bioRxiv Science⌕ Search

Biology subjects

Han, X.

Publications and source records attributed to Han, X..

At least 37 records · Page 2Linked to original sources

sxRaep: A Rapid and Accurate Enzyme Predictor for high-throughput mining of enzymatic sequences

MotivationMetagenomic sequencing generates petabyte-scale sequence datasets that strain both deep learning and alignment based enzyme annotation tools. A lightweight rapid and accurate filter tool is needed to filter and identify enzymatic sequences prior to resource-intensive functional prediction. ResultsWe present sxLaep (Lightweight and Accurate Enzyme Predictor), a resource-efficient framework using lightweight physicochemical features for enzyme pre-screening. On the external validation set, sxLaep completed prediction in only 0.002 s/sequence, which is 22.9-fold faster than Diamond (0.0457 s/sequence). It used 372.16 MB peak memory, corresponding to a 54.4% memory reduction relative to Diamond (815.64 MB). sxLaep achieved an accuracy of 99.34% and the highest recall in remote homology detection, including enzyme candidates missed by alignment-based methods. We further successfully applied sxLaep to a marine metagenomic enzyme-mining workflow, demonstrating its utility for high-throughput discovery from large-scale metagenomic sequences. Availability and ImplementationsxLaep is available as a Python package at https://pypi.org/project/sxlaep and is maintained as an open-source software repository at https://github.com/labxscut/sxLaep. Detailed installation, usage, and Docker deployment instructions are provided in the GitHub repository to support reproducible enzyme prediction and model execution. Contactlcxia@scut.edu.cn

bioinformatics↗

Microglia-derived IL-18 remodels hippocampal plasticity to constrain traumatic fear memory

Post-traumatic stress disorder (PTSD) involves complex neuroimmune-synaptic crosstalk in the hippocampus. Here we show that interleukin-18 (IL-18), an extensively studied pro-inflammatory cytokine, serves a protective role against traumatic fear memory through a microglia-to-neuron signaling axis. Traumatic stress induces sustained upregulation of IL-18 in the hippocampus. Exogenous IL-18 administration attenuates fear memory, whereas blockade of IL-18 signaling exacerbates it. Mechanistically, microglial-derived IL-18 acts on neuronal IL-18R1 to restore stress-impaired synaptic plasticity and reduce perineuronal net density, thereby facilitating structural synaptic remodeling. In addition, IL-18 modulates the synaptic organization of fear memory-encoding engram cells within hippocampal ensembles. Together, these findings redefine IL-18 as a homeostatic regulator of post-trauma hippocampal synaptic function and identify the hippocampal IL-18 pathway as a potential therapeutic target for PTSD.

neuroscience↗

Stromal Gasdermin D-mediated Pyroptosis Drives Maladaptive CD4⁺ T-cell Remodeling in Tet2-Deficient Hematopoiesis

An inflammatory bone marrow microenvironment is increasingly recognized as critical in myeloid disease evolution, yet how stromal inflammation interfaces with adaptive immunity remains poorly defined. Here, we show that stromal pyroptosis drives mutation-specific myeloid expansion by coordinating monocytic remodeling and CD4 T-cell activation. Genetic ablation of gasdermin D in the bone marrow stroma suppressed stromal pyroptosis and attenuated Tet2-deficient myeloid expansion. Tet2 deficiency skewed monocyte and macrophage differentiation toward an activated, antigen-presenting state that interacted with pyroptotic stromal cells to promote expansion of a distinct CD4 T-cell population. These cells expressed canonical T follicular helper markers (Bcl6, Cxcr5, Il21, and Cd40l) together with interferon-responsive and tissue-interaction programs, consistent with an inflammation-adapted TFH-like state. CD40L produced by these cells reinforced the expansion of Tet2-deficient monocytes and macrophages, establishing a feed-forward stromal-immune circuit. Disruption of this axis through stromal gasdermin D deficiency or CD40L blockade attenuated myeloid expansion in vivo. Consistent with these findings, patients with isolated TET2 loss-of-function mutations exhibited CD4 T-cell skewing and CD40L+ T-cell-rich tertiary lymphoid structures in the bone marrow. Together, these data identify a pyroptosis-dependent stromal-immune axis that links early myeloid inflammation to maladaptive remodeling of adaptive immunity and reveals a context-dependent therapeutic vulnerability in Tet2-deficient hematopoiesis.

