Biology subjects

Zheng, X.

Publications and source records attributed to Zheng, X..

At least 307 records · Page 17Linked to original sources

bioRxiv2019

Biochemical and structural characterization of a highly active branched-chain amino acid aminotransferase from Pseudomonas sp. for efficient biosynthesis of chiral amino acids

Aminotransferases (ATs) are important biocatalysts for the synthesis of chiral amines because of their capability of introducing amino group into ketones or keto acids as well as their high enantioselectivity, high regioselectivity and no requirement of external addition of cofactor. Among all ATs, branched-chain amino acid aminotransferase (BCAT) can reversibly catalyse branched-chain amino acids (BCAAs), including L-valine, L-leucine, and L-isoleucine, with -ketoglutaric acid to form the corresponding ketonic acids and L-glutamic acid. Alternatively, BCATs have been used for the biosynthesis of unnatural amino acids, such as L-tert-leucine. In the present study, the BCAT from Pseudomonas sp. (PsBCAT) was cloned and expressed in Escherichia coli for biochemical and structural analyses. The optimal reaction temperature and pH of PsBCAT were 40 {degrees}C and 8.5, respectively. PsBCAT exhibited a comparatively broader substrate spectrum, and showed remarkably high activity with L-leucine, L-valine, L-isoleucine and L-methionine with activities of 105 U/mg, 127 U/mg, 115 U/mg and 98 U/mg, respectively. Additionally, PsBCAT had activities with aromatic L-amino acids, L-histidine, L-lysine, and L-threonine. To analyse the catalytic mechanism of PsBCAT with the broad substrate spectrum, the crystal structure of PsBCAT was also determined. Finally, conjugated with the ornithine aminotransferase (OrnAT) from Bacillus subtilis, the coupled system was applied to the preparation of L-tert-leucine with 83% conversion, which provided an approximately 2.7-fold higher yield than the single BCAT reaction. IMPORTANCEDespite the enormous potential of BCATs, the vast majority of enzymes still lack suitably broad substrate scope and activity, thus new sources and novel enzymes are currently being investigated. Here, we described a previously uncharacterized PsBCAT, which showed a surprisingly wide substrate range and was more active towards BCAAs. This substrate promiscuity is unique for the BCAT family and could prove useful in industrial applications. Based on the determined crystal structure, we found some differences in the organization of the substrate binding cavity, which may influence the substrate specificity of the enzyme. Moreover, we demonstrated efficient biocatalytic asymmetric synthesis of L-tert-leucine using a coupling system, which can be used to remove the inhibitory by-product, and to shift the reaction equilibrium towards the product formation. In summary, the structural and functional characteristics of PsBCAT were analysed in detail, and this information will play an important role in the synthesis of chiral amino acids and will be conducive to industrial production of enantiopure chiral amines by aminotransferase.

biochemistry↗

bioRxiv2019

Rapid Detection of Burkholderia pseudomallei with a Lateral Flow Recombinase Polymerase Amplification Assay

Melioidosis is a severe infectious disease caused by gram-negative, facultative intracellular pathogen Burkholderia pseudomallei (B. pseudomallei). Although cases are increasing reported from other parts of the world, it is an illness of tropical and subtropical climates primarily found in southeast Asia and northern Australia. Because of a 40% mortality rate, this life-threatening disease poses a public health risk in endemic area. Early detection of B. pseudomallei infection benefits greatly to implement effective treatment timely, which is vital for prognosis of a melioidosis patient. In this study, a novel isothermal recombinase polymerase amplification combined with lateral flow dipstick (LF-RPA) assay was established for rapid detection of B.pseudomallei. A set of probe and primers targeting orf2 gene of B. pseudomallei were generated and parameters for the LF-RPA assay were optimized. Result can be easy visualized in 30 minutes with the limit of detection (LoD) as low as 20 femtogram (ca. 25.6 copies) of B. pseudomallei genomic DNA. The assay is highly specific as no cross amplification was observed with 35 non-B. pseudomallei pathogens. Isolates (N=19) from patients of Hainan province of China were retrospectively confirmed by the newly developed method. LoD for B. pseudomallei spiked soil and blood samples were 2.1x103 CFU/g and 4.2x103 CFU/ml respectively. Sensitivity of the LF-RPA assay was comparable to TaqMan Real-Time PCR, however, the LF-RPA assay exhibited a better tolerant to inhibitors in blood than the later. Our results showed that the LF-RPA assay is an alternative to existing PCR-based methods for detection of B. pseudomallei with a potentiality of early accurate diagnosis of melioidosis at point of care or in-field use.

microbiology↗

bioRxiv2019

Multiomic definition of generalizable endotypes in human acute pancreatitis.

