Biology subjects

Cai, X.

Publications and source records attributed to Cai, X..

At least 37 records · Page 2Linked to original sources

bioRxiv2026

An Integrated Computational-Experimental Strategy For the Prediction of Small Molecules as GLP-1R Agonists

The glucagon-like peptide-1 receptor (GLP-1R) plays a central role in metabolic regulation and is a major therapeutic target for obesity and diabetes. Peptide agonists, like semaglutide, targeting the GLP-1R remain among the most effective regulators of glucose metabolism and appetite. Nonetheless, recent reports about weight regain have limited the effectiveness of GLP1R peptide agonists, sustaining the interest in expanding the chemical diversity of GLP-1R ligands through drug discovery strategies. However, the structural complexity and conformational plasticity of class B1 GPCRs make conventional single-method virtual screening approaches prone to bias and limited chemotype recovery. Using an integrated ligand- and structure-based virtual screening pipeline, explicitly combining complementary ligand-based descriptors, multi-fingerprint similarity, electrostatic similarity, pharmacophore modeling, and multi-conformation docking under a consensus-driven selection strategy, we were able to identify three chemically distinct classes of GLP-1R agonist candidates: GQB47810, a non-peptidic molecule; neuromedin C, a peptide, and 2,5-Pen-enkephalin (DPDPE), a small peptide. From all of them, DPDPE showed the greatest effectiveness, reaching values similar to those of GLP-1, although with lower potency. Further in vitro characterization confirmed that pen-enkephalin behaved as a full agonist and exhibited dual GLP-1R/GIPR agonistic activity. These findings establish a consensus-driven and transferable computational framework for chemotype-diverse agonist discovery at conformationally flexible GPCR targets, and revealed a pentapeptide with GLP-1-like efficacy as a promising lead for next-generation small peptide therapeutics.

bioinformatics↗

bioRxiv2026

Mitochondrial ATP production promotes T cell differentiation and function by regulating chromatin accessibility

Immune elimination of chronic infection or cancer requires cytotoxic CD8+ T cells that adopt and maintain an effector phenotype. Cytotoxic T cell function is a bioenergetically demanding process and T cells subjected to chronic antigen exposure have compromised effector function despite high rates of glycolysis. Here we report the ability of the short-chain -hydroxy acid, D--hydroxybutyrate, to act as a signaling molecule that increases mitochondrial ATP production and drives the conversion of proliferating T cells into cytotoxic effector cells. DAHB signaling switches ATP production from glycolysis to oxidative phosphorylation supported by fatty acid oxidation, even in glucose-replete media. This conversion suppresses both AMPK phosphorylation and the integrated stress response (ISR) in activated T cells while significantly elevating the level of the phosphagen, phosphocreatine (PCr). Both the PCr bioenergetic reserve and oxidative phosphorylation were required for T cell effector differentiation. DAHB-induction of CD8-effector gene transcription was coupled to bioenergetics by enhanced ATP-dependent remodeling of chromatin accessibility at effector gene loci. DAHB enhanced CD8+ T cell antitumor activity both in vitro and in vivo, and DAHB treatment of transferred T cells led to persistent in vivo antitumor effects. Together, these findings link cellular bioenergetics to the regulation of chromatin accessibility and gene expression required to support effector function.

