Biology subjects

Schnoor, M.

Publications and source records attributed to Schnoor, M..

6 recordsLinked to original sources

bioRxiv2023

Arpin deficiency increases actomyosin contractility and vascular permeability

Arpin was discovered as an inhibitor of the Arp2/3 complex localized at the lamellipodial tip of fibroblasts, where it regulated migration steering. Recently, we showed that arpin stabilizes the epithelial barrier in an Arp2/3-dependent manner. However, expression and functions of arpin in endothelial cells (EC) have not yet been described. Arpin mRNA and protein are expressed in EC and downregulated by pro-inflammatory cytokines. Arpin depletion in HUVEC causes the formation of actomyosin stress fibers leading to increased permeability in an Arp2/3-independent manner. Instead, inhibitors of ROCK1 and ZIPK, kinases involved in the generation of stress fibers, normalize the loss-of-arpin effects on actin filaments and permeability. Arpin-deficient mice are viable but show a characteristic vascular phenotype in the lung including edema, microhemorrhage and vascular congestion, increased F-actin levels and vascular permeability. Our data show that, apart from being an Arp2/3 inhibitor, arpin is also a regulator of actomyosin contractility and endothelial barrier integrity. SUMMARYThe expression and functions of arpin in endothelial cells are unknown. We show that arpin controls actomyosin contractility and endothelial barrier integrity in an Arp2/3-independent manner via ROCK1/ZIPK. Arpin-deficient mice are viable, but also show increased basal and induced vascular permeability.

cell biology↗

bioRxiv2023

Paneth and Paneth-like cells undergoing necroptosis fuel intestinal epithelial cell proliferation following IFN-γ stimulation.

The quality of life in patients with inflammatory bowel diseases (IBD) is strongly impaired. Alterations of intestinal epithelial homeostasis contribute to the development and establishment of IBD. Intestinal Paneth and Paneth-like cells produce and secrete luminal proteins sustaining epithelial homeostasis. Here we show that IFN-{gamma} stimulates Paneth and Paneth-like cells degranulation that triggers the proliferation of intestinal epithelial cells (IEC) in a Wnt/{beta}-catenin independent manner. Degranulation in Paneth and Paneth-like cells was mTORC1 and necroptosis dependent. Remarkably, lack of IFN-{gamma}, inhibition of mTORC1, or impeding necroptosis reduces IEC proliferation cytokine-mediated. Our findings identify a new role for IFN-{gamma} in stimulating IEC proliferation through inducing degranulation of Paneth and Paneth-like cells which is mTORC1 and necroptosis- dependent. In a mouse model of colitis, mTORC1 activation and necroptosis regulate Paneth and Paneth-like cell secretion. Furthermore, the colitogenic environment triggers PC metaplasia in the distal region of the large intestine to simulate cell proliferation. HighlightsIFN-{gamma} stimulates proliferation, {beta}-catenin independent. IFN-{gamma} enhances mitochondrial activity and proliferation IFN-{gamma} regulates PC biogenesis. mTORC1-dependent necroptosis mediates secretion in Paneth and Paneth-like cells.

physiology↗

bioRxiv2021

ADAM17 inhibition prevents neutrophilia and lung injury in a mouse model of Covid-19

Severe coronavirus disease 2019 (Covid-19) is characterized by lung injury, cytokine storm and increased neutrophil-to-lymphocyte ratio (NLR). Current therapies focus on reducing viral replication and inflammatory responses, but no specific treatment exists to prevent the development of severe Covid-19 in infected individuals. Angiotensin-converting enzyme-2 ACE-2) is the receptor for SARS-CoV-2, the virus causing Covid-19, but it is also critical for maintaining the correct functionality of lung epithelium and endothelium. Coronaviruses induce activation of a disintegrin and metalloprotease 17 (ADAM17) and shedding of ACE-2 from the cell surface resulting in exacerbated inflammatory responses. Thus, we hypothesized that ADAM17 inhibition ameliorates Covid-19-related lung inflammation. We employed a pre-clinical mouse model using intra-tracheal instillation of a combination of polyinosinic:polycytidylic acid (poly-I:C) and the receptor-binding domain of the SARS-CoV-2 spike protein (RBD-S) to mimic lung damage associated with Covid-19. Histological analysis of inflamed mice confirmed the expected signs of lung injury including edema, fibrosis, vascular congestion and leukocyte infiltration. Moreover, inflamed mice also showed an increased NLR as observed in critically ill Covid-19 patients. Administration of the ADAM17 inhibitors apratastat and TMI-1 significantly improved lung histology and prevented leukocyte infiltration. Reduced leukocyte recruitment could be explained by reduced production of pro-inflammatory cytokines and lower levels of the endothelial adhesion molecules ICAM-1 and VCAM-1. Additionally, the NLR was significantly reduced by ADAM17 inhibition. Thus, we propose inhibition of ADAM17 as a novel promising treatment strategy in SARS-CoV-2-infected individuals to prevent the progression towards severe Covid-19.

