Biology subjects

Krueger, E.

Publications and source records attributed to Krueger, E..

7 recordsLinked to original sources

bioRxiv2026

Organelle Volume Facilitates Spindle Positioning During C. elegans Female Meiosis

Cortical positioning of oocyte meiotic spindles is required for reducing chromosome number by segregating chromosomes into polar bodies. In C. elegans, kinesin-1 transports membrane-bound organelles inward into a central ball that is hypothesized to push the meiotic spindle outward. Using focused ion beam scanning electron microscopy, we found that the percent volume occupied by membrane-bound organelles was 28% in a mature oocyte that has completed endocytosis of the yolk precursor, vitellogenin, compared to 17% in a less mature oocyte that has not yet endocytosed vitellogenin. We therefore hypothesized that blocking endocytosis of vitellogenin would reduce the size of the central ball of organelles packed inward by kinesin-1 and limit outward movement of the spindle. Depletion of vitellogenin or proteins required for endocytosis resulted in a smaller central volume of kinesin-coated organelles and defective spindle positioning. A computer simulation of a simple exclusion model faithfully recapitulated wildtype and mutant spindle position phenotypes. These results support a volume exclusion model for positioning acentriolar meiotic spindles.

cell biology↗

bioRxiv2025

Molecular mechanisms underlying the early steps of floral initiation in seasonal flowering genotypes of cultivated strawberry

Floral initiation is required for sexual reproduction in angiosperm plants, and has a significant impact on crop yields. In cultivated strawberry, the molecular basis of floral initiation is poorly understood and most studies have focused on a single genotype grown under controlled conditions. To gain more insight into this process, we conducted a study under natural conditions in two countries using two seasonal flowering cultivars. We focused on the early steps of floral initiation by using samples spanning key developmental stages of the shoot apical meristem. The analysis of differential gene expression in leaf and terminal bud tissues revealed enrichment for genes involved in carbohydrate metabolism and phytohormone pathways in leaves. Other protein classes that were enriched during early floral initiation were associated with cytoskeleton organization, cell cycle regulation, and chromatin structure. We also identified genes associated with the photoperiodic pathway, well-characterized floral integrators such as TFL1 and SOC1, and several linked to phytohormone regulation, such as XTH23, PP2 and EIN3.

plant biology↗

bioRxiv2024

Platelets induce cell apoptosis of cardiac cells via FasL after acute myocardial infarction

Acute myocardial infarction (AMI) is one of the leading causes of death worldwide. Cell apoptosis in the myocardium plays an important role in ischemia and reperfusion (I/R) injury, leading to cardiac damage and dysfunction. Platelets are major players of hemostasis and play a crucial role in vessel occlusion, inflammation and cardiac remodeling after I/R. Here, we studied the impact of platelets on cell apoptosis in the myocardium using a close-chest mouse model of AMI. We found caspase-3 positive resident cardiac cells while leukocytes were negative for caspase-3. Using two different mouse models of thrombocytopenia, we detected a significant reduction of caspase-3 positive cells in the infarct border zone after I/R injury. Further, we identified platelet FasL to induce cell apoptosis via the extrinsic pathway of Fas receptor activation of target cells. Mechanistically, hypoxia triggers platelet adhesion to FasR suggesting that platelet induced apoptosis is elevated after I/R. Platelet-specific FasL knock-out mice showed reduced Bax and BcL-2 expression suggesting that platelets modulate the intrinsic and the extrinsic pathway of apoptosis leading to reduced infarct size after myocardial I/R injury. Therefore, platelet induced cardiac damage needs to be taken into account while optimizing antithrombotic/antiplatelet strategies for patients with AMI.

molecular biology↗

bioRxiv2023

Collagen receptor GPVI-mediated platelet activation and pro-coagulant activity aggravates inflammation and aortic wall remodelling in abdominal aortic aneurysm

Platelets play an important role in cardio- and cerebrovascular diseases. Abdominal aortic aneurysm (AAA) is a highly lethal, atherosclerotic-related disease with characteristic features of progressive dilatation of the abdominal aorta and degradation of the vessel wall accompanied by chronic inflammation. Platelet activation and pro-coagulant activity play a decisive role in the AAA pathology as they might trigger AAA development in both mice and men. The present study investigated the impact of the major platelet collagen receptor glycoprotein (GP)VI in cellular processes underlying AAA initiation and progression. Genetic deletion of GPVI offered protection of mice against aortic diameter expansion in experimental AAA. Mechanistically, GPVI deficiency resulted in decreased inflammation with reduced infiltration of neutrophils and platelets into the aortic wall. Further, remodelling of the aortic wall was improved in absence of GPVI, indicated by reduced MMP2/9 and OPN plasma levels and an enhanced -SMA content within the aortic wall, accompanied by reduced cell apoptosis. As a result, an elevation in intima/media thickness and elastin content were observed in GPVI-deficient PPE mice, coursing a significantly reduced aortic diameter expansion and reduced aneurysm incidence. In AAA patients, enhanced plasma levels of soluble GPVI and fibrin, besides fibrin accumulation within the intraluminal thrombus (ILT) suggested that GPVI might serve as a biomarker and mediator in fibrin-supported stabilization of the ILT. In conclusion, our results emphasize the potential need for a GPVI-targeted anti-platelet therapy to reduce AAA initiation and progression, as well as to protect AAA patients from aortic rupture. Translational perspectiveAbdominal aortic aneurysm (AAA) is an atherosclerotic-related, cardiovascular disease (CVD) with high mortality. The impact of platelets in different cellular processes underlying AAA initiation and progression remains unclear.Therefore, we analysed the role of the major platelet collagen receptor GPVI in the pathogenesis of AAA. Results from platelet depleted mice and patients with AAA revealed a significant contribution of GPVI to the inflammatory response and remodelling process of the aorta. Further, elevated accumulation of fibrin, a recently identified ligand of GPVI in the intraluminal thrombus (ILT) and in the plasma of AAA patients, suggests that GPVI binding to fibrin plays a role in ILT formation and probably stabilization of the abdominal aorta. Furthermore, increased levels of sGPVI suggest that GPVI might serve as a clinical biomarker for AAA. Thus, therapeutic targeting of GPVI-mediated platelet activation might be an effective anti-thrombotic strategy for AAA patients.