immunology↗

bioRxiv2026

NINTEDANIB AND PIRFENIDONE AFFECT GROWTH AND DIFFERENTIATION OF HUMAN ALVEOLAR TYPE 2 CELLS

BackgroundIdiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease characterized by epithelial cell senescence. Pirfenidone and nintedanib are approved drugs for the treatment of IPF. They significantly slow disease progression, but their mechanisms of action, especially on alveolar type 2 (AT2) cells, are poorly understood. We addressed this question by evaluating colony formation and growth of human AT2 cells co-cultured with fibroblasts in organoid culture in the presence of pirfenidone and nintedanib. We further evaluated molecular changes induced by these drugs via single cell RNA-seq of treated organoids. MethodsAT2 cells isolated from normal donor lungs or IPF patients were mixed with human fibroblasts in 3D culture and grown in the absence or presence of pirfenidone or nintedanib. After 14 days in culture, the organoids were quantified and cells extracted from Matrigel for single cell RNA-seq. ResultsAT2 cell organoids cultured in the presence of pirfenidone or nintedanib resulted in increased colony formation and, in the case of nintedanib, in larger colonies. We observed that untreated or pirfenidone treated AT2 cells lost surfactant protein C (SFTPC) expression and acquired an expression profile consistent with keratin (KRT)17high/KRT5- basaloid cells, whereas a larger proportion of nintedanib treated cells retained SFTPC expression. In contrast, AT2 cells treated with TGF{beta} inhibitor exhibited intermediate (SFTPC-/KRT17low) gene expression profile. ConclusionThese results suggest that nintedanib maintains an AT2-like expression state in culture and acts proximal to TGF{beta}. Conflict of Interest StatementPJW was supported by grants from Boehringer Ingelheim, Roche, Sanofi, Pliant and Arda Therapeutics and received personal fees from Boehringer Ingelheim and Sanofi. None of these companies had a role in the design or analysis of the study or in the writing of the manuscript. ASM, GP, JRR and DG are employees of Genetech. The other authors have no conflicts of interest to declare.

cell biology↗

bioRxiv2026

Transplanting ANXA1- CD8+ Naive T cells Delay Aging Through Senolysis

Immunosenescence is a hallmark of aging, yet strategies using defined immune subsets to counteract it are largely unexplored. We performed paired scRNA/TCR-seq on CD45 cells from human bone marrow (15 donors, 3-91 years). T cells were the most altered lineage, with CD8 naive T cell contraction and functional impairment. We identified an expanding ANXA1 CD8 naive subset with senescence signatures and impaired function. ANXA1-deficient CD8 T cells exhibited increased resting stemness and enhanced activation/cytotoxicity upon stimulation. ANXA1- cells showed senolytic activity in vitro and reduced senescence burden in vivo. Monthly transfer of syngeneic ANXA1- CD8 naive T cells into aged mice extended median lifespan by >30 weeks, improving cardiac function, bone density, motor coordination, and marrow immune microenvironment. Our study identifies ANXA1 as critical in CD8 naive T cell aging and establishes ANXA1- cell transfer as a strategy to counter immunosenescence and promote healthy aging.

immunology↗

bioRxiv2026

TREM2 agonist antibody rebuilds the resident synovial macrophage lining barrier in rheumatoid arthritis

Rheumatoid arthritis (RA) can be viewed as a disease of barrier failure, in which CX3CR1+/TREM2+ synovial tissue-resident macrophages that form the lining barrier over cartilage and bone become fragmented and disorganized. However, how to therapeutically rebuild this barrier--and how macrophage states transition during repair--remain unclear. We engineered TR-Ab19, a mouse-selective agonistic antibody against TREM2, as a precision tool to initiate and interrogate barrier repair in vivo. TR-Ab19 engages TREM2-linked downstream signaling and redirects synovial macrophages from Clec4d+ inflammatory/proliferative programs toward TREM2+CX3CR1+Aqp1+ barrier-like states, thereby rebuilding the lining barrier. Across collagen-induced arthritis (CIA) and serum-transfer arthritis (STA) models, TR-Ab19 reduces synovitis, preserves cartilage and bone microarchitecture, limits osteoclastogenesis, and attenuates systemic cytokines and B-cell abnormalities. Single-cell RNA-seq with trajectory and cell-cell communication analyses reveal a TREM2-dependent shift toward a barrier-dominant macrophage ecosystem. Together, these findings establish antibody-mediated reprogramming of resident synovial macrophages as a barrier-centered strategy for RA and provide a framework for instructing macrophage niches in chronic inflammation.

bioengineering↗

bioRxiv2026

A dramatic protein fold switch powers a bactericidal nanomachine

Fold switching, where a protein region interconverts between entirely distinct three-dimensional structures, is emerging as vital for certain protein functions. Here, we report a remarkable example in the F7 pyocin, a phage tail-like bactericidal nanomachine. Cryogenic electron microscopy and tomography reveal that a 163-residue segment of the central tail fiber undergoes a dramatic transition--from a trimeric -helical coiled-coil to a triangular {beta}-prism--upon binding to the bacterial cell surface. This massive fold switch remodels the tail tip, ejects the internal tape measure protein, and drives membrane puncture. Site-directed mutations that selectively destabilize the {beta}-prism conformation completely abolish bactericidal activity without impairing particle assembly, implying that the energy released during this transition powers penetration. AlphaFold-based analyses further predict similar large-scale coiled-coil to {beta}-prism switches in diverse non-contractile phage tails. This discovery reveals a sophisticated, ATP-independent strategy for microbial warfare and opens exciting possibilities for engineering next-generation bacteriocins to combat multidrug-resistant pathogens.

