Biology subjects

Xu, P.

Publications and source records attributed to Xu, P..

At least 163 records · Page 9Linked to original sources

bioRxiv2022

Oscillatory dynamics underlying emotion-cognition integration: differential role of theta and alpha oscillations

A fundamental aspect of human mental life is the seamless ability for integration of emotion and cognition. Despite progress regarding the spatial architecture of Emotion-Cognition Integration (ECI), the time course of ECI processes remains unclear. To examine the temporal organization of brain oscillations underpinning ECI, we simultaneously manipulated emotional valence of stimuli and cognitive task demand while recording electrophysiological responses of 61 participants. They were asked to complete tasks with low (body-part judgement) and high (laterality judgement) cognitive demand while viewing other people photographs that varied on dimensions of laterality (left or right), body-part (hand or foot), and emotional valence (pain or no pain). We found increased reaction times and error rates in pain versus no pain during laterality judgement relative to body-part judgement, suggesting reciprocal inhibition between emotion and cognition. EEG results showed that 1) emotion processing (valence) occurred first in the theta band from 144 to 372 ms; 2) cognitive processing (laterality) took place in the theta band from 332 to 608 ms; 3) emotional and cognitive processes were integrated in the alpha band from 268 ms and lasted to 800 ms. These findings reveal oscillatory dynamics of the processing and integration of emotion and cognition, providing further insights into the underlying neurophysiology. This may ultimately contribute to our understanding of ECI processing in psychopathology.

neuroscience↗

bioRxiv2022

IRONMAN interacts with OsHRZ1 and OsHRZ2 to maintain Fe homeostasis

IRONMAN is a family of small peptides which positively regulate the Fe deficiency response. However, the molecular mechanism by which OsIMA1 and OsIMA2 regulate Fe homeostasis was unclear. Here, we reveal that OsIMA1 and OsIMA2 interact with the potential Fe sensors, OsHRZ1 and OsHRZ2. OsIMA1 and OsIMA2 contain a conserved 17-amino acid C-terminal region which is responsible for the interactions with OsHRZ1 and OsHRZ2. The OsIMA1 overexpressing plants have the increased seed Fe concentration and the reduced fertility, as observed in the hrz1-2 loss-of-function mutant plants. Moreover, the expression trends of Fe deficiency inducible genes in the OsIMA1 overexpressing plants are the same to those in the hrz1-2. Co-expression assays suggest that OsHRZ1 and OsHRZ2 promote the degradation of OsIMA1 proteins. As the interaction partners of OsHRZ1, the OsPRI proteins also interact with OsHRZ2. The conserved C-terminal region of four OsPRIs contributes to the interactions with OsHRZ1 and OsHRZ2. An artificial IMA (aIMA) derived from the C-terminal of OsPRI1 can be also degraded by OsHRZ1. Moreover, the aIMA overexpressing rice plants accumulate more Fe without reduction of fertility. This work establishes the link between OsIMAs and OsHRZs, and develops a new strategy for Fe fortification in rice.

molecular biology↗

bioRxiv2022

Structural insights into the peptide selectivity and activation of human neuromedin U receptors

Neuromedin U receptors (NMURs), including NMUR1 and NMUR2, are a group of Gq/11-coupled G protein-coupled receptors (GPCRs) related to pleiotropic physiological functions. Upon stimulation by two endogenous neuropeptides, neuromedin U and S (NMU and NMS) with similar binding affinities, NMUR1 and NMUR2 primarily display distinct peripheral tissue and central nervous system (CNS) functions, respectively, due to their distinct tissue distributions. These NMU receptors have triggered extensive attention as drug targets for obesity and immune inflammation. Specifically, selective agonists for NMUR1 in peripheral tissue show promising long-term anti-obesity effects with fewer CNS-related side effects. However, the mechanisms of peptide binding specificity and receptor activation remain elusive due to the lack of NMU receptor structures, which hamper drug design targeting NMU receptors. Here, we report four cryo-electron microscopy structures of Gq chimera-coupled NMUR1 and NMUR2 bound with NMU and NMS. These structures present the conserved overall peptide-binding mode and reveal the mechanism of peptide selectivity for specific NMURs, as well as the common activation mechanism of the NMUR subfamily. Together, these findings provide insights into the molecular basis of the peptide recognition selectivity and offer a new opportunity for designing selective drugs targeting NMURs.