Acute pancreatitis (AP) is sudden onset pancreas inflammation that causes multiple organ dysfunction syndrome (MODS) and death in certain individuals who develop AP yet minimal systemic inflammation in others. Here, we show that this observed diversity in systemic response and outcome is accompagnied by diversity in molecular subtypes that can be identified using computational analysis of clinical and multiomic data. We integrated co-incident whole blood transcriptomic, plasma proteomic, and serum metabolomic data at serial time points from a cohort of patients presenting with AP and systematically evaluated four different metrics for patient similarity, using unbiased mathematical, biological and clinical measures of internal and external validity. Our results identify four distinct and stable AP endotypes that are characterized by pathway and biomarker combination stereotypes into hypermetabolic, hepatopancreaticobiliary, catabolic and innate immune endotypes. The catabolic endotype in AP strikingly recapitulates a disease endotype previously reported in acute respiratory distress syndrome, a recognized complication of AP. Our findings demonstrate that clinically-relevant and generalizable endotypes exist in AP.

systems biology↗

bioRxiv2019

A plant protein NbP3IP induces autophagy and mediates the autophagic degradation of RSV p3 to inhibit viral infection

In plants, autophagy is involved in responses to viral infection. However, understanding of new host factors mediating autophagic clearance of plant viruses is very limited. We here identified a new host factor NbP3IP participating in autophagy-mediated plant defense against viral infection. NbP3IP interacted with p3, a RNA silencing suppressor encoded by Rice stripe virus (RSV), a negative-strand RNA virus, and mediated its autophagic degradation. NbP3IP could also interact with NbATG8f, which was required for NbP3IP-miediated p3 degradation. Overexpression of NbP3IP induced autophagy and down-regulation of NbP3IP reduced autophagy. Both overexpression of NbP3IP and silencing of GAPC, which also induces autophagy, inhibited RSV infection. In contrast, silencing of ATG7 promoted RSV infection. Thus, through identification of a new potential selective autophagy receptor P3IP, we revealed a new mechanism of autophagy-mediated plant defense against plant viruses and provided the first evidence that plant autophagy can also play an antiviral role against negative-strand RNA viruses.

plant biology↗

bioRxiv2018

Somatic LINE-1 retrotransposition in cortical neurons of Rett patients and healthy individuals

Mounting evidence supports that LINE-1 (L1) retrotransposition can occur postzygotically in healthy and diseased human tissues, contributing to genomic mosaicism in the brain and other somatic tissues of an individual. However, the genomic distribution of somatic L1Hs (Human-specific LINE-1) insertions and their potential impact on carrier cells remain unclear. Here, using a PCR-based targeted bulk sequencing approach, we profiled 9,181 somatic insertions from 20 postmortem tissues from five Rett patients and their matched healthy controls. We identified and validated somatic L1Hs insertions in both cortical neurons and non-brain tissues. In Rett patients, somatic insertions were significantly depleted in exons--mainly contributed by long genes--than healthy controls, implying that cells carrying MECP2 mutations might be defenseless against a second exonic L1Hs insertion. We observed a significant increase of somatic L1Hs insertions in the brain compared with non-brain tissues from the same individual. Compared to germline insertions, somatic insertions were less sense-depleted to transcripts, indicating that they underwent weaker selective pressure on the orientation of insertion. Our observations demonstrate that somatic L1Hs insertions contribute to genomic diversity and MECP2 dysfunction alters their genomic patterns in Rett patients. Author SummaryHuman-specific LINE-1 (L1Hs) is the most active autonomous retrotransposon family in the human genome. Mounting evidence supports that L1Hs retrotransposition occurs postzygotically in the human brain cells, contributing to neuronal genomic diversity, but the extent of L1Hs-driven mosaicism in the brain is debated. In this study, we profiled genome-wide L1Hs insertions among 20 postmortem tissues from Rett patients and matched controls. We identified and validated somatic L1Hs insertions in both cortical neurons and non-brain tissues, with a higher jumping activity in the brain. We further found that MECP2 dysfunction might alter the genomic pattern of somatic L1Hs in Rett patients.

