Biology subjects

Lee, J. C.

Publications and source records attributed to Lee, J. C..

At least 19 recordsLinked to original sources

bioRxiv2026

Integrin α3β1 is required for alveolar-capillary barrier formation through regulation of epithelial differentiation

Laminin-binding integrins regulate critical morphogenic processes, but their specific roles in lung development are unknown. In this study, we combined an in vivo model of epithelial 3 subunit deletion in the murine lung with a multiomics approach to investigate the role of the epithelial 3{beta}1 integrin during murine lung development. We demonstrate that 3{beta}1 integrin is dispensable for airway branching morphogenesis due to delayed epithelial expression. Instead, in vivo deletion of 3{beta}1 integrin impaired alveolar epithelial cell differentiation and disrupted alveolar-capillary barrier formation, functionally limiting gas exchange. A discontinuous alveolar BM contained abnormal collagen IV and laminin networks and widened the gap between epithelial and endothelial cells in the alveolar-capillary barrier niche. Mechanistically, mice deficient in epithelial 3{beta}1 integrin possessed an intracellular trafficking and secretion defect for BM components. Thus, integrin 3{beta}1 orchestrates the temporal maturation of alveolar epithelial cells required for organization of the alveolar-capillary barrier.

developmental biology↗

bioRxiv2026

Cascaded Nano-ring Dialyzer for Continuous Regenerative Peritoneal Dialysis

End-stage kidney disease (ESKD) requires lifelong kidney replacement therapy, yet conventional hemodialysis and peritoneal dialysis remain limited by intermittent treatment, restricted mobility, and repeated dialysate exchange. Here, we developed a continuous regenerative peritoneal dialysis platform based on a nano-ring-assisted nanoelectrokinetic dialyzer for portable artificial kidney applications. We first identified key geometric and electrokinetic parameters governing the removal performance of nano-ring meshes, including mesh dimension, nano-ring coating thickness, the number of cascaded nano-rings, and the relative orientation between fluid flow and the applied electric field. We then developed a single nano-ring dialyzer operating at 1.33 mL/min and scaled the treatment capacity to approximately 10 mL min/min through parallel integration of multiple modules. In a canine model, the closed-loop system achieved approximately 10 % reduction in circulating uremic toxin levels during continuous treatment. We further improved the biocompatibility of the regenerated dialysate by integrating plate-type electrodes, activated carbon, bicarbonate buffering, and UV-C treatment. In an unanesthetized canine model, the improved system sustained continuous toxin removal for 4 h while major hepatic and inflammatory markers remained within recoverable ranges. These results demonstrate that cascaded nano-ring enables continuous dialysate regeneration with scalable throughput, reduced dependence on fresh dialysate, and in vivo control of uremic toxins, providing a technological foundation for portable or wearable regenerative peritoneal dialysis systems.

bioengineering↗

bioRxiv2026

Neuronal p38α knockout protects against neurological consequences following repetitive mild traumatic brain injury

Mild traumatic brain injuries (mTBI) can substantially impact quality of life, and repetitive mTBIs (rmTBI) can amplify injury effects compared to a single injury. However, effective clinical treatments remain elusive, largely due to an incomplete understanding of the underlying injury mechanisms. Neuroinflammation has emerged as a key contributor to worse functional outcomes after mTBI/rmTBI. While microglia are traditionally viewed as primary mediators of post-injury inflammation, accumulating evidence suggests neurons play an immunomodulatory role in initiating the rmTBI inflammatory cascade through activation of intracellular proinflammatory pathways like p38 MAPK and secretion of cytokines that, in turn, stimulate microglial activation. Here, we tested whether inducible neuronal p38 knockout protects against functional, immune, and cerebrovascular consequences of a weight-drop closed head injury model of rmTBI. A battery of functional assays was conducted 4 weeks post-injury, and tissues were collected at both 4 hours and 4 weeks following final CHI. In males, neuronal p38 knockout protected against injury-induced depressive-like behavior, hyperactivity, synaptic loss, microglial reactivity, cytokine upregulation, and reduction in cerebral blood flow. In females, neuronal p38 knockout protected against risk-taking behavior and partially protected against cytokine upregulation but had limited effect on microglial reactivity and cerebral blood flow. Together, these findings identify neuronal p38 as a sex-dependent driver of rmTBI-associated neurological consequences, and they support neuronal p38-immune signaling as a mechanistically relevant therapeutic target for future studies.

