Biology subjects

Lin, C.

Publications and source records attributed to Lin, C..

At least 109 records · Page 6Linked to original sources

bioRxiv2022

Mechanisms of circadian clock timing and entrainment revealed by the structure of Cryptochrome bound to Timeless

Circadian rhythms influence many behaviors and diseases1, 2. They arise from oscillations in gene expression caused by repressor proteins that directly inhibit transcription of their own genes. The fly circadian clock offers a valuable model for studying these processes, wherein Timeless (TIM) plays a critical role in mediating nuclear entry of the transcriptional repressor Period (PER) and the photoreceptor Cryptochrome (CRY) entrains the clock by triggering TIM degradation in light2, 3. The cryo-EM structure of the CRY:TIM complex reveals how a light-sensing cryptochrome recognizes its target. CRY engages a continuous core of N-terminal TIM armadillo (ARM) repeats, resembling how photolyases recognize damaged DNA, and binds a C-terminal TIM helix reminiscent of the interactions between light-insensitive CRYs and their partners in mammals. The structure highlights how the CRY flavin cofactor undergoes conformational changes that couple to large-scale rearrangements at the molecular interface, and how a phosphorylated segment in TIM may impact clock period by regulating the binding of importin- and the nuclear import of TIM:PER4, 5. Moreover, the structure reveals that the TIM N-terminus inserts into the restructured CRY pocket to replace the autoinhibitory C-terminal tail released by light, thereby providing a possible explanation for how the LS-TIM polymorphism adapts flies to different climates6, 7.

molecular biology↗

bioRxiv2022

Neuroanatomy of stomatopod central complexes offers putative neural substrate for oriented behaviors in crustaceans

All insects studied to date possess a centrally located group of neuropils, known collectively as the central complex, that has been implicated in sensory integration and motor action selection. Among the functions prescribed to the central complex, none is perhaps as intriguing as its role in orientation and navigation. Neurobiological correlates of both current and desired headings have been described in insect CXs. Despite the diversity of arthropods, understanding of the CX as a navigational center originates entirely from terrestrial insects. Stomatopod crustaceans, commonly referred to as mantis shrimps, form an order of predatory marine crustaceans with intricate and diverse visual systems that maintain the distinction of being the only fully aquatic animal known to utilize the navigational strategy of path integration. They utilize idiothetic, celestial, and landmark cues to orient in the benthos. Here, we investigate the neuroanatomy of adult and developing mantis shrimp central complexes and associated neuropils to begin understanding this brain region in a sensorially and behaviorally complex crustacean.

neuroscience↗

bioRxiv2022

State-dependent protein-protein interactions mediating 4-1BB CAR Signaling

Cells rely on activity-dependent protein-protein interactions to convey biological signals, but the state-dependent interactome is notoriously cell-specific and undercharacterized1. In the case of chimeric antigen receptor (CAR) T cells containing a 4-1BB costimulatory domain, receptor engagement is thought to trigger the formation of protein complexes similar to those triggered by T cell receptor (TCR)-mediated signaling, but the number and type of protein-interaction-mediating binding domains differ between CARs and TCRs. Here, we performed co-immunoprecipitation mass spectrometry of a 2nd generation CD19-directed 4-1BB:zeta CAR (referred to as bb{zeta}CAR) and identified 67 proteins that increased their co-association after target engagement. We compared activity-induced TCR and CAR signalosomes using quantitative multiplex co-immunoprecipitation and showed that bb{zeta}CAR engagement leads to activation of two modules of protein interactions, one similar to TCR signaling that is more weakly engaged in bb{zeta}CAR vs. TCR, and one composed of TRAF signaling complexes that is not engaged by the TCR. Batch-to-batch and inter-individual variations in IL2 production correlated with differences in the magnitude of protein network activation. Future CAR T cell manufacturing protocols could measure, and eventually control, biological variation by monitoring these signalosome activation markers. One Sentence SummaryWe define a network of protein interactions engaged by chimeric antigen receptors following target binding, and show that the magnitude of network activation correlates with IL-2 secretion, a proxy measure for CAR T cell function.

immunology↗

bioRxiv2022

Design of a systemic small molecule clinical STING agonist using physics-based simulations and artificial intelligence