genomics↗

bioRxiv2018

Hyocholic acid species and the risk of type 2 diabetes

Hyocholic acid (HCA) and its derivatives are found in only trace amounts in human blood, but constitute approximately 76 % of the bile acid (BA) pool in the pig, a species known for its exceptional resistance to type 2 diabetes mellitus (T2DM). Here we show that HCA species play a crucial role in maintaining glucose homeostasis and preventing T2DM. We found that in two cohort studies (n=1,213), both obesity and diabetes were associated with lower serum concentrations of HCA species. Serum HCA levels in apparently healthy individuals (n=132) were found to be strong predictors for metabolic health 10 years later. Oral administration of HCA increased serum fasting GLP-1, to a greater extent than metformin, in healthy and diabetic mouse models. HCA upregulated GLP-1 secretion in intestinal enteroendocrine cells via simultaneously activating G-protein-coupled BA receptor, TGR5, and inhibiting farnesoid X receptor, a unique mechanism that is not found in other BA species.

systems biology↗

bioRxiv2018

Romantic jealousy is positively associated with fronto-striatal, insula and limbic responses to angry faces

Romantic jealousy is a complex social emotion combining the different primary emotions of anger, fear and sadness. Previous evidence has suggested the involvement of fronto-striatal dopaminergic circuitry in clinical pathological jealousy, although little is known about overlaps with the neural representation of primary emotions involved in non-morbid jealousy. In the current study, 85 healthy subjects underwent fMRI during resting state and an emotional face recognition paradigm. A total of 150 faces (happy, angry, fearful, sad, neutral) were presented and subjects were required to identify the expression and rate its intensity. Trait romantic jealousy was assessed using the Multidimensional Jealousy Scale. Behavioral results showed that only intensity ratings of angry faces were positively associated with subjects jealousy scores. During processing of angry versus neutral expression faces, subjects with higher jealousy scores exhibited greater activation in the right thalamus, insula, fusiform gyrus and hippocampus, left dorsal striatum and superior parietal lobule and bilateral cerebellum and inferior frontal gyrus after controlling for trait aggression and sex. Functional connectivity between the inferior frontal gyrus and caudate was also increased. No associations with resting state functional connectivity were found. Overall, the present study demonstrates an association between romantic jealousy and increased intensity ratings of angry faces as well as in activity and functional connectivity of dorsal striatal-inferior frontal circuitry. Thus, increased emotional responsivity to social threat and enhanced activity in limbic regions and dopaminergic fronto-striatal circuitry may be features of both non-morbid and pathological jealousy.

neuroscience↗

bioRxiv2018

Off-target effects of Cre recombinase reveal limits of adoptive T cell transfers and persistent proliferation of effector CD8 T-cells

Effector-memory T-cells (TEM) are assumed to be short-lived cells that poorly proliferate upon antigenic restimulation, thus depending on central-memory T-cells (TCM) to replenish their numbers during homeostasis, largely depending on adoptive transfer evidence. Here we analyzed T cells in their natural environment and observed robust long-term in vivo cycling within the TEM subset that was stronger than the one in the TCM subset. Murine Cytomegalovirus (MCMV) induces inflationary TEM responses that remain high during latency. We analyzed Ki67 expression during acute and latent MCMV infection and found Ki67hiBcl2lo TEM in latently infected mice, arguing for antigen-driven TEM proliferation. TEM acquired deuterium more rapidly than TCM in an in vivo labeling experiment, and were replenished more rapidly than TCM after memory depletion, suggesting that TEM cycle faster than TCM. We depleted selectively the proliferating T-cells by Cre-overinduction, which resulted in a selective loss of Ki67hiBCl2lo effector T-cells, and an increase in the death of TEM in the spleen, while it hardly affected the TCM subset, arguing for robust proliferation of TEM in the spleen. On the other hand, TEM homing to the spleen upon adoptive transfer was substantially poorer than TCM, explaining the previously reported expansions of TCM, but not TEM, upon transfer. In conclusion, our data suggest that memory inflation is maintained by proliferation of antigen-specific TEM, rather than by continued expansion and differentiation of TCM.\n\nAuthor SummaryThe naive T cell population consists of T cells that have the potential to recognize millions of different pathogens. Upon infection, naive T cells that recognize the pathogen expand, and differentiate into effector T cells that eliminate infected cells. Once the infection is contained, the T cell pool contracts and only a small population of central memory T cells remains that can expand quickly upon re-infection. Cytomegaloviruses cause persistent infections that are not cleared from the organism after the initial immune response. In infected individuals a pool of CMV-specific effector memory T cells dominates the immune system in a phenomenon called memory inflation. Previous research using the transfer of central memory or effector memory T cells from CMV-infected mice into mice with a matching infection, showed expansion of central memory T cells but not effector memory T cells. Here we show that effector memory T cells have a reduced capacity to home into lymphoid organs, where T cell activation takes place, compared to central memory T cells. Using methods that do not interfere with T cell differentiation and homing, we show that effector memory T cells are proliferating during the persistent phase of CMV infection, significantly contributing to the upkeep of the inflationary population.