neuroscience↗

bioRxiv2026

Ionic Regulation of Mechanosurveillance and Metastasis via the MRTFA/KCNMB1 Axis

Cellular stiffness profoundly impacts cancer metastasis at multiple levels, but mechanisms that regulate cancer cells stiffness remain poorly understood. Here, we identified potassium efflux and KCNMB1, an auxiliary subunit of the large conductance potassium efflux (BK) channels, as regulators of cellular stiffness downstream of myocardin related transcription factor A (MRTFA). In primary pericytes, KCNMB1 knockdown increased cellular stiffness, which is consistent with the role of potassium efflux in promoting relaxation during excitation-contraction coupling. In a striking contrast, however, KCNMB1 knockdown decreased cellular stiffness in cancer cells. Softer cancer cells were resistant to NK cell mediated cytotoxicity and the low KCNMB1 expression was associated with worse survival in breast cancer patients. Importantly, pharmacological activation of BK channels reduced metastatic burden in mice and improved lysis of cancer cells by cytotoxic T-lymphocytes. These results highlight the unique ionic regulation of stiffness in cancer cells and point to BK channel agonism as a new therapeutic approach in cancer.

cancer biology↗

bioRxiv2025

Rolling out plaque-2-sequence: a single plaque sequencing approach enabling rapid, low-cost sequencing of phages directly from plaques

Rapid, accurate, and scalable sequencing of bacteriophage genomes is critical to advance phage therapy, build phage biobanks and understand phage genomic diversity. Current methods are based on sequencing and assembling complete bacteriophage genomes using short- or long-read technologies. However, current protocols require large DNA input and are cost prohibitive which limits their application to phage collections that typically are large and have low-biomass. In order to address this we have developed plaque-2-sequence, a robust and cost-effective workflow for high-throughput phage genome sequencing that will transform the speed and cost of attaining phage genomes. Plaque-2-sequence combines low-input transposase-based library preparation, amplification, nanopore sequencing and optimised assembly steps tailored to phage genomes. We applied the method to phages isolated on seven genetically diverse bacterial hosts; Escherichia, Pseudomonas, Synechococcus, Enterococcus, Klebsiella , Serratia and Enterobacter. High quality genome assemblies were validated using CheckV and benchmarking against previously sequenced phage isolates. Compared to standard Illumina sequencing, plaque-2-sequence offers [~]10-fold savings in sequencing price for individual labs. Furthermore, it substantially decreases the time required to produce a phage genome, once a plaque is obtained. Offering the ability to routinely obtain hundreds of phage genome sequences a week, with minimal hands-on time. Plaque-2-sequence enables systematic genomic characterisation of phage isolates, facilitating taxonomic classification, for the development of large scale phage biobanks. Impact StatementHere we have optimised a method for high-throughput sequencing of bacteriophage genomes from single plaques (plaque-2-sequence). We present a robust, high-throughput and cost-effective workflow. Plaque-2-sequence combines low-input transposase-based library preparation, amplification, nanopore sequencing and optimised assembly steps tailored to phage genomes. We demonstrate the scalability of this approach by sequencing over 100 phages from multiple bacterial hosts. This marks a step-change for the field, allowing phage genome sequencing to keep pace with phage isolation rates, and transforming how rapidly we can explore and understand phage genomic diversity.

microbiology↗

bioRxiv2025

Encoded cell-material interactions to reroute cytokine signaling for regenerative medicine