cancer biology↗

Distinct cell-type contributions and network topography of theta-nested gamma oscillations in the medial entorhinal cortex

Theta-nested gamma oscillations in the medial entorhinal cortex (mEC) are essential for spatial coding and memory, but the underlying cellular mechanisms remain unclear. We combined optogenetics, whole-cell electrophysiology, intracellular voltage imaging, and local field potential (LFP) recordings in acute slices from CaMKII-ChR2 mice to investigate how excitation and inhibition shape theta-gamma coupling in layer II/III mEC. During theta-frequency stimulation, fast-spiking interneurons received strong gamma-frequency excitation and fired rhythmic bursts, whereas stellate and pyramidal neurons fired more sparsely and were dominated by gamma-frequency inhibition. This sparse firing could support the selective firing of grid cells. Excitatory post-synaptic currents in interneurons preceded inhibitory currents and LFP gamma by [~]3 ms, supporting a pyramidal-interneuron network gamma (PING) mechanism. Pyramidal neurons fired on the descending phase of the gamma cycle, whereas stellate cells and fast-spiking interneurons fired before and after the trough, respectively. Intracellular voltage imaging revealed network gamma synchronization among excitatory neurons at a population level, with topographic clustering of subthreshold membrane potentials, but not spike timing, while individual neurons often skipped gamma cycles. These findings identify the dominant role of reciprocal E-I interactions in generating theta-nested gamma oscillations and highlight distinct cell-type contributions to the temporal dynamics of the mEC. Further, a biophysically realistic computational model predicted gamma cycle skipping in stellate cells and burst firing in fast-spiking interneurons during PING. Our experimental and computational results provide mechanistic insight into how the intrinsic properties of mEC cell types generate oscillatory activity in a manner that could support grid cell function and spatial computation. Significance StatementTheta-nested gamma oscillations in the medial entorhinal cortex (mEC) are essential for spatial navigation and memory, yet the underlying circuit mechanisms remain incompletely understood. Using optogenetics, voltage imaging, electrophysiology, and biophysically realistic computational modeling, we show that reciprocal interactions between excitatory neurons and fast-spiking interneurons generate robust gamma oscillations through a pyramidal-interneuron network gamma (PING) mechanism. We reveal cell-type specific differences in gamma phase-locking and demonstrate that principal neurons synchronize at the population-level across large laminar distances (up to 800 {micro}m). Further, the voltage activity, but not spike timing, of principal neurons exhibited topographic clustering. These findings clarify how local circuits in mEC generate temporal dynamics critical for grid cell coding and further constrain computational models of spatial representation.

neuroscience↗

Generation and long-term expansion of human pancreatic islet organoids in vitro

The scarcity of expandable, functional human islet cells remains a major barrier to diabetes therapy. Here, we identify PROCR+ cells within adult human islets and establish a defined culture system to generate pancreatic islet organoids. These organoids self-organize into -, {beta}-, {delta}-, and PP cells at near-native ratios, exhibit regulated insulin and glucagon secretion, and support exponential in vitro expansion. Single-cell transcriptomics reveals a unique progenitor-like cell population that is transcriptionally primed for endocrine differentiation but shares molecular features with fetal trunk cells and endocrine progenitors. When transplanted, the organoids rapidly ameliorate hyperglycemia in diabetic mice. Importantly, in a non-human primate model, intraportal transplantation of these organoids reduced exogenous insulin requirements, restored glucose-stimulated C-peptide secretion, and achieved sustained glycemic control-representing a critical step toward clinical translation. This study provides a strategy for expanding human islet organoids, offering a scalable platform for diabetes treatment, disease modeling, and regenerative medicine.

cell biology↗

FABP4 Couples Lipid Metabolism to PD-L1 Stabilization in Immunosuppressive Macrophages

