Biology subjects

Zeidler, M. P.

Publications and source records attributed to Zeidler, M. P..

5 recordsLinked to original sources

bioRxiv2024

E-cadherin endocytosis promotes non-canonical EGFR:STAT signalling to induce cell death and inhibit heterochromatinisation

Signalling molecules often contribute to several signalling pathways that produce distinct transcriptional outputs and cellular phenotypes. One of the major unanswered questions in cell biology is how multiple activities of signalling molecules are coordinated in space and time in vivo. Here, we focus on the Signal Transducer and Activator of Transcription (STAT) protein as a paradigm of signalling molecules involved in several independent signalling pathways. In addition to the canonical pathways, whereby STAT is phosphorylated and activated by Janus Kinases, STAT is involved in at least two non-canonical pathways. In one pathway, STAT is activated by the Epidermal Growth Factor Receptor (EGFR) promoting apoptosis. In another, it binds the Heterochromatin Protein 1 (HP1) to enhance heterochromatin formation. Using Drosophila wing discs as an epithelial system, we demonstrate that all three STAT activities coexist in this tissue. We provide evidence that while the canonical STAT signalling is dominant over non-canonical pathways, EGFR:STAT and HP1:STAT pathways compete for the availability of unphosphorylated STAT. We also describe the role of the cell-cell adhesion protein E-cadherin in EGFR:STAT signalling. Both EGFR and STAT colocalise with E-cadherin at cell-cell junctions and on intracellular vesicles. Elevated intracellular E-cadherin promotes EGFR:STAT pathway leading to apoptosis, whereas blocking E-cadherin endocytosis prevents apoptosis induction. Altogether, we propose that E-cadherin endocytosis controls the balance between two non-canonical STAT activities in a potential tumour-suppressive mechanism - junctional disassembly in dysregulated epithelial-to-mesenchymal transitions would shift this balance towards the EGFR:STAT signalling to promote apoptosis.

cell biology↗

bioRxiv2023

Macrophage subpopulation identity in Drosophila is modulated by apoptotic cell clearance and related signalling pathways

In Drosophila blood, plasmatocytes of the haemocyte lineage represent the functional equivalent of vertebrate macrophages and have become an established in vivo model with which to study macrophage function and behaviour. However, the use of plasmatocytes as a macrophage model has been limited by a historical perspective that plasmatocytes represent a homogenous population of cells, in contrast to the high levels of heterogeneity of vertebrate macrophages. Recently, a number of groups have reported transcriptomic approaches which suggest the existence of plasmatocyte heterogeneity, while we identified enhancer elements that identify subpopulations of plasmatocytes which exhibit potentially pro-inflammatory behaviours, suggesting conservation of plasmatocyte heterogeneity in Drosophila. These plasmatocyte subpopulations exhibit enhanced responses to wounds and decreased rates of efferocytosis when compared to the overall plasmatocyte population. Interestingly, increasing the phagocytic requirement placed upon plasmatocytes is sufficient to decrease the size of these plasmatocyte subpopulations in the embryo. However, the mechanistic basis for this response was unclear. Here, we examine how plasmatocyte subpopulations are modulated by apoptotic cell clearance (efferocytosis) demands and associated signalling pathways. We show that loss of the phosphatidylserine receptor Simu prevents an increased phagocytic burden from modulating specific subpopulation cells, while blocking other apoptotic cell receptors revealed no such rescue. This suggests that Simu-dependent efferocytosis is specifically involved in determining fate of particular subpopulations. Supportive of our original finding, mutations in amo (the Drosophila homolog of PKD2), a calcium-permeable channel which operates downstream of Simu, phenocopy simu mutants. Furthermore, we show that Amo is involved in the acidification of the apoptotic cell-containing phagosomes, suggesting that this reduction in pH may be associated with macrophage reprogramming. Additionally, our results also identify Ecdysone receptor signalling, a pathway related to control of cell death during developmental transitions, as a controller of plasmatocyte subpopulation identity. Overall, these results identify fundamental pathways involved in the specification of plasmatocyte subpopulations and so further validate Drosophila plasmatocytes as a heterogeneous population of macrophage-like cells within this important developmental and immune model.

developmental biology↗

bioRxiv2020

Identification of functionally-distinct macrophage subpopulations regulated by efferocytosis in Drosophila

