Biology subjects

Xu, L.

Publications and source records attributed to Xu, L..

At least 235 records · Page 13Linked to original sources

bioRxiv2023

Membrane Lipids Augment Cell Envelope Stress Signaling and Resistance to Antibiotics and Antimicrobial Peptides in Enterococcus faecalis

Enterococci have evolved resistance mechanisms to protect their cell envelopes against bacteriocins and host cationic antimicrobial peptides (CAMPs) produced in the gastrointestinal environment. Activation of the membrane stress response has also been tied to resistance to the lipopeptide antibiotic daptomycin. However, the actual effectors mediating resistance have not been elucidated. Here, we show that the MadRS (formerly YxdJK) membrane antimicrobial peptide defense system controls a network of genes, including a previously uncharacterized three gene operon (madEFG) that protects the E. faecalis cell envelope from antimicrobial peptides. Constitutive activation of the system confers protection against CAMPs and daptomycin in the absence of a functional LiaFSR system and leads to persistence of cardiac microlesions in vivo. Moreover, changes in the lipid cell membrane environment alter CAMP susceptibility and expression of the MadRS system. Thus, we provide a framework supporting a multilayered envelope defense mechanism for resistance and survival coupled to virulence.

microbiology↗

bioRxiv2023

MALDI-IM-MS Imaging of Brain Sterols and Lipids in a Mouse Model of Smith-Lemli-Opitz Syndrome

Smith-Lemli-Opitz syndrome (SLOS) is a neurodevelopmental disorder caused by genetic mutations in the DHCR7 gene, which encodes the enzyme 3{beta}-hydroxysterol-{Delta}7-reductase (DHCR7) that catalyzes the last step of cholesterol synthesis, resulting in deficiency in cholesterol and accumulation of its precursor, 7-dehydrocholesterol (7-DHC). To understand how the brain regions are differentially affected by the defective Dhcr7, we aim to map the regional distribution of sterols and other lipids in neonatal brains from a Dhcr7-KO mouse model of SLOS, using mass spectrometry imaging (MSI). MSI enables spatial localization of biomolecules in situ on the surface of a tissue section, which is particularly useful for mapping the changes that occur within a metabolic disorder such as SLOS, and in an anatomically complex organ such as the brain. In this work, using MALDI-ion mobility (IM)-MSI, we successfully determined the regional distribution of features that correspond to cholesterol, 7-DHC/desmosterol, and the precursor of desmosterol, 7-dehydrodesmosterol, in WT and Dhcr7-KO mice. Interestingly, we also observed m/z values that match the major oxysterol metabolites of 7-DHC (DHCEO and hydroxy-7-DHC), which displayed similar patterns to 7-DHC. We then identified brain lipids using m/z and CCS at the Lipid Species-level and curated a collection of MALDI-IM-MS-derived lipid CCS values. Subsequent statistical analysis of regions-of-interest allowed us to identify differentially expressed lipids between Dhcr7- KO and WT brains, which could contribute to defects in myelination, neurogenesis, neuroinflammation, and learning and memory in SLOS.

neuroscience↗

bioRxiv2023

Neuroprotective Mechanism of Ribisin A on H 2 O 2 -induced PC12 cell injury model

Ribisin A has been shown to have neurotrophic activity. The aim of this study was to evaluate the neuroprotective effect of Ribisin A on injured PC12 cells and elucidate its mechanism. In this project, PC12 cells were induced by H2O2 to establish an injury model. After treatment with Ribisin A, the neuroprotective mechanism of Ribisin A was investigated by methyl tetrazolium (MTT) assay, Enzyme-linked immunosorbent assay (ELISA), flow cytometric analysis, fluorescent probe analysis, and western blot. We found that Ribisin A decreased the rate of lactate dehydrogenase (LDH) release, increased cellular superoxide dismutase (SOD) activity, decreased the levels of tumor necrosis factor- (TNF-), interleukin-6 (IL-6), Ca2+ expression and reactive oxygen species (ROS). Moreover, Ribisin A significantly increased mitochondrial membrane potential (MMP) and inhibited apoptosis of PC12 cells. Meanwhile, Ribisin A activated the phosphorylation of ERK1/2 and its downstream molecule CREB by upregulating the expression of Trk A and Trk B, the upstream molecules of the ERK signaling pathway. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/559840v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@ff9604org.highwire.dtl.DTLVardef@1d1ee75org.highwire.dtl.DTLVardef@17e4441org.highwire.dtl.DTLVardef@b347c4_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2023

