Biology subjects

Smith, T. E.

Publications and source records attributed to Smith, T. E..

6 recordsLinked to original sources

bioRxiv2025

A secreted endosymbiont protein essential for colonizing host cells

ABSTRACTIntracellular bacterial symbioses have arisen myriad times in eukaryotes, with dozens known from insects alone1,2. Beginning with Buchnera, the obligate endosymbiont of aphids, genomes of endosymbionts have illuminated their evolutionary origins and metabolic contributions to hosts3,4. However, the mechanisms by which nonculturable endosymbionts enter host cells and suppress cellular immune processes have remained unknown. We show that an uncharacterized Buchnera protein, here designated SyeA, was present in the Buchnera ancestor, is secreted and homologous to secreted effectors of bacterial pathogens and is essential for Buchnera transmission. Buchnera is transmitted via expulsion from specialized maternal cells and uptake by embryos5. Using immunofluorescence microscopy, we found that SyeA levels peak upon colonization, accompanied by actin accumulation at the entry site. SyeA localizes outside the host-derived membrane and actin layer surrounding each Buchnera cell and colocalizes in host cytoplasm with Rho1, which regulates actin polymerization. syeA knockdown disrupts colonization and embryonic development and elevates lysosomal activity, leading to Buchnera destruction6. Our findings provide rare insight into how an anciently associated, mutualistic endosymbiont achieves its intracellular existence. SyeA is a vestige of pathogenic origins followed by evolution of increased host control and erosion of the original, more complex pathogenicity machinery.

microbiology↗

bioRxiv2025

An ERα-Dependent Hypoxia Response Defines EMT-Adjacent Tumour Regions and Suppresses the Pro-survival Effects of Amiloride in Estrogen Receptor-Positive Breast Cancer

Estrogen receptor-positive (ER+) breast cancer carries a lifelong risk of recurrence and disease progression, with hypoxia-associated transcriptional signatures linked to poor prognosis and therapy resistance. While the effects of hypoxia on tumour progression are well studied, the impact on ER epigenomic regulation remains poorly characterised. Here, we demonstrate that activation of hypoxia-inducible factors (HIFs) dramatically remodels ER chromatin localisation in ER+ breast cancer cells. Transcripts of genes located near hypoxia-induced ER binding sites are significantly associated with reduced recurrence-free survival in breast cancer patients. Transcriptomic profiling under hypoxic conditions (1% oxygen), with and without ER depletion by fulvestrant, revealed a hypoxia-induced, ER-dependent gene expression programme, including upregulation of epithelial sodium channel (ENaC) regulatory subunits that results in acquired sensitivity to the ENaC inhibitor amiloride. Notably, this transcriptional response is spatially correlated with the epithelial-to-mesenchymal hallmark in patient tumours. Our findings establish an interdependence between ER signalling and the hypoxic response, and present functional evidence that ER reprogramming offers novel therapeutic opportunities that bypass the need to directly target the hypoxic response.

cancer biology↗

bioRxiv2024

A double ovulation protocol for Xenopus laevis produces doubled fertilisation yield and moderately transiently elevated corticosterone levels without loss of egg quality

The African claw-toed frog, Xenopus laevis, is a well-established laboratory model for the biology of vertebrate fertilisation and development. For ovulation, X. laevis females are usually injected with chorionic gonadotropin, whereupon they lay typically hundreds to thousands of eggs in a day. Animals are re-used after being rested for a minimum of three months. The literature suggests that adult females can lay much larger numbers of eggs in a short period. Here, we compared the standard "single ovulation" protocol with a "double ovulation" protocol, in which females were ovulated, then re-ovulated after seven days and then rested for three months before re-use. We quantified egg number, fertilisation rate (development to cleavage stage), and corticosterone secretion rate (a measure of stress response) over seven 3-month cycles. We found no differences in egg number-per-ovulation or fertilisation, and no long-term changes in any measures over the trial period. Corticosterone secretion was elevated by ovulation, similarly for the single ovulation as for the first ovulation in the double-ovulation protocol, but more highly for the second ovulation (to a level comparable to that seen following shipment). However, both groups exhibited the same baseline secretion rates by the time of the subsequent cycle. Double ovulation is thus transiently more stressful/demanding than single ovulation but within levels routinely experienced by laboratory X. laevis. Noting that "stress hormone" corticosterone/cortisol secretion is linked to physiological processes, such as ovulation, that are not necessarily harmful to the individual, we suggest that the benefits of a doubling in egg yield-per-cycle per animal without loss of egg quality or signs of acute or long-term harm may outweigh the relatively modest and transient corticosterone elevation we observed. The double ovulation protocol therefore represents a potential new standard practice for promoting the "3Rs" (animal use reduction, refinement and replacement) mission for Xenopus research.

