Biology subjects

Liu, L.

Publications and source records attributed to Liu, L..

At least 685 records · Page 38Linked to original sources

bioRxiv2021

The endoplasmic reticulum associated degradation adaptor Sel1L regulates T cell homeostasis and function

Suppressor/Enhancer of Lin-12-like (Sel1L) is a critical adaptor for endoplasmic reticulum-associated degradation (ERAD), a process that maintains cellular protein quality control through degradation of misfolded proteins. Here we investigate the role of Sel1L in T cell homeostasis and function. T cell-specific deletion of Sel1L profoundly impairs peripheral T cell survival and promotes apoptotic cell death. Furthermore, Sel1L is required to maintain naive CD8+ T cell homeostasis in a cell-intrinsic manner with loss of quiescence as evidenced by increased proliferation. Sel1L-deficient T cells exhibit enhanced activation of the mammalian target of rapamycin (mTOR) pathway and altered cellular metabolism, including increased cellular reactive oxygen species, mitochondrial mass and mitochondrial membrane potential in the naive CD8+ T cell compartment. Furthermore, loss of Sel1L impaired CD8+ T cell immune responses following bacterial infection. These results demonstrate a novel role for Sel1L/ERAD in T cell homeostasis and function.

immunology↗

bioRxiv2021

Single-dose AAV-based vaccine induces a high level of neutralizing antibodies and provides long-term protection against SARS-CoV-2 in rhesus macaques

Coronavirus disease 2019 (COVID-19), which is triggered by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, continues to threaten global public health. Developing a vaccine that only requires single immunization but provides long-term protection for the prevention and control of COVID-19 is important. Here, we developed an adeno-associated virus (AAV)-based vaccine expressing a stable receptor-binding domain (SRBD) protein. The vaccine requires only a single shot but provides effective neutralizing antibodies (NAbs) over 598 days in rhesus macaques (Macaca mulatta). Importantly, our results showed that the NAbs were kept in high level and long lasting against authentic wild-type SARS-CoV-2, Beta, Delta and Omicron variants using plaque reduction neutralization test. Of note, although we detected pre-existing AAV2/9 antibodies before immunization, the vaccine still induced high and effective NAbs against COVID-19 in rhesus macaques. AAV-SRBD immune serum also efficiently inhibited the binding of ACE2 with RBD in the SARS-CoV-2 B.1.1.7 (Alpha), B.1.351 (Beta), P.1/P.2 (Gamma), B.1.617.2 (Delta), B.1.617.1/3(Kappa), and C.37 (Lambda) variants. Thus, these data suggest that the vaccine has great potential to prevent the spread of SARS-CoV-2.

immunology↗

bioRxiv2021

Structure, immunogenicity, and conformation-dependent receptor binding of the post-fusion human metapneumovirus F protein

Human metapneumovirus (hMPV) is an important cause of acute viral respiratory infection. As the only target of neutralizing antibodies, the hMPV fusion (F) protein has been a major focus for vaccine development and targeting by drugs and monoclonal antibodies (mAbs). While X-ray structures of trimeric pre-fusion and post-fusion hMPV F proteins from genotype A, and monomeric pre-fusion hMPV F protein from genotype B have been determined, structural data for the post-fusion conformation for genotype B is lacking. We determined the crystal structure of this protein and compared the structural differences of post-fusion hMPV F between hMPV A and B genotypes. We also assessed the receptor binding properties of the hMPV F protein to heparan sulfate. A library of heparan sulfate (HS) oligomers was used to verify the HS binding activity of hMPV F, and several compounds showed binding to predominantly pre-fusion hMPV F, but had limited binding to post-fusion hMPV F. Furthermore, mAbs to antigenic sites III and the 66-87 intratrimeric epitope block heparan binding. In addition, we evaluated the efficacy of post-fusion hMPV B2 F protein as a vaccine candidate in BALB/c mice. Mice immunized with hMPV B2 post-fusion F protein showed a balanced Th1/Th2 immune response and generated neutralizing antibodies against both subgroup A2 and B2 hMPV strains, which protected the mice from hMPV challenge. Antibody competition analysis revealed the antibodies generated by immunization target two known antigenic sites (III and IV) on hMPV F. Overall, this study provides new characteristics of the hMPV F protein informative for vaccine and therapy development. ImportanceHuman metapneumovirus (hMPV) is an important cause of viral respiratory disease. In this paper, we report the X-ray crystal structure of the hMPV fusion (F) protein in the post-fusion conformation from genotype B. We also assessed binding of the hMPV F protein to heparin and heparan sulfate, a previously reported receptor for the hMPV F protein. Furthermore, we determined the immunogenicity and protective efficacy of post-fusion hMPV B2 F protein, which is the first study using a homogenous conformation of the protein. Antibodies generated in response to vaccination give a balanced TH1/TH2 response and target two previously discovered neutralizing epitopes.

