Biology subjects

Li, S.

Publications and source records attributed to Li, S..

At least 1,207 records · Page 67Linked to original sources

bioRxiv2019

Structure-function analyses of a keratin heterotypic complex identify specific keratin regions involved in intermediate filament assembly

Intermediate filaments (IFs) provide vital mechanical support in a broad array of cell types. Interference with this role causes cell fragility and accounts for a large number of human diseases. Gaining an understanding IF structure is paramount to understanding their function and designing therapeutic agents for relevant diseases. Here, we report the 2.6 [A] resolution crystal structure of a complex of interacting 2B domains of keratin 5 (K5) and K14. K5 and K14 form a long-range, left-handle coiled coil, with participating -helices aligned in parallel and in register. Follow-up mutagenesis revealed that specific contacts between interacting 2B domains play a crucial role during 10-nm IF assembly, likely at the step of octamer-octamer association. The resulting structural model represents the first atomic-resolution visualization of 2B-2B interactions consistent with the A22 dimer alignment and provide insight into the defects introduced by mutations in IF genes associated with human skin diseases.

biochemistry↗

bioRxiv2019

Novel regulation from novel interactions: Identification of an RNA sponge that controls the levels, processing and efficacy of the RoxS riboregulator of central metabolism in Bacillus subtilis

Small RNAs (sRNAs) are a taxonomically-restricted but transcriptomically-abundant class of post-transcriptional regulators. While potentially of importance, we know the function of few. This is in no small part because we lack global-scale methodology enabling target identification, this being especially acute in species without known RNA meeting point proteins (e.g. Hfq). We apply a combination of psoralen RNA cross-linking and Illumina-sequencing to identify RNA-RNA interacting pairs in vivo in Bacillus subtilis, resolving previously well-described interactants. Although sRNA-sRNA pairings are rare (compared with sRNA/mRNA), we identify a robust example involving the unusually conserved sRNA (RoxS/RsaE) and an unstudied sRNA that we term Regulator of small RNA A (RosA). This interaction is found in independent samples across multiple conditions. Given the possibility of a novel associated regulatory mechanism, and the rarity of well-characterised bacterial sRNA-sRNA interactions, we mechanistically dissect RosA and its interactants. RosA we show to be a sponge RNA, the first to be described in a Gram-positive bacterium. RosA interacts with at least two sRNAs, RoxS and FsrA. Unexpectedly, it acts differently on each. As expected of a sponge RNA, FsrA is sequestered by RosA. The RosA/RoxS interaction is more complex affecting not only the level of RoxS but also its processing and efficacy. Importantly, RosA provides the condition-dependent intermediary between CcpA, the key regulator of carbon metabolism, and RoxS. This not only provides evidence for a novel, and functionally important, regulatory mechanism, but in addition, provides the missing link between transcriptional and post-transcriptional regulation of central metabolism.

microbiology↗

bioRxiv2019

Amino and PEG-Amino Graphene Oxide Grids Enrich and Protect Samples for High-resolution Single Particle Cryo-electron Microscopy

Cryo-EM samples prepared using the traditional methods often suffer from too few particles, poor particle distribution, or strongly biased orientation, or damage from the air-water interface. Here we report that functionalization of graphene oxide (GO) coated grids with amino groups concentrates samples on the grid with improved distribution and orientation. By introducing a PEG spacer, particles are kept away from both the GO surface and the air-water interface, protecting them from potential denaturation.

biophysics↗

bioRxiv2019

Grass Carp Reovirus (GCRV) Giving Its All to Suppress IFN Production by Countering MAVS-TBK1 Activation .