Regenerative engineering harnesses materials science and stem cell biology to develop strategies to repair damaged and diseased tissue. Despite advances in designer materials, few techniques effectively provide auto-regulated feedback mechanisms that govern how cells sense and respond to discrete microenvironmental changes. Here, we demonstrate that the artificial, juxtacrine-like receptor synthetic Notch (synNotch) can be activated by endogenous multimeric cytokines in solution, without immobilizing materials, revealing a previously unreported activation modality and yielding up to 24-fold dynamic range. To broaden synNotch sensing to monomeric cytokines, we developed nMATRIX, a co-engineered material-cell platform that detects endogenous, soluble ligands and routes them to programmed gene circuits with spatially confined effects. nMATRIX can be tuned to recognize the interleukins IL-1{beta} and IL-6 using synNotch receptors plus cognate biomaterials, yielding up to 68-fold dynamic range and converting these inflammatory inputs into orthogonal outputs that reprogram nearby cell phenotypes. nMATRIX functions across multiple cell types and can incorporate the synNotch-related SNIPR synthetic receptor platform. nMATRIX repurposed inflammatory signals and converted them into anti-inflammatory cues to polarize macrophages (increased CD163, CD206; decreased CD86). Thus, nMATRIX couples native soluble cues to customized cellular responses with tunable sensitivity, offering a flexible materials-based approach for self-regulating regenerative therapies.

bioengineering↗

bioRxiv2025

Aβ-42 sidechain deamidation at Q15 and N27 modulate protein aggregation and microglial responses via altered cytokine production and CD68 expression

The progressive aggregation of amyloid beta (A{beta}) monomers into oligomers is a critical factor in Alzheimers disease (AD) pathogenesis. Although mutated forms of A{beta} have been shown to display altered aggregation dynamics, the specific effects of deamidated A{beta} on microglial function remain understudied. Our research group previously found that the deamidated variant A{beta}-42-N27D modified A{beta} aggregation, reduced neurotoxicity, and reduced microglial reactivity, but the impact of A{beta}-42 side chain deamidation in general on such parameters remained unclear. Here, we expanded on our prior work by investigating how two site-specific A{beta}-42 mutations (Q15E & N27D), where neutral amide side chains are replaced with negatively charged carboxylic acids, affect aggregation and microglial immune response using a mouse microglial cell line. Size exclusion chromatography revealed that A{beta}-42-Q15E and A{beta}-42-N27D exhibit distinct aggregation profiles compared to A{beta}-42 wild type (WT). Multiplexed analysis of 8 cytokines secreted into the culture medium revealed that A{beta}-42-Q15E and A{beta}-42-N27D decrease the expression of inflammatory cytokines such as IL-6, IP-10, and MIP-1 relative to A{beta}-42-WT. Immunocytochemistry revealed that A{beta}-42-Q15E and A{beta}-42-N27D decrease CD68 expression relative to A{beta}-42-WT. These findings demonstrate that deamidation significantly alters A{beta}-42 aggregation and microglial activation, suggesting structural modifications to A{beta}-42 modulate inflammatory signaling in AD. This work provides a foundation for future studies on A{beta}-42 post-translational modifications as potential therapeutic targets in AD.S

neuroscience↗

bioRxiv2025

A Simple Algorithm to Suppress Diagonal Peaks in High-Resolution Homonuclear Chemical Shift Correlation NMR Spectra

Previous experimental strategies aimed at completely suppressing diagonal peaks in NMR homonuclear correlation spectra often resulted in reduced sensitivity for cross peaks. In this work, we report a spectral shearing approach that transforms diagonal peaks along the diagonal axis of a homonuclear correlation spectrum into a zero-frequency line in the indirect dimension. This allows for effective extraction and substantial suppression of diagonal peaks using a recently proposed data processing algorithm based on quadrature-detected spin-echo diagonal peak suppression. Since the shearing process only rearranges the positions of cross peaks without affecting their intensities, the sensitivity of cross peaks is fully preserved while diagonal peaks are significantly reduced. The effectiveness of this method is demonstrated using uniformly 13C&15N labeled -synuclein amyloid fibril and aquaporin Z membrane protein samples.

