Th1 cell proliferation and histone acetylation. In contrast, we show that Complex I of the electron transport chain (ETC), the malate-aspartate shuttle, and citrate export from the mitochondria are required to maintain aspartate synthesis necessary for Th cell proliferation. Furthermore, we find that mitochondrial citrate export and malate-aspartate shuttle promote histone acetylation and specifically regulate the expression of a set of genes involved in T cell activation, proliferation, and metabolic programming. Combining genetic, pharmacological, and metabolomics approaches, we demonstrate that T helper cell differentiation and terminal effector function can be biochemically uncoupled. These findings support a model in which the malate-aspartate shuttle, citrate export, and Complex I supply the substrates needed for proliferation and epigenetic remodeling during early T cell activation, while Complex II consumes the substrates of these pathways, antagonizing differentiation and enforcing terminal effector function. Our data suggest that transcriptional programming works in concert with a parallel biochemical network to enforce cell state.

The incorporation of TiO2 nanoparticles into (ethylene-vinyl alcohol)-based food packaging copolymers affords an opportunity to synthesize polymer-based nanocomposite materials with novel and powerful biocidal and photodegradability properties, resulting in the production of an advanced, environmentally friendly system prepared using a cost-effective synthesis method via a simple melt compounding without the need of a coupling agent incorporation. The presented materials display an unprecedented performance in the killing of both Gram positive and negative bacteria without the necessity of being release to the media and an easy degradation under sunlight which favorably competes with biodegradation procedures.

Highlights d Epithelial and immune cell IL-18 are not required to combat S. typhimurium d Enteric neurons express IL-18 d Enteric neuronal IL-18 controls goblet cell antimicrobial protein expression d Neuronal IL-18 directs killing of enteric bacterial pathogens

Two-component systems (TCS) serve as stimulus-response coupling mechanisms to allow organisms to adapt to a variety of environmental conditions. The opportunistic pathogen Pseudomonas aeruginosa encodes for more than 100 TCS components. To avoid unwanted cross-talk, signaling cascades are very specific, with one sensor talking to its cognate response regulator (RR). However, cross-regulation may provide means to integrate different environmental stimuli into a harmonized output response. By applying a split luciferase complementation assay, we identified a functional interaction of two RRs of the OmpR/PhoB subfamily, namely PhoB and TctD in P. aeruginosa. Transcriptional profiling, ChIP-seq analysis and a global motif scan uncovered the regulons of the two RRs as well as a quadripartite binding motif in six promoter regions. Phosphate limitation resulted in PhoB-dependent expression of the downstream genes, whereas the presence of TctD counteracted this activation. Thus, the integration of two important environmental signals e.g. phosphate availability and the carbon source are achieved by a titration of the relative amounts of two phosphorylated RRs that inversely regulate a common subset of genes. In conclusion, our results on the PhoB and TctD mediated two-component signal transduction pathways exemplify how P. aeruginosa may exploit cross-regulation to adapt bacterial behavior to complex environments.