Oxytocin, but not vasopressin, decreases willingness to harm others by promoting moral emotions of guilt and shame

Prosocial and moral behaviors have overlapping neural systems but whether they involve similar neurochemical systems is unclear. In the current pre-registered randomized placebo controlled trial on 180 adult male and female subjects we investigated effects of intranasal administration of two prosocial neuropeptides, oxytocin or vasopressin, on moral emotion ratings for situations involving accidental or intentional harm to others and in judgments of moral dilemmas where harm is inflicted for a greater good. Oxytocin, but not vasopressin, enhanced feelings of guilt and shame only for intentional harm and reduced endorsement of choices where direct intentional harm to others could achieve a greater good. Effects of oxytocin on guilt and shame were partially mediated by trait empathy. Overall, findings demonstrate for the first time that oxytocin, but not vasopressin, promotes unwillingness to deliberately harm others irrespective of the consequences. This may reflect stronger associations between oxytocin and empathy and vasopressin with aggression.

neuroscience↗

bioRxiv2023

Structural Flexibility and Disassembly Kinetics of Single Ferritins using Optical Nanotweezers

Ferritin, a spherical protein shell assembled from 24 subunits, functions as an efficient iron storage and release system through its channels. Understanding how various chemicals affect the structural behaviour of ferritin is crucial for unravelling the origins of iron-related diseases in living organisms including humans. In particular, the influence of chemicals on ferritins dynamics and iron release is barely explored at the single-protein level. Here, by employing optical nanotweezers using double nanohole (DNH) structures, we examined the effect of ascorbic acid (reducing reagent) and pH on ferritins conformational dynamics. The dynamics of ferritin increased as the concentration of ascorbic acid approached saturation. At pH 2.0 ferritin exhibited significant structural fluctuations and eventually underwent a stepwise disassembly into fragments. This work, for the first time, tracked the disassembly pathway and kinetics of single ferritins in solution. We identified four critical fragments during its disassembly pathway, which are 22-mer, 12-mer, tetramer, and dimer subunits. Moreover, we presented the first single-molecule evidence of the cooperative disassembly of ferritin. Interrogating ferritins structural change in response to different chemicals holds importance for understanding their roles in iron metabolism, hence facilitating further development of medical treatments for the associated diseases.

biophysics↗

bioRxiv2023

Pharmacologic inhibition of BAF chromatin remodeling complexes as a therapeutic approach to transcription factor-dependent cancers

The BRG/Brahma-associated factors (BAF or mSWI/SNF) family of chromatin remodeling complexes are critical regulators of gene expression and are major determinants of cancer and other diseases. Two paralog ATPases, SMARCA4 and SMARCA2 (BRG1 and BRM, respectively), provide the enzymatic activity required for chromatin remodeling. Here, we discover and characterize a novel series of compounds that potently and selectively inhibit SMARCA4/SMARCA2. Mutational and biochemical studies demonstrate that these inhibitors act through a unique mode of inhibition, distinct from reported SMARCA4/SMARCA2 inhibitors. Across a range of cancer cell lines, SMARCA4/SMARCA2 inhibition resulted in lineage-specific changes in chromatin accessibility at binding sites for key transcription factors (TFs). In uveal melanoma (UM), BAF inhibition resulted in loss of enhancer occupancy of SOX10 and MITF, two essential TFs, leading to down-regulation of the melanocytic gene expression program. In a mouse xenograft model of UM, SMARCA4/SMARCA2 inhibition was well tolerated and resulted in dose-dependent tumor regression correlating with pharmacodynamic modulation of BAF-target gene expression. These data provide the foundation for first-in-human studies of BAF ATPase inhibition as a novel therapeutic to treat TF-dependent cancers.