developmental biology↗

bioRxiv2022

Cooperative host-microbe metabolism of a plant toxin in bees

During pollination, bees are exposed to a myriad of xenobiotics, including plant metabolites, which may exert a wide range of effects on their health. Although bees encode enzymes that help in the metabolism of xenobiotics, they still have reduced detoxification gene diversity when compared to other insects, and may rely on other components of their physiology, such as the microbiota, to degrade potentially toxic molecules. In this study, we show that amygdalin, a cyanogenic glycoside found in honey bee-pollinated almond trees, can be metabolized by both bees and members of the gut microbiota. In microbiota-deprived bees, amygdalin is degraded into prunasin, leading to prunasin accumulation in the midgut and hindgut. In microbiota-colonized bees, on the other hand, amygdalin is degraded even further, and prunasin does not accumulate in the gut, suggesting that the microbiota contribute to the full degradation of amygdalin into hydrogen cyanide. In vitro experiments demonstrated that amygdalin degradation by bee gut bacteria is strain-specific and not characteristic of a particular genus or species. We found strains of Bifidobacterium, Bombilactobacillus and Gilliamella that can degrade amygdalin, and the degradation mechanism appears to vary since only some strains produce prunasin as an intermediate. Finally, we investigated the basis of degradation in Bifidobacterium wkB204, a strain that fully degrades amygdalin. We found overexpression and secretion of several carbohydrate-degrading enzymes, including one in glycoside hydrolase family 3 (GH3). We expressed this GH3 in Escherichia coli and detected prunasin as a byproduct when cell lysates were cultured with amygdalin, supporting its contribution to amygdalin degradation. These findings demonstrate that both host and microbiota can act together to metabolize dietary plant metabolites. How amygdalin degradation into hydrogen cyanide affects bee health remains to be elucidated.

ecology↗

bioRxiv2020

cDC1 Coordinate Innate and Adaptive Responses in the Omentum required for T cell Priming and Memory

The omentum in the peritoneal cavity contains fat associated lymphoid clusters (FALCs) whose role in the response to microbial challenge are poorly understood. After intraperitoneal immunization with Toxoplasma gondii, type I dendritic cells (cDC1) were critical to induce innate sources of IFN-{gamma} required to recruit monocytes to the FALCs. The migration of infected peritoneal macrophages into T and B cell rich areas of the FALCs allowed the TCR-induced activation of parasite-specific T cells. Unexpectedly, cDC1 were not required for T cell priming but rather supported the expansion of parasite-specific CD8+ T cells. An agent-based mathematical model predicted that the lack of cDC1 would impact the early proliferative burst, and we confirmed that cDC1 were required for optimal T cell expression of nutrient uptake receptors and cell survival. These studies highlight that cDC1 in the FALCs have distinct roles in the co-ordination of the innate and adaptive responses to microbial challenge.

immunology↗

bioRxiv2020

Topsentinol L Trisulfate, a new Marine Natural Product, that Targets Basal-like and Claudin-low Breast Cancers

BackgroundBreast cancer is a heterogeneous disease. Genomic studies have revealed five different intrinsic subtypes - Luminal A, Luminal B, HER2-enriched, Claudin-low, and Basal-like. Patients diagnosed with Basal-like or Claudin-low breast cancer (BL-CL) suffer from poor prognosis and limited treatment options. Hence, there is an urgent need to identify a new therapeutic lead that can benefit patients with BL-CL breast cancer. MethodsWe used a step-wise screening approach to screen 2778 HP20 fractions from our Marine Invertebrate Compound Library (MICL) to identify compounds that specifically target BL-CL breast cancer. We also performed biochemical investigations to study the effect of the compound in the signaling pathway. Finally, we generated a drug response gene-expression signature and projected it against a human tumor panel of 12 different cancer types to identify other cancer types sensitive to the compound. ResultsWe identified a previously unreported trisulfated sterol, topsentinol L trisulfate (TLT) that exhibits increased efficacy against BL-CL relative to Luminal/HER2+ breast cancer. Biochemical investigation of the effects of TLT on BL-CL revealed its ability to inhibit activation of AMPK and CHK1 and promote activation of p38. The importance of targeting AMPK and CHK1 in BL-CL was validated by treating a panel of breast cancer cell lines with known small molecule inhibitors of AMPK (Dorsomorphin) and CHK1 (Ly2603618) and recording the increased effectiveness against BL-CL compared to Luminal/HER2+ breast cancer. The TLT sensitivity gene-expression signature identified breast and bladder cancer as the most sensitive to TLT while glioblastoma multiforme as least sensitive. ConclusionsOur study identified TLT, a previously uncharacterized trisulfated sterol, as a potential therapeutic selective against BL-CL. Our results also showed that inhibition of AMPK and/or CHK1 might be an effective therapy in BL-CL.

cancer biology↗