biophysics↗

bioRxiv2022

Improved fluorescent proteins for dual-color post-embedding CLEM

Post-embedding correlative light and electron microscopy (CLEM) has the advantage of high-precision registration and enables light and electron microscopy imaging of the same slice. However, its broad application has been hampered by the limited available fluorescent proteins (FPs) and low signal-to-background ratio (SBR). Here, we developed a green photoswitchable FP, mEosEM-E with substantially high on/off contrast in EM samples embedded in Epon resin which maximally preserves cellular structures but quenches the fluorescence of FPs. Taking advantage of the photoswitching property of mEosEM-E, the autofluorescence background from the resin was significantly reduced by a subtraction-based CLEM (sCLEM) method. Meanwhile, we identified a red fluorescent protein (RFP) mScharlet-H that exhibited higher brightness and SBR in resin than previously reported RFPs. With mEosEM-E and mScharlet-H, dual-color post-Epon-embedding CLEM images with high SBR and no cross-talk signal were successfully performed to reveal the organization of nucleolar proteins. Moreover, a dissection of the influences of different EM sample preparation steps on the fluorescence preservation for several RFPs provides useful guidance for further probe development.

biophysics↗

bioRxiv2022

OsIRO3 negatively regulates Fe homeostasis by repressing the expression of OsIRO2

Iron (Fe) is crucial for crop productivity and quality. However, Fe deficiency is prevalent worldwide, especially in alkaline soil. Plants have evolved sophisticated mechanisms to withstand Fe deficiency conditions. Oryza sativa IRON-RELATED BHLH TRANSCRIPTION FACTOR 3 (OsIRO3/OsbHLH63) has been identified as a negative regulator of Fe deficiency response signaling, however, the underlying mechanism remains unclear. In the present study, we constructed two iro3 mutants which generated leaves with necrotic lesions under Fe deficient conditions. Loss-of-function of OsIRO3 caused upregulation of Fe deficiency-associated genes in the root under Fe deficient conditions. Fe concentration measurement showed that the iro3 mutants had increased shoot Fe concentration only under Fe deficient conditions. Further analysis revealed that OsIRO3 directly regulated the expression of IRON-RELATED BHLH TRANSCRIPTION FACTOR 2 (OsIRO2) which encodes a positive regulator of Fe uptake system. Protein interaction tests indicated that OsIRO3 interacted with OsPRI1 and OsPRI2. Further investigation demonstrated that OsIRO3 repressed the transactivation of OsPRI1 and OsPRI2 towards OsIRO2. OsIRO3 contains an EAR motif which recruits the TOPLESS/TOPLESS-RELATED (OsTPL/OsTPRs) corepressors. Mutation of the EAR motif attenuated the repression ability of OsIRO3. This work sheds light on the molecular mechanism by which OsIRO3 modulates Fe homeostasis in rice.

plant biology↗

bioRxiv2022

Lyophilized mRNA-lipid nanoparticles vaccine with long-term stability and high antigenicity against SARS-CoV-2

Advanced mRNA vaccines play vital roles against SARS-CoV-2. However, due to their poor stability, most current mRNA delivery platforms need to be stored at -20{degrees}C or -70{degrees}C, which severely limits their distribution. Herein, we present lyophilized SARS-CoV-2 mRNA-lipid nanoparticle vaccines, which can be stored at room temperature with long-term thermostability. In the in vivo Delta virus challenge experiment, lyophilized Delta variant mRNA vaccine successfully protected mice from infection and cleared the virus. Lyophilized omicron mRNA vaccine enabled to elicit both potent humoral and cellular immunity. In booster immunization experiments in mice and old monkeys, lyophilized omicron mRNA vaccine could effectively increase the titers of neutralizing antibodies against wild-type coronavirus and omicron variants. In humans, lyophilized omicron mRNA vaccine as a booster shot could also engender excellent immunity and had less severe adverse events. This lyophilization platform overcomes the instability of mRNA vaccines without affecting their bioactivity, and significantly improved their accessibility, particularly in remote regions.