As a crucial signaling pathway for interferon (IFN) production, the RIG-I-like receptor (RLR) axis is usually the host target of viruses to enhance viral infection. To date, though immune evasion methods to contrapose IFN production have been characterized for a series of terrestrial viruses, the strategies employed by fish viruses remain unclear. Here, we report that all grass carp reovirus (GCRV) proteins encoded by segments S1 to S11 interact with fish RLR factors, specifically for mitochondrial antiviral signaling protein-TANK-binding kinase 1 (MAVS-TBK1) signaling transduction, leading to decreased IFN expression. First, the GCRV viral proteins blunted the MAVS-induced expression of IFN but had little effect on TBK1-induced IFN expression. Subsequently, interestingly, co-immunoprecipitation experiments demonstrated that all GCRV viral proteins interacted with several RLR cascades, especially with TBK1. To further illustrate the mechanisms of these interactions between GCRV viral proteins and host RLRs, two of the viral proteins, NS79 (S4) and VP3 (S3), were selected as representative proteins for the study. The obtained data demonstrated that NS79 did not affect the stability of the host RLR protein, but was phosphorylated by gcTBK1, leading to the reduction of host substrate gcIRF3/7 phosphorylation. On the other hand, VP3 degraded gcMAVS and the degradation was significantly reversed by 3-MA. The biological effects of both NS79 and VP3 were consistently found to be related to the suppression of IFN expression and the promotion of viral evasion. Our findings shed light on the special evasion mechanism utilized by fish virus through IFN regulation, which might differ between fish and mammals.\n\nAuthor summaryThe RLR signaling pathway is crucial for IFN induction when host cells are infected with virus and RLR factors are targeted by virus. To date, the evasion mechanisms of fish viruses remain mysterious. In this study, we reveal that all 11 GCRV proteins interact with fish RLR factors and suppress the activation of MAVS-TBK1 signaling transduction, leading to the reduction of IFN expression. Two viral proteins were employed as examples to investigate the different evasion mechanisms of GCRV. These findings reveal the novel countermeasures used by fish virus to avoid the host IFN response.

immunology↗

bioRxiv2019

The metalloproteinase Papp-aa functions as a molecular switch linking IGF signaling to adaptive epithelial growth

Human patients carrying inactivating mutations in the pregnancy-associated plasma protein-a2 (PAPP-A2) gene display short status and lower bone mineral density. The underlying mechanisms are not well understood. Using a zebrafish model, here we report a [Ca2+]-dependent mechanism by which Papp-aa regulates bone calcification via promoting Ca2+-transporting epithelial cell (ionocyte) reactivation. Ionocyte, normally quiescent, re-enter the cell cycle in response to low [Ca2+] stress. Deletion of Papp-aa abolished ionocyte reactivation and resulted in a complete lack of calcified bone. Re-expression of Papp-aa, but not its active site mutant, rescued ionocyte reactivation. Inhibition of Papp-aa activity pharmacologically or by overexpressing STC1 or STC2 impaired ionocyte reactivation. Loss of Papp-aa expression or activity resulted in diminished IGF1 receptor-mediated Akt-Tor signaling activity in ionocytes and expression of a constitutively active Akt rescued ionocyte reactivation. Biochemically, Papp-aa cleaved Igfbp5a, a high-affinity IGF binding protein specifically expressed in ionocytes. Under normal [Ca2+] conditions, the Papp-aa-mediated Igfbp5a proteolysis was suppressed and IGFs sequestered in the IGF/Igfbp5a complex. Forced release of IGFs from the complex was sufficient to activate the IGF-Akt-Tor signaling and promote ionocyte reactivation. These findings suggest that Papp-aa functions as a [Ca2+]-regulated molecular switch linking IGF signaling to adaptive epithelial growth and bone calcification.

developmental biology↗

bioRxiv2019

Systematic Establishment of Robustness and Standards in Patient-Derived Xenograft Experiments and Analysis

Patient-Derived Xenografts (PDXs) are tumor-in-mouse models for cancer. PDX collections, such as those supported by the NCI PDXNet program, are powerful resources for preclinical therapeutic testing. However, variations in experimental design and analysis procedures have limited interpretability. To determine the robustness of PDX studies, the PDXNet tested temozolomide drug response for three pre-validated PDX models (sensitive, resistant, and intermediate) across four blinded PDX Development and Trial Centers (PDTCs) using independently selected SOPs. Each PDTC was able to correctly identify the sensitive, resistant, and intermediate models, and statistical evaluations were concordant across all groups. We also developed and benchmarked optimized PDX informatics pipelines, and these yielded robust assessments across xenograft biological replicates. These studies show that PDX drug responses and sequence results are reproducible across diverse experimental protocols. Here we share the range of experimental procedures that maintained robustness, as well as standardized cloud-based workflows for PDX exome-seq and RNA-Seq analysis and for evaluating growth.

