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Chen, L.

Publications and source records attributed to Chen, L..

At least 937 records · Page 52Linked to original sources

Structural insights into the mechanism of the human soluble guanylate cyclase

Soluble guanylate cyclase (sGC) is the primary nitric oxide (NO) sensor. It plays a central role in NO signaling and is implicated in many essential physiological processes and disease conditions. The binding of NO leads to a significant boost in sGC enzymatic activity. However, the mechanism of NO activation remains incompletely understood. Here, we report the cryo-electron microscopy structures of the human sGC 1{beta}1 heterodimer in different functional states. These structures revealed that the transducer module bridges the NO sensor module and the catalytic module. NO binding to the {beta}1 H-NOX domain triggers the structural rearrangement of the sensor module and the bending-straightening conformational switch of the transducer module. The resulting movement of the N-termini of the catalytic domains drives the structural changes within the catalytic module, which in turn boost sGC enzymatic activity. These observations indicate the structural framework for the mechanism of sGC activation induced by NO binding.

biochemistry↗

Map3k2-Regulated Intestinal Stromal Cells (MRISC) Define a Distinct Sub-cryptic Stem Cell Niche for Damage Induced Wnt Agonist R-spondin1 Production

Intestinal stem cell propagation and differentiation are essential for rapid repair of tissue damage in the gut. While intestinal stromal cells were recently identified as key mediators of this process, the cellular and molecular mechanisms by which this diverse population induces tissue repair remains poorly understood. Here we show that Map3k2 has a colon stromal cell specific function critically required for maintenance of Lgr5+ intestinal stem cells and protection against acute intestinal damage. This Map3k2-specific function is mediated by enhancing Wnt agonist R-spondin1 production. We further reveal a unique novel cell population, named Map3k2-regulated intestinal stromal cells (MRISC), as the primary cellular source of R-spondin1 following intestinal injury. Together, our data identify a novel intestinal stem cell niche organized by MRISC, which specifically dependent on the Map3k2-signaling pathway to augment the production of Wnt agonist R-spondin1 and promote regeneration of the acutely damaged intestine.\n\nHighlightsO_LIMap3k2 protects mice from DSS-induced colitis by promoting intestinal stem cell regeneration.\nC_LIO_LIMap3k2-MAPK pathway cross-talks with Wnt signaling pathway via upregulation of R-spondin1.\nC_LIO_LIMap3k2-Regulated Intestinal Stromal Cells (MRISC) marked by co-expression of CD90, CD34 and CD81 defines a novel colonic stem cell niche.\nC_LI

cell biology↗

Crif1 Promotes Osteoporosis in Mice after Radiation

Radiation induces rapid bone loss and enhances bone resorption and RANKL expression. RANKL provides the crucial signal to induce osteoclast differentiation and plays an important role in bone resorption. However, the mechanisms of radiation-induced osteoporosis are not fully understood. Here, we show that Crif1 expression increases in bone marrow cells after radiation. Conditional Crif1 deletion in bone marrow cells causes decreases in RANKL expression and the RANKL/OPG ratio, and relieves bone loss after radiation in mice. We further demonstrated in vitro that Crif1 promotes RANKL secretion via the cAMP/PKA pathway. Moreover, protein-protein docking screening identified five compounds as Crif1 inhibitors; these compounds dramatically suppressed RANKL secretion and CREB phosphorylation when cells were exposed to forskolin. This study enriches current knowledge of the pathogenesis of osteoporosis and provides insights into potential therapeutic strategies for osteoporosis treatment.

cell biology↗

ProGeo-neo: a Customized Proteogenomic Workflow for Neoantigen Prediction and Selection