pathology↗

bioRxiv2020

Loss of Hem1 disrupts macrophage function and impacts on migration, phagocytosis and integrin-mediated adhesion

The hematopoietic-specific protein 1 (Hem1) comprises an essential subunit of the WAVE Regulatory Complex (WRC) in immune cells. WRC has a fundamental role in Arp2/3 complex activation and the protrusion of branched actin networks in motile cells. Hem1 deficiency leads to suppression of the entire WRC in immune cells. Defective WRC function in macrophages results in loss of lamellipodia and migration defects. Moreover, phagocytosis, commonly accompanied by lamellipodium protrusion during cup formation, is altered in Hem1 null cells concerning frequency and efficacy. When analyzing cell spreading, adhesion and podosome formation, we found that Hem1 null cells are capable, in principle, of podosome formation and consequently, do not show any quantitative differences in extracellular matrix degradation. Their adhesive behavior, however, was significantly altered. Specifically, adhesion as well as de-adhesion of Hem1 null cells was strongly compromised, likely contributing to the observed reduced efficiency of phagocytosis. In line with this, phosphorylation of the prominent adhesion component paxillin was diminished. Non-hematopoietic somatic cells disrupted in expression for both Hem1 and its ubiquitous orthologue Nck-associated protein 1 (Nap1) or the essential WRC components Sra-1/PIR121 did not only confirm defective paxillin phosphorylation, but also revealed that paxillin turnover in focal adhesions is accelerated in the absence of WRC. Finally, adhesion assays using platelets lacking functional WRC as model system unmasked radically decreased IIb{beta}3 integrin activation. Our results thus demonstrate that WRC-driven actin networks impact on integrin-dependent processes controlling formation and dismantling of different types of cell-substratum adhesion. One sentence summaryInterference of Hem1 function in mice and cells uncovers a hitherto unrecognized role in integrin-mediated cell adhesion that is crucial for macrophage function and connects to recently discovered immunodeficiencies in patients carrying Hem1 mutations.

cell biology↗

bioRxiv2019

Myo1e modulates the recruitment of B cells to inguinal lymph nodes

The recruitment of leukocyte to high endothelium venules and their migration to the lymph nodes are critical steps to initiate an immune response. Cell migration is regulated by the actin cytoskeleton where myosins have a very import role. Myo1e is a long tail class I myosin highly expressed in B cells that not have been studied in the context of cell migration. By using an in vivo model, through the use of intravital microscopy, we demonstrated the relevance of Myo1e in the adhesion and the migration of B cells in high endothelial venules. These observations were confirmed by in vitro experiments. We also registered a reduction in the expression of integrins and F-actin in the protrusion of B lymphocytes membrane. Deficiencies in vesicular trafficking can explain the decrease of integrins on the surface. Interestingly, Myo1e is associated with focal adhesion kinase (FAK). The lack of Myo1e affected the phosphorylation of FAK and AKT, and the activity of RAC-1, disturbing the FAK/PI3K/RAC-1 signaling pathway. Together, our results indicate critical participation of Myo1e in the mechanism of B cell migration.\n\nSummary statementMyo1e participate in the adhesion and migration in the high endothelial venules by regulation of integrins and the PI3K/FAK/RAC-1 signaling pathway.

immunology↗

bioRxiv2018

Hematopoietic Stem And Progenitor Cells Use Podosomes To Transcellularly Home To The Bone Marrow.

Bone marrow (BM) endothelium plays an important role in homing of hematopoietic stem and progenitor cells (HSPCs) upon transplantation, but surprisingly little is known on how endothelial cells regulate local permeability and HSPC transmigration. We show that temporal loss of VE-cadherin function promotes vascular permeability in BM, even upon low dose irradiation and strongly enhanced homing of transplanted HSPCs to BM of irradiated mice. Intriguingly, stabilizing junctional VE-cadherin in vivo reduced BM permeability, but did not prevent HSPC migration into the BM, suggesting that HSPCs enter the bone marrow by transcellularly crossing the endothelium. Indeed, HSPCs induce podosomes to cross human BM endothelial monolayers in a transcellular manner. By contrast, HSPC rather use the paracellular route when VE-cadherin function is inhibited. Taken together, VE-cadherin is crucial for BM vascular homeostasis and HSPC homing, and may therefore serve as a potential therapeutic target to improve HSPC homing strategies.

cell biology↗