cancer biology↗

bioRxiv2019

Uniform Genomic Data Analysis in the NCI Genomic Data Commons

The goal of the National Cancer Institute (NCI) Genomic Data Commons (GDC) is to provide the cancer research community with a data repository of uniformly processed genomic and associated clinical data that enables data sharing and collaborative analysis in the support of precision medicine. The initial GDC dataset include genomic, epigenomic, proteomic, clinical and other data from the NCI TCGA and TARGET programs. Data production for the GDC started in June, 2015 using an OpenStack-based private cloud. By June of 2016, the GDC had analyzed more than 50,000 raw sequencing data inputs, as well as multiple other data types. Using the latest human genome reference build GRCh38, the GDC generated a variety of data types from aligned reads to somatic mutations, gene expression, miRNA expression, DNA methylation status, and copy number variation. In this paper, we describe the pipelines and workflows used to process and harmonize the data in the GDC. The generated data, as well as the original input files from TCGA and TARGET, are available for download and exploratory analysis at the GDC Data Portal and Legacy Archive (https://gdc.cancer.gov/).

bioinformatics↗

bioRxiv2019

EphB6 regulates social behavior through gut microbiota-mediated vitamin B6 metabolism and excitation/inhibition balance of medial prefrontal cortex in mice

Autism spectrum disorder (ASD) is a developmental disorder with no effective pharmacological treatments so far. Gut microbiota has been suggested to contribute to autistic symptoms. However, the key genes and the mechanisms linking gut microbiota and brain dysfunctions in ASD are still unclear. Here, we found deletion of EphB6, an ASD-associated candidate gene, induced dysregulated gut microbiota and autism-like behavior in mice. More importantly, transplanting fecal microbiota from EphB6-deficient mice resulted in disturbed gut microbiota and autism-like behavior in antibiotics-treated C57BL/6J mice. Meanwhile, transplanting fecal microbiota from wild-type mice ameliorated disturbed gut microbiota and autism-like behavior in mice with deletion of EphB6. At the metabolic levels, dysregulated gut microbiota led to vitamin B6 and dopamine defects in EphB6-deficient mice. At the cellular levels, excitation/inhibition (E/I) imbalance in medial prefrontal cortex was induced by gut microbiota-mediated defects of vitamin B6 metabolism in EphB6-deficient mice. Our study uncovers a key role for EphB6 in regulation of social behavior by gut microbiota-mediated vitamin B6 metabolism, dopamine synthesis and E/I balance, suggesting a new strategy for treatment of ASD patients.

neuroscience↗

bioRxiv2019

CpG-ODN 2007 protects zebrafish against Vibrio vulnificus-induced infection

Vibrio vulnificus (V. vulnificus) is an aquatic pathogen that can cause primary sepsis and soft tissue infection. CpG oligodeoxynucleotides (CpG-ODN) are a type of essential immunomodulators, which can trigger or enhance immune responses in mammals, fish, and humans. In this study, we evaluated the effect of CpG-ODN 2007 as a potential immunostimulant for zebrafish infected with V. vulnificus (FJ03-X2). Fish injected with the CpG-ODN 2007 showed lower mortality rate compared with the fish that did not receive treatment. The survival rates of CpG-ODN 2007-treated group and PBS-treated group were 85% and 57.9%, respectively. In addition, our in vitro results demonstrated that CpG-ODN 2007 can effectively reduce the toxicity of V. vulnificus (FJ03-X2) to zebrafish embryonic fibroblast (ZF4) cells. Furthermore, we assessed immune-related genes expression patterns in FJ03-X2 infected zebrafish or ZF4 cells with and without CpG-ODN 2007 treatment, such as TLRs and IL-1{beta}. To sum up, our data indicated that CpG-ODN 2007 protects zebrafish against Vibrio vulnificus induced infection.

