Biology subjects

Zheng, Y.

Publications and source records attributed to Zheng, Y..

At least 181 records · Page 10Linked to original sources

bioRxiv2024

A CRISPR/SpCas9M-reporting system for efficient and rapid genome editing in Caulobacter crescentus

As members of the -proteobacteria group, Caulobacter crescentus and its relatives are known for their asymmetric life cycle and comprehensive applications in gene delivery, agricultural biotechnology, and the production of high-value compounds. However, genetic manipulations of these bacteria are often time-consuming and labor-intensive due to the lack of efficient genome editing tools. Here, we report a practical CRISPR/SpCas9M-reporting system that overcomes the limitations of SpCas9 expression, enabling efficient, markerless, and rapid genome editing in C. crescentus. As a demonstration, we successfully knocked out two genes encoding the scaffold proteins, achieving apparent editing efficiencies up to 80%. Key components, including the Cas protein, Cas inducer, sgRNA, homologous arms, and reporter, were systematically analyzed and optimized to enhance the editing efficiency or decrease the cell lethality. A nearly zero off-target ratio was observed after the curing of the editor plasmid in editing strains. Furthermore, we applied the CRISPR/SpCas9M-reporting system to two C. crescentus relatives, Agrobacterium fabrum and Sinorhizobium meliloti, establishing it as an efficient and reliable editing strategy. We anticipate that this system could be applied to other hard-to-edit organisms, accelerating both basic and applied research in -proteobacteria.

bioengineering↗

bioRxiv2024

Cardiac Applications of CRISPR/AAV-Mediated Precise Genome Editing

The ability to efficiently make precise genome edits in somatic tissues will have profound implications for gene therapy and basic science. CRISPR/Cas9 mediated homology-directed repair (HDR) is one approach that is commonly used to achieve precise and efficient editing in cultured cells. Previously, we developed a platform capable of delivering CRISPR/Cas9 gRNAs and donor templates via adeno-associated virus to induce HDR (CASAAV-HDR). We demonstrated that CASAAV-HDR is capable of creating precise genome edits in vivo within mouse cardiomyocytes at the neonatal and adult stages. Here, we report several applications of CASAAV-HDR in cardiomyocytes. First, we show the utility of CASAAV-HDR for disease modeling applications by using CASAAV-HDR to create and precisely tag two pathological variants of the titin gene observed in cardiomyopathy patients. We used this approach to monitor the cellular localization of the variants, resulting in mechanistic insights into their pathological functions. Next, we utilized CASAAV-HDR to create another mutation associated with human cardiomyopathy, arginine 14 deletion (R14Del) within the N-terminus of Phospholamban (PLN). We assessed the localization of PLN-R14Del and quantified cardiomyocyte phenotypes associated with cardiomyopathy, including cell morphology, activation of PLN via phosphorylation, and calcium handling. After demonstrating CASAAV-HDR utility for disease modeling we next tested its utility for functional genomics, by targeted genomic insertion of a library of enhancers for a massively parallel reporter assay (MPRA). We show that MPRAs with genomically integrated enhancers are feasible, and can yield superior assay sensitivity compared to tests of the same enhancers in an AAV/episomal context. Collectively, our study showcases multiple applications for in vivo precise editing of cardiomyocyte genomes via CASAAV-HDR.

genetics↗

bioRxiv2024

VaxLLM: Leveraging Fine-tuned Large Language Model for automated annotation of Brucella Vaccines