The protein STING (stimulator of interferon genes) is a central regulator of the innate immune system and plays an important role in antitumor immunity by inducing the production of cytokines such as type I interferon (IFN). Activation of STING stems from the selective recognition of endogenous cyclic dinucleotides (CDNs) by the large, polar, and flexible binding site, thus posing challenges to the design of small molecule agonists with drug-like physicochemical properties. In this work we present the design of SNX281, a small molecule STING agonist that functions through a unique self-dimerizing mechanism in the STING binding site, where the ligand dimer approximates the size and shape of a cyclic dinucleotide while maintaining drug-like small molecule properties. SNX281 exhibits systemic exposure, STING-mediated cytokine release, strong induction of type I IFN, potent in vivo antitumor activity, durable immune memory, and single-dose tumor elimination in mouse models via a Cmax-driven pharmacologic response. Bespoke computational methods - a combination of quantum mechanics, molecular dynamics, binding free energy simulations, and artificial intelligence - were developed during the course of the project to design SNX281 by explicitly accounting for the unique self-dimerization mechanism and the large-scale conformational change of the STING protein upon activation. Over the course of the project, we explored millions of virtual molecules while synthesizing and testing only 208 molecules in the lab. This work highlights the value of a multifaceted computationally-driven approach anchored by methods tailored to address target-specific problems encountered along the project progression from initial hit to the clinic.

cancer biology↗

bioRxiv2022

Actuating tension-loaded DNA clamps drives membrane tubulation

Membrane dynamics in living organisms can arise from proteins adhering to, assembling on, and exerting force on cell membranes. Programmable synthetic materials, such as self-assembled DNA nanostructures, offer the capability to drive membrane remodeling events in a way that resembles protein-mediated dynamics, but with user-defined outcomes. An example showcasing this capability is the tubular deformation of liposomes by DNA nanostructures with purposely designed shapes, surface modifications, and self-assembling properties. However, stimulus-responsive membrane tubulation mediated by DNA structure reconfiguration remains challenging. Here we present the triggered formation of membrane tubes in response to specific DNA signals that actuate membrane-bound DNA clamps from an open state to various predefined closed states, releasing pre-stored energy to activate membrane deformation. Using giant unilamellar vesicles (GUVs) as a model system, we show that the timing and efficiency of tubulation, as well as the width of membrane tubes, are modulated by the conformational change of DNA clamps, marking a solid step toward spatiotemporal control of membrane dynamics in an artificial system.

synthetic biology↗

bioRxiv2022

CLASP2 stabilizes GDP-associated terminal tubulins to prevent microtubule catastrophe

CLASPs are ubiquitous stabilizers of microtubule dynamics but their molecular targets at the microtubule plus-end are not understood. Using DNA origami-based reconstructions we show that clusters of human CLASP2 form a load-bearing bond with terminal GDP-tubulins at the stabilized microtubule tip. This activity relies on the unconventional TOG2 domain of CLASP2, which releases its high-affinity bond with the GDP-dimers upon their conversion into polymerization-competent GTP-tubulin. By tethering dynamic microtubule ends near immobilized CLASP2, we show that the targets for CLASP2 binding at the polymerizing tip arise stochastically, leading to nanoscale disruptions in microtubule tip integrity. The ability of CLASP2 to recognize nucleotide-specific tubulin conformation and stabilize the catastrophe-promoting GDP-tubulins intertwines with the previously underappreciated exchange between GDP and GTP at terminal tubulins, providing a distinct molecular mechanism to suppress microtubule catastrophe without affecting tubulin incorporation.

biophysics↗

bioRxiv2022

Cryo-EM Structure of R-loop monoclonal antibody S9.6 in recognizing RNA:DNA hybrids