immunology↗

bioRxiv2018

Ultra-Efficient Short Read Sequencing of Immune Receptor Repertoires

AbstractT cell receptor (TCR) repertoire sequencing is increasingly employed to characterize adaptive immune responses. However, current TCR sequencing methodologies are complex and expensive, limiting the scale of feasible studies. Here we present Framework Region 3 AmplifiKation sequencing (FR3AK-seq), a simplified multiplex PCR-based approach for the ultra-efficient analysis of TCR complementarity determining region 3 (CDR3) repertoires. By using minimal primer sets targeting a conserved region adjacent to CDR3, undistorted amplicons are analyzed via short read, single-end sequencing. We find that FR3AK-seq is sensitive and quantitative, performing comparably to two industry standards. FR3AK-seq was utilized to quickly and inexpensively characterize the T cell infiltrates of muscle biopsies obtained from 145 patients with idiopathic inflammatory myopathies and controls. A cluster of related TCRs was identified in samples from patients with sporadic inclusion body myositis, suggesting the presence of a shared antigen-driven response. The ease and minimal cost of FR3AK-seq removes critical barriers to routine, large-scale TCR CDR3 repertoire analyses.

immunology↗

bioRxiv2018

Mucosal CD8+ T cell responses induced by an MCMV based vaccine vector confer protection against influenza challenge

Cytomegalovirus (CMV) is a ubiquitous {beta}-herpesvirus that establishes life-long latent infection in a high percentage of the population worldwide. CMV induces the strongest and most durable CD8+ T cell response known in human clinical medicine. Due to its unique properties, the virus represents a promising candidate vaccine vector for the induction of persistent cellular immunity. To take advantage of this, we constructed a recombinant murine CMV (MCMV) expressing an MHC-I restricted epitope from influenza A virus (IAV) H1N1 within the immediate early 2 (ie2) gene. Only mice that were immunized intranasally (i.n.) were capable of controlling IAV infection, despite the greater potency of the intraperitoneally (i.p.) vaccination in inducing a systemic IAV-specific CD8+ T cell response. The protective capacity of the i.n. immunization was associated with its ability to induce IAV-specific tissue-resident memory CD8+ T (CD8TRM) cells in the lungs. Our data demonstrate that the protective effect exerted by the i.n. immunization was critically mediated by antigen-specific CD8+ T cells. CD8TRM cells promoted the induction of IFN{gamma} and chemokines that facilitate the recruitment of antigen-specific CD8+ T cells to the lungs. Overall, our results showed that locally applied MCMV vectors could induce mucosal immunity at sites of entry, providing superior immune protection against respiratory infections.\n\nAuthor summaryVaccines against influenza typically induce immune responses based on antibodies, small molecules that recognize the virus particles outside of cells and neutralize them before they infects a cell. However, influenza rapidly evolves, escaping immune recognition, and the fastest evolution is seen in the part of the virus that is recognized by antibodies. Therefore, every year we are confronted with new flu strains that are not recognized by our antibodies against the strains from previous years. The other branch of the immune system is made of killer T cells, which recognize infected cells and target them for killing. Influenza does not rapidly evolve to escape T cell killing; thus, vaccines inducing T-cell responses to influenza might provide long-term protection. We introduced antigen from influenza into the murine cytomegalovirus (MCMV) and used it as a vaccine vector inducing Killer T-cell responses of unparalleled strength. Our vector controlled flu replication and provided relief to infected mice, but only if we administered it through the nose, to activate killer T cells that will persist in the lungs close to the airways. Therefore, our data show that the subset of lung-resident killer T cells is sufficient to protect against influenza.