BackgroundVaccines play a vital role in enhancing immune defense and preventing the hosts against a wide range of diseases. However, research relating to vaccine annotation remains a labor-intensive task due to the ever-increasing volume of scientific literature. This study explores the application of Large Language Models (LLMs) to automate the classification and annotation of scientific literature on vaccines as exemplified on Brucella vaccines. ResultsWe developed an automatic pipeline to automatically perform the classification and annotation of Brucella vaccine-related articles, using abstract and title. The pipeline includes VaxLLM (Vaccine Large Language Model), which is a fine-tuned Llama 3 model. VaxLLM systematically classifies articles by identifying the presence of vaccine formulations and extracts the key information about vaccines, including vaccine antigen, vaccine formulation, vaccine platform, host species used as animal models, and experiments used to investigate the vaccine. The model demonstrated high performance in classification (Precision: 0.90, Recall: 1.0, F1-Score: 0.95) and annotation accuracy (97.9%), significantly outperforming a corresponding non-fine-tuned Llama 3 model. The outputs from VaxLLM are presented in a structured format to facilitate the integration into databases such as the VIOLIN vaccine knowledgebase. To further enhance the accuracy and depth of the Brucella vaccine data annotations, the pipeline also incorporates PubTator, enabling cross comparison with VaxLLM annotations and supporting downstream analyses like gene enrichment. ConclusionVaxLLM rapidly and accurately extracted detailed itemized vaccine information from publications, significantly outperforming traditional annotation methods in both speed and precision. VaxLLM also shows great potential in automating knowledge extraction in the domain of vaccine research. AvailabilityAll data is available at https://github.com/xingxianli/VaxLLM, and the model was also uploaded to HuggingFace (https://huggingface.co/Xingxian123/VaxLLM).

bioinformatics↗

bioRxiv2024

Tissue clocks derived from histological signatures of biological aging enable tissue-specific aging predictions from blood

Aging, the leading risk factor for numerous diseases, manifests through diverse structural and architectural changes in human tissues, providing an opportunity to quantify and interpret tissue-specific aging. To address this, we present a comprehensive assessment of tissue changes occurring during human aging, utilizing a vast array of whole slide histopathological images from the Genotype-Tissue Expression Project (GTEx), primarily reflecting non-diseased tissue samples. Using deep learning, we analyzed 25,712 images from 40 distinct tissue types across 983 individuals, quantifying nuanced morphological changes that tissues undergo with age. We developed tissue clocks--predictors of biological age based on tissue images--which achieved a mean prediction error of 4.9 years. These clocks were associated with established aging markers, including telomere attrition, subclinical pathologies, and comorbidities. In a systematic assessment of biological age rates across organs, we identified pervasive non-uniform rates of aging across the human lifespan, with some organs exhibiting earlier changes (20-40 years old) and others showing bimodal patterns of age-related changes. We also uncovered several associations between demographic, lifestyle, and medical history factors and tissue-specific acceleration or deceleration of biological age, highlighting potential modifiable risk factors that influenced the aging process at the tissue level. Finally, by combining paired histological images and gene expression data, we developed a strategy to predict tissue-specific age gaps from blood samples. This approach was validated in independent cohorts covering eight diseases, ranging from acute conditions like stroke to chronic diseases such as cystic fibrosis and Alzheimers disease. It successfully recovered significant associations with disease-relevant organs and revealed patterns of systemic and tissue-specific aging that may reflect broader physiological changes in health and disease. This work offers a new perspective on the aging process by positioning tissue structure as an integrator of cellular and molecular changes that reflect the physiological state of organs in health and disease. It underscores the value of histopathological imaging as a tool for understanding human aging and provides a foundation for the monitoring of tissue-specific aging processes in age-associated diseases.

physiology↗

bioRxiv2024

Reduction of DNA Topoisomerase Top2 reprograms the epigenetic landscape and extends health and life span across species

DNA topoisomerases are essential molecular machines that manage DNA topology in the cell and play important roles in DNA replication and transcription. We find that knocking down the enzyme Topoisomerase Top2 or its mammalian homolog Top2b increases the life span of S. cerevisiae, C. elegans, and mice. Top2b reduction also extends the health span of mice and alleviates the pathologies of aging in multiple tissues. At the cellular/molecular level, Top2b reduction attenuates the major hallmarks of aging, such as cellular senescence, de-regulated nutrient sensing, epigenetic alteration, and lysosomal biogenesis. We observed that Top2b reduction significantly changes the epigenetic landscape in various mouse tissues toward those of the young animals, and differentially down-regulates genes with active promoter and high expression. Our observations suggest that Top2 reduction confers longevity effect across species via a conserved mechanism, and may be used as a novel therapeutic strategy for countering aging.