Metabolic dysregulation in obesity reshapes immune function, but how lipid signals drive immune suppression remains unclear. Here, we identify a FABP4-PD-L1 axis that links lipid metabolism to immune checkpoint regulation in monocytes and macrophages. Single-cell transcriptomics revealed a distinct FABP4high immunosuppressive macrophage subset enriched under high-fat diet (HFD) conditions, characterized by impaired antigen presentation and elevated PD-L1 expression. Mechanistically, palmitic acid (PA) induces FABP4 and promotes PD-L1 palmitoylation, leading to its stabilization on the cell surface independent of transcriptional regulation. FABP4 is essential for this process, which enables PD-L1 surface stabilization, immunosuppression and mammary tumor progression. In humans, a conserved CD14intCD16 monocyte population exhibits elevated FABP4-PD-L1 signaling and correlates with obesity and invasive breast cancer. These findings establish PD-L1 as a metabolically regulated protein and reveal a mechanism by which lipid excess drives immune evasion, suggesting that targeting FABP4 may enhance responses to immune checkpoint blockade. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/717546v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@1fe3f2corg.highwire.dtl.DTLVardef@e587a7org.highwire.dtl.DTLVardef@12d0f75org.highwire.dtl.DTLVardef@151f916_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIFABP4 defines a lipid-responsive, immunosuppressive monocyte/macrophage subset C_LIO_LIFABP4 links lipid sensing to PD-L1 expression in macrophages C_LIO_LIFABP4 enables palmitic acid-dependent PD-L1 palmitoylation and stabilization C_LIO_LIFABP4-PD-L1 signaling correlates with obesity and invasive breast cancer in humans C_LI

immunology↗

A Non-Canonical Role of SMAD4 in Regulating 3D Genome Architecture to Inhibit Lung Squamous Cell Carcinoma Development

Lung squamous cell carcinoma (LUSC) lacks clearly defined key drivers and effective targeted therapies, reflecting an incomplete understanding of its molecular pathogenesis. Here, we identify SMAD4 as a critical regulator of three-dimensional (3D) genome organization in LUSC and uncover a mechanistic link between tumor suppressor loss and oncogenic transcriptional activation. By integrating clinical datasets, genetically engineered mouse models, human and murine LUSC cell lines, and multi-omics analyses, we demonstrate that SMAD4 deficiency promotes LUSC progression by unleashing EP300-mediated enhancer-promoter looping at the SOX2 locus. Mechanistically, SMAD4 does not directly bind SOX2 regulatory elements but instead constrains chromatin looping by sequestering EP300 away from loop anchor regions. Loss of SMAD4 leads to enhanced H3K27ac deposition, aberrant SOX2 activation, and increased LUSC tumor cell proliferation. Together, these findings reveal a non-canonical role for a transcription factor (e.g., SMAD4) in regulating dysregulated 3D genome architecture to inhibit tumor development.

cancer biology↗

Polyclonal-Monoclonal Transition in Lung Squamous Cell Carcinoma Evolution

The evolutionary trajectory of lung squamous cell carcinoma (LUSC) remains poorly defined, hindering the development of effective therapies. By integrating genomic and transcriptomic sequencing from human LUSC specimens, we delineated a polyclonal-to-monoclonal evolutionary trajectory during LUSC progression. This evolutionary pattern was corroborated by single-cell RNA sequencing, which revealed consistent tumor cell heterogeneity. Specifically, the SBS5 mutational signature was enriched and correlated with poor prognosis independent of tumor stage. By further utilizing the spontaneous LUSC mouse model to identify key genomic and genetic events in LUSC progression, we observed that the JNK pathway was inhibited and that cytoskeleton-related pathways were dysregulated during LUSC development, and identified the mutations in the JNK pathway (e.g., DACT1) and cytoskeletal regulators (e.g., KIF26A). Collectively, these findings established a polyclonal-monoclonal evolution paradigm for LUSC, potentially regulated by JNK pathways, which could benefit LUSC precision therapeutics.

genomics↗

Deep brain stimulation reduces subthalamic nucleus pathological dynamics and rescues gait deficits associated with dopamine loss

