Biology subjects

Kiermaier, E.

Publications and source records attributed to Kiermaier, E..

9 recordsLinked to original sources

bioRxiv2026

NLRP3 activators disrupt the endocytic AP2 complex and plasma membrane signaling

Organellar perturbations are linked to NLRP3 inflammasome activation, however, it remains unclear whether unrelated agonists converge on a common upstream pathway. Here, we traced intracellular organelle and protein movements by differential ultracentrifugation combined with mass spectrometry-based proteomics. We show that NLRP3 activators uniformly disrupt the endocytic Adaptor Protein 2 (AP2) complex, whereas other subcellular rearrangements are stimulus-specific. We discovered Dynasore as a K-efflux-independent NLRP3 activator that engages this signaling node irrespective of endocytosis inhibition. Pharmacological and genetic perturbation of AP2 renders cells unresponsive to extracellular cues, blunting GPCR signaling, cAMP production, and chemotaxis, thereby enforcing a frozen signaling state that propagates NLRP3 inflammasome activation. Collectively, our study reveals a common surveillance checkpoint linking impaired plasma membrane signaling to the execution of inflammation and cell death. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/707400v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@178eb1dorg.highwire.dtl.DTLVardef@193cb02org.highwire.dtl.DTLVardef@1f50080org.highwire.dtl.DTLVardef@1f3e3e4_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

Simulation-Based Inference of Cell Migration Dynamics in Complex Spatial Environments

To assess cell migration in complex spatial environments, microfabricated chips, such as mazes and pillar forests, are routinely used to impose spatial and mechanical constraints, and cell trajectories are followed within these structures by advanced imaging techniques. In systems mechanobiology, computational models serve as essential tools to uncover how physical geometry influences intracellular dynamics; however, decoding such complex behaviors requires advanced inference techniques. Here, we integrated experimental observations of dendritic cell migration in a geometrically constrained microenvironment into a Cellular Potts model. We demonstrated that these spatial constraints modulate the motility dynamics, including speed and directional changes. We show that classical summary statistics, such as mean squared displacement and turning angle distributions, can resolve key mechanistic features but fail to extract richer spatiotemporal patterns, limiting accurate parameter inference. To solve this, we applied neural posterior estimation with in-the-loop learning of summary features. This learned summary representation of the data enables robust and flexible parameter inference, providing a data-driven framework for model calibration and advancing quantitative analysis of cell migration in structured microenvironments.

cell biology↗

bioRxiv2024

Mechanical Centrosome Fracturing during Cell Navigation

The centrosome is the primary microtubule orchestrator in most eukaryotic cells, nucleating and anchoring microtubules that grow radially and exert forces on cargos. At the same time, mechanical stresses from the microenvironment and cellular shape changes compress and bend microtubules. Yet, centrosomes are membrane-less organelles, raising the question of how centrosomes withstand mechanical forces. Here we discover that centrosomes in non-dividing cells can mechanically fracture. We reveal that centrosomes experience mechanical deformations during microenvironmental confinement and navigational pathfinding by motile cells. Coherence of the centrosome is maintained by Dyrk3, preventing fracturing by mechanical forces. Centrosome fracturing impedes cellular function by generating coexisting microtubule organizing centers that compete during path navigation and thereby cause cellular entanglement in the microenvironment. Our findings show that non-dividing cells actively maintain the integrity of the centrosome to withstand mechanical forces. Given that almost all cells in multicellular organism experience forces, these results suggest that centrosome stability preservation is fundamental during development, tissue maintenance, immunology, and disease. One-Sentence SummaryPathfinding during cellular motility causes centrosome breakage counteracted by Dyrk3 activity.

cell biology↗

bioRxiv2024

A fluorescent probe enables the discovery of improved antagonists targeting the intracellular allosteric site of the chemokine receptor CCR7

Intracellularly acting ligands of G protein-coupled receptors (GPCRs) are gaining significant interest in GPCR drug discovery. In this study, we report the development of the fluorescent ligand Mz437 (4) targeting the CC chemokine receptor CCR7 at an intracellular allosteric site. We demonstrate its experimental power by applying 4 to identify two improved intracellular CCR7 antagonists, SLW131 (10) and SLW132 (21m), developed by converting two weakly active antagonists into single- or double-digit nanomolar ligands with minimal modifications. The thiadiazoledioxide 10 was derived from the CCR7 antagonist Cmp2105 by removing a methyl group from the benzamide moiety, while the squaramide 21m was obtained from the CXCR1/CXCR2 antagonist and clinical candidate navarixin by replacing the ethyl substituent by a tert-butyl group to engage a lipophilic subpocket. We show that 10 and 21m qualify to probe CCR7 biology both in recombinant cells and in the endogenous signaling environment of immune cells. Our novel probes are expected to facilitate the design of next-generation intracellular CCR7 ligands and serve as molecular tools to interrogate CCR7 biology in human and murine endogenous settings. Entry for the Table of Contents O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=109 SRC="FIGDIR/small/607356v1_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@1298d55org.highwire.dtl.DTLVardef@fdebf2org.highwire.dtl.DTLVardef@8d9aecorg.highwire.dtl.DTLVardef@b6308d_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2024

Multiple clustered centrosomes in antigen-presenting cells foster T cell activation without MTOC polarization