biochemistry↗

bioRxiv2024

Recurrent Inhibitory Dynamics in the Entorhinal Cortex Support Pattern Separation

The entorhinal cortex (EC) provides the major input to the hippocampus (HPC). Numerous computational models on the EC propose that its grid cells serve as a spatial metric, supporting path integration and efficient generalization. However, little is known about how these cells could contribute to episodic memory, which emphasizes episode-specific representations that align with pattern separation. Taking into consideration anatomical specifications of EC inputs to the HPC and computational principles underlying the EC-HPC memory system, we argue that EC layer IIa (EC2a) supports pattern separation and EC layer IIb/III (EC2b/3) supports generalization. Utilizing recurrent inhibition and the nature of single EC2a neurons binding converging inputs from the neocortex (i.e., conjunctive coding), we built a biologically-based neural network model of the EC-HPC system for episodic memory. By examining how EC2a transformed its cortical inputs and output them to the trisynaptic pathway (EC2a - Dentate Gyrus - CA3 - CA1), we found that instead of systematically generalizing across similar inputs, recurrent inhibition and conjunctive coding in EC2a neurons support strong pattern separation and increase mnemonic discrimination. Furthermore, lesioning EC2a neurons in the model resembled memory impairments found in people with Alzheimers Disease, suggesting an intertwined relationship between memory and the majority of pure grid cells in the EC. On the other hand, the topographically organized monosynaptic pathway (EC2b/3 - CA1) is computationally more suitable for efficient factorization and generalization. This model provides novel anatomically-based predictions regarding the computational roles of EC cells in pattern separation and generalization, which together form a critical computational framework for both episodic memory and spatial navigation.

neuroscience↗

bioRxiv2024

Human skin rejuvenation via mRNA

Aging is characterized by a gradual decline in function, partly due to accumulated molecular damage. Human skin undergoes both chronological aging and environmental degradation, particularly UV-induced photoaging. Detrimental structural and physiological changes caused by aging include epidermal thinning due to stem cell depletion and dermal atrophy associated with decreased collagen production. Here, we present a comprehensive single-cell atlas of skin aging, analyzing samples from young, middle-aged, and elderly individuals, including both sun-exposed and sun-protected areas. This atlas reveals age-related changes in cellular composition and function across various skin cell types, including epidermal stem cells, fibroblasts, hair follicles, and endothelial cells. Using our atlas, we have uncovered basal stem cells as a highly variable population across aging, more so than other skin cell populations, such as fibroblasts. In basal stem cells, we identified ATF3 as a novel regulator of skin aging. ATF3 is a transcriptional factor for genes involved in the aging process, with its expression reduced by 20% during aging. Based on this discovery, we developed an innovative mRNA-based treatment to mitigate the effects of skin aging. After treatment with ATF3 mRNA, cell senescence decreased 25%, and we observed an over 20% increase in proliferation in treated basal stem cells. Importantly, we also found communication between keratinocytes and fibroblasts as a critical component of therapeutic interventions, with ATF3 mRNA rescue of basal cells significantly enhancing fibroblast collagen production by approximately 200%. Furthermore, we validated the efficacy of ATF3 mRNA treatment in ex vivo human skin and in vivo mouse models. In ex vivo human skin, microneedle-mediated delivery of ATF3 mRNA induced robust rejuvenation, expanding the basal stem-cell population and enhancing dermal ECM reconstruction. In a wound healing mouse model, ATF3 mRNA reduced scarring, demonstrating strong regenerative potential for reversing age-related skin decline. We conclude that ATF3 mRNA treatment effectively reverses the effects of skin aging by modulating specific cellular mechanisms, offering a novel, targeted approach to human skin rejuvenation.

synthetic biology↗

bioRxiv2024

Genome-wide investigation of outer membrane protein families under mosaic evolution in Escherichia coli