The Subthalamic Nucleus (STN) regulates movement and is an important clinical target for deep brain stimulation (DBS) in Parkinsons Disease (PD). However, it remains unclear how dopamine loss and DBS influence STN gait encoding. We performed simultaneous recordings from multiple neurons and intermittent DBS in the STN of healthy and dopamine depleted PD mice during voluntary locomotion. We found that dopamine loss resulted in gait deficits manifested as altered stride length of both hindlimbs and forelimbs, which were rescued by intermittent DBS. Furthermore, dopamine loss exaggerated movement encoding of STN population dynamics, and elevates individual STN spiking during movement and beta-rhythmic firing at rest. Despite an overall increase in the fraction of neuron activated by movement, individual neurons gait encoding properties remain similar between healthy and PD mice. While DBS suppressed firing in both healthy and PD mice, it selectively reduced STN beta-rhythmic spiking, desynchronized STN networks, and rescued gait deficits associated with the loss of dopamine. These results suggest that pathological activation and beta synchronization of the STN contributes to motor deficits related to PD, and DBS-induced reduction of beta rhythmic spiking and STN network desynchronization contribute to the therapeutic effects of DBS in PD.

neuroscience↗

CEACAM5/6+ Tumor Cells and IL-1β+ Macrophages Drive Resistance to Chemo-immunotherapy in Gastric Cancer

Chemo-immunotherapy is a first-line treatment for advanced gastric cancer, yet response rates remain limited and resistance mechanisms are poorly defined. Here we generate a single-cell atlas of 542,121 cells from 35 patients treated with anti-PD-1 plus chemotherapy, profiling pre- and post-treatment tumors linked to clinical response. Integrating spatial transcriptomics, immunohistochemistry, and bulk RNA sequencing, we identify two temporally distinct resistance programs. Intrinsic resistance in pre-treatment non-responders is marked by enrichment of CEACAM5/6 tumor cells that form immune-excluded spatial niches characterized by macrophage recruitment and CD8 T-cell exhaustion. Acquired resistance in post-treatment non-responders is driven by expansion of IL-1{beta} macrophages, which induces coordinated NF-{kappa}B activation across tumor and stromal compartments, promoting PD-L1 upregulation, epithelial-mesenchymal transition, and chronic inflammation. These findings delineate an evolutionary trajectory of resistance and nominate CEACAM5/6 and IL-1{beta} as predictive biomarkers and therapeutic targets to improve anti-PD-1-based combination strategies.

cancer biology↗

Subthreshold membrane depolarization powerfully engages intracellular calcium dynamics in the brain

Membrane voltage (Vm) regulates spike timing and intracellular signaling. While Vm is extensively modulated by behavior, it is unclear how subthreshold Vm dynamics engage intracellular signaling in the awake mammalian brain. We developed a bicistronic viral vector to express genetically encoded and color compatible voltage and calcium (Ca2+) indicators in the same neuron, and simultaneously recorded cellular Vm and Ca2+ dynamics in awake mice. We report that prolonged subthreshold Vm depolarization is closely accompanied by prominent large amplitude Ca2+ elevation, whereas isolated spikes are coupled with weak Ca2+ rise. Additionally, individual spikes differentially engage intracellular Ca2+ dynamics depending on post-spiking Vm depolarization, consistent with a prominent role of slow Vm depolarization in regulating cellular signaling. While brief intracranial electrical stimulation consistently leads to Vm depolarization and Ca2+ increase, longer stimulation disrupts Vm and Ca2+ coupling, highlighting a tightly regulated cellular mechanism that relays slow Vm depolarization to intracellular signaling.

neuroscience↗

Non-enzymatic ABHD6 interacts with Akt-FoxO1 axis to regulate selective hepatic insulin resistance