immunology↗

bioRxiv2022

Molecular basis for allosteric agonism and G protein subtype selectivity of galanin receptors

Peptide hormones and neuropeptides are complex signaling molecules that predominately function through G protein-coupled receptors (GPCRs). Two fundamental questions remained in the field of peptide-GPCR signaling systems are the basis for the diverse binding mode of peptide ligands and the specificity of G protein coupling. Here we report the structures of a neuropeptide, galanin, bound to its receptors, GAL1R and GAL2R, in complex with their primary G protein subtypes Gi and Gq, respectively. The structures reveal a unique binding pose of galanin, which almost lay flat on the top of the receptor transmembrane domain pocket in an -helical conformation, and acts as an allosteric-like agonist via a distinct signal transduction cascade. The structures also uncover the important features of intracellular loop 2 (ICL2) that mediate specific interactions with Gq, thus determining the selective coupling of Gq to GAL2R. ICL2 replacement in Gi-coupled GAL1R, OR, 5-HT1AR, and Gs-coupled b2AR and D1R with that of GAL2R promotes Gq coupling of these receptors, highlighting the dominant roles of ICL2 in Gq selectivity. Together our results provide important insights into peptide ligand recognition and allosteric activation of galanin receptors and uncover a general structural element for Gq coupling selectivity.

molecular biology↗

bioRxiv2022

Mosquito odorant receptor sensitive to natural spatial repellents and inhibitory compounds

Previously, we have identified an odorant receptor (OR) from the southern house mosquito Culex quinquefasciatus, CquiOR32, which responded to both odorants (agonists) and inhibitory compounds (antagonists). CquiOR32/CquiOrco-expressing oocytes responded to methyl salicylate and other odorants with inward (regular) currents but gave currents in the reverse direction when challenged with eucalyptol and other inhibitors. To determine whether hitherto unknown ORs show this intrareceptor inhibition, we have now examined two other receptors in the same cluster, CquiOR27 and CquiOR28. We cloned and tested four variants of CquiOR28, but none of the 250 compounds in our panel of odorants, including an Orco ligand candidate (OCL12), elicited inward or outward currents. By contrast, CquiOR27/CquiOrco-expressing oocytes gave robust, dose-dependent inward currents when challenged with {gamma}-octalactone and other odorants. On the other hand, octylamine and other phenolic compounds elicited dose-dependent currents in the reverse direction. When stimulatory and inhibitory compounds were presented in binary mixtures, {gamma}-octalactone-elicited inward currents were attenuated in a dose-dependent manner according to the concentration of octylamine. As part of our chemical ecology approach, we tested the repellency activity of the best ligands in the surface landing and feeding assay and a newly reported hand-in cage assay. Protection elicited by {gamma}-octalactone did not differ significantly from that of DEET at the same dose. In the hand-in cage assay, a cream formulation of {gamma}-octalactone showed 97.0 {+/-} 1.3% protection, with 47.6 {+/-} 8.3% and 1.4 {+/-} 0.7% landings per trial in the hands covered with a control and {gamma}-octalactone cream, respectively (N=8, p=0.0078, Wilcoxon matched-pairs signed-rank test).

neuroscience↗

bioRxiv2022

Differential UBE2H-CTLH E2-E3 ubiquitylation modules regulate erythroid maturation