immunology↗

bioRxiv2019

Strain-level identification of bacterial tomato pathogens directly from metagenomic sequences

Routine strain-level identification of plant pathogens directly from symptomatic tissue could significantly improve plant disease control and prevention. Here we tested the Oxford Nanopore Technologies (ONT) MinION sequencer for metagenomic sequencing of tomato plants either artificially inoculated with a known strain of the bacterial speck pathogen Pseudomonas syringae pv. tomato (Pto), or collected in the field and showing bacterial spot symptoms caused by either one of four Xanthomonas species. After species-level identification using ONTs WIMP software and the third party tools Sourmash and MetaMaps, we used Sourmash and MetaMaps with a custom database of representative genomes of bacterial tomato pathogens to attempt strain-level identification. In parallel, each metagenome was assembled and the longest contigs were used as query with the genome-based microbial identification Web service LINbase. Both the read-based and assembly-based approaches correctly identified Pto strain T1 in the artificially inoculated samples. The pathogen strain in most field samples was identified as a member of Xanthomonas perforans group 2. This result was confirmed by whole genome sequencing of colonies isolated from one of the samples. Although in our case, metagenome-based pathogen identification at the strain-level was achieved, caution still needs to be exerted when interpreting strain-level results because of the challenges inherent to assigning reads to specific strains and the error rate of nanopore sequencing.

microbiology↗

bioRxiv2019

Analysis of continuous infusion functional PET (fPET) in the human brain

Functional positron emission tomography (fPET) is a neuroimaging method involving continuous infusion of 18-F-fluorodeoxyglucose (FDG) radiotracer during the course of the PET examination. Compared with the conventional bolus administered static FDG PET which provides only a snapshot of the averaged glucose uptake into the brain in a limited dynamic time window, fPET offers a significantly wider time window to study the dynamics of glucose uptake. Several earlier studies have applied fPET to investigate brain FDG uptake and study its relationship with functional magnetic resonance imaging (fMRI). However, due to the unique characteristics of fPET signals, modelling of the fPET signal is a complex task and poses challenges for accurate interpretation of the results. This study applies independent component analysis (ICA) to analyze resting state fPET data, and to compare the performance of ICA and general linear modelling (GLM) for estimation of brain activation in response to tasks. The fPET signal characteristics were compared using GLM and ICA methods to model the fPET visual activation data. Our aim was to evaluate GLM and ICA methods for analyzing task fPET datasets and present ICA method in the analysis of resting state fPET datasets. Using both simulation and in-vivo experimental datasets, we show that both methods can successfully identify task related brain activation. We report fPET metabolic resting state brain networks analyzed using the fPET ICA method in a cohort of healthy subjects. Functional PET provides a unique method to map dynamic changes of glucose uptake in the resting human brain and in response to extrinsic stimulation.

neuroscience↗

bioRxiv2019

Spatial transcriptional signatures define margin morphogenesis along the proximal-distal and medio-lateral axes in complex leaf species Solanum lycopersicum (tomato)

Leaf morphogenesis involves cell division, expansion, and differentiation in the developing leaf, cells at different positions along the medio-lateral and proximal-distal leaf axes divide, expand, and differentiate at different rates. The gene expression changes that control cell fate along these axes remain elusive due to difficulties in precisely isolating tissues. Here, we combined rigorous early leaf characterization, laser capture microdissection, and transcriptomic sequencing to ask how gene expression patterns regulate early leaf morphogenesis in wild-type tomato (Solanum lycopersicum) and the leaf morphogenesis mutant trifoliate. We observed transcriptional regulation of cell differentiation along the proximal-distal axis and identified molecular signatures delineating the classically defined marginal meristem/blastozone region during early leaf development. We describe the importance of endoreduplication during leaf development, when and where leaf cells first achieve photosynthetic competency, and the regulation of auxin transport and signaling along the leaf axes. Knockout mutants of BLADE-ON-PETIOLE2 exhibited ectopic shoot apical meristem formation on leaves, highlighting the role of this gene in regulating margin tissue identity. We mapped gene expression signatures in specific leaf domains and evaluated the role of each domain in conferring indeterminacy and permitting blade outgrowth. Finally, we generated a global gene expression atlas of the early developing compound leaf. One-sentence summaryRigorous structural characterization, laser capture microdissection, and transcriptomic sequencing reveal how gene expression patterns regulate early morphogenesis of the compound tomato leaf. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantcell.org) is Ciera C. Martinez (ccmartinez@berkeley.edu).

