Biology subjects

Krause, E.

Publications and source records attributed to Krause, E..

8 recordsLinked to original sources

bioRxiv2025

Distinct Flower signaling domains orchestrate cellular fitness via secreted vesicles in Aβ-induced neurodegeneration

Cellular fitness surveillance preserves tissue integrity, yet its regulation within the mammalian brain remains poorly understood. We identify a bifurcated mechanism in the transmembrane protein Flower--encoding both survival-promoting ("win") and apoptosis-inducing ("lose") isoforms. We demonstrate that astrocytes secrete specialized extracellular vesicles (EVs), termed "fitness vesicles," carrying Flower to facilitate competitive selection across distal cell populations. The N-terminal Flower domain acts extrinsically via these EVs to drive the elimination of less-fit neighbors. Conversely, the "win"-specific C-terminal domain functions as a cell-intrinsic module; it translocates to the nucleus under stress to repress Caspase-3 and provide resilience. In Alzheimers disease (AD) models and human AD brains, Flower-positive astrocytes accumulate around amyloid-{beta} (A{beta}) plaques. Under A{beta} stress, the "win" isoform reprograms astrocytes toward a neuroprotective state that enhances plaque clearance while ensuring cell-intrinsic survival. Our findings reveal how Flower couples long-range, EV-mediated cellular selection with cell-autonomous protection to coordinate astrocyte quality control and tissue resilience in neurodegeneration.

neuroscience↗

bioRxiv2025

IFNγ expression correlates with enhanced cytotoxicity in CD8+ T cells

BackgroundCD8+ T lymphocytes (CTLs) act as serial killers of infected or malignant cells by releasing large amounts of interferon-gamma (IFN{gamma}) and granzymes. Although IFN{gamma} is a pleiotropic cytokine with diverse immunomodulatory functions, its precise spatiotemporal regulation and role in CTL-mediated cytotoxicity remain incompletely characterized. MethodsUsing wild-type (WT) and granzyme B-mTFP knock-in mice, we combined in vitro approaches, including T-cell isolation and culture, plate-bound anti-CD3e stimulation, degranulation assays, flow cytometry, immunofluorescence, and structured illumination microscopy, to investigate IFN{gamma} dynamics in CTLs. ResultsIFN{gamma} expression in CTLs was rapid, transient, and strictly dependent on T-cell receptor (TCR) activation. We identified two functionally distinct IFN{gamma}-producing subsets: IFN{gamma}high (IFN{gamma}hi) and IFN{gamma}low (IFN{gamma}lo) CTLs. IFN{gamma}hi CTLs exhibited an effector/effector memory phenotype, significantly elevated CD107a surface expression (a marker of lytic granule exocytosis), and pronounced colocalization with cis-Golgi and granzyme B compared to IFN{gamma}lo CTLs. Furthermore, CRTAM, an early activation marker, correlated with IFN{gamma} expression in naive CTLs. ConclusionOur findings establish a link between elevated IFN{gamma} production and enhanced CTL cytotoxicity, implicating CRTAM as a potential regulator of early CTL activation and IFN{gamma} induction. These insights provide a foundation for optimizing T cell-based immunotherapies against infections and cancers.

molecular biology↗

bioRxiv2025

Lytic IFNγ is stored in granzyme B-containing cytotoxic granules and co-secreted by effector CD8⁺ T cells

Cytotoxic CD8 T cells form immunological synapses with target cells and release effector molecules, including IFN{gamma}, to mediate antitumor immunity. However, the mechanisms by which IFN{gamma} contributes to cytotoxicity remain incompletely understood. Here, we identify a subset of IFN{gamma} stored within GzmB cytotoxic granules (CGs) in activated mouse and human CD8 T cells, termed lytic IFN{gamma}. Lytic IFN{gamma} is polarized to the synapse and co-secreted with GzmB in both soluble and supramolecular attack particle (SMAP)-associated forms. Mouse CD8 T cells lacking the vesicle priming factor Munc13-4 exhibit impaired both CG and early IFN{gamma} release at the immunological synapse, while prolonged synaptic engagement restores IFN{gamma} secretion. Super-resolution imaging demonstrates that sustained synaptic interactions drive IFN{gamma} secretion at distal membrane sites, suggesting the existence of distinct IFN{gamma} populations with potentially diverse functions beyond lytic IFN{gamma}. These findings uncover an unrecognized mechanism of IFN{gamma} storage and release, underscoring its pivotal role in CD8 T cell-mediated tumor elimination.

immunology↗

bioRxiv2022

Pyrophosphoproteomics: extensive protein pyrophosphorylation revealed in human cell lines

Reversible protein phosphorylation is a central signaling mechanism in eukaryotic cells. While the identification of canonical phosphorylation sites using mass-spectrometry (MS) based proteomics has become routine, annotation of non-canonical phosphorylation has remained a challenge. Here, we report a tailored pyrophosphoproteomics workflow to detect and reliably assign protein pyrophosphorylation in two human cell lines, providing the first direct evidence of endogenous protein pyrophosphorylation. Detection of protein pyrophosphorylation was reproducible, specific and consistent with previous biochemical evidence relating the installation of the modification to inositol pyrophosphates (PP-InsPs). We manually validated 148 pyrophosphosites across 71 human proteins, the most heavily pyrophosphorylated of which were the nucleolar proteins NOLC1 and TCOF1. A predictive workflow based on the MS data set was established to recognize putative pyrophosphorylation sequences, and UBF1, a nucleolar protein incompatible with the proteomics method, was biochemically shown to undergo pyrophosphorylation. When the biosynthesis of PP-InsPs was perturbed in a model cell line, proteins expressed in this background exhibited lower levels of pyrophosphorylation. Disruption of PP-InsP biosynthesis also significantly reduced rDNA transcription, potentially by lowering pyrophosphorylation on regulatory proteins NOLC1, TCOF1, and UBF1. Overall, protein pyrophosphorylation emerges as an archetype of non-canonical phosphorylation, and should be considered in future phosphoproteomic analyses.