The development of haematopoietic stem cells into mature erythrocytes - erythropoiesis - is a controlled process characterized by cellular reorganisation and drastic reshaping of the proteome landscape. Failure of ordered erythropoiesis is associated with anaemias and haematological malignancies. Although the ubiquitin (UB) system is a known crucial post-translational regulator in erythropoiesis, how the erythrocyte is reshaped by the UB system is poorly understood. By measuring the proteomic landscape of in vitro human erythropoiesis models, we found dynamic differential expression of subunits of the CTLH E3 ubiquitin ligase complex that formed distinct maturation stage-dependent assemblies of structurally homologous RANBP9-and RANBP10-CTLH complexes. Moreover, protein abundance of CTLHs cognate E2-conjugating enzyme UBE2H increased during terminal differentiation, which depended on catalytically active CTLH E3 complexes. CRISPR-Cas9 mediated inactivation of all CTLH E3 assemblies by targeting the catalytic subunit MAEA, or UBE2H, triggered spontaneous and accelerated maturation of erythroid progenitor cells including increased heme and haemoglobin synthesis. Thus, the orderly progression of human erythropoiesis is controlled by the assembly of distinct UBE2H-CTLH modules functioning at different developmental stages.

cell biology↗

bioRxiv2021

Structures of the Omicron Spike trimer with ACE2 and an anti-Omicron antibody

The Omicron variant of SARS-CoV-2 has rapidly become the dominant infective strain and the focus efforts against the ongoing COVID-19 pandemic. Here we report an extensive set of structures of the Omicron spike trimer by its own or in complex with ACE2 and an anti-Omicron antibody. These structures reveal that most Omicron mutations are located on the surface of the spike protein, which confer stronger ACE2 binding by nearly 10 folds but become inactive epitopes resistant to many therapeutic antibodies. Importantly, both RBD and the closed conformation of the Omicron spike trimer are thermodynamically unstable, with the melting temperature of the Omicron RBD decreased by as much as 7{degrees}C, making the spiker trimer prone to random open conformations. An unusual RBD-RBD interaction in the ACE2-spike complex unique to Omicron is observed to support the open conformation and ACE2 binding, serving the basis for the higher infectivity of Omicron. A broad-spectrum therapeutic antibody JMB2002, which has completed Phase 1 clinical trial, is found to interact with the same two RBDs to inhibit ACE2 binding, in a mode that is distinguished from all previous antibodies, thus providing the structural basis for the potent inhibition of Omicron by this antibody. Together with biochemical data, our structures provide crucial insights into higher infectivity, antibody evasion and inhibition of Omicron.

biophysics↗

bioRxiv2021

Delivery of CAR-T Cells in a Transient Injectable Stimulatory Hydrogel Niche Improves Treatment of Solid Tumors

Adoptive cell therapy (ACT) has proven to be highly effective in treating blood cancers such as B cell malignancies, but traditional approaches to ACT are poorly effective in treating the multifarious solid tumors observed clinically. Locoregional cell delivery methods have shown promising results in treating solid tumors compared to standard intravenous delivery methods, but the approaches that have been described to date have several critical drawbacks ranging from complex manufacturing and poor modularity to challenging adminstration. In this work, we develop a simple-to-implement self-assembled and injectable hydrogel material for the controlled co-delivery of CAR-T cells and stimulatory cytokines that improves treatment of solid tumors. We evaluate a range of hydrogel formulations to optimize the creation of a transient inflammatory niche that affords sustained exposure of CAR-T cells and cytokines. This facile approach yields increased CAR-T cell expansion, induces a more tumor-reactive CAR-T phenotype, and improves efficacy in treating solid tumors in mice.