microbiology↗

bioRxiv2021

Dual functions of ZmGI1 in the photoperiodic flowering pathway and salt stress responses in maize

The circadian clock perceives photoperiodic changes and initiates processes leading to floral transition. GIGANTEA (GI) primarily functions as a principal clock component that integrates environmental cues into regulation of growth and development in Arabidopsis. However, it is unclear whether ZmGIs regulate photoperiodic flowering and abiotic stress response. Here, we demonstrated that the expression of ZmGI1 depicted a typical circadian pattern and was differentially expressed under LDs and SDs in photoperiodic sensitive and insensitive maize lines. The transcription level was significantly and positively correlated with days to silking and photoperiodic sensitivity in maize. Moreover, natural variation in ZmGI1 was associated with maize photoperiod response and the fine-tuning of plant development traits. Overexpression of ZmGI1Huangzao4 induced early flowering and enhanced salt tolerance in Arabidopsis relative to the wild-type and gi mutants. ZmGI1 formed a protein complex with ZmFKF1 and acted as a positive regulator of flowering time by regulating CONSTANS transcription in the photoperiod pathway. The ZmGI1/ZmThox complex regulates oxidative stress induced by salt stress via a redox balance pathway. Over all, we have provided compelling evidence to suggest that ZmGI1 is a pleotropic gene whose expression depicts a typical circadian rhythmic pattern and regulates flowering time and confers salt stress tolerance.

developmental biology↗

bioRxiv2021

Circulating CD138 (syndecan-1) enhances APRIL-mediated autoreactive B cell survival and differentiation in MRL/Lpr mice

High levels of serum CD138, a heparan sulfate-bearing proteoglycan, correlates with increased disease activity in systemic lupus erythematosus (SLE) patients. Mechanisms responsible for serum CD138 production and its biological function in SLE disease remain poorly understood. In this study, corroborating patient data, we detected an increase in serum CD138 in MRL/Lpr mice parallel to disease activity. Although TCR{beta}+CD138+ T cells expand in MRL/Lpr mice as the disease progresses, surprisingly, TCR{beta}+CD138- cells were the primary source of circulating CD138 as the transfer of TCR{beta}+CD138- cells to young MRL/Lpr mice, but not TCR{beta}+CD138+ cells, resulted with higher serum CD138 in the recipient mice. We found that elevated trypsin, expressed by TCR{beta}+CD138- cells, was able to cleave CD138 from T cells. Moreover, suggesting the contribution of cleaved CD138 to the increase in blood CD138, trypsin inhibitors defined trypsin inhibitor (DTI) or leupeptin increased CD138 expression on TCR{beta}+CD138- cells. Furthermore, soluble CD138 was able to bind a proliferation inducing ligand (APRIL) and enhanced APRIL-mediated plasma cell generation and autoreactive antibody production through the phosphorylation of extracellular-signal-regulated kinase (ERK) in B cells. APRIL receptor, transmembrane activator, calcium modulator, and cyclophilin ligand interactor (TACI) was involved in the enhancement of APRIL activity by CD138, as the synergistic effect of APRIL and CD138 was ablated on TACI deficient B cells. These findings indicate a regulatory role for soluble CD138 in B cell differentiation and autoreactive antibody secretion in SLE disease.

immunology↗

bioRxiv2021

Cell Surface Glycan Engineering Reveals that Matriglycan Alone can Recapitulate Dystroglycan Binding and Function