Neoantigens can be differentially recognized by T cell receptor (TCR) as these sequences are derived from mutant proteins and are unique to the tumor. The discovery of neoantigens is the first key step for tumor-specific antigen (TSA) based immunotherapy. Based on high-throughput tumor genomic analysis, each missense mutation can potentially give rise to multiple neopeptides, resulting in a vast total number, but only a small percentage of these peptides may achieve immune-dominant status with a given major histocompatibility complex (MHC) class I allele. Specific identification of immunogenic candidate neoantigens is consequently a major challenge. Currently almost all neoantigen prediction tools are based on genomics data. Here we report the construction of proteogenomics prediction of neoantigen (ProGeo-neo) pipeline, which incorporates the following modules: mining tumor specific antigens from next-generation sequencing genomic and mRNA expression data, predicting the binding mutant peptides to class I MHC molecules by latest netMHCpan (v.4.0), verifying MHC-peptides by MaxQuant with mass spectrometry proteomics data searched against customized protein database, and checking potential immunogenicity of T-cell-recognization by additional screening methods. ProGeo-neo pipeline achieves proteogenomics strategy and the neopeptides identified were of much higher quality as compared to those identified using genomic data only. The pipeline was constructed based on the genomics and proteomics data of Jurkat leukemia cell line but is generally applicable to other solid cancer research. With massively parallel sequencing and proteomics profiling increasing, this proteogenomics workflow should be useful for neoantigen oriented research and immunotherapy.

bioinformatics↗

The histone chaperone FACT induces Cas9 multi-turnover behavior and modifies genome manipulation in human cells

Cas9 is a prokaryotic RNA-guided DNA endonuclease that binds substrates tightly in vitro but turns over rapidly when used to manipulate genomes in eukaryotic cells. Little is known about the factors responsible for dislodging Cas9 or how they influence genome engineering. Using a proximity labeling system for unbiased detection of transient protein interactions in cell-free Xenopus laevis egg extract, we identified the dimeric histone chaperone FACT as an interactor of substrate-bound Cas9. Immunodepletion of FACT subunits from extract potently inhibits Cas9 unloading and converts Cas9s activity from multi-turnover to single-turnover. In human cells, depletion of FACT delays genome editing and alters the balance between indel formation and homology directed repair. Depletion of FACT also increases epigenetic marking by dCas9-based transcriptional effectors with concomitant enhancement of transcriptional modulation. FACT thus shapes the intrinsic cellular response to Cas9-based genome manipulation most likely by determining Cas9 residence times.

cell biology↗

Quantitative three-dimensional nondestructive imaging of whole anaerobic ammonium-oxidizing bacteria

Anaerobic ammonium-oxidizing (anammox) bacteria play a key role in the global nitrogen cycle and the treatment of nitrogenous wastewater. These functions are closely related to the unique biophysical structure of anammox bacteria. However, the research on the biophysical ultrastructure of intact anammox bacteria is lacking. In this study, in-situ three-dimensional nondestructive ultrastructure imaging of whole anammox cell was performed using synchrotron soft X-ray nano-computed tomography and the total variation-based simultaneous algebraic reconstruction technique (TV-SART). Statistical and quantitative analyses of the ultrastructures of intact anammox bacteria were performed. The linear absorption coefficient values of the ultrastructures of anammox bacteria were calculated and the asymmetric structure of the anammox bacteria was quantified. On this basis, the shape adaptation of the anammox bacteria responses to Fe2+ were explored, and the underlying regulation mechanism of Fe2+ on anammox bacteria was explored. Furthermore, a promising method to study the biophysical properties of cells in different environments and engineering processes was proposed.\n\nGraphical Abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=96 SRC=\"FIGDIR/small/709188v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (23K):\norg.highwire.dtl.DTLVardef@1994e5eorg.highwire.dtl.DTLVardef@1e80137org.highwire.dtl.DTLVardef@a7f418org.highwire.dtl.DTLVardef@8a77e5_HPS_FORMAT_FIGEXP M_FIG C_FIG Statement of SignificanceAnaerobic ammonium-oxidizing (anammox) bacteria play key role in global nitrogen cycle, and this physiological function depends on the unique morphology of anammox bacteria. In this study, synchrotron soft-X ray imaging technique coupled with simultaneous algebraic reconstruction technique with total variation (SART-TV) algorithm were performed to quantify the three-dimensional ultrastructure of the whole anammox bacteria for the first time. On this basis, the shape adaptation and mechanism of the anammox bacteria responses to Fe2+ were explored and a promising method for detecting the physiological properties of anammox bacteria was proposed.

cell biology↗

CD8+ T-cell-mediated immunoediting influences genomic evolution and immune evasion in murine gliomas