The three-stranded chromatin structure R-loop is commonly found in the genomes of different species, and functions as the double-edged sword in gene expression and genome stability. The monoclonal antibody S9.6 specifically recognizes RNA:DNA hybrids, and has been widely used as a powerful tool to detect R-loops genome-widely. However, the structure basis and the molecular recognition mechanism of S9.6 to the nucleic acid substrates is still limited. Here, applying cryo-electron microscopy, we have determined a 4.9 [A] structure of S9.6 antigen-binding fragment (Fab) complexed with RNA:DNA hybrids. We found that the native Fab cleaved from S9.6 antibody has much higher affinity to RNA:DNA hybrids than to the double-strand RNAs, and the minimum length of the hybrids should be more than 8 base-pair. The structure of Fab binding to the hybrids suggested one loop of S9.6 heavy chain inserts into the minor groove in the RNA:DNA hybrids, and the other three loops flank to the hybrids. The top of four loop all enrich with aromatic or positive charge residues which are potentially responsible for nucleic acids binding specificity. Our results revealed the recognition mechanism of S9.6 on R-loops, which directs the future engineering of S9.6, and thus could further promote R-loop biology studies.

molecular biology↗

bioRxiv2022

Gut microbiota-derived tryptamine impairs insulin sensitivity

Gut-microbiota plays a pivotal role in development of type 2 diabetes (T2D), yet the molecular mechanism remains elusive. Here, we show that tryptamine, a microbial metabolite of tryptophan, impairs glucose tolerance and insulin sensitivity. Tryptamine presents a higher level in monkeys with spontaneous diabetes and human with T2D and positively correlated with the glucose tolerance. In parallel, tryptamine level was suppressed by dietary fibers intervention in T2D subjects and negatively correlated with improvement of glucose tolerance. The inhibitory effect of tryptamine on insulin signaling as shown was dependent on a trace amine-associated receptor 1 (TAAR1)-extracellular signal-regulated kinase (ERK) signaling axis. Monoassociation of T2D-associated tryptamine-producing bacteria Ruminococcus gnavus impairs insulin sensitivity in pseudo germ-free mice. Our findings indicate gut microbiota-derived tryptamine contributes to the development of insulin resistance in T2D and may serve as a new target for intervention. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

microbiology↗

bioRxiv2022

SARS-CoV-2 Omicron-specific mRNA vaccine induces potent and broad antibody responses in vivo

The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has high transmissibility and recently swept the globe. Due to the extensive number of mutations, this variant has high level of immune evasion, which drastically reduced the efficacy of existing antibodies and vaccines. Thus, it is important to test an Omicron-specific vaccine, evaluate its immune response against Omicron and other variants, and compare its immunogenicity as boosters with existing vaccine designed against the reference wildtype virus (WT). Here, we generated an Omicron-specific lipid nanoparticle (LNP) mRNA vaccine candidate, and tested its activity in animals, both alone and as a heterologous booster to existing WT mRNA vaccine. Our Omicron-specific LNP-mRNA vaccine elicited strong and specific antibody response in vaccination-naive mice. Mice that received two-dose WT LNP-mRNA, the one mimicking the commonly used Pfizer/Moderna mRNA vaccine, showed a >40-fold reduction in neutralization potency against Omicron variant than that against WT two weeks post second dose, which further reduced to background level >3 months post second dose. As a booster shot for two-dose WT mRNA vaccinated mice, a single dose of either a homologous booster with WT LNP-mRNA or a heterologous booster with Omicron LNP-mRNA restored the waning antibody response against Omicron, with over 40-fold increase at two weeks post injection as compared to right before booster. Interestingly, the heterologous Omicron LNP-mRNA booster elicited neutralizing titers 10-20 fold higher than the homologous WT booster against the Omicron variant, with comparable titers against the Delta variant. All three types of vaccination, including Omicron mRNA alone, WT mRNA homologous booster, and Omicron heterologous booster, elicited broad binding antibody responses against SARS-CoV-2 WA-1, Beta, and Delta variants, as well as other Betacoronavirus species such as SARS-CoV, but not Middle East respiratory syndrome coronavirus (MERS-CoV). These data provided direct proof-of-concept assessments of an Omicron-specific mRNA vaccination in vivo, both alone and as a heterologous booster to the existing widely-used WT mRNA vaccine form.

immunology↗

bioRxiv2022

Naive arthritogenic SKG T cells have a defect in anergy and a repertoire pruned by superantigen