biophysics↗

bioRxiv2025

Endothelial Nucleoporin93 (Nup93) Maintains Vascular Function via Sun1-Dependent Regulation of RhoA-eNOS Signaling

As the innermost lining of blood vessels, endothelial cells (ECs) regulate blood flow, maintain vascular tone, and limit inflammation for vessel health. EC-derived nitric oxide (NO), synthesized by endothelial nitric oxide synthase (eNOS), is a vasodilator essential for improving blood flow and vascular homeostasis. The RhoA/ROCK pathway regulates eNOS levels, where overactivation decreases eNOS expression and downstream NO production. As such, RhoA/ROCK hyperactivity and increased pMLC have been identified as major contributors to age-associated vasoconstriction and hypertension. Intriguingly, recent studies identify Sun1, a key component of the linker of nucleoskeleton and cytoskeleton (LINC) complex, as a major regulator of RhoA/ROCK activity. Moreover, endothelial aging deteriorates nuclear pore complexes (NPCs) (i.e. nucleoporin [Nup93]) and impairs nucleocytoplasmic transport, thereby insinuating a role for nuclear envelope components in vessel homeostasis. Here, we show that targeted loss of endothelial Nup93 in adult mice significantly reduces eNOS expression and NO bioavailability for consequent defects in NO-dependent vasodilatory responses. In vitro knockdown of Nup93 in primary human ECs also decreases both eNOS expression and NO production. Mechanistically, we find that loss of Nup93 significantly reduces endothelial Sun1 levels for a concomitant increase in RhoA activity. Indeed, restoring Sun1 protein levels in Nup93-deficient ECs mitigates RhoA activity to rescue both eNOS expression and NO production. Taken together, we demonstrate endothelial Nup93, through Sun1 stabilization, as a novel regulator of eNOS-NO signaling and vessel reactivity, contributing to the growing importance of nuclear membrane components in EC and vascular biology.

cell biology↗

bioRxiv2025

Resorbable Poly-(D,L)-Lactide Anchorage of Nanoparticulate Mineralized Collagen Materials Maximizes In Vivo Skull Regeneration

BackgroundA clinical demand exists for bone biomaterials that mirror tissue-specific extracellular matrix (ECM) properties and regulate progenitor cell fate. Nanoparticulate mineralized collagen glycosaminoglycan (MC-GAG) scaffolds have demonstrated to promote skull regeneration in vivo without addition of growth factors or exogenous progenitor cells, offering a materials-only solution for cranial defect reconstructions. Further enhancement of the safety and regenerative potential of MC-GAG is however necessary for clinical translation. Here, we investigated the regenerative effect of MC-GAG scaffold fixation with a resorbable poly(D,L-lactide) (PDLLA) implant for cerebral protection. MethodsFourteen-millimeter cranial defects were created in New Zealand white rabbits, divided into four groups: 1) defect only, 2) defect with PDLLA, 3) MC-GAG, and 4) MC-GAG with PDLLA. Initial bone healing assessment was conducted at 3 and 9 months using microcomputed tomography (microCT), histology, reference point indentation, and scanning electron microscopy. Long-term effects were evaluated through in vivo microCT imaging at 3, 6, and 9 months, with biomechanical testing of explanted skulls at 9 months. ResultsAt 3 months, MC-GAG significantly enhanced mineralization compared to empty and PDLLA-treated defects, with even greater mineralization observed for MC-GAG-PDLLA. Histologically, MC-GAG demonstrated trabecular mineralization, while MC-GAG-PDLLA had a structural organization resembling native bone. Biomechanical assessment showed enhanced toughness and stiffness for both MC-GAG and MC-GAG-PDLLA. At 6 months, MC-GAG-PDLLA displayed the highest bone mass, and at 9 months, both MC-GAG-containing scaffolds demonstrated superior bone regeneration compared to controls. By 9 months, PDLLA implants were completely resorbed and MC-GAG-PDLLA exhibited mechanical properties surpassing those of all other groups. ConclusionsFixation of MC-GAG scaffolds with PDLLA implants improved mineralization and bone regeneration compared to either material alone for cranial defect reconstruction. Clinical Relevance StatementCranioplasties are essential for cerebral protection and neurological restoration, but current materials have limitations, necessitating alternative bone biomaterials for improved outcomes.

