Biology subjects

Sheppard, D.

Publications and source records attributed to Sheppard, D..

At least 19 recordsLinked to original sources

bioRxiv2026

Inhibition of integrin αvβ8-mediated TGFβ activation and active-TGFβ blockade promote anti-tumor immunity through distinct biological mechanisms

Transforming Growth Factor {beta} (TGF{beta}) is a potent immunosuppressor and a primary driver of resistance to cancer immunotherapy. While preclinical models have long suggested that TGF{beta} inhibition could synergize with immune checkpoint inhibitors, these effects have proven difficult to replicate in clinical settings. The highly regulated TGF{beta} pathway can be inhibited through various mechanisms, including neutralizing activated ligands or inhibiting upstream activators, such as integrins. Recent structural data demonstrated that integrin v{beta}8 can enable TGF{beta}1/3 signaling without releasing the active cytokines from their Latency-Associated Peptides, suggesting that ligand-blocking antibodies may have limited access to their epitopes. Here, we show that integrin v{beta}8 blockade, while achieving anti-tumor responses similar to those of anti-TGF{beta} antibodies, does so through a distinct mechanism of action. Anti-v{beta}8 is 3 orders of magnitude more potent at inhibiting v{beta}8-mediated TGF{beta} activity than a commonly used antibody against the mature form of the cytokine. Whereas TGF{beta} ligand inhibition has little effect on TGF{beta} signaling in tumor-draining lymph nodes (tdLN) and requires IFN{gamma} for its anti-tumor effects, v{beta}8 blockade strongly inhibits TGF{beta} signaling in tdLN and, in combination with PD-L1 blockade, drives tumor control through an IFN{gamma} -independent mechanism that strictly requires T cell egress from tdLN. Combined v{beta}8 and anti-PD-L1 blockade enhances antigen presentation in dendritic cells (DCs) and, unlike TGF{beta} ligand blockade, improves the efficiency of DC-induced T cell activation in response to cross-presented antigen. These findings suggest that v{beta}8 blockade can disable an immunologically critical source of TGF{beta} signaling that is not addressed by antibodies targeting TGF{beta} ligands, suggesting a promising new approach to TGF{beta} pathway modulation. One Sentence SummaryUnlike ligand-neutralizing antibodies, v{beta}8 blockade suppresses TGF{beta} in tdLN and boosts DC-T cell activation, a differentiated immunotherapy strategy.

immunology↗

bioRxiv2026

Lung adventitial fibroblasts support type 2 Tregs to shape the response to influenza infection

Viral pneumonias are lung infections that lead to both short- and long-term complications, including acute respiratory distress syndrome (ARDS) and pulmonary fibrosis. Lung stromal-immune interactions balance pathogen clearance with excessive immune-mediated injury, and healthy lung repair with necessary scarring. Here, we define the lung spatiotemporal stromal-immune response to Influenza A virus (IAV) infection, focusing on the underappreciated role of fibroblasts and their dynamic states. We used 3D quantitative microscopy and scRNAseq to identify IAV-driven fibroblast states, including inflammatory fibroblasts, profibrotic fibroblasts, and adventitial fibroblasts (AFs). Unexpectedly, loss of fibroblast TGF{beta} signaling led to early enhancement of immuno-modulatory AFs, driving activation of tissue-resident type 2 regulatory T cells (T2-Tregs) and ultimately improving lung functional outcomes. In vitro co-culture systems additionally revealed that AFs act as a niche to support T2-Tregs. Our data suggest an intimate fibroblast-immune crosstalk is required to temporally and spatially balance lung tissue inflammation and repair.

immunology↗

bioRxiv2026

Inhibition of the EBF1-ITGB8 Axis in Bone Marrow Niche Ameliorates Hallmarks of Myelofibrosis

