Biology subjects

Xie, X.

Publications and source records attributed to Xie, X..

At least 127 records · Page 7Linked to original sources

bioRxiv2023

Resistance mechanisms of SARS-CoV-2 3CLpro to the non-covalent inhibitor WU-04

Drug resistance poses a significant challenge in the development of effective therapies against SARS-CoV-2. Here, we identified two double mutations, M49K/M165V and M49K/S301P, in the 3C-like protease (3CLpro) that confer resistance to a novel non-covalent inhibitor, WU-04. Crystallographic analysis indicates that the M49K mutation destabilizes the WU-04 binding pocket, impacting the binding of WU-04 more significantly than the binding of 3CLpro substrates. The M165V mutation directly interferes with WU-04 binding. The S301P mutation, which is far from the WU-04 binding pocket, indirectly affects WU-04 binding by restricting the rotation of 3CLpros C-terminal tail and impeding 3CLpro dimerization. We further explored 3CLpro mutations that confer resistance to two clinically used inhibitors: ensitrelvir and nirmatrelvir, and revealed a trade-off between the catalytic activity, thermostability, and drug resistance of 3CLpro. We found that mutations at the same residue (M49) can have distinct effects on the 3CLpro inhibitors, highlighting the importance of developing multiple antiviral agents with different skeletons for fighting SARS-CoV-2. These findings enhance our understanding of SARS-CoV-2 resistance mechanisms and inform the development of effective therapeutics.

microbiology↗

bioRxiv2023

WTAP is Transcriptionally Regulated by p65 and Promotes Inflammation through m6A Modification and Phase Separation

Emerging evidence has linked dysregulation of N6-methyladenosine (m6A) to inflammation and inflammatory diseases, but the underlying mechanism still needs investigation. Here, we found that high m6A modification in a variety of hyperinflammatory states is p65-dependent, because Wilms tumor 1 associated protein (WTAP), a key component of the writer complex, is transcriptionally regulated by p65 and its overexpression can lead to higher m6A modification. Mechanistically, upregulated WTAP is more prone to phase separation to facilitate the aggregation of "writer" complex to nuclear speckles and the deposition of m6A marks onto transcriptionally active inflammatory transcripts, thereby accelerating proinflammatory response. Furthermore, myeloid deficiency of WTAP attenuates the severity of LPS-induced sepsis and DSS-induced IBD. Thus, the proinflammatory effect of WTAP is a general risk-increasing mechanism, and interrupting the assembly of m6A writer complex by targeting the phase separation of WTAP to reduce the global m6A level may be a potential and promising therapeutic strategy for alleviating hyperinflammation.

immunology↗

bioRxiv2023

Mammalian circadian clock proteins form dynamic interacting microbodies distinct from phase separation

Liquid-liquid phase separation (LLPS) underlies diverse biological processes. Because most LLPS studies were performed in vitro or in cells that overexpress protein, the physiological relevance of LLPS is unclear. PERIOD proteins are central mammalian circadian clock components and interact with other clock proteins in the core circadian negative feedback loop. Different core clock proteins were previously shown to form large complexes. Here we show that when transgene was stably expressed, PER2 formed nuclear phosphorylation-dependent LLPS condensates that recruited other clock proteins. Super-resolution microscopy of endogenous PER2, however, revealed formation of circadian-controlled, rapidly diffusing microbodies that were resistant to protein concentration changes, hexanediol treatment, and loss of phosphorylation, indicating that they are distinct from the LLPS condensates caused by overexpression. Surprisingly, only a small fraction of endogenous PER2 microbodies transiently interact with endogenous BMAL1 and CRY1, a conclusion that was confirmed in cells and in mice tissues, suggesting an enzyme-like mechanism in the circadian negative feedback process. Together, these results demonstrate that the dynamic interactions of core clock proteins is a key feature of mammalian circadian clock mechanism and the importance of examining endogenous proteins in LLPS and circadian studies.

genetics↗

bioRxiv2023

Less neutralization evasion of SARS-CoV-2 BA.2.86 than XBB sublineages and CH.1.1