cell biology↗

bioRxiv2023

Deep learning-based aberration compensation improves contrast and resolution in fluorescence microscopy

Optical aberrations hinder fluorescence microscopy of thick samples, reducing image signal, contrast, and resolution. Here we introduce a deep learning-based strategy for aberration compensation, improving image quality without slowing image acquisition, applying additional dose, or introducing more optics into the imaging path. Our method (i) introduces synthetic aberrations to images acquired on the shallow side of image stacks, making them resemble those acquired deeper into the volume and (ii) trains neural networks to reverse the effect of these aberrations. We use simulations and experiments to show that applying the trained de-aberration networks outperforms alternative methods, providing restoration on par with adaptive optics techniques; and subsequently apply the networks to diverse datasets captured with confocal, light-sheet, multi-photon, and super-resolution microscopy. In all cases, the improved quality of the restored data facilitates qualitative image inspection and improves downstream image quantitation, including orientational analysis of blood vessels in mouse tissue and improved membrane and nuclear segmentation in C. elegans embryos.

bioengineering↗

bioRxiv2023

Activating the NFE2L1-ubiquitin-proteasome system by DDI2 protects from ferroptosis

Ferroptosis is an iron-dependent, non-apoptotic form of cell death initiated by oxidative stress and lipid peroxidation. Recent evidence has linked ferroptosis to the action of the transcription factor Nuclear factor erythroid-2 derived,-like-1 (NFE2L1). NFE2L1 regulates proteasome abundance in an adaptive fashion, maintaining protein quality control to secure cellular homeostasis, but the regulation of NFE2L1 during ferroptosis and the role of the ubiquitin-proteasome system (UPS) herein are still unclear. In the present study, using an unbiased proteomic approach charting the specific ubiquitylation sites, we show that induction of ferroptosis leads to recalibration of the UPS. RSL3-induced ferroptosis inhibits proteasome activity and leads to global hyperubiquitylation, which is linked to NFE2L1 activation. As NFE2L1 resides in the endoplasmic reticulum tethered to the membrane, it undergoes complex posttranslational modification steps to become active and induce the expression of proteasome subunit genes. We show that proteolytic cleavage of NFE2L1 by the aspartyl protease DNA-damage inducible 1 homolog 2 (DDI2) is a critical step for the ferroptosis-induced feed-back loop of proteasome function. Cells lacking DDI2 cannot activate NFE2L1 in response to RSL3 and show global hyperubiquitylation. Genetic or chemical induction of ferroptosis in cells with a disrupted DDI2-NFE2L1 pathway diminishes proteasomal activity and promotes cell death. Also, treating cells with the clinical drug nelfinavir, which inhibits DDI2, sensitized cells to ferroptosis. In conclusion, our results provide new insight into the importance of the UPS in ferroptosis and highlight the role of the DDI2-NFE2L1 as a potential therapeutic target. Manipulating DDI2-NFE2L1 activity through chemical inhibition might help sensitizing cells to ferroptosis, thus enhancing existing cancer therapies. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/547652v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@b3f899org.highwire.dtl.DTLVardef@18625feorg.highwire.dtl.DTLVardef@287bcborg.highwire.dtl.DTLVardef@1d758d1_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2020

Immunoproteasome impairment via β5i/LMP7-deletion leads to sustained pancreatic injury and delayed recovery from experimental pancreatitis.

Background & AimsUncovering potential new targets involved in pancreas recovery may permit the development of new therapies and improvement of pancreatitis treatment. One disease mechanism comprises the endoplasmic reticulum stress response and a key regulator to prevent proteotoxic stress in an inflammatory context is the immunoproteasome, an induced form of the constitutive proteasome. Our aim was therefore to investigate the role of the immunoproteasome in acute pancreatitis. MethodsAcute pancreatitis was induced in wild type and LMP7-/- mice and several biochemical parameters for disease severity were addressed, including protease activities and histology of pancreatic damage. Real-time PCR was used to measure pro-inflammation and unfolded protein response. Serum IL-6 was detected by cytometric bead assay. Western blotting was used to quantify the ratio of ubiquitin-protein conjugates as well as unfolded protein response activation. Immunofluorescence identified leukocytes infiltration as well as ubiquitin-protein conjugates in the pancreas. ResultsIn this study, we demonstrate that the {beta}5i/LMP7-subunit deletion correlates with persistent pancreatic damage. Interestingly, immunoproteasome-deficient mice unveil increased activity of pancreatic enzymes as well as higher secretion of Interleukin-6 and transcript expression of the Interleukin IL-1{beta}, IFN-{beta} cytokines and the CXCL-10 chemokine. Thereafter, acinar cell death was increased, which appears to be due to the greater accumulation of ubiquitin-protein conjugates and prolonged unfolded protein response. ConclusionsOur findings suggest that the immunoproteasome plays a protective role in acute pancreatitis via its role in the clearance of damaged proteins and the balance of ER-stress responses in pancreatic acini as well as in macrophages cytokine production.

physiology↗