plant biology↗

bioRxiv2019

Structural changes in the gut microbiome of short-term and long-term medical workers compared to normal controls

ObjectiveHospital environment has been implicated in enrichment and exchange of pathogens and antibiotic resistances, but its potential in shaping the symbiotic microbial community of the hospital staff is unclear. This study was designed to evaluate the alteration of gut microbiome in medical workers compared to non-medical controls.\n\nDesignProspective cross-sectional cohort study.\n\nSettingIntensive care unit (ICU) and other departments from a center in northeast China.\n\nSubjects175 healthy medical workers (1-3 months short-term workers, n = 80; >1 year long-term workers, n = 95) and 80 healthy normal controls.\n\nInterventionsNone.\n\nMeasurements and Main ResultsFecal samples of all subjects were analyzed using the 16S rRNA gene sequencing. Medical workers exhibited remarkable deviation in gut microbial within-sample diversity and enterotypes stratification, and shift in overall microbial structure. Short-term workers were significantly more abundant in taxa including Lactobacillus, Butyrivibrio, Clostridiaceae_Clostridium, Ruminococcus, Dialister, Bifidobacterium, Odoribacter and Desulfovibrio, and with lower abundances of Bacteroides and Blautia compared with the controls. While long-term workers were enriched in taxa including Dialister, Veillonella, Clostridiaceae_Clostridium, Bilophila, Desulfovibrio, Pseudomonas and Akkermansia, with lower abundances of Bacteroides and Coprococcus compared with the controls. In addition, medical workers working years (short-term vs. long-term), hospital department (resident doctor vs. nursing staff) and work position (ICU vs. not-ICU) revealed considerable effects on their gut microbiome. Moreover, by analyzing the environmental samples (n = 9) around the inpatient wards and the hospital, we showed that the gut microbiota of medical workers was closer to environmental microbiota than that of the normal controls, probably in correlation to lasting exposure to the pathogenic taxa (e.g. Pseudomonas) in health workers.\n\nConclusionsOur findings demonstrated structural changes in the gut microbial community of the medical workers. Further studies are proposed for investigating the potentially physiological influence of the altered gut microbiome in medical participants.\n\nIMPORTANCEIn this study, we for the first time focused on the influence of hospital environmental factors on gut microbiota of medical workers. The significance of our study is not limited to revealing the remodeling effect of the hospital environment on the gut microbiota of medical workers. Based on these, we also propose targeted and operational recommendations that can promote the health of hospital staff.

microbiology↗

bioRxiv2019

Interplay between persistent activity and activity-silent dynamics in prefrontal cortex during working memory

Persistent neuronal spiking has long been considered the mechanism underlying working memory, but recent proposals argue for alternative, \"activity-silent\" substrates for memory. Using monkey and human electrophysiology, we show here that attractor dynamics that control neural spiking during mnemonic periods interact with activity-silent mechanisms in PFC. This interaction allows memory reactivation, which enhance serial biases in spatial working memory. Stimulus information was not decodable between trials, but remained present in activity-silent traces inferred from spiking synchrony in PFC. Just prior to the new stimulus, this latent trace was reignited into activity that recapitulated the previous stimulus representation. Importantly, the reactivation strength correlated with the strength of serial biases in both monkeys and humans, as predicted by a computational model integrating activity-based and activity-silent mechanisms. Finally, single-pulse TMS applied to human prefrontal cortex prior to trial start enhanced serial biases, demonstrating the causal role of prefrontal reactivations in determining working memory behavior.