The highly mutated BA.2.86, with over 30 spike protein mutations in comparison to Omicron BA.2 and XBB.1.5 variants, has raised concerns about its potential to evade COVID-19 vaccination or prior SARS-CoV-2 infection-elicited immunity. In this study, we employ a live SARS-CoV-2 neutralization assay to compare the neutralization evasion ability of BA.2.86 with other emerged SARS-CoV-2 subvariants, including BA.2-derived CH.1.1, Delta-Omicron recombinant XBC.1.6, and XBB descendants XBB.1.5, XBB.1.16, XBB.2.3, EG.5.1 and FL.1.5.1. Our results show that BA.2.86 is less neutralization evasive than XBB sublineages. Among all the tested variants, CH.1.1 exhibits the greatest neutralization evasion. In comparison to XBB.1.5, the more recent XBB descendants, particularly EG.5.1 and FL.1.5.1, display increased resistance to neutralization induced by parental COVID-19 mRNA vaccine and a BA.5-Bivalent-booster. In contrast, XBC.1.6 shows a slight reduction but remains comparable sensitivity to neutralization when compared to BA.5. Furthermore, a recent XBB.1.5-breakthrough infection significantly enhances the breadth and potency of cross-neutralization. These findings reinforce the expectation that the upcoming XBB.1.5 mRNA vaccine would likely boost the neutralization of currently circulating variants, while also underscoring the critical importance of ongoing surveillance to monitor the evolution and immune evasion potential of SARS-CoV-2 variants.

microbiology↗

bioRxiv2023

Identifying dysregulated regions in amyotrophic lateral sclerosis through DNA accessibility outliers

The high heritability of ALS and similar rare diseases contrasts with their low molecular diagnosis rate post-genetic testing, pointing to potential undiscovered genetic factors. Chromatin accessibility assays quantify the activity of functional elements genome-wide, offering invaluable insights into dysregulated regions. In this research, we introduced EpiOut, a computational toolbox to identify outliers in chromatin accessibility. These outliers represent dysregulated regions where chromatin accessibility uniquely diverges from the population baseline in a single or few samples. Annotation of accessible regions with histone ChIP-seq and Hi-C indicates that outliers are concentrated in functional loci, especially among promoters interacting with active enhancers. Across different omics levels, outliers are robustly replicated, and chromatin accessibility outliers are reliable predictors of gene expression outliers and aberrant protein levels. For example, 59% of gene expression outliers can be linked to aberration in chromatin accessibility. When promoter accessibility does not align with gene expression, our results indicate that molecular aberrations are more likely to be linked to post-transcriptional regulation rather than transcriptional regulation. Our findings demonstrate that the outlier detection paradigm can uncover dysregulated regions in rare diseases. EpiOut is open-sourced and freely available at github.com/uci-cbcl/EpiOut.

bioinformatics↗

bioRxiv2023

Double open syntaxin and UNC-18 P334A mutation leads to excitatory-inhibitory imbalance and impairs multiple aspects of C. elegans behavior

SNARE and Sec/Munc18 proteins are essential in synaptic vesicle exocytosis. Open form t-SNARE syntaxin and UNC-18 P334A are well-studied exocytosis-enhancing mutants. Here we investigate the interrelationship between the two mutations by generating double mutants in various genetic backgrounds in C. elegans. While each single mutation rescued the motility of CAPS/unc-31 and synaptotagmin/snt-1 mutants significantly, double mutations unexpectedly worsened motility or lost their rescuing effects. Electrophysiological analyses revealed that simultaneous mutations of open syntaxin and gain-of-function P334A UNC-18 induces a strong imbalance of excitatory over inhibitory transmission. In liposome fusion assays performed with mammalian proteins, the enhancement of fusion caused by the two mutations individually was abolished when the two mutations were introduced simultaneously, consistent with what we observed in C. elegans. We conclude that open syntaxin and P334A UNC-18 do not have additive beneficial effects, and this extends to C. elegans characteristics such as motility, growth, offspring bared, body size, and exocytosis, as well as liposome fusion in vitro. Our results also reveal unexpected differences between the regulation of exocytosis in excitatory versus inhibitory synapses.