microbiology↗

bioRxiv2026

Unmixing Spread Estimation Based on Residual Model in Spectral Flow Cytometry

Advances in spectral flow cytometry have enabled the simultaneous measurement of dozens of markers across millions of cells within a single experiment. Despite the increasing maximum perplexity achievable in spectral panels, panel design remains constrained. A central obstacle is signal spread-- unmixed fluorescence signal misattributed to unrelated channels--which reduces the resolution of cell populations. Here we introduce the Residual Model, a robust, scalable, and interpretable model-based approach for spread prediction during panel design. The Residual Model integrates statistical features derived from single-color controls and predicts spread under Ordinary Least Squares unmixing, the most widely used unmixing method. We demonstrate its reliable predictive performance across 141 single-color control samples measured on two instruments. To facilitate practical application, we developed the USERM R package, which implements the Residual Model and provides an out-of-box solution for interactive spread prediction and visualization.

immunology↗

bioRxiv2026

Polymer-lipid hybrid nanoparticle enhances mRNA delivery and T cell-mediated immunity

mRNA vaccines have transformed prophylactic immunization against infectious diseases as well as therapeutic interventions for cancer. However, their effectiveness against emerging viral variants and a range of malignancies continues to be hindered by suboptimal induction of T cell-mediated immunity. To overcome this limitation, here we developed a polymer-lipid hybrid nanoparticle (PLNP) platform engineered to improve mRNA delivery to antigen-presenting cells (APCs) and to potentiate T cell responses. Relative to conventional mRNA lipid nanoparticle (LNP) vaccines, mRNA PLNP vaccines demonstrated markedly improved lymph node targeting, APC activation, Th1-biased pro-inflammatory cytokine response, and antigen-specific T cell expansion while retaining robust humoral immunity. Remarkably, mRNA-PLNP vaccines generated approximately 50% more antigen-specific CD8+ T cells than mRNA-LNP vaccines across multiple antigens, including SARS-CoV-2 spike, influenza hemagglutinin, and ovalbumin. In prophylactic applications, mRNA PLNP vaccine provided complete protection against SARS-CoV-2 variants. As a therapeutic approach in a melanoma model, mRNA PLNP vaccination resulted in enhanced tumor control and significantly prolonged survival compared to LNP-based formulations. Collectively, these results establish PLNP as a versatile and broadly applicable platform for augmenting mRNA vaccine efficacy through improved mRNA delivery and T cell priming, offering promising implications for infection prevention and cancer immunotherapy.

immunology↗

bioRxiv2025

Structural, biophysical, and virological mechanistic characterization of HIV-1 capsid-targeting antivirals

Due to its significant role in virus replication, the HIV capsid is an attractive antiviral target. This is validated by the recent clinical approval of lenacapavir for both treatment and pre-exposure prophylaxis (PrEP). PF74 is a well-characterized capsid-targeting antiviral that was discontinued in further study due to potency and metabolic issues. We hypothesized that making chemical modifications at certain sites of PF74 could result in capsid-targeting antivirals with improved potency and bioavailability. Our cumulative studies show that making changes at the R1 and R3 positions of PF74 results in compounds with increased antiviral potency, increased stability of wild-type HIV capsid hexamers and virions, tighter binding to wild-type HIV capsid hexamer compared to PF74, and different interactions at the "FG" binding site of capsid compared to PF74. These data provide insights into the design of future capsid-targeting antivirals relevant for clinical use.

biochemistry↗

bioRxiv2025

Design, synthesis and profiling of highly potent antivirals targeting emerging drug-resistant HIV-1 variants

