Biology subjects

Schubert, A.

Publications and source records attributed to Schubert, A..

4 recordsLinked to original sources

bioRxiv2025

Independent signaling pathways provide a fail-safe mechanism to prevent tumorigenesis

Controlled signaling activity is vital for normal tissue homeostasis and oncogenic signaling activation facilitates tumorigenesis. Here we use single-cell transcriptomics to investigate the effects of pro-proliferative signaling on epithelial homeostasis using the Drosophila follicle cell lineage. Notably, EGFR-Ras overactivation induces cell cycle defects by activating the transcription factors Pointed and E2f1 and impedes differentiation. Hh signaling simultaneously promotes an undifferentiated state and induces differentiation via activation of EMT-associated transcription factors zfh1 and Mef2. As a result, overactivation of Hh signaling generates a transcriptional hybrid state comparable to epithelial-mesenchymal-transition. Co-overactivation of Hh signaling with EGFR-Ras signaling blocks differentiation and induces key characteristics of tumor cells including a loss of tissue architecture caused by reduced expression of cell adhesion molecules, sustained proliferation and an evasion of cell cycle checkpoints. These findings provide new insight into how non-interacting signaling pathways converge at the transcriptional level to prevent malignant cell behavior. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=194 HEIGHT=200 SRC="FIGDIR/small/640798v2_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@762724org.highwire.dtl.DTLVardef@103d1a6org.highwire.dtl.DTLVardef@1b90caforg.highwire.dtl.DTLVardef@1eff5a4_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2025

Image-based screens identify regulators of endogenous Dvl2 biomolecular condensates

Dishevelled (Dvl) proteins are essential transducers in Wnt signaling pathways, which have been implicated in development, stem cell maintenance, and human diseases such as cancer. Several studies have shown that Dvl proteins form dynamic biomolecular condensates. However, how cellular signals and cell states influence the formation of biomolecular condensates remains poorly understood. Here, we analyzed cells with endogenous Dvl2 condensates using image-based cell sorting in combination with phosphoproteomics and identified protein enrichment for Wnt/PCP signaling and the G2/M cell cycle transition. We then performed an image-based high-throughput screen to identify small molecule kinase inhibitors that affect Dvl2 liquid-liquid phase separation. Strikingly, CK1{delta}/{varepsilon} inhibition blocked Dvl2 condensate formation. Its effect on Wnt signaling was modulated in genetic epistasis experiments with loss-of-function alleles of APC, Axin1, and MCC. Our study highlights the interplay between post-translational modifications and condensate dynamics, opening new avenues for research on their role in cellular signaling and disease intervention.

cell biology↗

bioRxiv2024

Distinct Non-occluding Functions of Septate Junction Components in Signaling Pathway Regulation and Cell Polarity During Epithelial Development

Occluding junctions are essential for epithelial tissue integrity and barrier function but also exert non-occluding roles. Here we identify a several crucial function of the invertebrate occluding junction components Coracle, Nervana 2, Neurexin-IV, and Kune-kune in regulating cell polarity during follicle epithelium development. We show that the morphogenesis of the follicular stalk is an actin-driven process that requires intact apical-basal cell polarity, which is controlled by septate junction components. Occluding junction components further regulate signaling pathways in a cell-type specific manner. In undifferentiated stem cells and immediate daughters, septate junction components promote effective Wnt signaling to control proliferation, while they limit Jak-STAT signaling activity induced by polar cells. Together, our data emphasize the multiple roles of occluding junction components independent of their classical role in forming the paracellular barrier.

cell biology↗

bioRxiv2024

Molecular principles of redox-coupled sodium pumping of the ancient Rnf machinery

The Rnf complex is the primary respiratory enzyme of several anaerobic prokaryotes that transfers electrons from ferredoxin to NAD+ and pumps sodium ions (Na+) across a membrane, powering ATP synthesis. Rnf is widespread in primordial organisms and the evolutionary predecessor of the Na+-pumping NADH-quinone oxidoreductase (Nqr)1. By running in reverse, Rnf reduces ferredoxin with NADH as reductant at the expense of the transmembrane electrochemical ion gradient and provides low potential electrons for nitrogenases as well as CO2 reductases. Yet, the molecular principles that couple the long-range electron transfer to the Na+ translocation across the membrane remain elusive. Here we resolve key functional states along the electron transfer pathway using redox-controlled cryo-electron microscopy (cryo-EM) that, in combination with biochemical functional assays and atomistic molecular simulations, provide key insight into the redox-driven Na+ pumping mechanism. We show that the reduction of the unique membrane-embedded [2Fe2S] cluster in the vestibule between the RnfA/E subunits electrostatically attracts the sodium ions, and in turn, triggers an inward/outward transition with alternating membrane access driving the Na+ pump and the reduction of NAD+. Our study unveils an ancient mechanism for redox-driven ion pumping, and provides key understanding of the fundamental principles governing energy conversion in biological systems.

biochemistry↗