neuroscience↗

bioRxiv2023

Oxytocin alleviated colitis and colitis-associated colorectal tumorigenesis by targeting fucosylated MUC2

Colon cancer is commonly regarded as hormone-independent. However, there have been reports suggesting the involvement of sex hormones in colon cancer development. Nevertheless, the role of hormones from the hypothalamus-hypophysis axis in colitis-associated colorectal cancer (CAC) remains uncertain. In this study, we observed a significant reduction in the expression of the oxytocin receptor (OXTR) in colon samples from both colitis and CAC patients. To investigate further, we generated mice with an intestinal epithelium cell (IEC)-specific knockout of OXTR. These mice exhibited markedly increased susceptibility to dextran sulfate sodium (DSS)-induced colitis and DSS/Azoxymethane (AOM)-induced CAC compared to wild-type mice. Our findings indicate that OXTR depletion impaired the inner mucus of the colon epithelium. Mechanistically, oxytocin was found to regulate MUC2 maturation through B3GNT7-mediated fucosylation. Interestingly, we observed a positive correlation between B3GNT7 expression and OXTR expression in human colitis and CAC colon samples. Moreover, the administration of oxytocin significantly alleviated tumor burden. Hence, our study unveils oxytocins promising potential as an affordable and effective therapeutic intervention for individuals affected by colitis and CAC.

physiology↗

bioRxiv2023

NUCLEOPORIN1 mediates proteasome-based degradation of ABI5 to regulate Arabidopsis seed germination

NUCLEOPORIN1 (NUP1), a member of the Nuclear Pore Complex (NPC), is located on the inner side of the nuclear membrane. It is highly expressed in seeds; however, its role in seeds including germination has not been explored yet. Here, we identified an abscisic acid (ABA) hypersensitive phenotype of nup1 during germination. ABA treatment drastically changes the expression pattern of thousands of genes in nup1, including the major transcription factors (TFs) involved in germination, ABI3, ABI4, and ABI5. Double mutant analysis of NUP1 and these ABA-related genes showed that mutations in ABI5 can rescue the phenotype of nup1, suggesting that NUP1 acts upstream of ABI5 to regulate seed germination. ABI5, a key negative regulator of germination, is abundant in dry seeds and rapidly degrades during germination. However, its spatiotemporal regulation and interaction with other molecular players during degradation remained to be fully elucidated. We found that NUP1 is physically associated with ABI5 and the 26S proteasome. Mutation in NUP1 delayed ABI5 degradation through its post-translational retention in nucleolus under abiotic stress. Taken together, our findings suggest that NUP1 anchors the proteasome to NPC and modulates seed germination through proteasome-mediated degradation of ABI5 in the vicinity of NPC in the nucleoplasm.

plant biology↗

bioRxiv2023

Mecp2 Fine-tunes Quiescence Exit by Targeting Nuclear Receptors

Quiescence (G0) maintenance and exit are crucial for tissue homeostasis and regeneration in mammals. Here, we show that methyl-CpG binding protein 2 (Mecp2) expression is cell cycle-dependent and negatively regulates quiescence exit in cultured cells and in an injury-induced liver regeneration mouse model. Specifically, acute reduction of Mecp2 is required for efficient quiescence exit, as deletion of Mecp2 accelerates, while overexpression of Mecp2 delays quiescence exit, and forced expression of Mecp2 after Mecp2 conditional knockout rescues cell cycle reentry. The E3 ligase Nedd4 mediates the ubiquitination and degradation of Mecp2, and thus facilitates quiescence exit. Genome-wide study uncovered the dual role of Mecp2 in preventing quiescence exit by transcriptionally activating metabolic genes while repressing proliferation-associated genes. Particularly, disruption of two nuclear receptors (NRs), Rara or Nr1h3, accelerates quiescence exit, mimicking the Mecp2 depletion phenotype. Our studies unravel a previously unrecognized role for Mecp2 as an essential regulator of quiescence exit and tissue regeneration.

cell biology↗

bioRxiv2023

Amyloid β accelerates age-related proteome-wide protein insolubility.