Cancer immunoediting shapes tumor progression by the selection of tumor cell variants that can evade immune recognition. Given the immune evasion and intra-tumor heterogeneity intrinsic to gliomas, we hypothesized that CD8+ T-cells mediate immunoediting in these tumors. We evaluated glioma progression in the absence of CD8+ T-cells by depleting this immune cell population in transgenic murine gliomas. Upon transplantation, gliomas that developed in the absence of CD8+ T-cells engrafted poorly in recipients with intact immunity but engrafted well in those with CD8+ T-cell depletion. Gliomas developed in absence of CD8+ T-cells exhibited increased chromosomal instability, MAPK signaling, gene fusions, and macrophage/microglial infiltration. MAPK activation correlated with macrophage/microglial recruitment in this model and in the human disease. Our results indicate that CD8+ T-cells mediate immunoediting during gliomagenesis, influencing the genomic stability of glioma and its microenvironment, leading to immune evasion.\n\nSignificanceImmune evasion renders cancer resistant to anti-tumoral immunity. Therapeutic intervention often fails for gliomas because of the plasticity of tumor cell variants that resist immune surveillance. Our results demonstrate a mechanism of immune evasion in gliomas that derives from CD8+ T-cells during the development and progression of this disease.

cancer biology↗

Bacterial fucosidase enables the production of Bombay red blood cells

We present a method to produce H antigen-deficient red blood cells (RBCs) for transfusion to individuals with anti-H antibodies. A fucosidase from bacteria was heterologously expressed efficiently in E. coli and has been demonstrated to completely remove H antigens on the surface of human RBCs in a facile conversion process. The approach we describe here holds promise for making H-deficient RBCs available for a rare population beyond ABO types.

molecular biology↗

Systems-level analysis identifies key regulators driving epileptogenesis in temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most prevalent and often devastating form of epilepsy. The molecular mechanism underlying the development of TLE remains largely unknown, which hinders the discovery of effective anti-epileptogenic drugs. In this study, we built a systems-level analytic framework which integrates gene meta-signatures, gene coexpression network and cellular regulatory network to unveil the evolution landscape of epileptogenic process and to identify key regulators that govern the transition between different epileptogenesis stages. The time-specific hippocampal transcriptomic profiles from five independent rodent TLE models were grouped into acute, latent and chronic stages of epileptogenesis, and were utilized for generating stage-specific gene expression signatures. 13 cell-type specific functional modules were identified from the epilepsy-context coexpression network, and five of them were significantly associated with the entire epileptogenic process. By inferring the differential protein activity of gene regulators in each stage, 265 key regulators underlying epileptogenesis were obtained. Among them, 122 regulators were demonstrated being associated with high seizure frequency and/or hippocampal sclerosis in human TLE patients. Importantly, we discovered four new gene regulators (ANXA5, FAM107A, SEPT2 and SPARC) whose upregulation may drive the process of epileptogenesis and further lead to chronic recurrent seizures or hippocampal sclerosis. Our findings provide a landscape of the gene network dynamics underlying epileptogenesis and uncovered candidate regulators that may serve as potential targets for future anti-epileptogenic therapy development.

bioinformatics↗

The common neoantigens in colorectal cancer are predicted and validated to be presented or immunogenic

Colorectal cancer (CRC) is a malignant cancer with high incidence and mortality in the world, as the result of the traditional treatments. Immunotherapy targeting neoantigens can induce durable tumor regression in cancer patients, but is almost limited to individual treatment, resulting from the unique neoantigens. Many shared oncogenic mutations are detected, but whether the common neoantigens can be identified in CRC is unknown. Using the somatic mutations data from 321 CRC patients combined with a filter standard and 7 predicted algorithms, we screened and obtained 25 HLA-A*11:01 restricted common neoantigens with high binding affinity (IC50<50 nM) and presentation score (>0.9). Except the positive epitope KRAS_G12V8-16, 11 out of 25 common neoantigens were proved to be naturally processed and presented on constructed K562 cell surface by mass spectroscopy (MS), and 11 out of 25 common neoantigens specifically induced in vitro pre-stimulated cytotoxic lymphocyte (CTL) to secrete IFN-{gamma}. However, only 2 out of 25 common neoantigens were simultaneously presented and immunogenic. Moreover, using cell-sorting technology combined with single-cell RNA sequencing, the immune repertoire profiles of C1orf170_S418G413-421 and KRAS_G12V8-16-specific CTL were clarified. Therefore, common neoantigens with presentation and immunogenicity could be found in CRC, which would be developed as the universal targets for CRC immunotherapy.