How autoreactive CD4 T cells develop to cause rheumatoid arthritis remains unknown. We used a reporter for antigen-receptor signaling in the SKG autoimmune arthritis model to profile a T cell subpopulation enriched for arthritogenic naive CD4 T cells before arthritis onset by bulk and single cell RNA and T cell antigen-receptor (TCR) sequencing. Our analyses reveal that despite their impaired proximal TCR signaling, a subset of SKG naive CD4 T cells that have recently encountered endogenous antigen upregulate gene programs associated with positive regulation of T cell activation and cytokine signaling at higher levels than wild type cells in the pre-disease state. These arthritogenic cells also induce genes associated with negative regulation of T cell activation but do so less efficiently than wild type cells. Furthermore, their TCR sequences exhibit a previously unrecognized biased peripheral TCR V{beta} repertoire likely driven by endogenous viral superantigens. These particular V{beta}s, known to recognize endogenous mouse mammary tumor virus (MMTV) superantigen, are further expanded in arthritic joints. Our results demonstrate that autoreactive naive CD4 T cells which recognize endogenous viral superantigens are poised to cause disease by their altered transcriptome. Summary blurbSelf-reactive SKG T cells that escaped negative selection harbor an independent defect in anergy that, together with chronic antigen stimulation, sets the stage for disease. Moreover, we propose a novel role for endogenous mouse mammary tumor virus (MMTV) superantigen in promoting arthritogenic T cell responses.

immunology↗

bioRxiv2021

Isolating salient variations of interest in single-cell transcriptomic data with contrastiveVI

Single-cell datasets are routinely collected to investigate changes in cellular state between control cells and corresponding cells in a treatment condition, such as exposure to a drug or infection by a pathogen. To better understand heterogeneity in treatment response, it is desirable to disentangle latent structures and variations uniquely enriched in treated cells from those shared with controls. However, standard computational models of single-cell data are not designed to explicitly separate these variations. Here, we introduce Contrastive Variational Inference (contrastiveVI; https://github.com/suinleelab/contrastiveVI), a framework for analyzing treatment-control scRNA-seq datasets that explicitly disentangles the data into shared and treatment-specific latent variables. Using four treatment-control scRNA-seq dataset pairs, we apply contrastiveVI to perform a broad set of standard analysis tasks, including visualization, clustering, and differential expression testing. In each case, we find that our method consistently achieves results that agree with known biological ground truths, while previously proposed methods often fail to do so. We conclude by generalizing our framework to multimodal measurements and applying it to analyze a single-cell dataset with joint transcriptome and surface protein measurements.

bioinformatics↗

bioRxiv2021

Isolation and characterization of fucosylated extracellular vesicles based on a novel GlyExo-Capture technique

Owing to their diagnostic and therapeutic potential, extracellular vesicles (EVs) derived from tumour cells have recently garnered great interest. The presence of different glycosylation sites at the EV surface supports the need for efficient glycosylated EV isolation. Here, we developed a GlyExo-Capture technique for robustly capturing fucosylated EVs from sera and cell supernatants. Lens culinaris lectin (LCA)-immobilized magnetic complexes were found to capture approximately 60% of the total EVs from HepG2 cells. The capture efficiency was reduced to less than 40% in nontumorigenic MIHA cells. Notably, the cellular uptake pattern of highly fucosylated EVs was markedly different from that of EVs with low fucosylation. The unearthing of enriched fucosylated EV miRNA cargos by next-generation deep sequencing (NGS) revealed 75 differentially expressed miRNAs (DEMs) in hepatocellular carcinoma (HCC). Among them, a 4-miRNA panel was chosen and yielded an area under the ROC curve (AUC) of 0.86 and 0.84 for the detection of HCC from non-HCC controls in testing samples and independent validation samples, respectively. The 4-miRNA signature was independent of alpha-fetoprotein (AFP), and a combined model with AFP yielded an increased AUC of 0.92. In conclusion, we developed a high-throughput method for capturing fucosylated EVs efficiently and shed light on the use of fucosylated EVs as potential sources of miRNAs for cancer biomarker detection.

cancer biology↗

bioRxiv2021

Long Noncoding RNA RROL Provides Chromatin Scaffold for MYC-WDR82 Interaction to Impact Lipid Metabolism and Tumor Cell Growth in Multiple Myeloma