-Dystroglycan (-DG) is uniquely modified on O-mannose sites by a repeating disaccharide (-Xyl1,3-GlcA{beta}1,3-)n termed matriglycan, which is a receptor for laminin-G domain-containing proteins and employed by old-world arenaviruses for infection. Using chemoenzymatically synthesized matriglycans printed as a microarray, we demonstrated length-dependent binding to Laminin, Lassa virus GP1, and the clinically-important antibody IIH6. Utilizing an enzymatic engineering approach, an N-linked glycoprotein was converted into a IIH6-positive Laminin-binding glycoprotein. Engineering of the surface of cells deficient for either -DG or O-mannosylation with matriglycans of sufficient length recovered infection with a Lassa-pseudovirus. Finally free matriglycan in a dose and length dependent manner inhibited viral infection of wildtype cells. These results indicate that matriglycan alone is necessary and sufficient for IIH6 staining, Laminin and LASV GP1 binding, and Lassa-pseudovirus infection and support a model in which it is a tunable receptor for which increasing chain length enhances ligand-binding capacity. O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY Graphical Abstract C_FIG_DISPLAY

biochemistry↗

bioRxiv2021

Long-term stress and trait anxiety alter brain network balance in dynamic decisions during working memory

Long-term stress has a profound impact on the human brain and cognition, and trait anxiety influences stress-induced adaptive and maladaptive effects. However, the neurocognitive mechanisms underlying long-term stress and trait anxiety interactions remain elusive. Here we investigated how long-term stress and trait anxiety interact to affect dynamic decisions during working-memory (WM) by altering functional brain network balance. In comparison to controls, male participants under long-term stress experienced higher psychological distress and exhibited faster evidence accumulation but had a lower decision-threshold during WM. This corresponded with hyper-activation in the anterior insula, less WM-related deactivation in the default-mode network, and stronger default-mode network decoupling with the frontoparietal network. Critically, high trait anxiety under long-term stress led to slower evidence accumulation through higher WM-related frontoparietal activity, and increased decoupling between the default-mode and frontoparietal networks. Our findings provide neurocognitive evidence for long-term stress and trait anxiety interactions on executive functions with (mal)adaptive changes.

neuroscience↗

bioRxiv2021

Metabolic Complementation between Glucose and Amino Acid Drives Hepatic De Novo Lipogenesis and Steatosis

Increased de novo lipogenesis (DNL) is a hallmark of nonalcoholic fatty liver disease (NAFLD) in obesity, but the macronutrient source for >80% carbon backbone for fatty acid synthesis has not been determined. Here we take an integrated approach to dissect nutrient metabolism, both ex vivo and in vivo. We discover a castling effect of glucose and glutamine metabolism through ex vivo isotope tracing studies that limits the entrance of glucose carbon into the glutamine-dominated tricarboxylic acid cycle (TCA) and DNL pathways. In vivo tracing studies with a high carbohydrate drink (glucose/amino acid, 3:1, w/w) confirm dietary amino acids are twice more efficient than glucose in labeling the hepatic acetyl-CoA and fatty acid pool, and together they account for over 70% of hepatic DNL substrate. Both glucose and glutamine carbon flux into DNL pathways are increased in obese hepatocytes, and metabolic rerouting of substrate carbon toward glycogen synthesis and energy production through GYS2 and GLUD1 overexpression improves hepatic steatosis. Together, these data reveal the quantitative contribution of glucose and amino acid carbon toward hepatic DNL and the development of hepatic steatosis in obesity.

biochemistry↗

bioRxiv2021

Genetic characteristics of human papillomavirus type 16, 18, 52 and 58 in southern China

Persistent infections of high-risk human papillomaviruses (HPVs) are the leading cause of cervical cancers. We collected cervical exfoliated cell samples from females in Changsha city, Hunan Province and obtained 358 viral genomes of four major HPV types, including HPV 16 (n=82), 18 (n=35), 52 (n=121) and 58 (n=100). The lineage/sublineage distribution of the four HPVs confirmed previous epidemiological reports, with the predominant prevailing sublineage as A4 (50%), A1 (37%) and A3 (13%) for HPV16, A1 (83%) for HPV18, B2 (86%) for HPV52 and A1 (65%), A3 (19%) and A2 (12%) for HPV58. We also identified two potentially novel HPV18 sublineages, i.e. A6 and A7. Virus mutation analysis further revealed the presence of HPV16 and HPV58 strains associated with potentially high oncogenicity. These findings expanded our knowledge on the HPV genetic diversity in China, providing valuable evidence to facilitate HPV DNA screening, vaccine effectiveness evaluation and control strategy development.

