Biology subjects

Brennan, L.

Publications and source records attributed to Brennan, L..

7 recordsLinked to original sources

bioRxiv2026

Cannabinoid CB2 receptor activation drives glucose uptake, shifting T cell metabolism.

Cannabinoid receptor 2 (CB2R) is highly expressed on immune cells, but its role in T cell metabolism remains unclear. Here, we show that CB2R activation rapidly increases glucose uptake in human Jurkat T cells and drives a broader metabolic reprogramming away from glycolysis toward oxidative metabolism and the pentose phosphate pathway. Pharmacological CB2R activation increased mitochondrial mass, spare respiratory capacity, proton leak, and NADPH production, while CB2R inverse agonism produced the opposite effects. These metabolic changes were accompanied by upregulation of key pentose phosphate pathway enzymes, including GALT and TALDO1, and were abolished in CNR2-deficient cells, confirming receptor dependence. In primary human lamina propria mononuclear cells, CB2R signalling also influenced memory and gut-homing-associated T cell phenotypes, including integrin 4{beta}7 expression. Together, these findings identify CB2R as a regulator of T cell bioenergetics and suggest that cannabinoid signalling may promote metabolic states linked to memory and tissue-homing functions in chronic intestinal inflammation. Brief SummaryO_LICB2R agonist-mediated increased glucose uptake in human T cells is lost in CNR2-deficient cells, suggesting that the response is receptor-dependent. C_LIO_LICB2R activation rewires T-cell metabolism toward increased oxidative phosphorylation, spare respiratory capacity, mitochondrial mass, and pentose phosphate pathway metabolism, including higher NADPH and PPP-enzyme expression. C_LIO_LIIn primary human intestinal immune cells, CB2R also promotes gut-homing and memory-associated T-cell phenotypes, including 4{beta}7 and CD103 integrin induction ex vivo, suggesting a possible link to exacerbation of chronic intestinal inflammation. C_LI

immunology↗

bioRxiv2026

Tumour microenvironments impose translational repression that limits natural killer cell persistence

Natural killer (NK) cells infiltrate many solid tumours, yet the mechanisms that determine their functional heterogeneity across tumour types remain poorly understood. Differences in tumour immunogenicity, inhibitory signalling, and nutrient availability have all been implicated, but unifying explanations are lacking. Here, we compared four syngeneic tumour models implanted at identical anatomical sites to isolate tumour-intrinsic effects on NK-cell fate. Tumour-infiltrating NK cells displayed striking tumour-specific differences in cytokine production, cytotoxic protein expression, and persistence. These differences were not explained by cytokine availability or global features of the tumour metabolic environment. Instead, quantitative proteomics and time-resolved in vivo labelling revealed that NK cells enter tumours in a functionally competent state but rapidly diverge thereafter. In suppressive tumour microenvironments, NK cells undergo early mitochondrial loss, translational repression, and impaired proteostatic responses, accompanied by increased apoptotic priming. These defects result in reduced effector function and failure of intratumoural persistence despite preserved recruitment. In contrast, permissive tumours sustain NK-cell translational capacity, cytokine responsiveness, and long-term residency. Together, these findings identify disruption of translational and mitochondrial homeostasis as a central mechanism limiting NK-cell persistence in solid tumours. This work establishes early tumour-induced defects in protein synthesis and cellular fitness as key constraints on durable NK-cell immunity and provides a framework for restoring effective innate anti-tumour responses.

immunology↗

bioRxiv2026

AMPBAN: A Deep Learning Framework Integrating Protein Sequence and Structural Features for Antimicrobial Peptide Prediction