bioengineering↗

bioRxiv2021

Ubiquitination drives COPI priming and Golgi SNARE localization

Deciphering mechanisms controlling SNARE localization within the Golgi complex is crucial to understanding protein trafficking patterns within the secretory pathway. SNAREs are also thought to prime COPI assembly to ensure incorporation of these essential cargoes into vesicles but the regulation of these events is poorly understood. Here we report a roles for ubiquitin recognition by COPI in SNARE trafficking and in stabilizing interactions between Arf, COPI, and Golgi SNAREs. The ability of COPI to bind ubiquitin through its N-terminal WD repeat domain of {beta}COP or through an unrelated ubiquitin-binding domain (UBD) is essential for the proper localization of Golgi SNAREs Bet1 and Gos1. We find that COPI, the ArfGAP Glo3 and multiple Golgi SNAREs are ubiquitinated. Notably, the binding of Arf and COPI to Gos1 is markedly enhanced by ubiquitination of these components. Glo3 is thought to prime COPI-SNARE interactions; however, Glo3 is not enriched in the ubiquitin-stabilized SNARE-Arf-COPI complex but is instead enriched with COPI complexes that lack SNAREs. These results support a new model for how posttranslational modifications drive COPI priming events crucial for Golgi SNARE localization.

cell biology↗

bioRxiv2021

Inferring kinetic rate constants from single-molecule FRET trajectories - a blind benchmark of kinetic analysis tools

Single-molecule FRET (smFRET) is a versatile technique to study the dynamics and function of biomolecules since it makes nanoscale movements detectable as fluorescence signals. The powerful ability to infer quantitative kinetic information from smFRET data is, however, complicated by experimental limitations. Diverse analysis tools have been developed to overcome these hurdles but a systematic comparison is lacking. Here, we report the results of a blind benchmark study assessing eleven analysis tools used to infer kinetic rate constants from smFRET trajectories. We tested them against simulated and experimental data containing the most prominent difficulties encountered in analyzing smFRET experiments: different noise levels, varied model complexity, non-equilibrium dynamics, and kinetic heterogeneity. Our results highlight the current strengths and limitations in inferring kinetic information from smFRET trajectories. In addition, we formulate concrete recommendations and identify key targets for future developments, aimed to advance our understanding of biomolecular dynamics through quantitative experiment-derived models.

biophysics↗

bioRxiv2021

The different brain areas occupied for integrating information of hierarchical linguistic units: a study based on EEG and TMS

Human linguistic units are hierarchical, and our brain responds differently when processing linguistic units during sentence comprehension, especially when the modality of the received signal is different (auditory, visual, or audio-visual). However, it is unclear how the brain processes and integrates language information at different linguistic units (words, phrases, and sentences) provided simultaneously in audio and visual modalities. To address the issue, we presented participants with sequences of short Chinese sentences through auditory or visual or combined audio- visual modalities, while electroencephalographic responses were recorded. With a frequency tagging approach, we analyzed the neural representations of basic linguistic units (i.e., characters/monosyllabic words) and higher-level linguistic structures (i.e., phrases and sentences) across the three modalities separately. We found that audio-visual integration occurs at all linguistic units, and the brain areas involved in the integration varied across different linguistic levels. In particular, the integration of sentences activated the local left prefrontal area. Therefore, we used continuous theta-burst stimulation (cTBS) to verify that the left prefrontal cortex plays a vital role in the audio-visual integration of sentence information. Our findings suggest the advantage of bimodal language comprehension at hierarchical stages in language-related information processing and provide evidence for the causal role of the left prefrontal regions in processing information of audio-visual sentences.

neuroscience↗

bioRxiv2021

Single-cell metabolomics reveals the metabolic heterogeneity among microbial cells

In microbial research, the heterogeneity phenomenon is closely associated with microbial physiology in multiple dimensions. For now, A few studies were proposed in transcriptome and proteome analysis to discover the heterogeneity among single cells. However, microbial single cell metabolomics has not been possible yet. Herein, we developed a method, RespectM, based on discontinuous mass spectrometry imaging, which can detect more than 700 metabolites at a rate of 500 cells per hour. While ensuring the high throughput of RespectM, it integrates matrix sublimation, QC-based peak filtering, and batch correction strategies to improve accuracy. The results show that RespectM can distinguish single microbial cells from the blank matrix with an accuracy of 98.4%, depending on classification algorithms. Furthermore, to verify the accuracy of RespectM for distinguishing different single cells, we performed a classification test on Chlamydomonas reinhardtii single cells among allelic strains. The results showed an accuracy of 93.1%, which provides RespectM with enough confidence to perform microbial single cell metabolomics analysis. As we expected, untreated microbial cells will spontaneously undergo metabolic grouping coherence with genetic and biochemical similarities. Interestingly, the pseudo-time analysis also provided intuitive evidence on the metabolic dimension, indicating the cell grouping is based on microbial population heterogeneity. We believe that the RespectM can offer a powerful tool in the microbial study. Researchers can now directly analyze the changes in microbial metabolism at a single-cell level with high efficiency.