AbstractLenacapavir (LEN), the first-in-class HIV capsid inhibitor (CAI), is approved by FDA as a long acting injectable (LAI) for both treatment and pre-exposure prophylaxis (PrEP). Despite its exceptional potency and long pharmacokinetics (PK), a few major resistant mutations have been selected in LEN-treated patients, underscoring the need to develop second-generation LEN analogs to mitigate resistance. Particularly, the M66I mutation confers an extraordinarily high-level LEN resistance, essentially abrogating LEN potency. In this work, we have designed and synthesized LEN analogs featuring a cycloalkyl R2 in subunit B drastically different from known analogs. Against wild-type HIV-1, the potency of our analog 3 (EC50 = 0.073 nM) was 2.6-fold higher than LEN (EC50 = 0.19 nM). More importantly, against the M66I mutant, 3 (EC50 = 5.8 nM) was decisively more potent than LEN (EC50 > 15 M) or any known analogs. We have also shown that the size of the R2 cycloalkyl ring is a major pharmacophore factor as a smaller (cyclopropyl, analog 1) or bigger (cyclohexyl, analog 4) ring confers weaker antiviral potency against both WT HIV-1 and M66I. The vastly improved profile of our lead 3 against M66I was confirmed in the target binding thermal shift assay. These results strongly validate our design and may represent a breakthrough in LEN-based HIV therapy and prophylaxis.

microbiology↗

bioRxiv2025

Rapid fluorescence lifetime sensor development of LifeCamp enables transient and baseline absolute calcium measurements

Genetically encoded calcium sensors (GECIs) have been instrumental for studying neuronal activity and intracellular signaling. GECIs are typically fluorescence-intensity sensors that change brightness upon calcium binding. Iterative improvements in GECIs have yielded indicators that report action potential-evoked calcium entry with high sensitivity and temporal resolution, enabling measurement of network activity across thousands of neurons. However, fluorescence intensity-based measurements generally cannot report baseline or absolute calcium levels and may confound neuromodulatory regulation of calcium handling with changes in action potential firing. Fluorescence lifetime sensors are insensitive to many artifacts that plague intensity-based measures and report absolute substrate levels, including those at rest. However, relatively few lifetime sensors for neuronal signals exist, and developing new sensors is typically difficult and low-yield. Here, we introduce a new rapid lifetime sensor development (RALISED) platform, which we use to build a new GCaMP8m-based high-speed lifetime calcium sensor, termed LifeCamp. We show that LifeCamp enables comparison of baseline calcium signals in cell culture, brain slices, and mice. In addition, we show that LifeCamp enables the detection of fast action potential-evoked calcium transients in single neurons from brain slices and in behaving mice. Using LifeCamp, we discovered calcium baseline changes associated with neuronal activity in brain slices and behaving mice, as well as slow average calcium changes in neuronal populations of freely moving mice. Altogether, this study highlights the utility of the RALISED method to rapidly develop new lifetime sensors and the application of the LifeCamp calcium lifetime sensor to study fast and slow calcium signaling. Significance statementWe developed a new high-speed, sensitive calcium lifetime sensor (LifeCamp) using a novel rapid lifetime sensor development (RALISED) platform. LifeCamp has high sensitivity and a large substrate-dependent lifetime change (<1ns), allowing for the capture of baseline calcium levels, transient calcium changes, and neuronal firing in vitro and behaving animals. LifeCamp lifetime measurement is insensitive to artifacts that plague conventional intensity imaging and enables absolute comparison of baseline and transient calcium changes across cells, brain regions, and experimental conditions. Hence, LifeCamp is a powerful tool that enables a more accurate and in-depth understanding of neuronal activity and calcium signaling.

neuroscience↗

bioRxiv2025

IGHV3-53 antibody abundance drives divergent SARS-CoV-2 immune imprinting

The mechanisms driving divergent SARS-CoV-2 immune imprinting in populations with distinct SARS-CoV-2 exposure histories remain unclear. However, conventional wild-type mouse models fail to recapitulate severe imprinting, even after potent ancestral-strain mRNA immunization, hindering imprinting-related mechanistic investigation and vaccine evaluation. Here, we surprisingly found that V(D)J-humanized mice could faithfully recapitulate human severe imprinting phenotypes. Comprehensive antibody repertoire analysis and deep mutational scanning-based epitope mapping of 583 monoclonal antibodies from these models revealed that the pre-existing IGHV3-53/66 antibody abundance determine imprinting severity through antibody-mediated masking of Omicron-specific epitopes. Both passive IGHV3-53/66 antibody transfer and IGHV3-53 knock-in were sufficient to induce severe imprinting in wild-type mice. Together, these findings demonstrate that the V(D)J germline repertoire--even a single germline-encoded antibody response--can profoundly shape humoral imprinting severity. Accordingly, we established an IGHV3-53 knock-in mouse model that accurately recapitulates the human antibody landscape, providing a valuable tool for guiding future COVID-19 vaccine updates.