genomics↗

bioRxiv2021

RNA-CLAMP Enables Photo-activated Control of CRISPR-Cas9 Gene Editing by Site-specific Intramolecular Cross-linking of the sgRNA

Here we introduce RNA-CLAMP, a technology which enables site-specific and enzymatic cross-linking (clamping) of two selected stem loops within an RNA of interest. Intramolecular clamping of the RNA can disrupt normal RNA function, whereas subsequent photo-cleavage of the crosslinker restores activity. We applied the RNA-CLAMP technique to the single guide RNA of the CRISPR-Cas9 gene editing system. By clamping two stem loops of the single-guide RNA (sgRNA) with a photo-cleavable cross-linker, gene editing was completely silenced. Visible light irradiation cleaved the crosslinker and restored gene editing with high spatiotemporal resolution. Furthermore, by designing two photo-cleavable linkers which are responsive to different wavelength of lights, we achieved multiplexed photo-activation of gene editing in mammalian cells. Notably, although the Cas9-sgRNA RNP is not capable of DNA cleavage activity upon clamping, it maintained the capability to bind to the target DNA. The RNA-CLAMP enabled photo-activated CRISPR-Cas9 gene editing platform offers clean background, free choice of activation wavelength and multiplexing capability. We believe that this technology to precisely and rapidly control gene editing will serve as a versatile tool in the future development of stimuli responsive gene editing technologies. Beyond gene editing, RNA-CLAMP provides a site-specific tool for manipulating the internal structure of functional RNAs.

biochemistry↗

bioRxiv2021

Nodal is a short-range morphogen with activity that spreads through a relay mechanism in human gastruloids

Morphogens are signaling molecules that convey positional information and dictate cell fates during development. Little is known about how morphogen gradients are created and interpreted during mammalian embryogenesis. Here we take advantage of a human gastruloid model to visualize endogenous Nodal protein in living cells. We show that Nodal is extremely short range so that Nodal protein is limited to the immediate neighborhood of source cells. Nodal activity spreads through a relay mechanism in which Nodal production induces neighboring cells to transcribe Nodal. We further show that the Nodal inhibitor Lefty, while biochemically capable of long-range diffusion, also acts locally to control the timing of Nodal spread and therefore of mesoderm differentiation during patterning. Our study establishes a novel paradigm for tissue patterning by an activator-inhibitor pair.

developmental biology↗

bioRxiv2021

Synthetic biology meets proteomics: Construction of a la carte QconCATs for absolute protein quantification

We report a new approach to the assembly and construction of QconCATs, quantitative concatamers for proteomic applications that yield stoichiometric quantities of sets of stable isotope-labelled internal standards. The new approach is based on synthetic biology precepts of biobricks, making use of loop assembly to construct larger entities from individual biobricks. It offers a major gain in flexibility of QconCAT implementation and enables rapid and efficient editability that permits, for example, substitution of one peptide for another. The basic building block (a Qbrick) is a segment of DNA that encodes two or more quantification peptides for a single protein, readily held in a repository as a library resource. These Qbricks are then assembled in a one tube ligation reaction that enforces the order of assembly, to yield short QconCATs that are useable for small quantification products. However, the DNA context of the short also allows a second cycle of assembly such that five different short QconCATs can be assembled into a longer QconCAT in a second, single tube ligation. From a library of Qbricks, a bespoke QconCAT can be assembled quickly and efficiently in a form suitable for expression and labelling in vivo or in vitro. We refer to this approach as the ALACAT strategy as it permits a la carte design of quantification standards.

