The death of a cell is an inevitable part of its biology. During homeostasis, most cells die through apoptosis. If homeostasis is disturbed, cell death can switch to proinflammatory forms of death, such as necroptosis, pyroptosis, or NETosis. We demonstrate that the formation of neutrophil extracellular traps (NETs), a special form of neutrophil cell death that releases chromatin structures to the extracellular space, is dependent on gasdermin D (GSDMD). GSDMD is a pore-forming protein and an executor of pyroptosis. We screened a chemical library and found a small molecule based on the pyrazolo-oxazepine scaffold that efficiently blocks NET formation and GSDMD-mediated pyroptotic cell death in human cells. During NETosis, GSDMD is proteolytically activated by neutrophil proteases and, in turn, affects protease activation and nuclear expansion in a feed-forward loop. In addition to the central role of GSDMD in pyroptosis, we propose that GSDMD also plays an essential function in NETosis.

Tumour metastasis is the primary cause of mortality in cancer patients and remains the key challenge for cancer therapy. New therapeutic approaches to block inhibitory pathways of the immune system have renewed hopes for the utility of such therapies. Here we show that genetic deletion of the E3 ubiquitin ligase Cbl-b (casitas B-lineage lymphoma-b) or targeted inactivation of its E3 ligase activity licenses natural killer (NK) cells to spontaneously reject metastatic tumours. The TAM tyrosine kinase receptors Tyro3, Axl and Mer (also known as Mertk) were identified as ubiquitylation substrates for Cbl-b. Treatment of wild-type NK cells with a newly developed small molecule TAM kinase inhibitor conferred therapeutic potential, efficiently enhancing anti-metastatic NK cell activity in vivo. Oral or intraperitoneal administration using this TAM inhibitor markedly reduced murine mammary cancer and melanoma metastases dependent on NK cells. We further report that the anticoagulant warfarin exerts anti-metastatic activity in mice via Cbl-b/TAM receptors in NK cells, providing a molecular explanation for a 50-year-old puzzle in cancer biology. This novel TAM/Cbl-b inhibitory pathway shows that it might be possible to develop a 'pill' that awakens the innate immune system to kill cancer metastases.

Differentiation and survival of neuronal cell types requires the action of neurotrophic polypeptides such as nerve growth factor (NGF). In the central and peripheral nervous system and the phaeochromocytoma cell model PC12, NGF exerts its effects through the activation of the signalling capacity of Trk, a receptor tyrosine kinase (RTK) which upon interaction with NGF becomes phosphorylated on tyrosines and thereby acquires the potential to interact with signal‐transducing proteins such as phospholipase C‐gamma (PLC gamma), phosphatidylinositol‐3′‐kinase (PI3′‐K) and SHC. Mutagenesis of the specific binding sites for these src homology 2 (SH2) domain‐containing substrates within the Trk cytoplasmic domain suggests a non‐essential function of PI3′‐K and reveals a major role for the signal controlled by the SHC binding site at tyrosine 490 and a co‐operative function of the PLC gamma‐mediated pathway for neuronal differentiation of PC12 cells.

Cell migration requires precise control, which is altered or lost when tumor cells become invasive and metastatic. Although the integrity of cell-cell contacts, such as adherens junctions, is essential for the maintenance of functional epithelia, they need to be rapidly disassembled during migration. The transmembrane cell adhesion protein E-cadherin and the cytoplasmic catenins are molecular elements of these structures. Here we demonstrate that epithelial cell migration is accompanied by tyrosine phosphorylation of ␤-catenin and an increase of its free cytoplasmic pool. We show further that the protein-tyrosine phosphatase LAR (leukocyte common antigen related) colocalizes with the cadherincatenin complex in epithelial cells and associates with ␤-catenin and plakoglobin. Interestingly, ectopic expression of protein-tyrosine phosphatase (PTP) LAR inhibits epithelial cell migration by preventing phosphorylation and the increase in the free pool of ␤-catenin; moreover, it inhibits tumor formation in nude mice. These data support a function for PTP LAR in the regulation of epithelial cell-cell contacts at adherens junctions as well as in the control of ␤-catenin signaling functions. Thus PTP-LAR appears to play an important role in the maintenance of epithelial integrity, and a loss of its regulatory function may contribute to malignant progression and metastasis.The cadherins represent a family of transmembrane receptors that mediate homophilic, Ca 2ϩ -dependent cell-cell adhesion. In epithelial cells, the members of this family, such as the classical E-, N-, and P-cadherins, are primarily found at the adherens junctions of adjacent cells (1). ␤-Catenin as well as plakoglobin (␥-catenin) associate directly with the highly conserved cytoplasmic domain of classical cadherins in a mutually exclusive manner (2, 3). The cadherin-catenin complex is linked via ␣-catenin either directly (4) or indirectly to the actin filament network via the actin-binding proteins ␣-actinin or vinculin (5, 6). The association of the cadherin-catenin complex with the cytoskeleton is essential for tight cell-cell interaction.Nevertheless, cadherin/catenin-mediated cell-cell contacts have to be highly dynamic because, particularly during embryonic development or wound healing, adherens junctions have to be rapidly disassembled and reassembled (7). Down-regulation of cadherins results in the separation of neighboring cells, a phenomenon that is observed during embryonic development at the epithelial-mesenchymal transition (EMT) 1 of forming mesoderm (8) as well as in tumor cells, allowing their invasion and dissemination throughout the body (9). During epithelialmesenchymal transition, cells transiently lose their epithelial features and acquire a fibroblastoid morphology (10). The critical importance of an intact cadherin-catenin complex is underscored by the observation that down-regulation of any of its components resulting in the loss of the tumor-suppressive actions of adherens junctions correlates with tumor invasion and metastasis (11...

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