cancer biology↗

bioRxiv2023

New tree shrew Parkinson's model: a cost-effective alternative to monkey models

The surge in demand for experimental monkeys has led to a rapid increase in their associated costs. Consequently, there is a growing need for the development of a cost-effective model for Parkinsons disease (PD) that exhibits all core clinical and pathological phenotypes of PD. Evolutionarily, tree shrews (Tupaia belangeri) are much closer to primates in comparison to rodents and share more similar PD-related brain structures and movement ability with monkeys. As such, tree shrews represent an ideal small animal species for modeling PD. To develop a tree shrew PD model, we used the 1-Methyl-4-phenylpyridinium (MPP+) metabolite, derived from the well-established PD modeling drug 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), to induce lesions in the dopaminergic neurons of the unilateral substantia nigra. After determining the optimal modeling dosage, the tree shrews consistently exhibited and maintained all classic clinical manifestations of PD for a 5-month period. The symptoms closely resembled the ones observed in PD monkeys and included bradykinesia, rest tremor, postural instability, and apomorphine-induced rotations, a classic phenotype of unilateral PD models. Immunostaining showed a significant loss of dopaminergic neurons (approximately 95%) in the substantia nigra on the lesioned side of the brain, a crucial pathological marker of PD. Further cytomorphological analysis revealed that the size of nigral dopaminergic neurons in tree shrews exceeded that of rodents and more closely approximated that of macaques. Based on the principle that structure determines function, the morphological similarity between tree shrews and monkeys may be an important structural basis for the manifestation of the highly similar phenotypes between monkey and tree shrew PD models. Collectively, this study successfully developed a PD model in a small animal species that faithfully recapitulated the classical clinical symptoms and key pathological indicators of PD monkeys. In addition to the well-recognized monkey models, the tree shrew model provides a novel avenue for the evaluation of PD treatments and underlying mechanisms.

neuroscience↗

bioRxiv2023

Losartan rewires ovarian cancer tumor-immune microenvironment and suppresses IGF-1 to amplify chemo-immunotherapy sensitivity

Ovarian cancer (OvCa) is the most lethal of the gynecologic malignancies. Immune checkpoint inhibitors, which have revolutionized the treatment of multiple malignancies, have had limited efficacy in OvCa patients. Here, using syngeneic OvCa models and genetic and pharmacologic perturbations, we discovered that losartan - a widely prescribed anti-hypertensive drug - exhibits dual effects on both the tumor microenvironment and cancer cells to sensitize OvCa to chemo-immunotherapy. Specifically, losartan treatment i) reprograms the tumor microenvironment leading to increased vascular perfusion, and thus enhances drug delivery and immune effector cell intratumoral infiltration and function; and ii) rewires the OvCa cells by suppressing the IGF-1 signaling, resulting in enhanced chemosensitivity. As a result of the combined tumor and stromal effects, losartan treatment enhances the efficacy of chemo-immunotherapy in OvCa models. The safety and low cost (less than $1-2/day) of losartan warrant rapid translation of our findings to patients with OvCa.

cancer biology↗

bioRxiv2023

Genome analyses reveal the secondary metabolites potentially influence the geographical distribution of Fusarium pseudograminearum populations