Fibrotic remodeling of the bone marrow (BM) niche is a characteristic feature of myelofibrosis (MF) that contributes to disease progression. In MF, mesenchymal stromal cells (MSCs) produce excessive amounts of inflammatory cytokines and extracellular matrix, leading to BM fibrosis, impaired blood production, extramedullary hematopoiesis, and progressive BM failure. While the genetic events that initiate MF in hematopoietic cells are well defined, our understanding of the mechanisms responsible for BM fibrosis remains incomplete. Here, we show that transcription factor EBF1 is a key regulator of the fibrotic gene program in mouse and human MSCs. EBF1 is upregulated in pre-fibrotic MSCs, while mice with MSC-specific deletion of Ebf1 exhibit reduced BM fibrosis, decreased expansion of myeloid cells and splenomegaly when transplanted with hematopoietic progenitors harboring the MF driver mutation MPLW515L. Moreover, we identify ITGB8 as an EBF1-regulated gene with therapeutic potential. MF mice treated with ITGB8-neutralizing antibodies or with MSC-specific Itgb8 deletion show reduced disease burden, as indicated by decreased marrow fibrosis, significantly reduced frequencies of MPL mutant cells, and reduced inflammation in the BM. Our data indicate that targeting the EBF1-ITGB8 axis in the MF MSCs may have therapeutic benefits.

cell biology↗

bioRxiv2025

Engineering lung-sensing T cells using synthetic receptors targeting RAGE

Our goal was to leverage synthetic biology approaches to engineer lung-sensing T cells that trigger synthetic transcriptional programs only when in the lung. First, we identified a lung-specific cell surface protein, receptor for advanced glycation endproducts (RAGE), expressed at high levels exclusively in the lung. Then, we engineered chimeric antigen receptors (CAR) and synthetic notch receptors (SynNotch) to bind this protein. We showed that anti-RAGE CAR-T cells traffic to and proliferate in the lung exclusively. Anti-RAGE SynNotch receptors activate transcription of a fluorescent reporter only when co-cultured with RAGE+ cell lines or primary lung cells. Finally, we tested an anti-RAGE SynNotch to anti-CD19 CAR circuit in vivo in mice implanted with lung and flank tumors and found that this approach cleared CD19-expressing lung tumors without affecting CD19-expressing flank tumors. Thus, we demonstrate that RAGE is a lung-specific target and that T cells expressing anti-RAGE receptors can sense and activate lung-specific therapeutic transcriptional programs. This approach could be extended to allow cell-based therapies that target and deliver genetically encoded payloads to treat lung diseases while avoiding systemic toxicity.

synthetic biology↗

bioRxiv2025

Clonal Expansion of Alveolar Fibroblast Progeny Drives Pulmonary Fibrosis

Pulmonary fibrosis has been called a fibroproliferative disease but the functional importance of proliferating fibroblasts to pulmonary fibrosis has not been systematically examined. In response to alveolar injury, resting alveolar fibroblasts differentiate into fibrotic fibroblasts that express high levels of collagens. However, what role, if any, proliferation plays in the accumulation of fibrotic fibroblasts remains unclear. Through EdU incorporation, genetic lineage tracing, and single cell RNA sequencing, we resolve the proliferation dynamics of lung fibroblasts during post-injury fibrogenesis. Our data show substantial DNA replication in progeny of alveolar fibroblasts in two models of pulmonary fibrosis. By genetically labeling individual cells, we observe clonal expansion of alveolar fibroblast descendants principally in regions of fibrotic remodeling. The transcriptome of proliferating fibroblasts closely resembles that of fibrotic fibroblasts, suggesting that fibroblasts can first differentiate into fibrotic fibroblasts and then proliferate. Genetic ablation of proliferating fibroblasts and selective inhibition of cytokinesis in alveolar fibroblast descendants significantly mitigates pulmonary fibrosis and rescues lung function. Furthermore, fibroblasts in precision-cut lung slices from human fibrotic lungs exhibit higher proliferation rates than those in non-diseased lungs. This work establishes fibroblast proliferation as a critical driver of pulmonary fibrosis and suggests that specifically targeting fibroblast proliferation could be a new therapeutic strategy for fibrotic diseases.