Several genes in Gram-negative bacteria encoding outer membrane proteins (OMPs) have been reported to show patterns of mosaic evolution featured by mixture of negative selection and local recombination. Here, we proposed a strategy, and applied it to screen OMPs under mosaic evolution in Escherichia coli in the genome level. In total, 21 OMP families, including 16 new ones, were detected with the typical patterns of mosaic evolution. An abosolute majority of the protein families are conserved in E. coli for the composition, genomic loci and the overall structures. Highly Variable Regions (HVRs) can be recognized, which are frequently located extracellularly within the protruding loops. There are only limited number of major HVR sequence types, within which positively selected sites can be detected ocassionally. Based on the simulated results of multiple models, the OMPs under mosaic evolution are often with good antigenicity, with HVRs of various sequence types coinciding with the B-cell epitopes of the strongest immunogenicity. The study futher broadened our understanding of the characteristics of mosaic evolution and the functions of OMPs in Gram-negative bacteria, laying an important foundation for their potential translational applications. ImportanceIt is important to understand the evolutionary mechanisms of bacterial OMP-encoding genes, which would facilitate the development of anti-bacterial reagents. This study made the first genome-wide screening of bacterial OMPs under mosaic evolution, and increased the list of candidate OMP families by 3 folds in E. coli, far more than we expected. The study further confirmed the hypothesis about the evolutionary, micro-evolutionary and structural features of these OMPs, and facilitated the functional theory of mosaic evolution. Moreover, the findings of limited HVR sequence types and strong immunogenicity of HVRs paved important foundation for application of these OMPs and their HVRs in development of antibodies or other anti-bacterial treatment.

microbiology↗

bioRxiv2024

Mechanism of N-Myc Downstream Regulated Gene-1 regulating Integrin expression to inhibit gastric cancer metastasis

BackgroundN-myc downstream regulated gene-1 (NDRG1), the first member of the NDRG family, is widely distributed in various tissues and organs. In gastric cancer, the hypo-expression of NDRG1 has been positively associated with malignant biological behavior and poor prognosis. In-depth investigation of the potential regulatory mechanism of NDRG1 on gastric cancer is crucial for understanding the pathogenesis of this disease, identifying new therapeutic targets, and developing personalized treatment strategies. This study aims to explore the significance of NDRG1 in regulating the expression of integrins during the progression of gastric cancer. MethodsThe expression of NDRG1 in gastric cancer was analyzed using R software v4.0.3, Boxplot, and the Kaplan-Meier Plotter. Stable cell lines with NDRG1 knockdown and overexpression were subjected to wound healing assays, transwell migration assays, CCK8 assays, and colony formation assays, in order to determine the effects of NDRG1 on the migration and proliferation of gastric cancer cells. Western blotting was employed to examine the impact of NDRG1 on the expression of integrin-related proteins. Immunostaining was used to comprehensively analyze the in vitro experimental results. ResultsThe mRNA and protein levels of NDRG1 were downregulated substantially in gastric cancer, which was inversely correlated with the malignancy of pathological behavior and poor prognosis in gastric cancer. Knockdown of the NDRG1 gene significantly enhanced the proliferation and migration capabilities of gastric cancer cells, whereas overexpression of NDRG1 reduced their metastatic potential and inhibited both migration and proliferation. NDRG1 was found to regulate the expression of fibronectin 1, which in turn influenced the expression of a series of integrins, including v, 5, {beta}1, and {beta}3. This regulatory mechanism may play a crucial role in the early distant metastasis observed in gastric cancer. ConclusionsThis study demonstrated that NDRG1 could regulate the expression levels of integrins through specific signaling pathways, thereby interfering the adhesive and migratory capacities of gastric cancer cells. NDRG1 could serve as a valuable biomarker for the diagnosis and prognosis of gastric cancer, offering new potential targets for its treatment.

cancer biology↗

bioRxiv2024

Understanding the epidemiology and pathogenesis of Mycobacterium tuberculosis with non-redundant pangenome and population genetics