The escalating crisis of antimicrobial resistance poses a devastating and immediate threat to human life. Antimicrobial peptides (AMPs) are a promising antibiotic substitute to combat antimicrobial resistance. Compared with the traditional wet-lab screening approaches, computational models have largely improved the efficiency of predicting antimicrobial peptide. However, most computational models overlook or underutilize the evolution and structural information of peptides, which is crucial for understanding the peptide functions. Here, we proposed a sophisticated deep learning model to predict AMPs, Antimicrobial Peptide Bilinear Attention Network (AMPBAN), which incorporates peptide evolution features from ESM3 protein language model, structure features from ESMFold predicted with equivariant graph neural network (EGNN), and the joint information from sequence and structure learned via Bilinear Attention Network. AMPBAN consistently demonstrated superior accuracy and generalization compared to nine state-of-the-art AMP prediction models across multiple independent benchmarks. Furthermore, an ablation study confirms that our multimodal fusion strategy significantly refines the integration of sequence and structural signals, yielding superior predictive balance over single-modality models. This framework provides a robust tool for the accelerated discovery of novel AMPs and the advancement of next-generation antimicrobial drug development. The datasets, source code and models are available at https://github.com/baiwenhuim/ampban.

bioinformatics↗

bioRxiv2026

Active Site-Directed Probes for targeting Bacterial Phosphoarginine Phosphatases

Canonical protein phosphorylation patterns are a thoroughly studied post-translational modification (PTM) driving distinct regulatory mechanisms in both prokaryotes, and eukaryotes. In contrast, the identification and investigation of essential components that regulate non-canonical phosphorylation has received considerably less attention, although these PTMs are associated with important functions. One notable example is arginine phosphorylation which modulates processes such as protein degradation, transcriptional regulation and spore germination in bacteria. Herein we introduce the first in class covalent activity-based probes to study phosphoarginine-phosphatases. We identify unsaturated phosphonamidic acids as bespoke electrophilic phosphoarginine (pArg) mimics, which allowed to uncover a series of unprecedented pArg-phosphatases, which in part had been previously annotated as low molecular weight tyrosine-phosphatases across phylogenetically distinct microbial species. This work, which serves as the first example of proteome-wide activity-based profiling of pArg phosphatases will help inform the development of new therapeutic modalities and expand our understanding of bacterial signal transduction.

microbiology↗

bioRxiv2024

Identification of potential sepsis therapeutic drugs using a zebrafish rapid screening approach

In the military, combat wound infections can progress rapidly to life-threatening sepsis. Discovery of effective small molecule drugs to prevent and/or treat sepsis is a priority. To identify potential sepsis drug candidates, we used an optimized larval zebrafish model of endotoxicity/sepsis (Philip et al., 2017) to screen commercial libraries of U.S. Food and Drug Administration (FDA)- approved drugs and other active pharmaceutical ingredients (API) known to affect pathways implicated in the initiation and progression of sepsis in humans (i.e., inflammation, mitochondrial dysfunction, coagulation, and apoptosis). We induced endotoxicity in 3- and 5-day post fertilization larval zebrafish (characterized by mortality and tail fin edema (vascular leakage)) by immersion exposure to Pseudomonas aeruginosa 60 g/mL lipopolysaccharide (LPS) for 24 hours, then screened for the rescue potential of 644 selected drugs simultaneously with LPS at 10 M. After LPS exposure, we used a neurobehavioral assay (light-dark test) to further evaluate rescue from endotoxicity and to determine possible off-target drug side effects. We identified 29 drugs with > 60% rescue of tail edema and mortality. Three drugs (Ketanserin, Tegaserod, and Brexpiprazole) produced 100% rescue and did not differ from the controls in the light-dark test, suggesting a lack of off-target neurobehavioral effects. Further testing of these three drugs at a nearly 100% lethal concentration of Klebsiella pneumoniae LPS (45 g/mL) showed 100% rescue from mortality and 88%-100% mitigation against tail edema. The success of the three identified drugs in a zebrafish endotoxicity/sepsis model warrants further evaluation in mammalian sepsis models.

pharmacology and toxicology↗

bioRxiv2022

Liquid-liquid phase separation recapitulates the thermodynamics and kinetics of heterochromatin formation