cell biology↗

bioRxiv2025

β-III tubulin identifies anti-fibrotic state of pericytes in pulmonary fibrosis

Pericytes have been implicated in pulmonary fibrosis, yet their activated cellular states and functional roles remain largely unclear. Here, we identified {beta}-III tubulin (Tuj1) as a distinctive marker for fibrosis-associated lung pericytes. Most pericytes in fibrotic regions are Tuj1-positive and interact uniquely with multiple endothelial cells, localizing near collagen-producing fibroblasts and pro-fibrotic SPP1+/arginase+ macrophages. Tuj1 expression is predominantly induced in pericytes during the fibrotic phase, and Tuj1 gene (Tubb3) knockout in mice exacerbates lung fibrosis, accompanied by an increase in the neighboring pro-fibrotic fibroblasts and macrophages, suggesting an anti-fibrotic role for Tuj1-expressing pericytes. Mechanistically, the anti-fibrotic chemokine CXCL10 is upregulated in Tuj1-expressing pericytes, whereas this upregulation is not observed in Tubb3 knockout. Moreover, CXCL10 inhibits the pro-fibrotic differentiation of macrophages induced by lung fibroblasts in culture, implying that CXCL10 may mediate the anti-fibrotic effects of Tuj1-expressing pericytes. These findings underscore the role of lung pericytes in negatively regulating fibrotic process and their potential as therapeutic targets for pulmonary fibrosis patients. SummaryIn response to fibrotic stimuli, lung pericytes upregulate {beta}-III tubulin (Tuj1) expression, adopting an anti-fibrotic phenotype. This phenotype acts as a negative immune regulator of pro-fibrotic macrophage differentiation by releasing CXCL10, thereby counteracting the progression of pulmonary fibrosis.

pathology↗

bioRxiv2025

Artificial intelligence-augmented drug discovery identifies gefitinib as a potential treatment for ALS

Amyotrophic lateral sclerosis (ALS) is characterised by motor neuron (MN) death; however, astrocytes play a key role in disease pathogenesis. Developments in the field of artificial intelligence (AI) have the potential to impact drug discovery in multiple ways, including the rapid identification of drug repurposing candidates. A combination of natural language processing and deep learning algorithms was used to generate a knowledge graph based on scientific literature, omics and chemical databases, and other public sources with the aim to identify drug repurposing candidates for ALS. The aim of the study was to determine the effect of a cancer compound identified by AI, gefitinib, on MN survival, and to decipher its mode of action inin vitroandin vivomodels of ALS. We used co-cultures of healthy motor neurons with ALS patient-derived astrocytes (iAstrocytes), obtained through a semi-direct conversion protocol, to assess the neuroprotective properties of gefitinib. Compound treatment led to a significant rescue of MNs cultured with ALS iAstrocytes and a significant reduction in the levels of cleaved TDP-43 fragments in ALS iAstrocytes. Our data suggest that gefitinib-mediated activation of autophagy decreased the 35 kDa fragments of TDP-43. In a proof-of-conceptin vivostudy in SOD1G93Amice, gefitinib treatment significantly delayed the onset of neurological symptoms, thus showing the potential of AI-augmented drug discovery for neurodegenerative disorders.Significance StatementThis study presents an AI-augmented method of identifying potential repurposing candidates for disease with an unprecedented speed. The AI’s results were validatedin vitrousing iAstrocytes differentiated from induced neuronal progenitor cells (iNPCs), which are pathophysiologically relevant models suitable for studying neurodegeneration. iNPCs recapitulate many pathological hallmarks of the disease and they retain the ageing phenotype of the patient that they are obtained from. TDP-43 proteinopathy is one of the disease hallmarks observed in patients and is present in 97% of ALS patients. Here, we show gefitinib, a repurposing candidate identified by AI, improves survival of MNs in a co-culture with patient-derived astrocytes and can modulate TDP-43 proteinopathy.

neuroscience↗

bioRxiv2024

Structural and functional analysis of Pseudomonas aeruginosa PelA provides insight into the modification of the Pel exopolysaccharide