The enzymatic function of ABHD6 on insulin secretion and insulin resistance is well documented. However, its non-enzymatic function, especially its effects on selective hepatic insulin resistance and metabolic dysfunction-associated steatotic liver disease (MASLD) is completely unexplored. ABHD6 is elevated under conditions of diet-induced obesity and aging. To define the role of ABHD6 in liver physiology, we generated liver-specific ABHD6 knockout mice, as well as liver specific overexpression of native and enzymatic inactive mutant ABHD6 mouse models. We demonstrated that ABHD6 is an unidentified regulator of selective hepatic insulin resistance and contributes to MASLD and liver fibrosis. Furthermore, we found that non-enzymatic ABHD6, rather than its enzymatic form, contributes to this regulation. Mechanistically, we found that ABHD6 translocated into the nucleus and interacted with Akt/FoxO1 axis to regulate its function. In addition, knockdown of FoxO1 in primary hepatocytes or overexpression of constitutively active mutant FoxO1 by AAV approach could completely abolish the effects of ABHD6 on glucose tolerance and gluconeogenesis. Our study reveals an entirely different mechanism underlying selective hepatic insulin resistance that involves a previously unknown non-enzymatic function of ABHD6. This study opens an avenue for the development of a novel class of ABHD6 inhibitors to treat MASLD and liver fibrosis. HighlightsO_LIABHD6 expression in the liver is increased with obesity and aging. C_LIO_LIABHD6 manipulation affects selective hepatic insulin resistance, MASLD and liver fibrosis. C_LIO_LINon-enzymatic ABHD6 interacts with Akt/FoxO1 axis to regulate FoxO1 transcriptional activity. C_LIO_LIThe effects of ABHD6 on glucose tolerance and hepatic gluconeogenesis are completely dependent on FoxO1 activity. C_LI

physiology↗

Rapid and Quantitative Phage Susceptibility Test by Ramanome

Antimicrobial resistance poses an escalating global threat, renewing interest in bacteriophage therapy as a precision alternative to antibiotics. However, clinical translation remains hindered by the lack of rapid and quantitative phage susceptibility testing (PST) platforms capable of evaluating host range, infection potency, and effective multiplicity of infection (MOI). Here we present RPST, a ramanome-based phenotypic platform that captures infection-induced remodeling of bacterial macromolecular composition to unify these diagnostic requirements within a single workflow. RPST integrates four Raman biomarkers into a Composite Infection Index (CII), enabling rapid and lysis-independent discrimination between susceptible and resistant bacterial populations within [~]1 hour, with 96.0% categorical concordance (24/25) to plaque assays. As a continuous population-level metric, CII quantifies the proportion of infected cells, allowing quantitative ranking of phage potency against shared hosts. By resolving CII trajectories across the MOI and time, RPST further determines the minimal effective MOI, which is the lowest phage-to-bacterium ratio sustaining self-propagating infection, thereby defining the lower boundary for therapeutic feasibility. Together, these capabilities transform PST from static compatibility assays into a dynamic and quantitative framework that bridges in vitro infectivity assessment and infection dynamics relevant to phage therapy. Impact StatementBased on the rapid emergence of antimicrobial resistance, this study introduces RPST, a novel ramanome-based phage susceptibility testing platform. RPST detects phage-induced biochemical remodeling in bacteria within [~]1 hour, achieving 96.0% concordance with gold-standard plaque assays. By integrating four Raman biomarkers into a Composite Infection Index, it not only distinguishes susceptible from resistant strains but also quantifies phage potency and determines the minimal effective multiplicity of infection required for self-sustaining infection. This transformative approach moves beyond binary diagnostics to offer a dynamic, quantitative framework for precision phage therapy, significantly accelerating therapeutic decision-making and enhancing our ability to combat resistant infections.

microbiology↗

Single-nuclei RNA-sequencing uncovers sexually divergent exercise signatures partially mimicked by TFEB overexpression in mouse skeletal muscle