immunology↗

bioRxiv2018

Antiviral Functions of ARGONAUTE Proteins During Turnip Crinkle Virus Infection Revealed by Image-based Trait Analysis in Arabidopsis

RNA-based silencing functions as an important antiviral immunity mechanism in plants. Plant viruses evolved to encode viral suppressors of RNA silencing (VSRs) that interfere with the function of key components in the silencing pathway. As effectors in the RNA silencing pathway, ARGONAUTE (AGO) proteins are targeted of by some VSRs, such as that encoded by Turnip crinkle virus (TCV). A VSR-deficient TCV mutant was used to identify AGO proteins with antiviral activities during infection. A quantitative phenotyping protocol using an image-based color trait analysis pipeline on the PlantCV platform, with temporal red, green and blue (RGB) imaging and a computational segmentation algorithm, was used to measure plant disease after TCV inoculation. This process captured and analyzed growth and leaf color of Arabidopsis plants in response to virus infection over time. By combining this quantitative phenotypic data with molecular assays to detect local and systemic virus accumulation, AGO2, AGO3, and AGO7 were shown to play antiviral roles during TCV infection. In leaves, AGO2 and AGO7 functioned as prominent non-additive, anti-TCV effectors, while AGO3 played a minor role. Other AGOs were required to protect inflorescence tissues against TCV. Overall, these results indicate that distinct AGO proteins have specialized, modular roles in antiviral defense across different tissues, and demonstrate the effectiveness of image-based phenotyping to quantify disease progression.\n\nAuthor SummaryPlant viruses caused substantial losses in crop production and quality worldwide. Precisely measuring plant health is critical for better understanding the mechanisms underlying plant virus and host interactions. Advances in high-resolution imaging technologies and deep-learning tools have made acquiring and analyzing \"big data\" of disease traits possible. In this study, we have developed a high-throughput, image-based trait phenotyping pipeline to quantify disease severity in Arabidopsis thaliana infected by Turnip Crinkle Virus (TCV). Our aim is to understand how the antiviral RNA silencing machinery is tuned to protect the host from invading virus infection. We focused on ARGONAUTE proteins, which are the effectors in the RNA silencing pathway. A mutant line of TCV with a dysfunctional silencing suppressor (P38) was used to investigate which ago mutation could compensate for the dysfunctional silencing suppressor and facilitate the development of disease symptoms. We demonstrated that specific AGO proteins contribute to protecting leaves from TCV infection in a non-additive manner. Our results also implied that distinct AGOs are required to function collectively to silence TCV in inflorescence tissues. More evidence is still needed to further understand how these antiviral AGOs interact with suppressor proteins molecularly during TCV infection.

plant biology↗

bioRxiv2018

Modular, part-based control of gene expression response time using protein degradation tags

A fundamental principle of cellular signal processing is the encoding of information within the temporal dynamics of regulatory circuits. If synthetic circuits are to achieve the versatility and effectiveness of naturally-occurring circuits, it is necessary to develop simple, effective methods for the control of the dynamical properties of genetic circuits. However, current approaches to dynamical control often require extensive rewiring of circuit architecture, which hinders their implementation in a variety of systems. Therefore, it is essential that simple, modular, genetic parts-based frameworks are created to control the dynamical properties of circuits. Here we address this need by implementing a modular, genetic parts-based system which tunes the response time of a genes expression by tuning its degradation rate via the application of protein degradation tags with various affinities to their protease. This system provides a simple, easily- applicable framework for controlling the temporal aspects of genetic circuit behavior.

bioengineering↗

bioRxiv2018

aFARP-ChIP-seq, a convenient and reliable method for genome profiling in as few as 100 cells with a capability for multiplexing ChIP-seq