A major biofilm matrix determinant of Pseudomonas aeruginosa is the partially deacetylated -1,4 linked N-acetylgalactosamine polymer, Pel. After synthesis and transport of the GalNAc polysaccharide across the inner membrane, PelA partially deacetylates and hydrolyzes Pel before its export out of the cell via PelB. While the Pel modification and export proteins are known to interact in the periplasm, it is unclear how the interaction of PelA and PelB coordinates these processes. To determine how PelA modifies the polymer, we determined its structure to 2.1 [A] and found a unique arrangement of four distinct domains. We have shown previously that the hydrolase domain exhibits endo--1,4-N-acetylgalactosaminidase activity. Characterization of the deacetylase domain revealed that PelA is the founding member of a new carbohydrate esterase family, CE#. Further, we found that the PelAB interaction enhances the deacetylation of N-acetylgalactosamine oligosaccharides. Using the PelA structure in conjunction with AlphaFold2 modelling of the PelAB complex, we propose a model wherein PelB guides Pel to the deacetylase domain of PelA and subsequently to the porin domain of PelB for export. Perturbation or loss of the PelAB interaction would result in less efficient deacetylation and potentially result in increased Pel hydrolysis. In PelA homologues across many phyla, the predicted structure and active sites are conserved, suggesting that there is a common modification mechanism in Gram-negative bacterial species that contain a functional pel operon.

microbiology↗

bioRxiv2024

IL-13 and IL-17A Activate β1 Integrin through an NF-κB/Rho kinase/PIP5K1γ pathway to Enhance Force Transmission in Airway Smooth Muscle

Integrin activation resulting in enhanced adhesion to the extracellular matrix plays a key role in fundamental cellular processes. Although G-protein coupled receptor-mediated integrin activation has been extensively studied in non-adherent migratory cells such as leukocytes and platelets, much less is known about the regulation and functional impact of integrin activation in adherent stationary cells such as airway smooth muscle. Here we show that two different asthmagenic cytokines, IL-13 and IL-17A, activate type I and IL-17 cytokine receptor families respectively, to enhance adhesion of muscle to the matrix. These cytokines also induce activation of {beta}1 integrins as detected by the conformation-specific antibody HUTS-4. Moreover, HUTS-4 binding is significantly increased in the smooth muscle of patients with asthma compared to healthy controls, suggesting a disease-relevant role for aberrant integrin activation. Indeed, we find integrin activation induced by a {beta}1 activating antibody, the divalent cation manganese, or the synthetic peptide {beta}1-CHAMP, dramatically enhances force transmission in collagen gels, mouse tracheal rings, and human bronchial rings even in the absence of cytokines. We further demonstrate that cytokine-induced activation of {beta}1 integrins is regulated by a common pathway of NF-O_SCPLOWKC_SCPLOWB-mediated induction of RhoA and its effector Rho kinase, which in turn stimulates PIP5K1{gamma}-mediated synthesis of PIP2 resulting in {beta}1 integrin activation. Taken together, these data identify a previously unknown pathway by which type I and IL-17 cytokine receptor family stimulation induces functionally relevant {beta}1 integrin activation in adherent smooth muscle and help explain the exaggerated force transmission that characterizes chronic airways diseases such as asthma. SIGNIFICANCE STATEMENTIntegrin activation plays a central role in regulating cellular adhesion and migration. While chemokine-mediated integrin activation has been extensively studied in circulating cells, the role and impact of other cytokine families on non-migratory cells remains incompletely characterized. Here, we demonstrate in airway smooth muscle that asthmagenic cytokines IL-13 and IL-17A stimulate type I and IL-17 cytokine receptor families to induce {beta}1 integrin activation and enhance adhesion. We also identify a common pathway linking NF-O_SCPLOWKC_SCPLOWB/RhoA/Rho kinase with PIP5K1{gamma}/PIP2/{beta}1 integrin activation. We show that airway biopsies from asthmatic patients have increased active {beta}1 integrin staining in the muscle, and furthermore that {beta}1 integrin activation alone dramatically enhances force transmission, underscoring the disease-relevant impact of cytokine-mediated integrin activation in adherent muscle.