Exercise induces extensive, cell-type-specific transcriptional remodeling in skeletal muscle to support metabolic flexibility and adaptation. However, the regulatory mechanisms underlying these transcriptional programs, and the extent to which they differ between sexes, remain poorly defined. We previously reported that lifelong, muscle-specific overexpression of human Transcription Factor E-B (cTFEB;HSACre transgenic mice) recapitulates many adaptive features of endurance training in both sexes, leading to profound geroprotective effects during aging even in the absence of exercise. Here, we profile transcriptional adaptations to voluntary wheel running (VWR) and TFEB-overexpression at single-nucleus resolution in young male and female mouse tibialis anterior muscle. This represents, to our knowledge, the first integrated analysis of exercise and TFEB signaling using sex as a biological variable. Using robust bioinformatic and single-nuclei RNA-sequencing approaches, we profiled six muscle-resident cell populations and uncover previously unrecognized, sex-dependent signaling nodes governing exercise-associated metabolic plasticity. TFEB activation and endurance training by VWR elicit strongly correlated transcriptional programs enriched for lipid metabolism, mitochondrial remodeling, and immune modulation, establishing TFEB-overexpression as a partial exercise mimetic. In general, female muscle exhibited enhanced extracellular matrix and lipid-associated responses to endurance training and TFEB overexpression, whereas males preferentially engaged in angiogenic and oxidative networks, revealing distinct sex-specific, sex-dimorphic, or sex-agnostic regulatory routes to metabolic flexibility. Integration with independent multi-omics datasets from endurance-trained rats (MoTrPAC) confirms the conservation of TFEB-exercise transcriptional convergence in skeletal muscle across species and potentially muscle types. Together, these findings define TFEB as a regulator of exercise transcriptional programs and reveal sex-specific molecular frameworks that drive metabolic adaptation in skeletal muscle. Furthermore, the resulting sex-resolved, single-nucleus transcriptional atlas provides a unique resource for the field, enabling comparative, mechanistic, and hypothesis-driven exploration of exercise-responsive skeletal muscle regulatory networks across sexes.

physiology↗

Hepatic ketogenesis supports liver lipid homeostasis during acute exercise but is not required for exercise training to mitigate liver steatosis in mice

The acceleration of hepatic lipid disposal during acute exercise has been proposed as a contributor to the anti-steatotic effects of exercise training. Ketogenesis, which produces acetoacetate (AcAc) and {beta}-hydroxybutyrate ({beta}OHB) from fatty acids, is among the lipid disposal pathways stimulated by exercise. This study tested the hypothesis that hepatic ketogenesis is necessary for exercise training to lower liver lipids. Liver-specific 3-hydroxymethylglutaryl-CoA synthase 2 knockout (HMGCS2 KO) mice and wild type (WT) littermates underwent sedentary, acute exercise, and exercise training protocols. Liver ketone bodies and lipids were determined via mass spectrometry platforms. Stable isotope infusions in conscious, unrestrained mice defined mitochondrial oxidative fluxes at rest and during exercise. Loss of hepatic HMGCS2 decreased liver AcAc and {beta}OHB concentrations and impaired their increase during exercise. Liver triacylglycerides (TAGs) were comparable between genotypes at rest (i.e., ad libitum fed and short fasted conditions). In contrast, liver TAGs were elevated in HMGCS2 KO mice following acute, non-exhaustive exercise. Liver TCA cycle flux was higher in KO mice at rest. During exercise, TCA cycle flux increased in both WT and KO mice but was not different between genotypes with greater exercise duration. This suggests that enhanced disposal of lipids via the TCA cycle may prevent liver lipid accumulation in HMGCS2 KO mice under sedentary conditions, but not during exercise. Unexpectedly, exercise training decreased liver TAGs similarly in both HMGCS2 KO and WT mice. In conclusion, hepatic ketogenesis supports liver lipid homeostasis during acute exercise, but is not required for exercise training to lower liver lipids. NEW & NOTEWORTHYExercise training has been proposed to mitigate liver steatosis partly through enhanced hepatic lipid disposal. During acute exercise, the disposal of fatty acids to ketone bodies is stimulated. This study tested the hypothesis that hepatic ketogenesis was required for exercise training to reduce liver fat in mice. The results show that hepatic ketogenesis is needed to prevent lipid accumulation during acute exercise, but is not necessary for exercise training to lower liver lipids.