biochemistry↗

bioRxiv2021

Adipsin promotes bone marrow adiposity by priming mesenchymal stem cells

BackgroundBone marrow (BM) adipose tissue (BMAT) has been shown to be vital for regulating metabolism and maintaining skeletal homeostasis in the marrow niche. As a reflection of BM remodeling, BMAT is highly responsive to nutrient fluctuations, hormonal changes and metabolic disturbances such as obesity and diabetes mellitus. Expansion of BMAT has also been strongly associated with bone loss in mice and humans. However, the regulation of BM plasticity remains poorly understood, as does the mechanism that links changes in marrow adiposity with bone remodeling. MethodsUsing C57BL/6 mice as a model, we employed the bone-protected PPAR{gamma} constitutive deacetylation (2KR), Adipsin, and its downstream effector, C3, knockout mice. These mice were challenged to thiazolidinedione treatment, calorie restriction, or aging in order to induce bone loss and MAT expansion. Analysis of bone density and marrow adiposity was performed using a CT scanner and by RNA analysis to assess adipocyte and osteoblast markers. For in vitro studies, primary bone marrow stromal cells (BMSCs) were isolated and subjected to osteoblastogenic or adipogenic differentiation or chemical treatment followed by morphological and molecular analyses. Clinical data was obtained from samples of a previous clinical trial of fasting and high calorie diet in healthy human volunteers. ResultsWe have shown that Adipsin is the most up-regulated adipokine during BMAT expansion in mice and humans, in a PPAR{gamma} acetylation-dependent manner. Ablation of Adipsin in mice specifically inhibited BMAT expansion but not peripheral adipose depots, and improved bone mass during calorie restriction, thiazolidinedione treatment, and aging. These effects were mediated through its downstream effector, complement component C3, to prime common progenitor cells toward adipogenesis rather than osteoblastogenesis through inhibiting Wnt/{beta}- catenin signaling. ConclusionsAdipsin promotes new adipocyte formation and affects skeletal remodeling in the BM niche. Our study reveals a novel mechanism whereby the BM sustains its own plasticity through paracrine and endocrine actions of a unique adipokine. FundingThis work was supported by the National Institutes of Health T32DK007328 (NA), F31DK124926 (NA), R01DK121140 (JCL), R01AR068970 (BZ), R01AR071463 (BZ), R01DK112943 (LQ), and P01HL087123 (LQ).

molecular biology↗

bioRxiv2021

Structural Insights Into the Initiation and Elongation of Ubiquitination by Ubr1

The N-end rule pathway was one of the first ubiquitin (Ub)-dependent degradation pathways to be identified. Ubr1, a single-chain E3 ligase, targets proteins bearing a destabilizing residue at the N-terminus (N-degron) for rapid K48-linked ubiquitination and proteasome-dependent degradation. How Ubr1 catalyses the initiation of ubiquitination on the substrate and elongation of the Ub chain in a linkage-specific manner through a single E2 ubiquitin-conjugating enzyme (Ubc2) remains unknown. Here, we report the cryo-electron microscopy structures of two complexes representing the initiation and elongation intermediates of Ubr1 captured using chemical approaches. In these two structures, Ubr1 adopts different conformations to facilitate the transfer of Ub from Ubc2 to either an N-degron peptide or a monoubiquitinated degron. These structures not only reveal the architecture of the Ubr1 complex but also provide mechanistic insights into the initiation and elongation steps of ubiquitination catalysed by Ubr1.

biophysics↗

bioRxiv2021

Nosocomial Pseudomonas aeruginosaregulates alginate biosynthesis and Type VI secretion system during adaptive and convergent evolution for coinfection in critically ill COVID-19 patients

COVID-19 pandemic has caused millions of death globally and caused huge impact on the health of infected patients. Shift in the lung microbial ecology upon such viral infection often worsens the disease and increases host susceptibility to secondary infections. Recent studies have indicated that bacterial coinfection is an unignorable factor contributing to the aggravation of COVID-19 and posing great challenge to clinical treatments. However, there is still a lack of in-depth investigation on the coinfecting bacteria in COVID-19 patients for better treatment of bacterial coinfection. With the knowledge that Pseudomonas aeruginosa is one of the top coinfecting pathogens, we analyzed the adaptation and convergent evolution of nosocomial P. aeruginosa isolated from two critical COVID-19 patients in this study. We sequenced and compared the genomes and transcriptomes of P. aeruginosa isolates longitudinally and parallelly for its evolutionary traits. P. aeruginosa overexpressed alginate and attenuated Type VI secretion system (T6SS) during coinfection for excessive biofilm formation and suppressed virulence. Results of bacterial competition assay and macrophage cytotoxicity test indicated that P. aeruginosa reduced its virulence towards both prokaryotic competitors and eukaryotic host through inhibiting its T6SS during evolution. P. aeuginosa T6SS is thus one of the reasons for its advantage to cause coinfection in COVID-19 patients while the attenuation of T6SS could cause a shift in the microecological composition in the lung. Our study will contribute to the development of therapeutic measures and the discovery of novel drug target to eliminate P. aeruginosa coinfection in COVID-19 patient.