biochemistry↗

bioRxiv2021

Dendritic membrane resistance modulates activity-induced Ca2+ influx in oxytocinergic magnocellular neurons of mouse PVN

Hypothalamic oxytocinergic magnocellular neurons have a fascinating ability to release peptide from both their axon terminals and from their dendrites. Existing data indicates there is a flexible relationship between somatic activity and dendritic release, but the mechanisms governing this relationship are not completely understood. Here we use a combination of electrical and optical recording techniques to quantify activity-dependent calcium influx in proximal vs. distal dendrites of oxytocinergic magnocellular neurons located in the paraventricular nucleus of the hypothalamus (OT-MCNs). Results reveal that the dendrites of OT-MCNs are weak conductors of somatic voltage changes, and yet activity-induced dendritic calcium influx can be robustly regulated by a diverse set of stimuli that open or close ionophores located along the dendritic membrane. Overall, this study reveals that dendritic membrane resistance is a dynamic and endogenously regulated feature of OT-MCNs that is likely to have substantial functional impact on central oxytocin release. IMPACT STATEMENTActivity-induced dendritic calcium influx in oxytocinergic magnocellular neurons can be robustly modulated by a highly diverse set of stimuli acting on distinct types of ionophores expressed along the dendritic membrane.

neuroscience↗

bioRxiv2020

Central and peripheral GLP-1 systems independently and additively suppress eating

The anorexigenic peptide glucagon-like peptide-1 (GLP-1) is secreted from gut enteroendocrine cells and brain preproglucagon (PPG) neurons, which respectively define the peripheral and central GLP-1 systems. As peripheral satiation signals are integrated in the nucleus tractus solitarius (NTS), PPGNTS neurons are assumed to link the peripheral and central GLP-1 systems, forming a unified GLP-1 gut-brain satiation circuit. This hypothesis, however, remains unsubstantiated. We report that PPGNTS neurons encode satiation in mice, consistent with vagal gastrointestinal distension signalling. However, PPGNTS neurons predominantly receive vagal input from oxytocin receptor-expressing vagal neurons, rather than those expressing GLP-1 receptors. Furthermore, PPGNTS neurons are not necessary for eating suppression induced by the GLP-1 receptor agonists liraglutide or semaglutide, and semaglutide and PPGNTS neuron activation additively suppress eating. Central and peripheral GLP-1 systems thus suppress eating via independent gut-brain circuits, hence PPGNTS neurons represent a rational pharmacological target for anti-obesity combination therapy with GLP-1 receptor agonists. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/234427v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@1c7643aorg.highwire.dtl.DTLVardef@18520daorg.highwire.dtl.DTLVardef@12fc8fdorg.highwire.dtl.DTLVardef@34809b_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract: C_FIG

neuroscience↗

bioRxiv2020

Neuronal autophagy regulates presynaptic neurotransmission by controlling the axonal endoplasmic reticulum

Information processing in the brain is encoded as electrical impulses in neurons that are relayed from the presynaptic compartment to postsynaptic neurons by regulated neurotransmitter release. Neurons are known to rely on autophagy for the removal of defective proteins or organelles to maintain synaptic neurotransmission and to counteract neurodegeneration. In spite of its importance for neuronal health, the physiological substrates of neuronal autophagy in the absence of proteotoxic challenge have remained largely elusive. We use knockout mice conditionally lacking the essential autophagy protein ATG5 and quantitative proteomics to demonstrate that loss of neuronal autophagy causes the selective accumulation of tubular endoplasmic reticulum (ER) in axons, resulting in increased excitatory neurotransmission and compromised postnatal viability in vivo. The gain in excitatory neurotransmission is shown to be a consequence of elevated calcium release from ER stores via ryanodine receptors accumulated in axons and at presynaptic sites. We propose a model in which neuronal autophagy controls axonal ER calcium stores to regulate neurotransmission in healthy neurons and in the brain.

neuroscience↗

bioRxiv2019

Dynamic Palmitoylation Events Following T-Cell Receptor Signaling

Palmitoylation is the reversible addition of palmitate to cysteine via a thioester linkage. Following stimulation of the T-cell receptor we find a number of proteins are newly palmitoylated, including those involved in vesicle-mediated transport and Ras signal transduction. Among these stimulation-dependent palmitoylation targets are the v-SNARE VAMP7, important for docking of vesicular LAT during TCR signaling, and the largely undescribed palmitoyl acyltransferase DHHC18 that is expressed in two isoforms in T cells. Using our newly developed On-Plate Palmitoylation Assay (OPPA), we show DHHC18 is capable of palmitoylating VAMP7 at Cys183. Cellular imaging shows that the palmitoylation-deficient protein fails to be retained at the Golgi.

biochemistry↗