immunology↗

bioRxiv2025

Dentate gyrus drives pattern separation in proximal CA3 during rate, but not global, remapping

The dentate gyrus (DG) transforms overlapping experiences into discrete memory traces, yet how DG output shapes population coding within the hippocampus remains unclear. We combined selective DG lesions with large-scale recordings across the CA3 proximo-distal axis as rats explored environments varying in contextual similarity. Global remapping in CA3 remained robust following DG lesion, whereas rate-based contextual coding was substantially attenuated, most strongly in proximal CA3 and attenuating distally, paralleling mossy-fiber topography. Granule cells and mossy cells additionally coded complementary aspects of local objects and mediated CA3 responses to object manipulation. These data causally link the enhanced rate coding of proximal CA3 to its preferential DG innervation and support a dual organization of contextual discrimination: categorical changes in environmental identity are signaled independently of the DG, whereas fine-grained discrimination is facilitated by DG-mediated rate modulation. By selectively amplifying rate-coded discrimination of subtle contextual differences, the DG sharpens the hippocampal network's capacity to resolve overlapping experiences into distinct representations.

neuroscience↗

bioRxiv2025

IFN-I exacerbates the inflammatory response of epithelial cells to Chlamydia trachomatis infection by enhancing TLR3 expression

The inflammation induced by Chlamydia trachomatis infection in the female genital tract (FGT) can have severe consequences. Recent observations in women and mice infected with Chlamydia suggest that type I interferon (IFN-I) may have deleterious effects. This study aimed at elucidating the consequences of IFN-I production on C. trachomatis-induced inflammation in epithelial cells and the molecular pathway(s) involved. We showed that combination of IFN-I and Chlamydia resulted in a stronger induction of inflammation than Chlamydia alone, while IFN-I alone had no effect. Inhibiting AKT and mTOR, but not silencing STAT1, significantly attenuated the synergetic effect between IFN-I and bacteria on inflammation. Inhibition of ERK also blocked this synergistic effect, although ERK were not activated by IFN-I. We hypothesized that IFN-I enhanced the expression of a pathogen recognition receptor of the host, thereby potentiating detection of the bacteria and the subsequent inflammatory response. IFN-I, but not C. trachomatis infection, increased the expression of Toll-like receptor 3 (TLR3), and silencing or knocking-out TLR3 prevented the synergetic effect between infection and IFN-I. Furthermore, our data support the presence of dsRNA in infected cells and the activation of the MAPK/ERK and AP-1/ATF2 signaling cascades downstream of TLR3. Taken together, our data demonstrate that IFN-I exacerbates the host inflammatory response triggered by Chlamydia by increasing TLR3 expression and activation, leading to hyperinflammation. The identified signaling cascades represent potential targets for therapeutical intervention to limit tissue damage upon Chlamydia infection.

microbiology↗

bioRxiv2025

Transposon targeting non-coding RNA transcription targets G/C-rich tracts and is facilitated by an intrinsically disordered protein in Tetrahymena

Tetrahymena is a well-established ciliate model organism, known for its nuclear dualism and unique mechanism for transposon defense, wherein transposons are kept within the highly heterochromatinized micronucleus (MIC), which is transcriptionally inert except during meiosis. The discovery of preferential transcription in the meiotic MIC at regions enriched with transposons, and the identification of MIC transcription regulatory proteins, emphasizes the necessity to elucidate the underlying mechanisms driving this process. In this study, we demonstrate that G/C-rich tracts are overrepresented in meiotic non-coding RNA (ncRNA) transcription regions and that RNA polymerase II (Pol II) is highly enriched at and around these tracts. Further analysis revealed that Pol IIs association with G/C-rich tracts is not abolished in cells lacking Rib1, a Mediator complex-associated protein essential for MIC ncRNA biogenesis. Nevertheless, in the absence of Rib1, Pol II showed abnormal association with the meiotic MIC chromatin, suggesting that Rib1 is critical for maintaining Pol IIs binding specificity. Through Rib1 truncation analysis, we found that the intrinsically disordered region, which contains putative phase-separating peptides, is crucial for its function. Disruption of phase-separation, either by deleting these peptides or by treating cells with a phase-separation disruption reagent, leads to aberrant localization of both Rib1 and Pol II on the MIC chromatin, implicating that Rib1 likely facilitates the MIC ncRNA transcription via phase-separation.

