Biology subjects

Todd, K.

Publications and source records attributed to Todd, K..

10 recordsLinked to original sources

bioRxiv2026

Small-Molecule Inhibitors Allosterically Control Bruton's Tyrosine Kinase Assembly on the Membrane

Bruton's tyrosine kinase (Btk) is the target of small-molecule, active site inhibitors for treatment of lymphomas and leukemias. Beyond its catalytic activity, Btk participates in signaling assemblies through scaffolding functions that can contribute to drug resistance. Here, we show that Btk forms micron-scale assemblies on membranes and that this behavior is allosterically controlled by ligand binding at the active site. Using supported lipid bilayers and total internal reflection fluorescence microscopy, we find that nucleotides and inhibitors including ibrutinib, acalabrutinib, and dasatinib promote assembly, whereas fenebrutinib and pirtobrutinib prevent assembly. Membrane organization is independent of catalysis but correlates with ligand-dependent changes in Btk conformational flexibility measured by hydrogen-deuterium exchange. These results reveal a previously unrecognized connection between active-site ligand binding and mesoscale membrane organization, demonstrating that kinase inhibitors can control Btk behavior beyond suppression of catalytic activity.

biophysics↗

bioRxiv2026

Selective GRAB sensors reveal distinct endocannabinoid dynamics in vivo

The endocannabinoid system modulates diverse physiological processes via two endogenous lipid ligands, 2-arachidonoylglycerol (2-AG) and anandamide (AEA); however, their specific spatiotemporal dynamics remain poorly understood owing to the lack of selective probes. Here, we developed GRAB2-AG2.0 and GRABAEA2.0, two genetically encoded fluorescent sensors that selectively detect 2-AG and AEA, respectively. Both sensors exhibited high apparent affinity and molecular specificity for their respective ligands, enabling the real-time detection of 2-AG and AEA release evoked by electrical stimulation in cultured neurons and acute brain slices. In freely behaving mice, these sensors revealed ligand- and context-specific eCB dynamics: aversive stimulation preferentially evoked 2-AG, whereas psychoactive drugs produced distinct 2-AG and AEA responses. Notably, {Delta}9-THC elicited a sustained 2-AG signal in the nucleus accumbens shell, and local deletion of Dagla markedly attenuated both this signal and {Delta}9-THC-induced hypolocomotion. These sensors therefore enable detecting 2-AG and AEA signaling seperately and reveal an endogenous 2-AG component of the behavioral response to {Delta}9-THC.

neuroscience↗

bioRxiv2026

Repurposing antiviral drugs as a new avenue for Klebsiella pneumoniae decolonization

Klebsiella pneumoniae (Kp) is a common antibiotic-resistant pathogen that colonizes the gastrointestinal tract and can disseminate to peripheral sites, causing a range of infections including bacteremia, urinary tract infections, and pneumonia. Intestinal colonization with Kp is a risk factor for subsequent infection, as the colonizing strain frequently corresponds to the infecting isolate. Accordingly, targeting Kp prior to dissemination at the site of colonization through decolonization strategies offers a promising approach to mitigate infection risk. In this study, we evaluated the repurposing of existing drugs with previously uncharacterized antibacterial activity as candidates for Kp decolonization. To this end, we screened an antiviral compound library for their activity against Kp. We identified and validated six compounds with previously uncharacterized activity against Kp. Then, we screened a library of clinical Kp strains against a subset of these compounds and found that their activity was strain-specific to degrees that differed based on the compound. Finally, we tested the activity of these compounds in conditions relevant to the human gut. We determined the activity of these candidates was dependent on biological context. Collectively, these findings support further investigation of antiviral drugs as potential gut decolonization therapies for Kp.

microbiology↗

bioRxiv2025

Pseudomonas aeruginosa phenazines dictate site-specific competitive interactions with Klebsiella pneumoniae