Long noncoding RNAs (lncRNA) can drive the tumorigenesis and be susceptible to therapeutic intervention. To define the landscape of therapeutically actionable lncRNA dependencies in multiple myeloma (MM), we coupled our extensive lncRNA transcriptomic profile with lncRNA targeted CRISPR interference viability screen and identified RNA Regulator of Lipogenesis (RROL) as a leading lncRNA dependency in MM. RROL shares its origin with the microRNA locus MIR17HG, however supports the proliferation and survival of MM cells in a microRNA- and DROSHA- independent manner. We found that RROL provides a chromatin scaffold for the functional interaction between c-MYC and WDR82 to promote the regulation of the lipogenic pathways via the transcriptional control of the rate-limiting enzyme ACC1 in MM cells. Inhibition of RROL with clinically applicable antisense molecules disrupts its transcriptional and functional activities causing potent anti-tumor effects both in vitro and in vivo in two pre-clinical animal models. This study establishes lncRNA RROL as a therapeutically actionable dependency with a unique mechanism of action in support of myeloma cell growth.

cancer biology↗

bioRxiv2021

Systems immune profiling of variant-specific vaccination against SARS-CoV-2

Lipid-nanoparticle(LNP)-mRNA vaccines offer protection against COVID-19. However, multiple variant lineages caused widespread breakthrough infections. There is no report on variant-specific vaccines to date. Here, we generated LNP-mRNAs specifically encoding wildtype, B.1.351 and B.1.617 SARS-CoV-2 spikes, and systematically studied their immune responses in animal models. All three LNP-mRNAs induced potent antibody responses in mice. However, WT-LNP-mRNA vaccination showed reduced neutralization against B.1.351 and B.1.617; and B.1.617-specific vaccination showed differential neutralization. All three vaccine candidates elicited antigen-specific CD8 and CD4 T cell responses. Single cell transcriptomics of B.1.351-LNP-mRNA and B.1.617-LNP-mRNA vaccinated animals revealed a systematic landscape of immune cell populations and global gene expression. Variant-specific vaccination induced a systemic increase in reactive CD8 T cell population, with a strong signature of transcriptional and translational machineries in lymphocytes. BCR-seq and TCR-seq unveiled repertoire diversity and clonal expansions in vaccinated animals. These data provide direct systems immune profiling of variant-specific LNP-mRNA vaccination in vivo.

immunology↗

bioRxiv2021

Multi-omics Analyses Provides Insight into the Biosynthesis Pathways of Fucoxanthin in Isochrysis galbana

Isochrysis galbana is considered an ideal bait for functional foods and nutraceuticals in humans because of its high fucoxanthin (Fx) content. However, multi-omics analysis of the regulation networks for Fx biosynthesis in I. galbana has not been reported. In this study, we report a high-quality genome sequence of I. galbana LG007, which has a 92.73 Mb genome size, with a contig N50 of 6.99 Mb and 14,900 protein-coding genes. Phylogenomic inferences confirmed the monophyly of Haptophyta, with I. galbana sister to Emiliania huxleyi and Chrysochromulina tobinii. Evolutionary analysis revealed an estimated divergence time between I. galbana and E. huxleyi of ~ 133 million years ago (Mya). Gene family analysis indicated that lipid metabolism-related genes exhibited significant expansion, including IgPLMT, IgOAR1 and {Delta}-4 desaturase. Metabolome analysis showed that the content of carotenoid in I. galbana cultured under green light for 7 days was higher than that of white light, and {beta}-carotene was the main carotenoids, accounting for 79.09% of the total carotenoids. Comprehensive analysis of multi-omics analysis revealed that {beta}-carotene, antheraxanthin, zeaxanthin, and Fx content was increased by green light induction, which was significantly correlated with the expression of IgMYB98, IgZDS, IgPDS, IgLHCX2, IgZEP, IgLCYb, and IgNSY. These findings contribute to understanding Fx biosynthesis and its regulation, providing a valuable reference for food and pharmaceutical applications.

bioinformatics↗

bioRxiv2021

Distinct neurocognitive bases for social trait judgments of faces in autism spectrum disorder