Tuberculosis is a major public health threat demanding more than one million lives every year. Many challenges exist to defeat this deadly infectious disease which address the importance of a thorough understanding of the biology of the causative agent Mycobacterium tuberculosis (MTB). We generated a non-redundant pangenome of 420 epidemic MTB strains from China. We estimate that MTB strains have a pangenome of 4,278 genes encoding 4,183 proteins, of which 3,438 of which are core genes. However, due to 99,694 interruptions in 2,447 coding genes, only 1,651 may be translated in all samples, which dramatically reduces the number of active core genes. Of these interruptions, 67,315 (67.52%) could be classified by various genetic variations detected by currently available tools, and more than half of them are due to structure variations, mostly small indels. We further describe differential evolutionary patterns of genes under the influences of selective pressure, population structure and background selection. While selective pressure is ubiquitous among these coding genes, evolutionary adaptations primarily occur in 1,313 genes. Genes located in the cell wall and membrane region are under the strongest selective pressure, while biological processes including regulation of transcription, translation and regulation of growth are under strongest background selection in MTB. The metabolism of fatty acids may be an outstanding example of evolutionary adaption for MTB under current selective pressure. This study provides a comprehensive view on the genetic diversity and evolution patterns of coding genes in MTB which may deepen our understanding of its epidemiology and pathogenicity.

microbiology↗

bioRxiv2024

Genomic diversity and underlying metabolic variations of the human gut microbiome between populations at single nucleotide resolution

BackgroundA comprehensive and representative reference database is crucial for accurate taxonomic and functional profiling of the human gut microbiome in population-level studies. However, with 70% of current microbial reference data derived from Europeans and the Americans, East Asia, especially China, remain underrepresented. MethodsWe constructed the human Gut Microbiome Reference (GMR), comprising 478,588 high-quality microbial genomes from Chinese (247,134) and non-Chinese (231,454) populations. Species-level clustering and protein annotations were performed to characterize microbial diversity and function. We further integrated novel genomes into taxonomic profiling database and validated the improvements using independent cohort data. ResultsThe GMR dataset spans 6,664 species, including 26.4% newly classified species, and encodes over 20 million unique proteins, with 47% lacking known functional annotations. Notably, we observed that 35.35% and 32.46% of species unique to Chinese and non-Chinese populations, respectively. For 2,145 species shared between populations, 74% of 304 species with balanced prevalence between populations exhibited population-specific phylogenetic stratification, involving health relevant functionalities such as antibiotic resistance. Integration of novel genomes into taxonomic improved population-level species profiling by up to 23% and uncovered replicable associations between novel species and host physiological traits. ConclusionsOur study largely expands the compositional and functional landscape of the human gut microbiome, providing a crucial resource for studying the role of gut microbiome for regional health disparities.

genomics↗

bioRxiv2024

Loss of Cdc42 causes abnormal optic cup morphogenesis and microphthalmia in mouse

Congenital ocular malformations originate from defective morphogenesis during early eye development and cause 25% of childhood blindness. Formation of the eye is a multi-step, dynamic process; it involves evagination of the optic vesicle, followed by distal and ventral invagination, leading to the formation of a two-layered optic cup with a transient optic fissure. These tissue folding events require extensive changes in cell shape and tissue growth mediated by cytoskeleton mechanics and intercellular adhesion. We hypothesized that the Rho GTPase Cdc42 may be an essential, convergent effector downstream of key regulatory factors required for ocular morphogenesis. CDC42 controls actin remodeling, apicobasal polarity, and junction assembly. Here we identify a novel essential function for Cdc42 during eye morphogenesis in mouse; in Cdc42 mutant eyes expansion of the ventral optic cup is arrested, resulting in microphthalmia and a wide coloboma. Our analyses show that Cdc42 is required for expression of the polarity effector proteins PRKCZ and PARD6, intercellular junction protein tight junction protein 1, {beta}-catenin, actin cytoskeleton F-actin, and contractile protein phospho myosin light chain 2. Expression of RPE fate determinants OTX2 and MITF, and formation of the RPE layer are severely affected in the temporal domain of the proximal optic cup. EdU incorporation is significantly downregulated. In addition, mitotic retinal progenitor cells mis-localized deeper, basal regions, likely contributing to decreased proliferation. We propose that morphogenesis of the ventral optic cup requires Cdc42 function for coordinated optic cup expansion and establishment of subretinal space, tissue tension, and differentiation of the ventral RPE layer.