Fusarium crown rot (FCR), caused by Fusarium pseudograminearum, significantly impacts wheat yield and quality in Chinas Huanghuai region. The rapid F. pseudograminearum epidemic and FCR outbreak within a decade remain unexplained. In this study, two high-quality, chromosome-level genomes of F. pseudograminearum strains producing 3-acetyl-deoxynivalenol (3AcDON) and 15-acetyl-deoxynivalenol (15AcDON) toxins were assembled. Additionally, 38 related strains were resequenced. Genomic differences such as single nucleotide polymorphisms (SNPs), insertions/deletions (indels), and structural variations (SVs) among F. pseudograminearum strains were analyzed. The whole-genome SNP locus based population classification mirrored the toxin chenotype (3AcDON and 15AcDON)-based classification, indicating the presence of genes associated with the trichothecene toxin gene cluster. Further analysis of differential SNP, indel, and SV loci between the 3AcDON and 15AcDON populations revealed a predominant connection to secondary metabolite synthesis genes. Notably, the majority of the secondary metabolite biosynthesis gene cluster (SMGC) loci were located in SNP-dense genomic regions, suggesting high mutability and a possible contribution to F. pseudograminearum population structure and environmental adaptability. This study provides insightful perspectives on the distribution and evolution of F. pseudograminearum, and for forecasting the spread of wheat FCR, thereby aiding in the development of preventive measures and control strategies.

microbiology↗

bioRxiv2023

WOX11-mediated adventitious lateral root formation modulates tolerance of Arabidopsis to cyst nematode infections

The transcription factor WUSCHEL-RELATED HOMEOBOX 11 (WOX11) in Arabidopsis initiates the formation of adventitious lateral roots upon mechanical injury in primary roots. Root-invading nematodes also induce de novo root organogenesis leading to excessive root branching, but it is not known if this symptom of disease involves mediation by WOX11 and if it benefits the plant. Here, we show with targeted transcriptional repression and reporter gene analyses in Arabidopsis that the beet cyst nematode Heterodera schachtii activates WOX11-adventitious lateral rooting from primary roots close to infection sites. The activation of WOX11 in nematode-infected roots occurs downstream of jasmonic acid-dependent damage signaling via ETHYLENE RESPONSIVE FACTOR109, linking adventitious lateral root formation to nematode damage to host tissues. By measuring different root system components, we found that WOX11-mediated formation of adventitious lateral roots compensates for nematode-induced inhibition of primary root growth. Our observations further demonstrate that WOX11-mediated rooting reduces the impact of nematode infections on aboveground plant development and growth. Altogether, we conclude that the transcriptional regulation by WOX11 modulates root system plasticity under biotic stress, which is one of the key mechanisms underlying tolerance of Arabidopsis to cyst nematode infections.

plant biology↗

bioRxiv2023

Microbiome single cell atlases generated with a commercial instrument

Single cell sequencing is useful for resolving complex systems into their composite cell types and computationally mining them for unique features that are masked in pooled sequencing. However, while commercial instruments have made single cell analysis widespread for mammalian cells, analogous tools for microbes are limited. Here, we present EASi-seq (Easily Accessible Single microbe sequencing). By adapting the single cell workflow of the commercial Mission Bio Tapestri instrument, this method allows for efficient sequencing of individual microbes genomes. EASi-seq allows thousands of microbes to be sequenced per run and, as we show, can generate detailed atlases of human and environmental microbiomes. The ability to capture large shotgun genome datasets from thousands of single microbes provides new opportunities in discovering and analyzing species subpopulations. To facilitate this, we develop a companion bioinformatic pipeline that clusters genome by sequence similarity, improving whole genome assembly, strain identification, taxonomic classification, and gene annotation. In addition, we demonstrate integration of metagenomic contigs with the EASi-seq datasets to reduce capture bias and increase coverage. Overall, EASi-seq enables high quality single cell genomic data for microbiome samples using an accessible workflow that can be run on a commercially available platform.

bioengineering↗

bioRxiv2023

Rapid and unbiased enrichment of extracellular vesicles via meticulously engineered peptide