molecular biology↗

bioRxiv2024

Dynamic fibroblast-immune interactions shape wound healing after brain injury

Fibroblasts coordinate the response to tissue injury, directing organ regeneration versus scarring. In the central nervous system (CNS), fibroblasts are uncommon cells enriched at tissue borders, and their molecular, cellular, and functional interactions after brain injury are poorly understood. Here we define the fibroblast response to sterile brain damage across time and space. Early pro-fibrotic myofibroblasts infiltrated CNS lesions and were functionally and spatially organized by fibroblast TGF{beta} signaling, pro-fibrotic macrophages and microglia, and perilesional brain glia that activated TGF{beta} via integrin v{beta}8. Early myofibroblasts subsequently transitioned into a variety of late states, including meningeal and lymphocyte-interactive fibroblasts that persisted long term. Interruption of this dynamic fibroblast-macrophage-glial coordination impaired brain wound healing and the resolution of neuroinflammation, disrupted generation of late de novo CNS lymphocyte niches, and increased mortality in a stroke model. This work highlights an unexpected role of fibroblasts as coordinate regulators of CNS healing and neuroinflammation after brain injury.

immunology↗

bioRxiv2023

Impaired Myofibroblast Proliferation is a Central Feature of Pathologic Post-Natal Alveolar Simplification

Premature infants with bronchopulmonary dysplasia (BPD) have impaired alveolar gas exchange due to alveolar simplification and dysmorphic pulmonary vasculature. Advances in clinical care have improved survival for infants with BPD, but the overall incidence of BPD remains unchanged because we lack specific therapies to prevent this disease. Recent work has suggested a role for increased transforming growth factor-beta (TGF{beta}) signaling and myofibroblast populations in BPD pathogenesis, but the functional significance of each remains unclear. Here, we utilize multiple murine models of alveolar simplification and comparative single-cell RNA sequencing to identify shared mechanisms that could contribute to BPD pathogenesis. Single-cell RNA sequencing reveals a profound loss of myofibroblasts in two models of BPD and identifies gene expression signatures of increased TGF{beta} signaling, cell cycle arrest, and impaired proliferation in myofibroblasts. Using pharmacologic and genetic approaches, we find no evidence that increased TGF{beta} signaling in the lung mesenchyme contributes to alveolar simplification. In contrast, this is likely a failed compensatory response, since none of our approaches to inhibit TGFb signaling protect mice from alveolar simplification due to hyperoxia while several make simplification worse. In contrast, we find that impaired myofibroblast proliferation is a central feature in several murine models of BPD, and we show that inhibiting myofibroblast proliferation is sufficient to cause pathologic alveolar simplification. Our results underscore the importance of impaired myofibroblast proliferation as a central feature of alveolar simplification and suggest that efforts to reverse this process could have therapeutic value in BPD.

physiology↗

bioRxiv2023

Reciprocal inflammatory signals establish profibrotic cross-feeding metabolism

Idiopathic pulmonary fibrosis (IPF) is a disease of progressive lung remodeling and collagen deposition that leads to respiratory failure. Myeloid cells are abundant in IPF lung and in murine lung fibrosis, but their functional effects are incompletely understood. Using mouse and human lung models, we show that ornithine produced by myeloid cells expressing Arg1 serves as a substrate for proline and collagen synthesis by lung fibroblasts. The predominant Arg1-expressing myeloid cells in mouse lung were macrophages, but in IPF lung, high-dimensional imaging revealed ARG1 to be expressed mainly in neutrophils. Arg1 inhibition suppressed both ornithine levels and collagen expression in cultured, precision-cut IPF lung slices and in murine lung fibrosis. These results were confirmed in macrophage-specific Arg1 KO mice. Furthermore, we find that this pathway is regulated by cell-to-cell crosstalk, starting with purinergic signaling: Fibroblast eATP receptor P2rx4 was necessary for fibroblast IL-6 expression, which in turn was necessary for Arg1 expression by myeloid cells. Taken together, our findings define an immune-mesenchymal circuit that governs profibrotic metabolism in lung fibrosis.

immunology↗

bioRxiv2023

CD56-mediated activation of human natural killer cells is triggered by Aspergillus fumigatus galactosaminogalactan