Much effort has been devoted to understand how chromatin modification regulates development and disease. Despite recent progress, however, it remains difficult to achieve high sensitivity and reliability of chromatin-immunoprecipitation-coupled deep sequencing (ChIP-seq) to map the epigenome and global transcription factor binding sites in cell populations of low cell abundance. We present a new Atlantis dsDNase-based technology, aFARP-ChIP-seq, that provides accurate profiling of genome-wide histone modifications in as few as 100 cells. By mapping histone lysine trimethylation (H3K4me3) and H3K27Ac in group I innate lymphoid cells from different tissues, aFARP-ChIP-seq uncovers potentially distinct active promoter and enhancer landscapes of several tissue-specific NK and ILC1. aFARP-ChIP-seq is also highly effective in mapping transcription factor binding sites in small number of cells. Since aFARP-ChIP-seq offers reproducible DNA fragmentation, it should allow multiplexing ChIP-seq of both histone modifications and transcription factor binding sites for low cell samples.

genomics↗

bioRxiv2018

SMUT: multi-SNP Mediation intersection-Union Test

Tens of thousands of reproducibly identified GWAS (Genome-Wide Association Studies) variants, with the vast majority falling in non-coding regions resulting in no eventual protein products, call urgently for mechanistic interpretations. Although numerous methods exist, there are few, if any methods, for simultaneously testing the mediation effects of multiple correlated SNPs via some mediator (for example, the expression of a gene in the neighborhood) on phenotypic outcome. We propose SMUT, multi-SNP Mediation intersection-Union Test to fill in this methodological gap. Our extensive simulations demonstrate the validity of SMUT as well as substantial, up to 92%, power gains over alternative methods. In addition, SMUT confirmed known mediators in a real dataset of Finns for plasma adiponectin level, which were missed by many alternative methods. We believe SMUT will become a useful tool to generate mechanistic hypotheses underlying GWAS variants, facilitating functional follow-up. The R package SMUT is publicly available from CRAN at https://CRAN.R-project.org/package=SMUT.

genetics↗

bioRxiv2018

Bacterial T6SS Effector EvpP Inhibits Neutrophil Recruitment via Jnk-Caspy Inflammasome Signaling In vivo

The type VI secretion system (T6SS) comprises dynamic complex bacterial contractile nanomachines and is used by many bacteria to inhibit or kill other prokaryotic or eukaryotic cells. Previous studies have revealed that T6SS is constitutively active in response to various stimuli, or fires effectors into host cells during infection. It has been proposed that the T6SS effector EvpP in Edwardsiella piscicida can inhibit NLRP3 inflammasome activation via the Ca2+-dependent JNK pathways. Here, we developed an in vivo infection model by microinjecting bacteria into the tail vein muscle of 3-day-post-fertilized zebrafish larvae, and found that both macrophages and neutrophils are essential for bacterial clearance. Further study revealed that EvpP plays a critical role in promoting the pathogenesis of E. piscicida via inhibiting the phosphorylation of Jnk signaling to reduce the expression of cxcl8a, mmp13 and IL-1{beta} in vivo. Subsequently, by utilizing Tg (mpo:eGFP+/+) zebrafish larvae for E. piscicida infection, we found that the EvpP-inhibited Jnk-caspy inflammasome signaling axis significantly suppressed the recruitment of neutrophils to infection sites, and the caspy- or IL-1{beta}-MO knockdown larvae were more susceptible to infection and failed to restrict bacterial colonization in vivo.\n\nIMPORTANCEInnate immunity is regulated by phagocytic cells and is critical for host control of bacterial infection. In many bacteria, T6SSs can affect bacterial virulence in certain environments, but little is known about the mechanisms underlying T6SS regulation of innate immune responses during infection in vivo. Here, we investigated the role of an E. piscicida T6SS effector EvpP in manipulating the reaction of neutrophils in vivo. We show that EvpP inhibits the activation of Jnk-caspy inflammasome pathway in zebrafish larvae, and reveal that macrophages are essential for neutrophil recruitment in vivo. This interaction improves our understanding about the complex and contextual role of a bacterial T6SS effector in modulating the action of myeloid cells during infection, and offers new insights into the warfare between bacterial weapons and host immunological surveillance.

microbiology↗

bioRxiv2018

Cell type-specific role of lamin-B1 and its inflammation-driven reduction in organ building and aging