neuroscience↗

bioRxiv2019

Expressed barcodes enable clonal characterization of chemotherapeutic responses in chronic lymphocytic leukemia

The remarkable evolutionary capacity of cancer is a major challenge to current therapeutic efforts. Fueling this evolution is its vast clonal heterogeneity and ability to adapt to diverse selective pressures. Although the genetic and transcriptional mechanisms underlying these responses have been independently evaluated, the ability to couple genetic alterations present within individual clones to their respective transcriptional or functional outputs has been lacking in the field. To this end, we developed a high-complexity expressed barcode library that integrates DNA barcoding with single-cell RNA sequencing through use of the CROP-seq sgRNA expression/capture system, and which is compatible with the COLBERT clonal isolation workflow for subsequent genomic and epigenomic characterization of specific clones of interest. We applied this approach to study chronic lymphocytic leukemia (CLL), a mature B cell malignancy notable for its genetic and transcriptomic heterogeneity and variable disease course. Here, we demonstrate the clonal composition and gene expression states of HG3, a CLL cell line harboring the common alteration del(13q), in response to front-line cytotoxic therapy of fludarabine and mafosfamide (an analog of the clinically used cyclophosphamide). Analysis of clonal abundance and clonally-resolved single-cell RNA sequencing revealed that only a small fraction of clones consistently survived therapy. These rare highly drug tolerant clones comprise 94% of the post-treatment population and share a stable, pre-existing gene expression state characterized by upregulation of CXCR4 and WNT signaling and a number of DNA damage and cell survival genes. Taken together, these data demonstrate at unprecedented resolution the diverse clonal characteristics and therapeutic responses of a heterogeneous cancer cell population. Further, this approach provides a template for the high-resolution study of thousands of clones and the respective gene expression states underlying their response to therapy.

cancer biology↗

bioRxiv2019

A novel xenograft model of human HCC in immunocompetent mouse

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors that threaten human health; thus, the establishment of an animal model with clinical features similar to human liver cancer is of important practical significance. Taking advantage of the novel microcarrier-6, human HCC cells was injected into immunocompetent mice to establish a novel human HCC patient-derived xenograft (PDX) model. Primary HCC cells were isolated from fresh liver cancer tissues, which were subsequently co-cultured with microcarrier-6 to construct a three-dimensional tumor cell culture model in vitro. The HCC-microcarrier complex was implanted into mice by subcutaneous inoculation, and the tumor formation time, tumor formation rate, and pathological manifestation were recorded. Changes of immune parameters in mice were detected by flow cytometry. The success rate was 60% (6/10) in the establishment of liver cancer PDX mouse model, and the total tumor formation rate of the tumor-forming model is 80-100%. H&E staining and immunohistochemical experiments indicate that the model well retained the characteristics of the primary tumor. Interestingly, M2 macrophages in tumor-bearing mice increased significantly, and the levels of CD4+ T cells were significantly reduced. Through the application of the microcarrier-6 in immunocompetent mice, we successfully established a novel human HCC PDX model, which can be used to better study and further elucidate the occurrence and pathogenic mechanism of HCC.

cancer biology↗

bioRxiv2019

Fluoxetine improves behavioural deficits induced by chronic alcohol addiction by alleviating RNA editing of 5-HT2C receptors in astrocytes

The alcoholism and major depressive disorder are common comorbidity, with alcohol-induced depressive symptoms being eased by selective serotonin re-uptake inhibitors (SSRIs), although the mechanisms underlying pathology and therapy are poorly understood. Chronic alcohol consumption affects the activity of serotonin 2C receptors (5-HT2CR) by regulating adenosine deaminases acting on RNA (ADARs) in neurones. Astrogliopathic changes contribute to alcohol addiction, while decreased release of ATP from astrocytes can trigger depressive-like behaviours in mice. In this study, we discovered that chronic alcohol addiction increased editing of RNA of 5-HT2CR via up-regulating the expression of ADAR2, consequnetly reducing the release of ATP from astrocytes induced by 5-HT2CR agonist, MK212. At the same time SSRI antidepressant fluoxetine decreased the expression of ADAR2 through the transactivation of EGFR/PI3K/AKT/cFos signalling pathway. Reduction in ADAR2 activity eliminated the RNA editing of 5-HT2CR in vivo and increased release of astroglial ATP which was suppressed by chronic alcohol consumption. Meanwhile, fluoxetine improved the behavioural and motor symptoms induced by alcohol addiction and decreased the alcohol intake. Our study suggests that the astrocytic 5-HT2CR contribute to alcohol addiction; fluoxetine thus can be used to alleviate depression, treat alcohol addiction and improve motor coordination.