systems biology↗

bioRxiv2021

Structure Insight into Photosystem I Octamer from Cyanobacteria

Diversity of photosystem oligomers is essential to understand how photosynthetic organisms adopted to light conditions. Given by the structural and physiological significance, the assemblies of PSI supercomplex is of great interest in both chloroplast and cyanobacteria recently. In this study, two novel photosystem I supercomplexes were isolated for the first time from the low light incubated culture of filamentous cyanobacterium Anabaena sp. PCC 7120. These complexes were defined as PSI hexamers and octamers through biochemical and biophysical characterization. Their 77K emission spectra indicated that the red forms of chlorophylls seemed not to be affected during oligomerization. By cryo-EM single particle analysis, a near-atomic (7.0 [A]) resolution structure of PSI octamer was resolved, and the molecular assemblies of stable PSI octamer was revealed.

biophysics↗

bioRxiv2021

Direct carbon capture for production of high-performance biodegradable plastic by cyanobacterial cell factory

Plastic pollution has become one of the most pressing environmental issues today, leading to an urgent need to develop biodegradable plastics1-3. Polylactic acid (PLA) is one of the most promising biodegradable materials because of its potential applications in disposable packaging, agriculture, medicine, and printing filaments for 3D printers4-6. However, current biosynthesis of PLA entirely uses edible biomass as feedstock, which leads to competition for resources between material production and food supply7,8. Meanwhile, excessive emission of CO2 that is the most abundant carbon source aggravates global warming, and climate instability. Herein, we first developed a cyanobacterial cell factory for the de novo biosynthesis of PLA directly from CO2, using a combinational strategy of metabolic engineering and high-density cultivation (HDC). Firstly, the heterologous pathway for PLA production, which involves engineered D-lactic dehydrogenase (LDH), propionate CoA-transferase (PCT), and polyhydroxyalkanoate (PHA) synthase, was introduced into Synechococcus elongatus PCC7942. Subsequently, different metabolic engineering strategies, including pathway debottlenecking, acetyl-CoA self-circulation, and carbon-flux redirection, were systematically applied, resulting in approximately 19-fold increase to 15 mg/g dry cell weight (DCW) PLA compared to the control. In addition, HDC increased cell density by 10-fold. Finally, the PLA titer of 108 mg/L (corresponding to 23 mg/g DCW) was obtained, approximately 270 times higher than that obtained from the initially constructed strain. Moreover, molecular weight (Mw, 62.5 kDa; Mn, 32.8 kDa) of PLA produced by this strategy was among the highest reported levels. This study sheds a bright light on the prospects of plastic production from CO2 using cyanobacterial cell factories.

bioengineering↗

bioRxiv2021

LM-GVP: A Generalizable Deep Learning Framework for Protein Property Prediction from Sequence and Structure

Proteins perform many essential functions in biological systems and can be successfully developed as bio-therapeutics. It is invaluable to be able to predict their properties based on a proposed sequence and structure. In this study, we developed a novel generalizable deep learning framework, LM-GVP, composed of a protein Language Model (LM) and Graph Neural Network (GNN) to leverage information from both 1D amino acid sequences and 3D structures of proteins. Our approach outperformed the state-of-the-art protein LMs on a variety of property prediction tasks including fluorescence, protease stability, and protein functions from Gene Ontology (GO). We also illustrated insights into how a GNN prediction head can guide the protein LM to better leverage structural information. We envision that our deep learning framework will be generalizable to many protein property prediction problems to greatly accelerate protein engineering and drug development.

synthetic biology↗