immunology↗

Discovery and Multi-center Verification of Prostate Cancer Protein Biomarkers using Single-shot Short Gradient Microflow SWATH and MRMHR Mass Spectrometry

We report and evaluated a microflow, single-shot, short gradient SWATH MS method intended to accelerate the discovery and verification of protein biomarkers in clinical specimens. The method uses 15-min gradient microflow-LC peptide separation, an optimized SWATH MS window configuration and OpenSWATH software for data analysis.\n\nWe applied the method to a cohort 204 of FFPE prostate tissue samples from 58 prostate cancer patients and 10 prostatic hyperplasia patients. Altogether we identified 27,976 proteotypic peptides and 4,043 SwissProt proteins from these 204 samples. Compared to a reference SWATH method with 2-hour gradient the accelerated method consumed only 27% instrument time, quantified 80% proteins and showed reduced batch effects. 3,800 proteins were quantified by both methods in two different instruments with relatively high consistency (r = 0.77). 75 proteins detected by the accelerated method with differential abundance between clinical groups were selected for further validation. A shortlist of 134 selected peptide precursors from the 75 proteins were analyzed using MRM-HR, exhibiting high quantitative consistency with the 15-min SWATH method (r = 0.89) in the same sample set. We further verified the capacity of these 75 proteins in separating benign and malignant tissues (AUC = 0.99) in an independent prostate cancer cohort (n=154).\n\nOverall our data show that the single-shot short gradient microflow-LC SWATH MS method achieved about 4-fold acceleration of data acquisition with reduced batch effect and a moderate level of protein attrition compared to a standard SWATH acquisition method. Finally, the results showed comparable ability to separate clinical groups.

cancer biology↗

Integrated Identification of Disease Specific Pathways Using Multi-omics data

MotivationIdentification of biological pathways plays a central role in understanding both human health and diseases. Although much work has previously been done to explore the biological pathways by using single omics data, little effort has been reported using multi-omics data integration, mainly due to methodological and technological limitations. Compared to single omics data, multi-omics data will help identifying disease specific functional pathways with both higher sensitivity and specificity, thus gaining more comprehensive insights into the molecular architecture of disease processes.\n\nResultsIn this paper, we propose two computational approaches that integrate multi-omics data and identify disease-specific biological pathways with high sensitivity and specificity. Applying our methods to an experimental multi-omics data dataset on muscular dystrophy subtypes, we identified disease-specific pathways of high biological plausibility. The developed methodology will likely have a broad impact on improving the molecular characterization of many common diseases.\n\nContactyuewang@vt.edu\n\nSupplementary informationSupplementary information attached.

bioinformatics↗

High-throughput proteomic analysis of FFPE tissue samples facilitates tumor stratification

Formalin-fixed, paraffin-embedded (FFPE), biobanked tissue samples offer an invaluable resource for clinical and biomarker research. Here we developed a pressure cycling technology (PCT)-SWATH mass spectrometry workflow to analyze FFPE tissue proteomes and applied it to the stratification of prostate cancer (PCa) and diffuse large B-cell lymphoma (DLBCL) samples. We show that the proteome patterns of FFPE PCa tissue samples and their analogous fresh frozen (FF) counterparts have a high degree of similarity and we confirmed multiple proteins consistently regulated in PCa tissues in an independent sample cohort. We further demonstrate temporal stability of proteome patterns from FFPE samples that were stored between one to 15 years in a biobank and show a high degree of the proteome pattern similarity between two types histological region of small FFPE samples, i.e. punched tissue biopsies and thin tissue sections of micrometer thickness, despite the existence of certain degree of biological variations. Applying the method to two independent DLBCL cohorts we identified myeloperoxidase (MPO), a peroxidase enzyme, as a novel prognostic marker. In summary, this study presents a robust proteomic method to analyze bulk and biopsy FFPE tissues and reports the first systematic comparison of proteome maps generated from FFPE and FF samples. Our data demonstrate the practicality and superiority of FFPE over FF samples for proteome in biomarker discovery. Promising biomarker candidates for PCa and DLBCL have been discovered.