neuroscience↗

bioRxiv2019

Arginine-GlcNAcylation of death domain and NleB/SseK proteins is crucial for bacteria pathogenesis by regulating host cell death

Death receptor signaling is critical for cell death, inflammation, and immune homeostasis. Hijacking death receptors and their corresponding adaptors through type III secretion system (T3SS) effectors has been evolved to be a bacterial evasion strategy. NleB from enteropathogenic Escherichia coli (EPEC) and SseK1/2/3 from Salmonella enterica serovar Typhimurium (S. Typhimurium) can modify some death domains involved in death receptor signaling through arginine-GlcNAcylation. This study applied a limited substrate screen from 12 death domain proteins with conserved arginines during EPEC and Salmonella infection and found that NleB from EPEC hijacked death receptor signaling tumor necrosis factor receptor 1 (TNFR1)-associated death domain protein (TRADD), FAS-associated death domain protein (FADD), and receptor-interacting serine/threonine-protein kinase 1 (RIPK1), whereas SseK1 and SseK3 disturbed TNFR signaling through the modification of TRADD Arg235/245 and TNFR1 Arg376, respectively. SseK1 and SseK3 delivered by Salmonella inhibited TNF-- but not TNF-related apoptosis-inducing ligand (TRAIL)-induced cell death, which was consistent with their host substrate recognition specificity. Taking advantage of the substrate specificity of SseK effectors, we found that only SseK1 fully rescued the bacteria colonization deficiency contributed by NleBc in Citrobacter rodentium infection animal model, indicating that TRADD was likely to be the preferred in vivo substrate corresponding to NleB/SseK1-induced bacterial virulence. Furthermore, novel auto-arginine-GlcNAcylation was observed in NleB and SseK1/3, which promoted the enzyme activity. These findings suggest that arginine-GlcNAcylation in death domains and auto-arginine-GlcNAcylation catalyzed by type III-translocated bacterial effector proteins NleB/SseKs are crucial for bacteria pathogenesis in regulating nuclear factor-{kappa}B (NF-{kappa}B) and death receptor signaling pathways. This study provides an insight into the mechanism by which EPEC and Salmonella manipulate death receptor signaling and evade host immune defense through T3SS effectors.\n\nAuthor SummaryEnteropathogenic Escherichia coli (EPEC) and Salmonella enterica serovar Typhimurium (S. Typhimurium) are important food-borne pathogens infecting the intestine. They deliver type III secretion system effector NleB/SseKs to modify host death domain proteins by arginine GlcNAcylation. We screened the modification of 12 death domains containing conserved arginine in human genome by NleB, SseK1, SseK2, and SseK3 through ectopic co-expression and bacterial infection. Unlike multiple death receptor signaling inhibition by NleB, we found that SseK1 and SseK3 specifically hijacked tumor necrosis factor receptor 1 (TNFR1)-mediated death signaling through targeting TNFR1-associated death domain protein (TRADD) and receptor TNFR1, respectively. We identified the modification sites and suggested that TRADD was the in vivo target of NleB in mice infection model by utilizing the substrate specificity of SseK1 and SseK3, which highlighted anti-bacterial infection role of TRADD in death receptor signaling and non-death receptor signaling. In addition to the modification on host death domain substrates, we firstly elucidated the effect of auto-modification of the arginine GlcNAc transferases on the enzymatic activity, which widened our understanding of the newly discovered post translational modification in the process of pathogen-host interaction.

microbiology↗