bioengineering↗

bioRxiv2024

Comparative single-cell lineage bias in human and murine hematopoietic stem cells

The commitment of hematopoietic stem cells (HSC) to myeloid, erythroid, and lymphoid lineages is influenced by microenvironmental cues, and governed by cell-intrinsic and epigenetic characteristics that are unique to the HSC population. To investigate the nature of lineage commitment bias in human HSC, mitochondrial single cell (sc) ATAC-Sequencing (mt-scATAC-Seq) was used to identify somatic mutations in mitochondrial DNA to act as natural genetic barcodes for tracking the ex vivo differentiation potential of HSC to mature cells. Clonal lineages of human CD34+ cells and their mature progeny were normally distributed across the hematopoietic lineage tree without evidence of significant skewing. To investigate commitment bias in vivo, mice were transplanted with limited numbers of long-term HSC (LT-HSC). Variation in the ratio of myeloid and lymphoid cells between donors, although suggestive of a skewed output, was not altered by increasing numbers of LT-HSC. These data suggest that the variation in myeloid and lymphoid engraftment is a stochastic process influenced by the irradiated recipient niche and not a cell-intrinsic lineage bias of LT-HSC.

genomics↗

bioRxiv2024

Prediction error determines how memories are organized in the brain: a study of Pavlovian fear extinction in rats

How is new information organized in memory? According to latent state theories, this is determined by the level of surprise, or prediction error, generated by the new information: small prediction error leads to updating of existing memory, large prediction error leads to encoding of a new memory. We tested this idea using a protocol in which rats were first conditioned to fear a stimulus paired with shock. The stimulus was then gradually extinguished by progressively reducing the shock intensity until the stimulus was presented alone. Consistent with latent state theories, this gradual extinction protocol (small prediction errors) was better than standard extinction (large prediction errors) in producing long-term suppression of fear responses; and the benefit of gradual extinction was due to updating of the conditioning memory with information about extinction. Thus, prediction error determines how new information is organized in memory, and latent state theories adequately describe the ways in which this occurs.

animal behavior and cognition↗

bioRxiv2023

Endothelial stiffening induced by CD36-mediated lipid uptake leads to endothelial barrier disruption and contributes to atherosclerotic lesions

BackgroundTo determine the impact of endothelial stiffening induced by CD36-mediated lipid uptake in the disruption of aortic endothelial barrier and development of atherosclerosis in mouse models of obesity and hypercholesterolemia. Approach and ResultsEndothelial-specific inducible downregulation of CD36 results in abrogating the stiffening of aortic endothelium induced by a short-term (6-8 weeks) high-fat Western diet in intact freshly isolated mouse aortas of Cdh5.CreERT2CD36fl/fl mice, as assessed by atomic force microscopy. No effect was observed on the stiffness of aortic vascular wall assessed in the same groups of mice by echocardiography. Prevention of WD-induced endothelial stiffening by the downregulation of endothelial CD36 was associated with a protective effect against endothelial barrier disruption, assessed by morphological analysis of VE-cadherin junctions and penetration of Evans blue dye into the aortic wall. These protective effects were independent of the changes in the serum lipid profiles. Furthermore, endothelial specific downregulation of CD36 in hypercholesterolemic Cdh5.CreERT2CD36fl/flLDLR-/- mice also led to significant decrease in endothelial stiffening after 4-5 months of high fat diet and a significant decrease in the areas of atherosclerotic lesion. In both models, significant endothelial stiffening was observed specifically in male mice, while female mice exhibited less endothelial stiffening and less severe atherosclerosic phenotype, consistent with endothelial stiffening playing an important role in aortic vascular disease in a sex-dependent way. Mechanistically, we show in vitro that CD36-mdiated uptake of long chain saturated fatty acids, particularly palmitic acid, induces endothelial stiffening via activation of RhoA/ROCK pathway. Moreover, palmitic acid-induced endothelial stiffening critically depends on the expression of a RhoA inhibitory protein, Rho-GDI-1. ConclusionsWe conclude that stiffening of the aortic endothelium by CD36-mediated uptake of fatty acids contributes significantly to WD-induced vascular dysfunction and atherosclerosis. We further propose that fatty acids may activate RhoA by inducing its dissociation from Rho-GDI-1.