Extracellular vesicles (EVs) have garnered significant attention in biomedical applications, particularly as biomarkers and therapeutic agents for cancer diagnosis and treatment. However, the rapid, efficient, and unbiased separation of EVs from complex biological fluids remains a challenge due to their heterogeneity and low abundance concentration in biofluids. Herein, we report a novel approach to reconfigure and modify an artificial insertion peptide for the rapid isolation of EVs in 20 min with [~] 80% recovery. By inserting the peptide into the phospholipid bilayer of EVs, our method enables the unbiased isolation of EVs. Moreover, our approach demonstrates exceptional anti-interference capability and achieves a high purity of EVs comparable to standard ultracentrifugation and other methods. Importantly, we show that the isolated EVs could be directly applied for downstream protein and nucleic acids analyses, including proteomics analysis, exome sequencing analysis, as well as the detection of EGFR and KRAS gene mutation in clinical plasma samples. Our approach offers new possibilities for utilizing EVs in cancer diagnostics through liquid biopsy, as well as in various other biomedical applications.

bioengineering↗

bioRxiv2023

Multi-color live-cell optical nanoscopy using phasor analysis

Stimulated emission depletion microscopy (STED) is a powerful tool for studying nanoscale cell structure and activity, but the difficulties it encounters in multicolor imaging limit its application in biological research. To overcome the disadvantages of limited number of channels and high cost of multicolor STED imaging based on spectral identity, we introduced lifetime into live-cell multicolor STED imaging by separating selected dyes of the same spectrum by phasor analysis. Experimental results show that our method enables live-cell STED imaging with at least 4 colors, enabling observation of cellular activity beyond the diffraction limit.

cell biology↗

bioRxiv2023

Molecular Basis of Cell Membrane Adaptation in Daptomycin-Resistant Enterococcus faecalis

Daptomycin is a last-resort lipopeptide antibiotic that disrupts cell membrane (CM) and peptidoglycan homeostasis. Enterococcus faecalis has developed a sophisticated mechanism to avoid daptomycin killing by re-distributing CM anionic phospholipids away from the septum. The CM changes are orchestrated by a three-component regulatory system, designated LiaFSR, with a possible contribution of cardiolipin synthase (Cls). However, the mechanism by which LiaFSR controls the CM response and the role of Cls are unknown. Here, we show that cardiolipin synthase activity is essential for anionic phospholipid redistribution and daptomycin resistance since deletion of the two genes (cls1 and cls2) encoding Cls abolished CM remodeling. We identified LiaY, a transmembrane protein regulated by LiaFSR, as an important mediator of CM remodeling required for re-distribution of anionic phospholipid microdomains via interactions with Cls1. Together, our insights provide a mechanistic framework on the enterococcal response to cell envelope antibiotics that could be exploited therapeutically.

microbiology↗

bioRxiv2023

O-GlcNAcylation of Keratin 18 coordinates TCA cycle to promote cholangiocarcinoma progression

Glycosylation in human cholangiocarcinoma (CCA) actively contributes to pathophysiological steps of tumor progression. Of note is the dynamic modification of proteins by O-linked {beta}-N-acetyl-glucosamine (O-GlcNAcylation) that modulates various tumor-associated biological activities. By using a cutting-edge chemical proteomic methodology for intact glycopeptide analysis, we show herein that O-GlcNAcylation of Keratin 18 (K18) coordinates the tricarboxylic acid (TCA) cycle enzymes, namely isocitrate dehydrogenases (IDHs), to promote CCA progression. Mechanistically, site-specific O-GlcNAcylation of K18 on Ser 30 stabilizes K18, which benefits the expression of cell cycle checkpoints to enhance cell cycle progression and cell growth. Interaction with IDHs down-regulates the level of citrate and isocitrate, while up-regulates the level of -ketoglutarate (-KG). Our study thus expands the current understanding of protein O-GlcNAcylation, and adds another dimension of complexity to post-translational control over metabolism and tumorigenesis.