Pseudomonas aeruginosa and Klebsiella pneumoniae are Gram-negative opportunistic pathogens that frequently colonize the human body and are major causes of infection. These bacteria are often co-isolated in polymicrobial urinary tract and lung infections, the latter of which is associated with increased disease severity and worse clinical outcomes. Despite their overlapping niches and clinical relevance, little is known about how these two pathogens interact and how those interactions influence human health. Given the growing recognition that microbial interactions are key drivers of disease, we investigated how P. aeruginosa and K. pneumoniae influence one another. We discovered an antagonistic interaction in which P. aeruginosa restricts the growth of K. pneumoniae. This inhibition is driven by phenazine production in P. aeruginosa, specifically the secondary metabolites pyocyanin and pyorubin, which are both necessary and sufficient to suppress K. pneumoniae growth. Using a diverse set of clinical isolates, we found that this antagonism is strain dependent. Both the susceptibility of K. pneumoniae to phenazines and the ability of P. aeruginosa to restrict K. pneumoniae growth varies between strains. Moreover, the necessity of phenazine production is specific to the site of infection. Together, these findings demonstrate that strain background and environmental context are critical determinants of pathogen interactions. Our work underscores the importance of considering these variables when investigating how microbial interactions influence infection and disease outcomes.

microbiology↗

bioRxiv2024

Type-2 diabetes mellitus enhances Klebsiella pneumoniae pathogenesis

Klebsiella pneumoniae is an opportunistic pathogen and an important cause of pneumonia, bacteremia, and urinary tract infection. K. pneumoniae infections are historically associated with diabetes mellitus. There is a fundamental gap in our understanding of how diabetes mellitus, specifically type 2 diabetes, influences K. pneumoniae pathogenesis. K. pneumoniae pathogenesis is a multifactorial process that often begins with gut colonization, followed by an escape from the gut to peripheral sites, leading to host damage and infection. We hypothesized that type 2 diabetes enhances K. pneumoniae pathogenesis. To test this, we used well-established mouse models of K. pneumoniae colonization and lung infection in conjunction with a mouse model of spontaneous type 2 diabetes mellitus (T2DM). We show that T2DM enhances susceptibility to both K. pneumoniae colonization and infection. The enhancement of gut colonization is dependent on T2DM-induced modulation of the gut microbiota community structure. In contrast, lung infection is exacerbated by the increased availability of amino acids in the lung, which is associated with higher levels of vascular endothelial growth factor. These data lay the foundation for mechanistic interrogation of the relationship between K. pneumoniae pathogenesis and type 2 diabetes mellitus, and explicitly establish T2DM as a risk factor for K. pneumoniae disease.

microbiology↗

bioRxiv2021

Disrupted Peyer's patch microanatomy in COVID-19 including germinal centre atrophy independent of local virus

Confirmed SARS-coronavirus-2 infection with gastrointestinal symptoms and changes in microbiota associated with coronavirus disease 2019 (COVID-19) severity have been previously reported, but the disease impact on the architecture and cellularity of ileal Peyers patches (PP) remains unknown. Here we analysed post-mortem tissues from throughout the gastrointestinal (GI) tract of patients who died with COVID-19. When virus was detected by PCR in the GI tract, immunohistochemistry identified virus in epithelium and lamina propria macrophages, but not in lymphoid tissues. Immunohistochemistry and imaging mass cytometry (IMC) analysis of ileal PP revealed depletion of germinal centres (GC), disruption of B cell/T cell zonation and decreased potential B and T cell interaction and lower nuclear density in COVID-19 patients. This occurred independent of the local viral levels. The changes in PP demonstrate that the ability to mount an intestinal immune response is compromised in severe COVID-19, which could contribute to observed dysbiosis.

immunology↗

bioRxiv2021

Two subsets of human marginal zone B cells resolved by global analysis of lymphoid tissues and blood

B cells generate antibodies that are essential for immune protection. Major events driving B cell responses occur in lymphoid tissues, which guide antigen acquisition and support cellular interactions, yet complexities of B cell subsets in human lymphoid tissues are poorly understood. Here we perform undirected, global profiling of B cells in matched human lymphoid tissues from deceased transplant organ donors and tracked dissemination of B cell clones. In addition to identifying unanticipated features of tissue-based B cell differentiation, we resolve two clonally independent subsets of marginal zone B cells that differ in cell surface and transcriptomic profiles, tendency to disseminate, distribution bias within splenic marginal zone microenvironment and immunoglobulin repertoire diversity and hypermutation frequency. Each subset is represented in spleen, gut-associated lymphoid tissue, mesenteric lymph node, and also blood. Thus, we provide clarity and diffuse controversy surrounding human MZB - the elephant in the room of human B cell biology.

immunology↗

bioRxiv2020

Immunogenomic profile of colorectal cancer response to immune checkpoint blockade