cell biology↗

bioRxiv2023

Highly conserved, positively charged tandem repeats mediate multimerization of ice nucleation proteins

In nature, frost can form at a few degrees below 0 {degrees}C. However, this process requires the assembly of tens of thousands of ice-like water molecules that align together to initiate freezing at these relatively high temperatures. Water ordering on this scale is mediated by the ice nucleation proteins of common environmental bacteria like Pseudomonas syringae and P. borealis. However, individually, these 100-kDa proteins are too small to organize enough water molecules for frost formation, and it is not known how giant, megadalton-sized multimers, which are crucial for ice nucleation at high sub-zero temperatures, form. The ability of multimers to self-assemble was suggested when the transfer of an ice nucleation protein gene into Escherichia coli led to efficient ice nucleation. Here we demonstrate that a positively-charged sub-domain at the C-terminal end of the central beta-solenoid of the ice nucleation protein is crucial for multimerization. Truncation, relocation, or change of the charge of this subdomain caused a catastrophic loss of ice nucleation ability. Cryo-electron tomography of the recombinant E. coli showed that the ice nucleation protein multimers form fibres that are [~] 5 nm across and up to 200 nm long. A model of these fibres as an overlapping series of antiparallel dimers can account for all their known properties and suggests a route to making cell-free ice nucleators for biotechnological applications.

biochemistry↗

bioRxiv2023

Beclin1 is essential for intestinal homeostasis.

BECLIN1 is a component of Class III phosphatidylinositol 3-kinase complexes that orchestrates autophagy initiation and endocytic trafficking. Here we show intestinal epithelium-specific BECLIN1 deletion in adult mice led to rapid fatal enteritis with compromised gut barrier integrity, highlighting its intrinsic critical role in gut maintenance. BECLIN1-deficient intestinal epithelial cells exhibited extensive apoptosis, impaired autophagy, and stressed endoplasmic reticulum and mitochondria. Remaining absorptive enterocytes and secretory cells displayed morphological abnormalities. Deletion of the autophagy regulator, ATG7, failed to elicit similar effects, suggesting novel autophagy-independent functions of BECLIN1 distinct from ATG7. Indeed, organoids derived from BECLIN1 KO mice showed E-cadherin mislocalisation providing a mechanism linking endocytic trafficking mediated by Beclin1 and loss of intestinal barrier integrity. Our findings establish an indispensable role of BECLIN1 in maintaining mammalian intestinal homeostasis and uncover its involvement in endocytic trafficking in this process. Hence, this study has significant implications for our understanding of intestinal pathophysiology.

cell biology↗

bioRxiv2023

A disease-associated gene desert orchestrates macrophage inflammatory responses via ETS2

Increasing global rates of autoimmune and inflammatory disease present a burgeoning threat to human health1. This is compounded by the limited efficacy of available treatments1 and high failure rates during drug development2 - underscoring an urgent need to better understand disease mechanisms. Here we show how genetics could address this challenge. By investigating an intergenic haplotype on chr21q22, independently linked to inflammatory bowel disease (IBD), ankylosing spondylitis, primary sclerosing cholangitis and Takayasus arteritis3-6, we discover that the causal gene, ETS2, is a master regulator of inflammatory responses in human macrophages and delineate how the risk haplotype increases ETS2 expression. Genes regulated by ETS2 were prominently expressed in affected tissues from chr21q22-associated diseases and more enriched for IBD GWAS hits than almost all previously described pathways. Overexpressing ETS2 in resting macrophages produced an activated effector state that phenocopied intestinal macrophages from IBD7, with upregulation of multiple drug targets including TNF and IL-23. Using a database of cellular signatures8, we identify drugs that could modulate this pathway and validate the potent anti-inflammatory activity of one class of small molecules in vitro and ex vivo. Together, this highlights the potential for common genetic associations to improve both the understanding and treatment of human disease.