cancer biology↗

bioRxiv2023

Temporal transcriptomic dynamics in developing macaque neocortex

Despite intense research on mice, the transcriptional regulation of neocortical neurogenesis remains limited in humans and non-human primates. Cortical development in rhesus macaque is known to recapitulate multiple facets of cortical development in humans, including the complex composition of neural stem cells and the thicker supragranular layer. To characterize temporal shifts in transcriptomic programming responsible for differentiation from stem cells to neurons, we sampled parietal lobes of rhesus macaque at E40, E50, E70, E80, and E90, spanning the full period of prenatal neurogenesis. Single-cell RNA sequencing produced a transcriptomic atlas of the developing rhesus macaque neocortex parietal lobe. Identification of distinct cell types and neural stem cells emerging in different developmental stages revealed a terminally bifurcating trajectory from stem cells to neurons. Notably, deep-layer neurons appear in the early stages of neurogenesis, while upper-layer neurons appear later. While these different lineages show overlap in their differentiation program, cell fates are determined post-mitotically. Pseudotime trajectories from vRGs to oRGs revealed differences in dynamic gene expression profiles and identified divergence in their activation of BMP, FGF, and WNT signaling pathways. These results provide a comprehensive picture of the temporal patterns of gene expression leading to different fates of radial glial progenitors during neocortex layer formation.

developmental biology↗

bioRxiv2023

Epitope Engineered Human Haematopoietic Stem Cells are Shielded from CD123-targeted Immunotherapy

Targeted eradication of transformed or otherwise dysregulated cells using monoclonal antibodies (mAb), antibody-drug conjugates (ADC), T cell engagers (TCE) or chimeric antigen receptor (CAR) cells is very effective for haematologic diseases. Unlike the breakthrough progress achieved for B cell malignancies, there is a pressing need to find suitable antigens for immunotherapy of myeloid malignancies. CD123, the interleukin-3 (IL-3) receptor alpha-chain, is highly expressed in various haematological malignancies, including acute myeloid leukaemia (AML) and blastic plasmacytoid dendritic cell neoplasm (BPDCN). However, shared expression of CD123 on healthy haematopoietic stem and progenitor cells (HSPCs) bears the risk for extensive myelotoxicity upon targeted depletion. Here, we demonstrate that rationally designed, epitope-engineered HSPCs were completely shielded from CD123-targeted immunotherapy but remained fully functional while CD123-deficient HSPCs displayed a competitive disadvantage. Thus, molecularly shielded HSPCs could allow tumor-selective targeted immunotherapy and in parallel enable rebuilding a fully functional haematopoietic system. We envision that this approach is broadly applicable to many targets and cells, could render hitherto undruggable targets accessible to immunotherapy and will allow continued posttransplant immunotherapy, for instance to treat minimal residual disease (MRD) or be used as a salvage therapy. Since the function of the engineered targets is preserved, multiplexed molecular shielding could also enable targeted combination immunotherapies to address tumor heterogeneity. More generally, epitope shielding will be applicable for replacement of other cell types including the many immune cells which are currently being considered for engineered cellular therapies.

bioengineering↗

bioRxiv2023

A framework for Frizzled-G protein coupling and implications to the Wnt-PCP signaling pathways

The ten Frizzled receptors (FZDs) are essential in Wnt signaling and play important roles in embryonic development and tumorigenesis. Among these, FZD6 is closely associated with lens development. Understanding FZD activation mechanism is key to unlock these emerging targets. Here we present the cryo-EM structures of FZD6 and FZD3 which are known to relay non-canonical Wnt-PCP (planar cell polarity) signaling pathways as well as FZD1 in their G protein-coupled (active) and G protein-free (inactive) states, respectively. Comparison of the three inactive/active pairs unveiled a shared activation framework among all ten FZDs. Mutagenesis along with imaging and functional analysis on the human lens epithelial tissues suggested potential crosstalk between G-protein binding and Wnt-PCP signaling pathways. Together, this study provides an integrated understanding of FZD structure and function, and lays the foundation for developing therapeutic modulators to activate or inhibit FZD signaling for a range of disorders including cancers and cataracts.

biochemistry↗