physiology↗

Targeting Circulating FABP4 Ameliorates Obesity-Associated Hepatic Steatosis

Obesity is a major driver of hepatic steatosis, yet the molecular link between excess adiposity and hepatocellular lipid accumulation remains incompletely defined. Here, we identify circulating fatty acid-binding protein 4 (FABP4) as a key mediator of adipocyte-hepatocyte lipid crosstalk in obesity. Analyses of human liver specimens and mouse models reveal aberrant accumulation of FABP4 protein--but not transcript--in hepatocytes during steatosis, indicating an extrinsic source. Genetic deletion of FABP4, specifically in adipocytes, protects against high fat diet-induced hepatic steatosis without altering obesity or systemic lipid levels. Mechanistically, circulating FABP4 directly binds to hepatocytes, facilitating free fatty acid uptake. Furthermore, we developed a high-affinity humanized monoclonal antibody that selectively neutralizes circulating FABP4, blocks hepatocyte binding, suppresses fatty acid uptake, and markedly attenuates hepatic steatosis in multiple obese mouse models. These findings establish circulating FABP4 as a pathogenic lipid chaperone and a promising therapeutic target for obesity-associated hepatic steatosis. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=180 SRC="FIGDIR/small/701451v1_ufig1.gif" ALT="Figure 1"> View larger version (61K): org.highwire.dtl.DTLVardef@5b91d5org.highwire.dtl.DTLVardef@1c34892org.highwire.dtl.DTLVardef@1d17ea9org.highwire.dtl.DTLVardef@d2b43c_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIHepatocytic accumulation of extrinsic FABP4 links adiposity to liver lipid deposition. C_LIO_LISpecific deletion of FABP4 in adipocytes prevents hepatic steatosis without affecting systemic lipid levels or obesity. C_LIO_LICirculating FABP4 derived from adipocytes directly binds hepatocytes to facilitate free fatty acid transfer. C_LIO_LIBlocking circulating FABP4 with a high-affinity anti-FABP4 monoclonal antibody inhibits hepatocyte lipid uptake and attenuates steatosis in multiple obese mouse models. C_LI

pathology↗

Surf2Spot: A Surface-Informed Geometry-Aware Model for Predicting Binder and Nanobody Design Hotspots

Protein-protein interactions (PPIs) and nanobody-antigen interactions (NAIs) play essential roles in cellular function, yet accurate hotspot prediction remains challenging. We present Surf2Spot, a deep learning framework that integrates sequence embeddings, structural features, and protein surface properties to predict interaction hotspots. By jointly modeling structural and physicochemical determinants, Surf2Spot achieves superior performance on curated PPI and NAI datasets, improving F1-scores by 45.9-46.9% and AUPRC by 43.2% over existing methods. Case studies on NbPDS1 and VdPDA1 demonstrate that Surf2Spot accurately recovers experimentally validated hotspots clustered within functional domains. When incorporated into binder design pipelines (RFdiffusion and BindCraft), Surf2Spot-guided designs yielded a 4-fold increase in successful design throughput and enhanced binding affinities compared to baseline strategies. These results establish Surf2Spot as a powerful tool for hotspot discovery and rational protein engineering.

bioinformatics↗

Antitoxin-induced auto-phosphorylation neutralizes the nucleotidyltransferase toxin AbiEii from Streptococcus agalactiae to safeguard global translation

Nucleotidyltransferases (NTases) control diverse physiological processes, including DNA replication and repair, antibiotic resistance, and RNA modification. The Streptococcus agalactiae abortive infection family toxin, AbiEii, belongs to the DUF1814 superfamily of NTases and blocks bacterial growth through an as yet unknown mechanism. Antitoxin AbiEi has been reported to antagonize AbiEii as part of a Type IV toxin-antitoxin system. Here, we demonstrate through structural, biochemical, and biophysical studies that AbiEi binds to AbiEii to form a stable toxin-antitoxin complex in solution. Antitoxin binding ultimately leads to AbiEii auto-phosphorylation and an abolition of NTase activity. These data reclassify AbiE systems as Type VII toxin-antitoxin systems. Toxin phosphorylation appears to be a dynamic and reversible process, and we show that the sole serine/threonine phosphatase SaSTP of S. agalactiae can efficiently dephosphorylate AbiEii in vitro. Mutagenesis studies and functional assays indicate that a widespread mechanism of toxin auto-phosphorylation accounts for AbiEii neutralization, further supporting recent hypotheses outlining control of homologous MenAT toxin-antitoxin systems from Mycobacterium tuberculosis.

molecular biology↗