Colorectal cancers (CRCs) show variable response to immune checkpoint blockade, which can only partially be explained by the variability of tumour mutational burden. To dissect the cellular and molecular determinants of response we performed a multi-omic screen of 721 cancer regions from patients treated with Pembrolizumab (KEYNOTE 177 clinical trial) or Nivolumab. Multi-regional whole exome, RNA and T-cell receptor sequencing show that, within hypermutated CRCs, response to both anti-PD1 agents is not positively associated with tumour mutational burden but with high clonality of immunogenic mutations, expanded T cells, low activation of the WNT pathway and active immune escape mechanisms. Coupling high-dimensional imaging mass cytometry with multiplexed immunofluorescence and computational spatial analysis, we observe that responsive hypermutated CRCs are rich in cytotoxic and proliferating PD1-expressing CD8 cells interacting with high-density clusters of PDL1-expressing antigen presenting macrophages. We propose that anti-PD1 agents release the PD1-PDL1 interaction between CD8 T cells and macrophages thus promoting cytotoxic anti-tumour activity.

cancer biology↗

bioRxiv2020

Inflammatory cytokine profile and plasticity of brain and spinal microglia in response to ATP and glutamate

Microglia are the primary cells in the central nervous system that identify and respond to injury or damage. Such a perturbation in the nervous system induces the release of molecules including ATP and glutamate that act as damage-associated molecular patterns (DAMPs). DAMPs are detected by microglia, which then regulate the inflammatory response in a manner sensitive to their surrounding environment. The available data indicates that ATP and glutamate can induce the release of pro inflammatory factors TNF (tumor necrosis factor), IL-1{beta} (interleukin 1 beta) and NO (nitric oxide) from microglia. However, non-physiological concentrations of ATP and glutamate were often used to derive these insights. Here, we have compared the response of spinal cord microglia (SM) relative to brain microglia (BM) using physiologically relevant concentrations of glutamate and ATP that mimic injured conditions in the central nervous system. The data show that ATP and glutamate are not significant modulators of the release of cytokines from either BM or SM. Consistent with previous studies, spinal microglia exhibited a general trend towards reduced release of inflammatory cytokines relative to brain-derived microglia. Moreover, we demonstrate that the responses of microglia to these DAMPs can be altered by modifying the biochemical milieu in their surrounding environment. Preconditioning brain derived microglia with media from spinal cord derived mixed glial cultures shifted their release of IL-{beta}, IL-6 and IL-10 to a less inflammatory phenotype consistent with a spinal microglia.

neuroscience↗

bioRxiv2020

Anti-inflammatory role of GM1 and modulatory effects of gangliosides on microglia functions

Gangliosides are sialic acid-containing glycosphingolipids highly enriched in the brain. Located mainly at the plasma membrane, gangliosides play important roles in signaling and cell-to-cell communication. Lack of gangliosides causes severe early onset neurodegenerative disorders, while more subtle deficits have been reported in Parkinsons disease and in Huntingtons disease, two misfolded protein diseases with a neuroinflammatory component. On the other hand, administration of ganglioside GM1 provides neuroprotection in both diseases and in several other models of neuronal insult. While most studies have focused on the role of endogenous gangliosides and the effects of exogenously administered GM1 in neurons, their contribution to microglia functions that are affected in neurodegenerative conditions is largely unexplored. Microglia are the immune cells of the brain and play important homeostatic functions in health and disease. In this study, we show that administration of exogenous GM1 exerts a potent anti-inflammatory effect on microglia activated with LPS, IL-1{beta} or upon phagocytosis of latex beads. These effects are partially reproduced by L-t-PDMP, a compound that stimulates the activity of the ganglioside biosynthetic pathway, while inhibition of ganglioside synthesis with GENZ-123346 increases microglial transcriptional response to LPS. We further show that administration of GM1 increases the uptake of apoptotic bodies and latex beads by microglia, as well as microglia migration and chemotaxis in response to ATP. On the contrary, decreasing microglial ganglioside levels results in a partial impairment in both microglial activities. Finally, increasing cellular ganglioside levels results in decreased expression and secretion of microglial brain derived neurotrophic factor (BDNF). Altogether, our data suggest that gangliosides are important modulators of microglia functions that are crucial to healthy brain homeostasis, and reveal that administration of ganglioside GM1 exerts an important anti-inflammatory activity that could be exploited therapeutically.

neuroscience↗