Loss of proteostasis is a highly conserved feature of aging across model organisms and typically results in the accumulation of insoluble protein aggregates. Protein insolubility is a central feature of major age-related neurodegenerative diseases, including Alzheimers Disease (AD), where hundreds of insoluble proteins associate with aggregated amyloid beta (A{beta}) in senile plaques. Moreover, proteins that become insoluble during aging in model organisms are capable of accelerating A{beta} aggregation in vitro. Despite the connection between aging and AD risk, therapeutic approaches to date have overlooked aging-driven protein insolubility as a contributory factor. Here, using an unbiased proteomics approach, we questioned the relationship between A{beta} and age-related protein insolubility. We demonstrate that A{beta} expression drives proteome-wide protein insolubility in C. elegans and this insoluble proteome closely resembles the insoluble proteome driven by normal aging, suggesting the possibility of a vicious feedforward cycle of aggregation in the context of AD. Importantly, using human genome-wide association studies (GWAS), we show that the CIP is replete with biological processes implicated not only in neurodegenerative diseases but also across a broad array of chronic, age-related diseases (CARDs). This provides suggestive evidence that age-related loss of proteostasis could play a role in general CARD risk. Finally, we show that the CIP is enriched with proteins that modulate the toxic effects of A{beta} and that the gut-derived metabolite, Urolithin A, relieves A{beta} toxicity, supporting its use in clinical trials for dementia and other age-related diseases.

systems biology↗

bioRxiv2023

Rapid Prototyping of Thermoplastic Microfluidic 3D Cell Culture Devices by Creating Regional Hydrophilicity Discrepancy

Microfluidic three-dimensional cell culture devices that enable the recapitulation of key aspects of organ structures and functions in vivo represent a promising preclinical platform to improve translational success during drug discovery. Essential to these engineered devices is the spatial patterning of cells from different tissue types within a confined microenvironment. Traditional fabrication strategies lack the scalability, cost-effectiveness, and rapid prototyping capabilities required for industrial applications, especially for processes involving thermoplastic materials. Here, we introduce an approach to pattern fluid guides inside microchannels by establishing differential hydrophilicity using pressure-sensitive adhesives as masks and a subsequent selective coating with a biocompatible polymer. We identified optimal coating conditions using polyvinylpyrrolidone, which resulted in rapid and consistent hydrogel flow in both the open-chip prototype and the fully bonded device containing additional features for medium perfusion. We tested the suitability of our device for dynamic 3D cell culture by growing human hepatocytes in the device under controlled fluid flow for a 14-day period. Additionally, we demonstrated the potential of using our device for pharmaceutical high-throughput screening applications, such as predicting drug-induced liver injury. Our approach offers a facile strategy of rapid prototyping thermoplastic microfluidic organ chips with varying geometries, microstructures, and substrate materials.

bioengineering↗

bioRxiv2023

SRSF1-mediated alternative splicing of Tial1/Tiar is essential for homing and self-renewal in mouse spermatogonial stem cells

AbstractSpermatogonial stem cells (SSCs) are essential for continuous spermatogenesis and male fertility. The underlying mechanisms of alternative splicing (AS) in mouse SSCs are still largely unclear. We demonstrated that SRSF1 is essential for gene expression and splicing in mouse SSCs. Crosslinking immunoprecipitation and sequencing (CLIP-seq) data revealed that spermatogonia-related genes (e.g., Plzf, Id4, Setdb1, Stra8, Tial1/Tiar, Bcas2, Ddx5, Srsf10, Uhrf1, and Bud31) were bound by SRSF1 in the mouse testes. Specific deletion of Srsf1 in mouse germ cells impairs homing of precursor SSCs leading to male infertility. Whole-mount staining data showed the absence of germ cells in the testes of adult conditional knockout (cKO) mice, which indicates Sertoli cell-only syndrome (SCOS) in cKO mice. The expression of spermatogonia-related genes (Gfra1, Pou5f1, Plzf, Dnd1, Stra8, and Taf4b) was significantly reduced in the testes of cKO mice. Moreover, multiomics analysis suggests that SRSF1 may affect survival of spermatogonia by directly binding and regulating Tial1/Tiar expression through AS. In addition, immunoprecipitation mass spectrometry (IP-MS) and co-immunoprecipitation (Co-IP) data showed that SRSF1 interacts with RNA splicing-related proteins (SART1, RBM15, and SRSF10). Collectively, our data reveal the critical role of SRSF1 in spermatogonia survival, which may provide a framework to elucidate the molecular mechanisms of the posttranscriptional network underlying homing of precursor SSCs.