Invasive aspergillosis causes significant morbidity and mortality in immunocompromised patients. Natural killer (NK) cells are pivotal for antifungal defense. Thus far, CD56 is the only known pathogen recognition receptor on NK cells triggering potent antifungal activity against Aspergillus fumigatus. However, the underlying cellular mechanisms and the fungal ligand of CD56 have remained unknown. Using purified cell wall components, biochemical treatments, and A. fumigatus mutants with altered cell wall composition, we herein found that CD56 interacts with the A. fumigatus cell wall carbohydrate galactosaminogalactan (GAG). This interaction induced NK cell activation, degranulation, and secretion of immune-enhancing chemokines and cytotoxic effectors. Supernatants from GAG-stimulated NK cells elicited antifungal activity and enhanced antifungal effector responses of polymorphonuclear cells. In conclusion, we identified A. fumigatus GAG as a ligand of CD56 on human primary NK cells, stimulating potent antifungal effector responses and activating other immune cells.

microbiology↗

bioRxiv2023

Radial glia control microglial differentiation via integrin avb8-dependent trans-activation of TGFB1

Microglia diversity emerges from interactions between intrinsic genetic programs and environment-derived signals, but how these processes unfold and interact in the developing brain remains unclear. Here, we show that radial glia-expressed integrin beta 8 (ITGB8) expressed in radial glia progenitors activates microglia-expressed TGF{beta}1, permitting microglial development. Domain-restricted deletion of Itgb8 in these progenitors establishes complementary regions with developmentally arrested "dysmature" microglia that persist into adulthood. In the absence of autocrine TGF{beta}1 signaling, we find that microglia adopt a similar dysmature phenotype, leading to neuromotor symptoms almost identical to Itgb8 mutant mice. In contrast, microglia lacking the TGF{beta} signal transducers Smad2 and Smad3 have a less polarized dysmature phenotype and correspondingly less severe neuromotor dysfunction. Finally, we show that non-canonical (Smad-independent) signaling partially suppresses disease and development associated gene expression, providing compelling evidence for the adoption of microglial developmental signaling pathways in the context of injury or disease.

immunology↗

bioRxiv2022

Anti-integrin αvβ6 autoantibodies are a novel predictive biomarker in ulcerative colitis

Background and AimsBetter biomarkers for prediction of ulcerative colitis (UC) development and prognostication are needed. Anti-integrin v{beta}6 autoantibodies (anti-v{beta}6) have been described in UC patients. Here, we tested for the presence of anti-v{beta}6 antibodies in the pre-clinical phase of UC and studied their association with disease-related outcomes after diagnosis. MethodsAnti-v{beta}6 were measured in 4 longitudinal serum samples collected from 82 subjects who later developed UC and 82 matched controls from a Department of Defense pre-clinical cohort (PREDICTS). In a distinct, external validation cohort (GEM), we tested 12 pre-UC subjects and 49 matched controls. Further, anti-v{beta}6 were measured in 2 incident UC cohorts (COMPASS n=55 and OSCCAR n=104) and associations between anti-v{beta}6 and UC-related outcomes were defined using Cox proportional-hazards model. ResultsAnti-v{beta}6 were significantly higher among individuals who developed UC compared to controls up to 10 years before diagnosis in PREDICTS. The anti-v{beta}6 seropositivity was 12.2% 10 years before diagnosis and increased to 52.4% at the time of diagnosis in subjects who developed UC compared with 2.7% in controls across the 4 timepoints. Anti-v{beta}6 predicted UC development with an AUC of at least 0.8 up to 10 years before diagnosis. The presence of anti-v{beta}6 in pre-clinical UC samples was validated in the GEM cohort. Finally, high anti-v{beta}6 was associated with a composite of adverse UC-outcomes including hospitalization, disease extension, colectomy, systemic steroid use and/or escalation to biologic therapy in recently diagnosed UC. ConclusionAnti-integrin v{beta}6 auto-antibodies precede the clinical diagnosis of UC by up to 10 years and are associated with adverse UC-related outcomes.