biochemistry↗

GATA2 controls lymphatic endothelial cell junctional integrity and lymphovenous valve morphogenesis through miR-126

Mutations in the transcription factor GATA2 cause lymphedema. GATA2 is necessary for the development of lymphatic valves (LVs) and lymphovenous valves (LVVs), and for the patterning of lymphatic vessels. Here, we report that GATA2 is not necessary for valvular endothelial cell (VEC) differentiation. Instead, GATA2 is required for VEC maintenance and morphogenesis. GATA2 is also necessary for the expression of cell junction molecules VE-Cadherin and Claudin5 in lymphatic vessels. We identified miR-126 as a target of GATA2, and miR-126-/- embryos recapitulate the phenotypes of mice lacking GATA2. Primary human lymphatic endothelial cells (HLECs) lacking GATA2 (GATA2{Delta}HLEC) have altered expression of Claudin5 and VE-Cadherin, and blocking miR-126 activity in HLECs phenocopies these changes in expression. Importantly, overexpression of miR-126 in GATA2{Delta}HLEC significantly rescues the cell junction defects. Thus, our work defines a new mechanism of GATA2 and uncovers miR-126 as a novel regulator of mammalian lymphatic vascular development.\n\nNon-standard abbreviationsLECs, lymphatic endothelial cells; LVs, lymphatic valves; LV-ECs, lymphatic valve-forming endothelial cells; LVVs, lymphovenous valves; LVV-ECs, lymphovenous valve-forming endothelial cells; HLEC, primary human LECs; OSS, Oscillatory shear stress; IHC, immunohistochemistry.

developmental biology↗

Enriched G-quadruplexes on the Drosophila Male X Chromosome Function as Insulators of Dosage Compensation Complex

The evolution of sex chromosomes has resulted in half X chromosome dosage in males as females. Dosage compensation, or the two-fold upregulation in males, was thus evolved to balance the gene expression between sexes. However, the step-wise evolutionary trajectory of dosage compensation during Y chromosome degeneration is still unclear. Here, we show that the specific structured elements G-quadruplexes (G4s) are enriched on the X chromosome in Drosophila melanogaster. Meanwhile, on the X chromosome, the G4s are underrepresented on the H4K16 acetylated regions and the binding sites of dosage compensation complex male-specific lethal (MSL) complex. Peaks of G4 density and potential are observed at the flanking regions of MSL binding sites, suggesting G4s act as insulators to precisely up-regulate certain regions in males. Thus, G4s may be involved in the evolution of dosage compensation process through fine-tuning one-dose proto-X chromosome regions around MSL binding sites during the gradual Y chromosome degeneration.\n\nOne Sentence SummaryG-quadruplexes act as insulators to precisely up-regulate X chromosome in males.

evolutionary biology↗

SEQdata-BEACON: a comprehensive database of sequencing performance and statistical tools for performance evaluation and yield simulation in BGISEQ-500

BackgroundBGISEQ-500 is based on DNBSEQ technology and superior in providing high outputs and requiring less cost. This sequencer has been widely used in various areas of scientific and clinical research. A better understanding of the sequencing process and sequencer performance is essential for stabilizing sequencing process, accurately interpreting sequencing results and efficiently solving sequencing troubles. To solve these problems, a comprehensive database SEQdata-BEACON was constructed to accumulate sequencing performance data in BGISEQ-500.\n\nMethodsTotally 60 BGISEQ-500 sequencers in BGI-Wuhan lab were used to collect the sequencing performance data. Those lanes in paired-end 100 sequencing using 10bp barcode were chosen, and each lane containing 66 metrics was assigned a unique entry number as ID. The database was constructed in MySQL server 8.0 and the website was built on Apache (2.4.33 win64 VC15 server). The statistical analysis and linear regression models were generated by R program based on the data from November 2018 to April 2019.\n\nResultsA total of 2236 entries were recorded in the database, including sample ID, yield, quality, machine state and supplies information. According to correlation matrix, the 52 numerical metrics were clustered into three groups signifying yield-quality, machine state and sequencing calibration. The metrics distributions also delivered some patterns and rendered clues for further explanation or analysis of the sequencing process. Using the data of total 200 cycles, the linear regression model well simulated the final outputs. Moreover, the predicted final yield could be provided in the 15th cycle of the early stage of sequencing and the corresponding coefficient of determination R2 of the 200th and 15th cycle models were 0.97 and 0.81 respectively. The data source, statistical findings and application tools were all available in our website http://seqBEACON.genomics.cn:443/home.html. These resources can be used as a constantly updated reference for BGISEQ-500 users to comprehensively understand DNBSEQ technology, solve sequencing problems and optimize the sequencing process.