Cellular polarization plays a pivotal role in regulating immunological processes and is often associated with centrosome reorientation. During immune synapse (IS) formation centrosome repositioning in lymphocytes assists in T cell activation. While a single centrosome, consisting of two centrioles, is present in T cells, antigen-presenting cells (APCs) such as dendritic cells (DCs) amplify centrioles during maturation leading to increased centrosome numbers upon immune activation. How centrosome amplification in DCs affects IS formation and T cell activation is unclear. In this study, we combine experimental data with mathematical and computational modelling to provide evidence that centrosome amplification in DCs enhances antigen-specific T cell activation. Extra centrioles in DCs form active centrosomes, which cluster during DC-T cell interactions and unlike in T cells, localize close to the cell center. Perturbing either centriole numbers or centrosome configuration in DCs results in impaired T cell activation. Collectively, our results highlight a crucial role for centrosome amplification and optimal centrosome positioning in APCs for controlling T cell responses.

cell biology↗

bioRxiv2024

Exact centriole counts are critical for B cell development but not function

Centrioles define centrosome structure and function. Deregulation of centriole numbers can cause developmental defects and foster malignant disease. The p53 tumor suppressor limits the growth of cells lacking or harboring additional centrioles and can be engaged by the "mitotic surveillance" or the "PIDDosome pathway", respectively. Here, we show that early B cell progenitors frequently present extra centrioles that are rapidly lost during maturation. Increasing centriole counts beyond physiological levels by Polo-like kinase 4 (PLK4) overexpression induces apoptosis, suggesting clearance of such cells during development. Remarkably, this apoptotic response is independent of PIDD1 or p53, but can be blocked by excess BCL2. In contrast, loss of centrosomes upon Plk4 deletion arrests B cell development at the pro B cell stage. This defect can be rescued by co-deletion of Usp28, a critical component of the mitotic surveillance pathway that restores cell number and function in the absence of centrioles. In both scenarios, too many and too few centrosomes, mitochondrial apoptosis is engaged to kill B cells with abnormal centriole counts during their development with progenitor B cells being intolerant to centriole loss but permissive to centriole amplification. Unexpectedly, our findings show that centrioles are dispensable for mounting an effective humoral immune response.

cell biology↗

bioRxiv2023

Fetal liver macrophages contribute to the hematopoietic stem cell niche by controlling granulopoiesis

During embryogenesis, the fetal liver becomes the main hematopoietic organ, where stem and progenitor cells as well as immature and mature immune cells form an intricate cellular network. Hematopoietic stem cells (HSCs) reside in a specialized niche, which is essential for their proliferation and differentiation. However, the cellular and molecular determinants contributing to this fetal HSC niche remain largely unknown. Macrophages are the first differentiated hematopoietic cells found in the developing liver, where they are important for fetal erythropoiesis by promoting erythrocyte maturation and phagocytosing expelled nuclei. Yet, whether macrophages play a role in fetal hematopoiesis beyond serving as a niche for maturing erythroblasts remains elusive. Here, we investigate the heterogeneity of macrophage populations in the fetal liver to define their specific roles during hematopoiesis. Using a single-cell omics approach combined with spatial proteomics and genetic fate-mapping models, we found that fetal liver macrophages cluster into distinct yolk sac-derived subpopulations and that long-term HSCs are interacting preferentially with one of the macrophage subpopulations. Fetal livers lacking macrophages show a delay in erythropoiesis and have an increased number of granulocytes, which can be attributed to transcriptional reprogramming and altered differentiation potential of long-term HSCs. Together, our data provide a detailed map of fetal liver macrophage subpopulations and implicate macrophages as part of the fetal HSC niche.

developmental biology↗

bioRxiv2022

GPR183 targets lung-resident CD301b+ conventional dendritic cells type 2 to a subtissular TSLP-TSLP receptor-mediated survival niche within the adventitial cuff

Conventional dendritic cells (cDCs) are strategically localized throughout non-lymphoid tissues. How such spatially regulated subtissular placement is achieved remains largely elusive. Here, we reveal that GPR183 targets CD301b+ cDC2 to a TSLP-dependent survival niche within the adventital cuff. We identified a close association of CD301b+ cDC2 with PDGFR+ fibroblasts within the adventitial region of the lung. Genetic ablation of GPR183 within the cDC lineage leads to a selective loss of CD301b+ cDC2 in conjunction with the loss of CD301b+ cDC2 : fibroblast colocalization. Next bone marrow chimeric experiments and expression studies suggested adventitial fibroblasts as the main source of 7,25 hydroxycholesterol, the natural ligand of GPR183. Single cell transcriptomic receptor ligand inference and subsequent genetic validation revealed TSLP receptor signalling as a crucial fibroblast derived CD301b+ cDC2 survival factor. These data expose a subtissular localization mechanism for tissue-specific functionalization of CD301b+ cDC2.

immunology↗

bioRxiv2019

Microtubules coordinate protrusion-retraction dynamics in migrating dendritic cells

Cells navigating through tissues face a fundamental challenge: while multiple cellular protrusions explore different paths through the complex geometry of an interstitial matrix the cell needs to avoid becoming too long or ramified, which might ultimately lead to a loss of physical coherence. How a cell surveys its own shape to inform the actomyosin system to retract entangled or stretched protrusions is not understood. Here, we demonstrate that spatially distinct microtubule (MT) dynamics regulate amoeboid cell migration by locally specifying the retraction of explorative protrusions. In migrating dendritic cells (DCs), the microtubule organizing center (MTOC) guides the path through a three dimensional (3D) interstitium and local MT depolymerization in protrusions remote from the MTOC triggers myosin II dependent contractility via the RhoA exchange factor Lfc. Depletion of Lfc leads to aberrant myosin localization, thereby causing two effects that rate-limit locomotion: i) impaired cell edge coordination during path-finding and ii) defective adhesion-resolution. Such compromised cell shape control is particularly hindering when cells navigate through geometrically complex microenvironments, where it leads to entanglement and ultimately fragmentation of the cell body. Our data demonstrate that MTs control cell shape and coherence by locally controlling protrusion-retraction dynamics of the actomyosin system.

cell biology↗