microbiology↗

bioRxiv2021

HandyCNV: Standardized Summary, Annotation, Comparison, and Visualization of CNV, CNVR and ROH

Here we present an R package for summarizing, annotating, converting, comparing and visualizing CNV (copy number variants) and ROH (runs of homozygosity) detected from SNP (single nucleotide polymorphism) genotyping data. This one-stop post-analysis system is standardized, comprehensive, reproducible, timesaving and user friendly for research in humans and most diploid livestock species. Availability and ImplementationThe source code, demo data and vignettes can be found at https://github.com/JH-Zhou/HandyCNV

bioinformatics↗

bioRxiv2021

Substitutions and codon usage in SARS-CoV-2 in mammals indicate natural selection and host adaptation

The outbreak of COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, rapidly spread to create a global pandemic and has continued to spread across hosts from humans to animals, transmitting particularly effectively in mink. How SARS-CoV-2 evolves in animals and humans and the differences in the separate evolutionary processes remain unclear. We analyzed the composition and codon usage bias of SARS-CoV-2 in infected humans and animals. Compared with other animals, SARS-CoV-2 in mink had the most substitutions. The substitutions of cytidine in SARS-CoV-2 in mink account for nearly 50% of the substitutions, while those in other animals represent only 30% of the substitutions. The incidence of adenine transversion in SARS-CoV-2 in other animals is threefold higher than that in mink-CoV (the SARS-CoV-2 virus in mink). A synonymous codon usage analysis showed that SARS-CoV-2 is optimized to adapt in the animals in which it is currently reported, and all the animals showed decreased adaptability relative to that of humans, except for mink. A binding affinity analysis indicated that the spike protein of the SARS-CoV-2 variant in mink showed a greater preference for binding with the mink receptor ACE2 than with the human receptor, especially as the mutation Y453F and F486L in mink-CoV lead to improvement of binding affinity for mink receptor. Our study focuses on the divergence of SARS-CoV-2 genome composition and codon usage in humans and animals, indicating possible natural selection and current host adaptation.

evolutionary biology↗

bioRxiv2021

New metabolic alterations and predictive marker pipecolic acid in sera for esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a major histological subtype of esophageal cancer with dismal prognosis. Although several serum metabolomic investigations have been reported, ESCC tumor-associated metabolic alterations along with predictive biomarkers in sera were not defined. Here we enrolled 34 treatment-naive ESCC patients and collected their pre-and post-esophagectomy sera together with sera from 34 healthy volunteers for metabolomic survey. Our comprehensive analysis discerned ESCC tumor-associated metabolic alterations as represented by a panel of 12 serum metabolites. Notably, postoperative abrosia and parenteral nutrition significantly perturbed the serum metabolome. Furthermore, we performed examination using sera from carcinogen-induced mice at dysplasia and ESCC stages, and identified three ESCC tumor-associated metabolites conserved between mice and humans. Notably, among these metabolites, pipecolic acid was progressively increased in mouse sera from dysplasia to cancerization, and it could accurately discriminate between mice at dysplasia stage and healthy control mice. Furthermore, this metabolite was essential for ECSS cells to oppose oxidative stress-induced DNA damage and cell proliferation arrest. Together, this study uncovered 12 ESCC tumor-associated serum metabolites with potential for monitoring therapeutic efficacy and disease relapse, presented evidence for refining parenteral nutrition composition, and highlighted serum pipecolic acid as an attractive biomarker for prediction of ESCC tumorigenesis.

cancer biology↗