bioinformatics↗

Kaposi sarcoma-associated herpesvirus infection in HIV patients: potential role of HIV-associated extracellular vesicles

Kaposi sarcoma-associated herpesvirus (KSHV) is the causal agent for Kaposi sarcoma (KS), the most common malignancy in people living with HIV/AIDS. The oral cavity is a major route for KSHV infection and transmission. However, how KSHV breaches the oral epithelial barrier for spreading to the body is not clear. Here we show that extracellular vesicles (EVs) purified from saliva of HIV-positive individuals and secreted by HIV-1-infected T cells promote KSHV infectivity in both monolayer and 3-dimensional models of immortalized and primary human oral epithelial cells, establishing the latency of the virus. The HIV trans-activation response (TAR) element RNA in HIV-associated EVs contributes to the infectivity of KSHV through the epidermal growth factor receptor (EGFR). Cetuximab, a monoclonal neutralizing antibody to EGFR, blocks HIV-associated EV-enhanced KSHV infection. Our findings reveal that saliva containing HIV-associated EVs is a risk factor for enhancement of KSHV infection and that inhibition of EGFR serves as a novel strategy for controlling KSHV infection and transmission in the oral cavity.\n\nAuthor summaryKaposi sarcoma-associated herpesvirus (KSHV) is a causal agent for Kaposi sarcoma (KS), the most common malignancy in HIV/AIDS patients. Oral transmission through saliva is considered the most common route for spreading of the virus among HIV/AIDS patients. However, the role of HIV-specific components in co-transfection of KSHV is unclear. We demonstrate that extracellular vesicles (EV) purified from saliva of HIV patients and secreted by HIV-infected T cells promote KSHV infectivity in immortalized and primary oral epithelial cells. HIV-associated EVs promote KSHV infection depends on the HIV trans-activation element (TAR) RNA and EGFR of oral epithelial cells, both can be targeted for reducing KSHV infection. These results reveal that HIV-EVs is a risk factor for KSHV co-infection in the HIV-infected population.

microbiology↗

Branched-Chain Amino Acid Metabolic Reprogramming Orchestrates Drug Resistance to EGFR Tyrosine Kinase Inhibitors

Drug resistance is a significant hindrance to effective cancer treatment. Although resistance mechanisms of epidermal growth factor receptor (EGFR)-mutant cancer cells to lethal EGFR tyrosine kinase inhibitors (TKI) treatment have been investigated intensively, how cancer cells orchestrate adaptive response under sublethal drug challenge remains largely unknown. Here we find that 2-hour sublethal TKI treatment elicits a transient drug-tolerant state in EGFR-mutant lung cancer cells. Continuous sublethal treatment reinforces this tolerance and eventually establishes long-term TKI resistance. This adaptive process involves H3K9 demethylation-mediated epigenetic upregulation of branched-chain amino acid aminotransferase 1 (BCAT1) and subsequent metabolic reprogramming, which promotes TKI resistance through attenuating reactive oxygen species (ROS) accumulation. Combinational treatment with TKI and ROS-inducing reagents overcomes this drug resistance in preclinical mouse models. Clinical information analyses support the correlation of BCAT1 expression with EGFR TKI response. Collectively, our findings reveal the importance of epigenetically regulated BCAT1-engaged metabolism reprogramming in TKI resistance in lung cancer.\n\nHIGHLIGHTSSublethal EGFR TKI treatment induces transient drug-tolerant state and long-term resistance in EGFR-mutant lung cancer cells\n\nEpigenetically regulated BCAT1-mediated metabolic reprogramming orchestrates EGFR TKI-induced drug resistance\n\nCombinational treatment with TKI and ROS-inducing agents overcomes the drug resistance induced by EGFR TKI treatment

cancer biology↗