developmental biology↗

bioRxiv2023

Humanized yeast to study the role of human ECE-1 isoforms in apoptosis in congenital heart diseases

Endothelin convert enzyme-1(ECE-1) plays a significant role in cardiovascular development including four isoforms with unclear function. Therefore, we are interested in studying the function of ECE-1 isoforms through mitochondria due to the high correlation between congenital heart disease (CHD) and apoptosis. Since the expression of human Bax and Bcl-xL in budding yeast (Saccharomyces cerevisiae) results in similar effects in mammalian cells, a yeast system was generated for mimicking human Bax-induced apoptosis and the expression of human ECE-1 isoforms was involved. The correlation between Bax-induced growth defect and the candidates of apoptosis via mitochondrial pathway was preliminarily investigated in this system. Furthermore, the phenotypes of ECE-1 isoforms have been identified through yeast growth defect. Individual ECE-1 isoform does not affect yeast growth but act as enhancers for the Bax-induced growth defect. ECE-1c is the strongest enhancer that affect the expression of candidates of outer membrane translocases. This study indicates that ECE-1 might play an important role in inducing apoptosis and we speculate these findings are possible to provide new perspectives with clarifying the mechanism of CHD.

molecular biology↗

bioRxiv2023

Genetic evidence for functions of Chloroplast CA in Pyropia yezoensis: decreased CCM but increased starch accumulation

To adapt to the change of intertidal environment, intertidal macroalgae have evolved complicated Ci utilization mechanism. However, our knowledge regarding the CO2 concentrating mechanism (CCM) of macroalgae is limited. Carbonic anhydrase (CA), a key component of CCM, plays important roles in many physiological reactions in various organisms. While there are a large number of genes encoding CA in the Pyropia yezoensis genome, the exact function of specific CA in P. yezoensis remains elusive. To explore the specific function of chloroplast CA in intertidal macroalgae, we produced chloroplast-localized {beta}CA1 knockdown mutants of P. yezoensis through RNA interference, and Pyca1i mutants showed a notable decrease in leaf area and overall biomass, as well as decreased soluble protein and unsaturated fatty acid content under different DIC conditions. However, Pyca1i mutants showed relatively higher starch content compared to the wild-type. The activity of enzymes involved in Calvin cycle, photorespiration, Pentose-phosphate pathway and floridean starch synthesis of P.yezoensis indicated an effective starch accumulation pathway after interference of {beta}CA1. All results suggest that the decreased activity of Py{beta}CA1 impaired the CCM and development of thalli of P.yezoensis, but stimulated starch accumulation in the cytoplasm through feedback to the photorespiration pathway and PP pathway to replenish intermediates for the Calvin cycle. This study is the first to explore the specific function of chloroplast CA in intertidal macroalgae using genomic technology. The results provide valuable insights into the adaption mechanisms of intertidal macroalgae to their environment.

molecular biology↗

bioRxiv2023

Living cell mTORC1 inhibition reporter mTIR reveals nutrient-sensing targets of histone deacetylase inhibitor

Mammalian or mechanistic target of rapamycin complex 1 (mTORC1) is a clinically effective therapeutic target for diseases such as cancer, diabetes, aging, and neurodegeneration, yet an efficient tool to monitor mTORC1 inhibition in living cells or tissues is still lacking. Here we devised a genetically encoded mTORC1 inhibition reporter termed mTIR that exhibits a highly contrasted fluorescence puncta pattern in response to mTORC1 inhibition. mTIR specifically senses physiological, pharmacological and genetic inhibition of mTORC1 signaling in living cells and tissues. Importantly, mTIR can be applied as an powerful tool for imaging-based visual screening of mTORC1 inhibitors. By this method, we identified histone deacetylase inhibitors (HDACi) that selectively inhibit mTORC1 by inducing nutrient-sensing gene expression. Thus, mTIR is a unique living cell reporter efficiently detecting the inhibition of mTORC1 activity, and the HDACi Panobinostat transcriptionally target mTORC1 signaling via amino acids sensing.