Macrophages are a highly heterogeneous population of cells, with this diversity stemming in part from the existence of tissue resident populations and an ability to adopt a variety of activation states in response to stimuli. Drosophila blood cells (hemocytes) are dominated by a lineage of cells considered to be the functional equivalents of mammalian macrophages (plasmatocytes). Until very recently plasmatocytes were thought to be a homogeneous population. Here, we identify enhancer elements that label subpopulations of plasmatocytes, which vary in abundance across the lifecourse of the fly. We demonstrate that these plasmatocyte subpopulations behave in a functionally-distinct manner when compared to the overall population, including more potent migratory responses to injury and decreased clearance of apoptotic cells within the developing embryo. Additionally, these subpopulations display differential localisation and dynamics in pupae and adults, hinting at the presence of tissue-resident macrophages in the fly. Our enhancer analysis also allows us to identify novel candidate genes involved in plasmatocyte behaviour in vivo. Misexpression of one such enhancer-linked gene (calnexin14D) in all plasmatocytes improves wound responses, causing the overall population to behave more like the subpopulation marked by the calnexin14D-associated enhancer. Finally, we show that, we are able to modulate the number of cells within some subpopulations via exposure to increased levels of apoptotic cell death, thereby decreasing the number of plasmatocytes within more wound-responsive subpopulations. Taken together our data demonstrates the existence of macrophage heterogeneity in Drosophila and identifies mechanisms involved in the specification and function of these plasmatocyte subpopulations. Furthermore, this work identifies key molecular tools with which Drosophila can be used as a highly genetically-tractable, in vivo system to study the biology of macrophage heterogeneity.

developmental biology↗

bioRxiv2020

Zoledronate extends healthspan and survival via the mevalonate pathway in a FOXO-dependent manner

Increased longevity has not been paralleled by extended healthspan, resulting in more years spent with multiple diseases in older age. As such, interventions to improve healthspan are urgently required. Zoledronate is a nitrogen containing bisphosphonate, which inhibits the farnesyl pyrophosphate synthase (FPPS) enzyme, central to the mevalonate pathway. It is already used clinically to prevent fractures in osteoporotic patients, who have been reported to derive unexpected and unexplained survival benefits. In this study we show that zoledronate has beneficial effects on both lifespan and healthspan using Drosophila as a model. We found that zoledronate extended lifespan, improved climbing activity and reduced intestinal epithelial dysplasia and permeability in aged flies. Mechanistic studies showed that zoledronate conferred resistance to oxidative stress and reduced accumulation of X-ray-induced DNA damage via inhibition of FPPS. Moreover, zoledronate inhibited pAKT in the mTOR pathway and functioned via dFOXO, a molecule associated with increased longevity, downstream of the mevalonate pathway. Taken together, our work indicates that zoledronate, a drug already widely used and dosed only once a year to prevent osteoporosis, modulates important mechanisms of ageing. Its repurposing holds great promise as a treatment to improve healthspan.

pharmacology and toxicology↗

bioRxiv2017

A genome-wide RNAi screen identifies MASK as a positive regulator of cytokine receptor stability

In order for cells to sense and thus respond to their environment, they require transmembrane receptors, which bind extracellular ligands and then transduce this signal within the cell. A subset of receptors, with single-pass transmembrane domains are known as cytokine receptors and act via the Janus Kinase and Signal Transducer and Activator of Transcription (JAK/STAT) pathway. These receptors are essential for processes such as haematopoiesis, immune responses and tissue homeostasis. In order to transduce ligand activation, cytokine receptors must dimerise. However, mechanisms regulating their dimerisation are largely unknown. In order to better understand the processes regulating cytokine receptor levels, activity and dimerisation, we used the highly conserved JAK/STAT pathway in Drosophila, which acts via a single receptor, known as Domeless. We have performed a genome-wide RNAi screen in Drosophila cells, identifying MASK as a positive regulator of Domeless dimerisation and protein levels. We show that MASK is able to regulate JAK/STAT signalling both in vitro and in vivo. We go on to show that MASK is able to bind to Domeless via its Ankyrin repeat domains and alters the stability of the receptor. Finally, we extend our observations to the human homologue, ANKHD1, and demonstrate functional conservation, with ANKHD1 able to regulate JAK/STAT signalling and the levels of a subset of pathway receptors in human cells. Taken together, we have identified MASK as a conserved regulator of cytokine receptor levels, which may have implications for human health.

cell biology↗