Autism spectrum disorder (ASD) is characterized by difficulties in social processes, interactions, and communication. Yet, the neurocognitive bases underlying these difficulties are unclear. Here, we triangulated the trans-diagnostic approach to personality, social trait judgments of faces, and neurophysiology to investigate (1) the relative position of autistic traits in a comprehensive social-affective personality space and (2) the distinct associations between the social-affective personality dimensions and social trait judgment from faces in individuals with ASD and neurotypical individuals. We collected personality and facial judgment data from a large sample of online participants (N = 89 self-identified ASD; N = 308 neurotypical controls). Factor analysis with 33 sub-scales of 10 social-affective personality questionnaires identified a 4-dimensional personality space. This analysis revealed that ASD and control participants did not differ significantly along the personality dimensions of empathy and prosociality, antisociality, or social agreeableness. However, the associations between these dimensions and judgments of facial trustworthiness and warmth differed across groups. Neurophysiological data also indicated that ASD and control participants might rely on distinct neuronal representations for judging trustworthiness and warmth from faces. These results suggest that the atypical association between social-affective personality and social trait judgment from faces may contribute to the social and affective difficulties associated with ASD.

neuroscience↗

bioRxiv2021

Structural basis of main proteases of coronavirus bound to drug candidate PF-07321332

The high mutation rate of COVID-19 and the prevalence of multiple variants strongly support the need for pharmacological options to complement vaccine strategies. One region that appears highly conserved among different genus of coronaviruses is the substrate binding site of the main protease (Mpro or 3CLpro), making it an attractive target for the development of broad-spectrum drugs for multiple coronaviruses. PF-07321332 developed by Pfizer is the first orally administered inhibitor targeting the main protease of SARS-CoV-2, which also has shown potency against other coronaviruses. Here we report three crystal structures of main protease of SARS-CoV-2, SARS-CoV and MERS-CoV bound to the inhibitor PF-07321332. The structures reveal a ligand-binding site that is conserved among SARS-CoV-2, SARS-CoV and MERS-CoV, providing insights into the mechanism of inhibition of viral replication. The long and narrow cavity in the cleft between domains I and II of main protease harbors multiple inhibitor binding sites, where PF-07321332 occupies subsites S1, S2 and S4 and appears more restricted compared with other inhibitors. A detailed analysis of these structures illuminated key structural determinants essential for inhibition and elucidated the binding mode of action of main proteases from different coronaviruses. Given the importance of main protease for the treatment of SARS-CoV-2 infection, insights derived from this study should accelerate the design of safer and more effective antivirals.

biophysics↗

bioRxiv2021

Crocin inhibited amyloid-beta (Aβ) generation via promoting non-amyloidogenic APP processing and suppressed ER stress UPR signaling in N2a/APP cells

BackgroundCrocin is a major active component of saffron (Crocus sativus) with many beneficial effects. More recently, crocin has been proposed for management of neurodegenerative diseases such as Alzheimers disease (AD). Here, we demonstrated for the first time that crocin reduced amyloid-beta (A{beta}) generation through promoting -cleavage of APP processing and inhibited ER stress by attenuating UPR signaling in N2a/APP cells. MethodologyMouse neuroblastoma N2a cells stably transfected with the Swedish mutant APP (N2a/APP) was used as a cellular model for AD pathogenesis. Vector transfected cells (N2a/vector) were employed to serve as control. The toxicity of crocin was first evaluated and non-toxic treatment of crocin (>30 {micro}M for 24 h) was used for further investigations. A{beta} levels were determined by ELISA. Expression levels of UPR signaling proteins were determined by using Western blot. ResultsCrocin significantly inhibited the protein expression of total APP in N2a/APP cells and promoted -cleavage of APP processing to increase sAPP generation, but only modestly reduced BACE-1 and PS1, suggesting A{beta} reduction by crocin was mainly associated with the non-amyloidogenic APP processing. Further investigation on ER stress related protein expressions showed that GRP78, CHOP, p-PERK, p-eIF2, p-IRE1, XBP1, ATF6 and PDI were all significantly elevated in N2a/APP cells compared to N2a/vector. Crocin effectively reduced the levels of GRP78 and CHOP, and significantly inhibited p-PERK/p-eIF2 amd AT6 while slightly reduced p-IRE1. ConclusionThe present study showed that crocin was effective at blocking A{beta} generation and inhibiting ER stress associated overactivation of UPR signaling in AD cell model N2a/APP. The results provided evidence for crocin as useful natural product for the treatment of AD.

neuroscience↗