cell biology↗

bioRxiv2023

Design of multi-epitope vaccine candidate against Brucella type IV secretion system (T4SS)

Objective the dominant epitopes of T and B cells of VirB8 and VirB10 of Brucella type IV. Secretory systems were predicted and analyzed by bioinformatics, and then multi-epitope vaccines were constructed by reverse vaccination. Methods The amino acid sequences of VirB8 and VirB10 were obtained from the UniProt database, T and B cell dominant epitopes were selected and supplemented with adjuvants to construct a multi-epitope vaccine, SOPMA and RoseTTAFold were applied to predict secondary and tertiary structures respectively for immune simulations. Finally, molecular dynamics simulations of iMEV-TLR4 were then performed. Results one cytotoxic T lymphocyte (CTL) epitope, five helper T lymphocyte (HTL) epitopes, two linear B cell epitopes and three conformational B cell epitopes were obtained in VirB8. 1 cytotoxic T lymphocyte (CTL) epitope, 4 helper T lymphocyte (HTL) epitopes, 4 linear B cell epitopes, and 3 conformational B cell epitopes were obtained in VirB10. The resulting multiepitope vaccine is a protein with good antigenicity, hydrophilicity, and stability. Conclusion a novel brucella multiepitope vaccine was designed by reverse vaccination, and this study provides a theoretical basis for further research.

bioinformatics↗

bioRxiv2023

A single-dose of intranasal vaccination with a live-attenuated SARS-CoV-2 vaccine candidate promotes protective mucosal and systemic immunity

An attenuated SARS-CoV-2 virus with modified viral transcriptional regulatory sequences and deletion of open-reading frames 3, 6, 7 and 8 ({triangleup}3678) was previously reported to protect hamsters from SARS-CoV-2 infection and transmission. Here we report that a single-dose intranasal vaccination of {triangleup}3678 protects K18-hACE2 mice from wild-type or variant SARS-CoV-2 challenge. Compared with wild-type virus infection, the {triangleup}3678 vaccination induces equivalent or higher levels of lung and systemic T cell, B cell, IgA, and IgG responses. The results suggest {triangleup}3678 as an attractive mucosal vaccine candidate to boost pulmonary immunity against SARS-CoV-2.

microbiology↗

bioRxiv2023

Computational pathology infer clinically relevant protein levels and drug efficacy in breast cancer by weakly supervised contrastive learning

Visual inspection of histopathology slides via optical microscope is the routine medical examination for clinical diagnosis of tumors. Recent studies have demonstrated that computational pathology not only automate the tumor diagnosis, but also showed great potential to uncover tumor-related genetic alterations and transcriptomic patterns. In this paper, we propose wsi2rppa, a weakly supervised contrastive learning framework to infer the protein levels of tumor biomarkers from whole slide images (WSIs) in breast cancer. We firstly conducted contrastive learning-based pre-training on tessellated tiles to extract histopathological features, which are then aggregated by attention pooling and adapted to downstream tasks. Our extensive experiments showed that our method achieved state-of-the-art performance in tumor diagnostic task, and also performed well in predicting clinically relevant protein levels and drug response. To show the model interpretability, we spatially visualized the WSIs colored the tiles by their attention scores, and found that the regions with high scores were highly consistent with the tumor and necrotic regions annotated by a 10-year experienced pathologist. Moreover, spatial transcriptomic data further verified that the heatmap generated by attention scores agree greatly with the spatial expression landscape of two typical tumor biomarker genes. In particular, our method achieved 0.79 AUC value in predicting the response of breast cancer patients to the drug trastuzumab treatment. These findings showed the remarkable potential of deep learning-based morphological feature is very indicative of clinically relevant protein levels, drug response and clinical outcomes.

bioinformatics↗