immunology↗

bioRxiv2022

Tracing the origin of pathologic pulmonary fibroblasts

Fibroblasts substantially remodel extracellular matrix (ECM) in response to tissue injury and generate fibrotic scars in chronic diseases. Recent studies have identified diverse fibroblast subsets in healthy and injured tissues. However, the origin(s) and functional importance of injury-induced fibroblast lineages remain unclear. Here we show that alveolar fibroblasts, which provide a niche for maintaining alveolar type 2 cells in uninjured lungs, are the dominant source of multiple emergent fibroblast subsets that sequentially arise to facilitate fibrosis after lung injury. We demonstrate that Cthrc1+ fibroblasts, which express the highest levels of ECM proteins at injured sites, are effector cells for fibrogenesis using a novel mouse tool, Cthrc1-CreER. We use another novel mouse tool, Scube2-CreER, that uniquely targets alveolar fibroblasts, to reveal that alveolar fibroblasts are the dominant origin for multiple fibroblast subsets that emerge after lung injury. Pseudotime and in vitro analysis suggest that inflammatory cytokines initially induce chemokine-producing inflammatory fibroblasts from alveolar fibroblasts, which can differentiate into Cthrc1+ fibrotic fibroblasts in response to TGF-{beta}. We identify similar fibroblast lineages from scRNA-seq in human pulmonary fibrosis. These results elucidate the pathologic fibroblast lineage development in response to lung injury and suggest that targeting key steps in transitions among these subsets could provide novel strategies for the treatment of fibrotic diseases.

pathology↗

bioRxiv2022

Full structure/function analysis of all the pilin subunits in a type 4 pilus: a complex of minor pilins in Streptococcus sanguinis mediates binding to glycans

Type 4 filaments (T4F) - of which type 4 pili (T4P) are the archetype - are a superfamily of filamentous nanomachines nearly ubiquitous in prokaryotes. T4F are polymers of one major pilin that also contain minor pilins whose roles are often poorly understood. Here, we complete the structure/function analysis of the full set of T4P pilins in the opportunistic pathogen Streptococcus sanguinis. We determined the structure of the minor pilin PilA, which is unexpectedly similar to one of the subunits of a tip-located complex of four minor pilins, widely conserved in T4F. We found that PilA interacts and dramatically stabilises the minor pilin PilC. We determined the structure of PilC, showing that it is a modular pilin with a lectin module binding a specific subset of glycans prevalent in the human glycome, the host of S. sanguinis. Altogether, our findings support a model whereby the minor pilins in S. sanguinis T4P form a tip-located complex promoting adhesion to various host receptors. Our findings have general implications for a group of minor pilins widely conserved in T4F.

microbiology↗

bioRxiv2021

Identification of Serum Bridging Molecules that Mediate Human Endothelial Cell Invasion by Candida species

During hematogenously disseminated candidiasis, blood borne fungi must invade the endothelial cells that line the blood vessels to infect the deep tissues. Although Candida albicans, which forms hyphae, readily invades endothelial cells, other medically important species of Candida are poorly invasive in standard in vitro assays. Here, we show that Candida glabrata, Candida tropicalis, Candida parapsilosis, and Candida krusei can bind to vitronectin and high molecular weight kininogen present in human serum. Acting as bridging molecules, vitronectin and kininogen bind to v integrins and the globular C1q receptor (gC1qR), inducing human endothelial cells to endocytose the fungus. This mechanism of endothelial cell invasion is poorly supported by mouse endothelial cells, but can be restored when mouse endothelial cells are engineered to express human gC1qR or v integrin. Overall, these data indicate that bridging molecule-mediated endocytosis is a common pathogenic strategy used by many medically important Candida spp. to invade human vascular endothelial cells. SignificanceThe invasion of vascular endothelial cells is a key step in the pathogenesis of hematogenously disseminated candidiasis. How species of Candida other than C. albicans invade endothelial cells is poorly understood because these fungi are weakly invasive in serum-free media. Here, we demonstrate that C. glabrata and other Candida spp. bind to the serum proteins kininogen and vitronectin, which act as bridging molecules and mediate the adherence and endocytosis of the organisms by endothelial cells. These serum proteins induce endocytosis when they interact with the globular C1q receptor and v integrins on human, but not mouse endothelial cells. Thus, bridging molecule-mediated endocytosis is a common mechanism by which medically important Candida spp. invade human endothelial cells.

microbiology↗