developmental biology↗

bioRxiv2024

Mechanical control of germ cell specification in Arabidopsis anthers

A central question in developmental biology is how the germline is established. We have studied the specification of the male germ cells (GCs) within the anther1-3. Hereby, we have focused on the potential role of mechanics, an aspect of anther development which has been very poorly characterized2,4. Using a combination of live imaging and mechanical measurements, we provide evidence that GCs originate in a special micro-mechanical niche, where inner tissues exert push on outer cell layers, placing them under compression. Mechanical perturbations significantly disrupted the GC specification and patterning. Moreover, we found that the master genetic regulator SPOROCYTELESS/NOZZLE (SPL/NZZ)5,6 is central in establishing this micro-mechanical environment by softening the cell wall. The mechanical cues, in turn, stabilize the transcription of SPL/NZZ. We propose here an intrinsic growth-derived mechano-chemical feedback loop that drives germ-cell fate acquisition.

developmental biology↗

bioRxiv2024

Exploring the Antifibrotic Potential of the heparan sulfate mimetic OTR4120: Insights from Preclinical Models

RationaleIdiopathic pulmonary fibrosis (IPF) is a debilitating lung disease characterized by excessive deposition of extracellular matrix (ECM), resulting in lung function impairment. Heparan sulfate mimetics (HSm) have been suggested to have potential antifibrotic effects by regulating ECM. This study aims to investigate the impact of a specific HSm named OTR4120 on fibrotic processes in ex vivo, in vitro and in vivo models. MethodsHuman Precision Cut Lung Slices (hPCLS) treated with a fibrotic cocktail alone or with OTR4120 were evaluated using second-harmonic imaging microscopy (SHIM) to assess collagen deposition. Human embryonic fibroblast WI-38 cell line and primary fibroblasts obtained from human donors were differentiated into myofibroblasts (MYF) using TGF-{beta}1 and treated with OTR4120 or a control vehicle. Gene expression analysis for MYF markers was performed using quantitative PCR (qPCR). Protein expression of MYF markers was evaluated using immunofluorescence techniques. Bulk-RNA sequencing analysis on WI-38 cells cultured under different experimental conditions was conducted. Finally, the therapeutic effects of OTR4120 on a bleomycin-induced fibrosis mouse model were investigated. ResultsSHIM analysis on OTR4120-treated hPCLS showed a decrease in collagen deposition. OTR4120 treatment of primary fibroblasts and WI-38 cells exposed to TGF-{beta}1 significantly reduced the expression of MYF markers. Bulk-RNA sequencing analysis on OTR4120-treated WI-38 cells showed significant impacts on fibrosis-related processes. Therapeutic application of OTR4120 in vivo to bleomycin-induced fibrosis mice resulted in enhanced fibrosis resolution. ConclusionOTR4120 has potential therapeutic benefits as an antifibrotic agent in the context of lung fibrosis. Further investigations are necessary to understand the precise mechanism through which OTR4120 exerts its antifibrotic effects.

cell biology↗

bioRxiv2024

Domain Specific AI Segmentation of IMPDH2 Rod/Ring Structures in Mouse Embryonic Stem Cells

BackgroundInosine monophosphate dehydrogenase 2 (IMPDH2) is an enzyme that catalyses the rate limiting step of guanine nucleotides. In mouse embryonic stem cells (ESCs) IMPDH2 is held as large multi-protein complexes known as rod-ring (RR) structures that dissociate when ESCs differentiate. Manual analysis of RR structures from confocal microscopy images, although possible, is not feasible on a large scale due to the quantity of RR structures present in each field of view. To address this analysis bottleneck, we have created a fully automatic RR image classification pipeline to segment, characterise and measure feature distributions of these structures in ESCs. ResultsWe find that this model can automatically segment images with a Dice score of over 80% for both rods and rings for in-domain images compared to expert annotation, with a slight drop to 70% for datasets out of domain. Important feature measurements derived from these segmentations show high agreement with the measurements derived from expert annotation, achieving an R2 score of over 90% for counting the number of rings and rods over the dataset. ConclusionsWe have established for the first time a quantitative baseline for RR distribution in pluripotent ESCs and have made a pipeline available for training to be applied to other models in which RR remain an open topic of study.