immunology↗

bioRxiv2023

Rare SH2B3 coding variants identified in lupus patients impair B cell tolerance and predispose to autoimmunity

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease, with a clear genetic component. While most SLE patients carry rare gene variants in lupus risk genes, little is known about their contribution to disease pathogenesis. Amongst them, SH2B3 - a negative regulator of cytokine and growth factor receptor signaling - harbors rare coding variants in over 5% of SLE patients. Here we show that unlike the variant found exclusively in healthy controls, most SH2B3 rare variants found in lupus patients are predominantly hypomorphic alleles. Generation of two mouse lines carrying variants orthologous to those found in patients revealed SH2B3 is important to limit the numbers of immature and transitional B cells. Furthermore, hypomorphic SH2B3 was shown to impair negative selection of immature/transitional self-reactive B cells and accelerate autoimmunity in sensitized mice, at least in part due to increased IL-4R signaling and BAFF-R expression. This work identifies a previously unappreciated role for SH2B3 in human B cell tolerance and lupus risk. SummaryZhang et al. reveal a role for hypomorphic SH2B3 in lupus risk. The study shows rare and damaging variants identified in lupus patients enable breach of B cell immune tolerance checkpoints and suggests involvement for dysregulated IL-4R signaling and BAFF-R expression.

immunology↗

bioRxiv2023

Staphylococcus aureus delta toxin modulates both extracellular membrane vesicle biogenesis and amyloid formation

Staphylococcus aureus secretes phenol-soluble modulins (PSMs), a family of small, amphipathic, secreted peptides with multiple biologic activities. Community-acquired S. aureus strains produce high levels of PSMs in planktonic cultures, and PSM alpha peptides have been shown to augment the release of extracellular membrane vesicles (MVs). We observed that amyloids, aggregates of proteins characterized by a fibrillar morphology and stained with specific dyes, co-purified with MVs harvested from cell-free culture supernatants of community-acquired S. aureus strains. {delta}-toxin was a major component of amyloid fibrils that co-purified with strain LAC MVs, and {delta}-toxin promoted the production of MVs and amyloid fibrils in a dose-dependent manner. To determine whether MVs and amyloid fibrils were generated under in vivo conditions, we inoculated mice with S. aureus harvested from planktonic cultures. Bacterial MVs could be isolated and purified from lavage fluids recovered from infected animals. Although {delta}-toxin was the most abundant PSM in lavage fluids, amyloid fibrils could not be detected in these samples. Our findings expand our understanding of amyloid fibril formation in S. aureus cultures, reveal important roles of {delta}-toxin in amyloid fibril formation and MV biogenesis, and demonstrate that MVs are generated in vivo in a staphylococcal infection model. ImportanceExtracellular membrane vesicles (MVs) produced by Staphylococcus aureus in planktonic cultures encapsulate a diverse cargo of bacterial proteins, nucleic acids, and glycopolymers that are protected from destruction by external factors. {delta}-toxin, a member of the phenol soluble modulin family, was shown to be critical for MV biogenesis. Amyloid fibrils co-purified with MVs generated by virulent, community-acquired S. aureus strains, and fibril formation was dependent on expression of the S. aureus {delta}-toxin gene (hld). Mass spectrometry data confirmed that the amyloid fibrils were comprised of {delta}-toxin. Although S. aureus MVs were produced in vivo in a localized murine infection model, amyloid fibrils were not observed in the in vivo setting. Our findings provide critical insights into staphylococcal factors involved in MV biogenesis and amyloid formation.

microbiology↗