The spatial segregation of pericentromeric heterochromatin (PCH) into distinct, membrane-less nuclear compartments involves the binding of Heterochromatin Protein 1 (HP1) to H3K9me2/3-rich genomic regions. While HP1 exhibits liquid-liquid phase separation properties in vitro, its mechanistic impact on the structure and dynamics of PCH condensate formation in vivo remains largely unresolved. Here, using biophysical modeling, we systematically investigate the mutual coupling between self-interacting HP1-like molecules and the chromatin polymer. We reveal that the specific affinity of HP1 for H3K9me2/3 loci facilitates coacervation in nucleo, and promotes the formation of stable PCH condensates at HP1 levels far below the concentration required to observe phase separation in purified protein assays in vitro. These heterotypic HP1-chromatin interactions give rise to a strong dependence of the nucleoplasmic HP1 density on HP1-H3K9me2/3 stoichiometry, consistent with the thermodynamics of multicomponent phase separation. The dynamical crosstalk between HP1 and the viscoelastic chromatin scaffold also leads to anomalously-slow equilibration kinetics, which strongly depend on the genomic distribution of H3K9me2/3 domains, and result in the coexistence of multiple long-lived, microphase-separated PCH compartments. The morphology of these complex coacervates is further found to be governed by the dynamic establishment of the underlying H3K9me2/3 landscape, which may drive their increasingly abnormal, aspherical shapes during cell development. These findings compare favorably to 4D microscopy measurements of HP1 condensates that we perform in live Drosophila embryos, and suggest a general quantitative model of PCH formation based on the interplay between HP1-based phase separation and chromatin polymer mechanics. SIGNIFICANCE STATEMENTThe compartmentalization of pericentromeric heterochromatin (PCH), the highly-repetitive part of the genome, into membrane-less organelles enriched in HP1 proteins, is critical to both genetic stability and cell fate determination. While HP1 can self-organize into liquid-like condensates in vitro, the roles of HP1 and the polymer chromatin in forming 3D PCH domains in vivo are still unclear. Using molecular simulations, we show that key kinetic and thermodynamic features of PCH condensates are consistent with a phase-separation mode of organization driven by the genomic distribution of methylated domains and HP1 self-attraction and affinity for heterochromatin. Our predictions are corroborated by live-microscopy performed during early fly embryogenesis, suggesting that a strong crosstalk between HP1-based phase separation and chromosome mechanics drive PCH condensate formation.

biophysics↗

bioRxiv2017

Rapid Agrobacterium-mediated transformation of tobacco cotyledons using toothpicks

Tobacco is a model plant for genetic transformation, with leaf-disk transformation being the most commonly used method for its transformation. One disadvantage of leaf-disk transformation is obtaining an adequately sized leaf. Cotyledons from young seedlings are considered too small and fragile to use. In an attempt to overcome this drawback, a protocol was developed using toothpicks as a tool to inoculate cotyledons ~2mm in diameter. Agrobacterium tumefaciens LBA4404 hosting two different plasmids (pC35.BNK.2 or pRB140-Bxb1-op) was used for transformation. Fifty-six putative transgenic shoots (T0) were obtained from pC35.BNK.2 transformation. Among them, 38 (68%) grew roots in kanamycin-containing medium. Approximately, 35% of transgenic lines contained a single-copy transgenic locus based on Mendelian inheritance analysis and chi-square ({chi}2) test of T1 seedlings from 17 lines. To simplify the protocol, water-prepared Agrobacterium inoculum was used in pRB140-Bxb1-op (containing gus gene) transformation. This resulted in ~35% putative T0 transgenic lines stained strong blue with GUS histochemical staining assay. Both sets of results demonstrate toothpick inoculation to be an effective approach for Agrobacterium-mediated tobacco cotyledon transformation. This reduces wait time required in existing leaf-disk transformation method using mature leaves. Removal of step requiring submersion of explants in Agrobacterium liquid culture, the protocol also has advantages by minimizing Agrobacterium overgrowth and maintaining explant fitness for later tissue-culturing.

plant biology↗