Cellular architectural proteins often participate in organ development and maintenance. Although functional decay of some of these proteins during aging is known, the cell-type specific developmental role and the cause and consequence of their subsequent decay remain to be established especially in mammals. By studying lamins, the nuclear structural proteins, we demonstrate that lamin-B1 functions specifically in the thymic epithelial cells (TECs) for proper thymus organogenesis. An upregulation of proinflammatory cytokines in the intra-thymic myeloid immune cells during aging accompanies a gradual reduction of adult TEC lamins-B1. These cytokines cause adult TEC senescence and lamin-B1 reduction. We identify 17 adult TEC subsets and show that TEC lamin-B1 maintains the composition of these TECs. Lamin-B1 supports the expression of TEC genes needed for maintaining adult thymic architecture and function. Thus, structural proteins involved in organ building and maintenance can undergo inflammation-driven decay which can in turn contribute to age-associated organ degeneration.

immunology↗

bioRxiv2018

Flavor compounds in fermented Chinese alcoholic beverage alter gut microbiota and attenuate ethanol-induced liver

Alcoholic beverages which are consumed widely in most parts of the world have long been identified as a major risk factor for all liver diseases, particularly alcohol-induced liver disease (ALD). Recent compositional analyses suggest that Chinese Baijiu (CB), a clear alcoholic liquid distilled from fermented grains, contains large amounts of small molecule bioactive compounds in addition to a significant amount of ethanol. Here, in an experimental mouse model, we show that CB caused lower degrees of liver injury than pure ethanol by protecting against the decrease of the relative abundance of Akkermansia and increased relative abundance of Prevotella in the gut thereby preventing the destruction of the intestinal barrier. Furthermore, we demonstrated that ethanol-induced alteration of the gut microbiota profoundly affected the host metabolome. Compared with ethanol feeding, CB feeding resulted in higher concentrations of functional saturated LCFAs and SCFAs. Our results provide supporting evidence that ALD was profoundly influenced by host-gut microbiota metabolic interactions and that small molecule organic compounds in CB could attenuate ALD.

microbiology↗

bioRxiv2018

The seven transmembrane domain protein MoRgs7 functions in surface perception and undergoes coronin MoCrn1-dependent endocytosis in complex with Gα subunit MoMagA to promote cAMP signaling and appressorium formation in Magnaporthe oryzae

Regulator of G-protein signaling (RGS) proteins primarily function as GTPase-accelerating proteins (GAPs) to promote GTP hydrolysis of G subunits, thereby regulating G-protein mediated signaling. RGS proteins could also contain additional domains such as GoLoco to inhibit GDP dissociation. The rice blast fungus Magnaporthe oryzae encodes eight RGS and RGS-like proteins (MoRgs1 to MoRgs8) that have shared and distinct functions in growth, appressorium formation and pathogenicity. Interestingly, MoRgs7 and MoRgs8 contain a C-terminal seven-transmembrane domain (7-TM) motif typical of G-protein coupled receptor (GPCR) proteins, in addition to the conserved RGS domain. We found that MoRgs7, together with G MoMagA but not MoRgs8, undergoes endocytic transport from the plasma membrane to the endosome upon sensing of surface hydrophobicity. We also found that MoRgs7 can interact with hydrophobic surfaces via a hydrophobic interaction, leading to the perception of environmental hydrophobic cues. Moreover, we found that MoRgs7-MoMagA endocytosis is regulated by actin patch-associated protein MoCrn1, linking it to cAMP signaling. Our studies provided evidence suggesting that MoRgs7 could also function in a GPCR-like manner to sense environmental signals and it, together with additional proteins of diverse functions, promotes cAMP signaling required for developmental processes underlying appressorium function and pathogenicity.\n\nAuthor summaryThe 7-TM domain is considered the hallmark of GPCR proteins, which activate G proteins upon ligand binding and undergo endocytosis for regeneration or recycling. Among eight RGS and RGS-like proteins of M. oryzae, MoRgs7 and MoRgs8 contain the 7-TM domain in addition to the RGS domain. We found that MoRgs7 can form hydrophobic interactions with the hydrophobic surface. This interaction is important in sensing hydrophobic cues by the fungus. We also found that, in response to surface hydrophobicity, MoRgs7 couples with G subunit MoMagA to undergo endocytosis leading to the activation of cAMP signaling. Moreover, we found that such an endocytic event requires functions of the actin-binding protein MoCrn1. Our results revealed MoRgs7 functions as a GPCR-like receptor protein to sense surface cues and activate signaling required for pathogenesis, providing new insights into G-protein regulatory mechanisms in this and other pathogenic fungi.

microbiology↗