molecular biology↗

bioRxiv2025

Engineered Promoter System Enables High-efficiency Transgenic CRISPR Editing in Malaria Transmitting Mosquito Anopheles sinensis

The CRISPR/Cas9 system deployed through crosses of transgenic lines expressing Cas9 and gRNA facilitates efficient mutagenesis. However, its application in non-model insects remains limited, primarily due to a lack of well-characterized promoters capable of driving robust and stable expression of Cas9 and gRNA. In the malaria mosquito Anopheles sinensis, we evaluated several ovary-biased promoters--Asvasa2, Aszpg, and Asnanos--for driving Cas9 expression. Notably, the Asvasa2 promoter mediated mutagenesis in nearly 60% of G0 individuals following microinjection of gRNAAswhite. Among four RNA polymerase III promoters derived from AsU6 genes, AsU6-1 yielded the highest gRNA transcriptional output, enabling 62% editing efficiency in G0 offspring. In addition, hybrid crosses between established transgenic lines demonstrated that the Asvasa2-Cas9 and AsU6-1-gRNA combination enabled complete germline editing penetrance, where all F2 progeny inherited the intended mutations. This work provides a essential genetic toolkit for synthetic biology applications in Anopheles mosquitoes and a scalable framework for engineering other non-model insects.

genetics↗

bioRxiv2025

CenSegNet: a generalist high-throughput deep learning framework for centrosome phenotyping at spatial and single-cell resolution in heterogeneous tissues

Centrosome abnormalities (CA) are a hallmark of epithelial cancers, yet their spatial complexity and phenotypic heterogeneity remain poorly resolved due to limitations in conventional image analysis. We present CenSegNet (Centrosome Segmentation Network), a modular deep learning framework for high-resolution, context-aware segmentation of centrosomes and epithelial architecture across diverse tissue types. Integrating a dual-branch architecture with uncertainty-guided refinement, CenSegNet achieves state-of-the-art performance and generalisability across both immunofluorescence and immunohistochemistry modalities, outperforming existing models in accuracy and morphological fidelity. Applied to tissue microarrays (TMAs) containing 911 breast cancer sample cores from 127 patients, CenSegNet enables the first large-scale, spatially resolved quantification of numerical and structural CA at single-cell resolution. These CA subtypes are mechanistically uncoupled, exhibiting distinct spatial distributions, age-dependent dynamics, and associations with histological tumour grade, hormone receptor status, genomic alterations, and nodal involvement. Structural CA levels are additionally associated with overall survival, supporting the clinical relevance of spatially resolved CA patterns. Discordant CA profiles at tumour margins are linked to local aggressiveness and stromal remodelling. To support broad adoption and reproducibility, CenSegNet is released as an open-source Python library. Together, our findings establish CenSegNet as a scalable, generalisable platform for spatially resolved centrosome phenotyping in intact tissues, enabling systematic dissection of the biology of this organelle and its dysregulation in cancer and other epithelial diseases.

cell biology↗

bioRxiv2025

Output-Contingent Working Memory and Decision-Making in Economic Choices

In daily life, economic decisions often unfold sequentially. The brain is thought to compute the subjective value of each option, and comparisons can occur in different reference frames, for example, based on the commodity or presentation order. While primate prefrontal recordings have identified various reference frames for economic choice, it remains unclear how distinct neural mechanisms support them even in similar tasks. To address this, we trained recurrent neural networks (RNNs) on two sequential economic decision-making tasks differing only in output contingencies. Analysis of RNN activity, combined with latent connectivity inference, revealed distinct regimes: commodity-based choices with attractor dynamics and order-based choices with rotational dynamics. Moreover, value and choice representations in the order-based tasks aligned with neural data from a novel experiment where reference frames were not explicitly constrained. Our results suggest that different reference frames emerge depending on task demands and engage distinct working memory and decision-making mechanisms.

neuroscience↗