bioinformatics↗

bioRxiv2024

Deciphering RNA regulation with a foundation language model

RNA metabolism is tightly regulated by cis-elements and trans-acting factors. Most information guiding such regulation is encoded in RNA sequences. Considering the similarities in semantic and syntactic features between RNAs and human language, we developed LAMAR, a transformer-based foundation language model for RNA regulation, to decipher general rules underlying RNA processing. The model was pretrained on approximately 15 million sequences from both genome and transcriptome of 225 mammals and 1569 viruses, and further fine-tuned with labeled datasets for various tasks. The resulting fine-tuned models outperformed the state-of-the-art methods in predicting mRNA translation efficiency and mRNA half-life, while achieving comparable accuracy to specifically designed methods in predicting splice sites of pre-mRNAs and internal ribosome entry sites. Our results indicated that a single foundation language model is applicable in the comprehensive analysis of different aspects of RNA regulation, providing new insight into the design and optimization of RNA drugs.

bioinformatics↗

bioRxiv2024

Structure and function of the yeast amino acid-sensing SEAC-EGOC supercomplex

The Seh1-associated complex (SEAC) transduces amino acid signals to the Target of Rapamycin Complex 1 (TORC1), a master regulator of cell growth located on the vacuole membrane. The SEAC acts as a GTPase activating protein (GAP) for Gtr1, a small GTPase that forms a heterodimer with Gtr2, and as part of the EGO complex (EGOC), relays nutrient signals to TORC1. The SEAC is composed of two subcomplexes, SEACIT, an inhibitor of TORC1 that contains the GAP activity, and SEACAT, that has been proposed to regulate the activity of SEACIT. However, molecular details of its regulation are unclear. Here, we determined the cryo-electron microscopy structure of the SEAC-EGOC supercomplex and studied its function in TORC1 amino acid signalling. A single SEAC can interact with two EGOC molecules via SEACIT, binding exclusively to the "active" version of the EGOC as their interaction depends on Gtr1 being loaded with GTP. SEACAT does not modulate nor interact with the EGOC. The GAP activity of the SEAC is essential for the regulation of TORC1 by amino acids, and its loss phenocopies the lack of Gtr1-Gtr2, establishing the SEAC-EGOC complex as an amino acid-sensing hub. Despite being located far from the active site, deletion of Sea2, or its N-terminal {beta}-propeller domain, also results in defects in amino acid signalling to TORC1. We propose that the SEAC-EGOC supercomplex integrates coatomer-like mechanisms of regulation via bidirectional feedback between GAP-GTPase (SEACIT-EGOC) and coat (SEACAT) modules that explain the functional interaction between Sea2 and the GAP activity. Given the conservation between the SEAC and its mammalian ortholog GATOR, we envision that this mechanism is similar in different organisms.

biochemistry↗

bioRxiv2024

Dissociable after-effects of prosocial acts: Effort is costly for others but valued for self

Engaging in prosocial behavior requires effort, yet people are often averse to exerting effort for others benefit. However, it remains unclear how effort exertion affects subsequent reward evaluation during prosocial acts. Here, we combined high-temporal-resolution electroencephalography with a paradigm that independently manipulated effort and reward for self and others to elucidate the neural mechanisms underlying the reward after-effect of prosocial effort expenditure. We found dissociable reward after-effects for self-benefiting and other-benefiting effort. For self-benefiting rewards, the reward positivity (RewP) increased with effort demand, suggesting an effort-enhancement effect. In contrast, for other-benefiting rewards, the RewP decreased as effort increased, demonstrating an effort-discounting effect. Critically, this dissociation was contingent upon high reward magnitude and modulated by individual differences in effort discounting, yet remained distinct from performance evaluation. Our findings reveal distinct neural computations for self- and other-benefiting efforts, offering new insights into how prior effort expenditure shapes reward evaluation during prosocial behavior.

neuroscience↗