Lipid peroxidation regulates long-range wound detection through 5-lipoxygenase in zebrafish

Rapid wound detection by distant leukocytes is essential for antimicrobial defence and post-infection survival1. The reactive oxygen species hydrogen peroxide and the polyunsaturated fatty acid arachidonic acid are among the earliest known mediators of this process2–4. It is unknown whether or how these highly conserved cues collaborate to achieve wound detection over distances of several hundreds of micrometres within a few minutes. To investigate this, we locally applied arachidonic acid and skin-permeable peroxide by micropipette perfusion to unwounded zebrafish tail fins. As in wounds, arachidonic acid rapidly attracted leukocytes through dual oxidase (Duox) and 5-lipoxygenase (Alox5a). Peroxide promoted chemotaxis to arachidonic acid without being chemotactic on its own. Intravital biosensor imaging showed that wound peroxide and arachidonic acid converged on half-millimetre-long lipid peroxidation gradients that promoted leukocyte attraction. Our data suggest that lipid peroxidation functions as a spatial redox relay that enables long-range detection of early wound cues by immune cells, outlining a beneficial role for this otherwise toxic process

Author Correction: Lipid peroxidation regulates long-range wound detection through 5-lipoxygenase in zebrafish

A Correction to this paper has been published: https://doi.org/10.1038/s41556-021-00683-0

Interaction between FIP200 and ATG16L1 distinguishes ULK1 complex-dependent and -independent autophagy

Autophagy is a finely orchestrated cellular catabolic process that requires multiple autophagy-related gene products (ATG proteins). The ULK1 complex functions to integrate upstream signals to downstream ATG proteins through an unknown mechanism. Here we have identified an interaction between mammalian FIP200 and ATG16L1, essential components of the ULK1 and ATG5 complexes, respectively. Further analyses show this is a direct interaction mediated by a short domain of ATG16L1 that we term the FIP200-binding domain (FBD). The FBD is not required for ATG16L1 self-dimerization or interaction with ATG5. Notably, an FBD-deleted ATG16L1 mutant is defective in mediating amino acid starvation-induced autophagy, which requires the ULK1 complex. However, this mutant retains its function in supporting glucose deprivation-induced autophagy, a ULK1 complex-independent process. This study therefore identifies a previously uncharacterized interaction between the ULK1 and ATG5 complexes that can distinguish ULK1-dependent and -independent autophagy processes

Ferroptosis-like cell death promotes and prolongs inflammation in Drosophila

Ferroptosis is a distinct form of necrotic cell death caused by overwhelming lipid peroxidation, and emerging evidence indicates a major contribution to organ damage in multiple pathologies. However, ferroptosis has not yet been visualized in vivo due to a lack of specific probes, which has severely limited the study of how the immune system interacts with ferroptotic cells and how this process contributes to inflammation. Consequently, whether ferroptosis has a physiological role has remained a key outstanding question. Here we identify a distinct, ferroptotic-like, necrotic cell death occurring in vivo during wounding of the Drosophila embryo using live imaging. We further demonstrate that macrophages rapidly engage these necrotic cells within the embryo but struggle to engulf them, leading to prolonged, frustrated phagocytosis and frequent corpse disintegration. Conversely, suppression of the ferroptotic programme during wounding delays macrophage recruitment to the injury site, pointing to conflicting roles for ferroptosis during inflammation in vivo

Molecular mechanisms of cell death:recommendations of the Nomenclature Committee on Cell Death 2018

Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field.</p

Mitosis can drive cell cannibalism through entosis.

Entosis is a form of epithelial cell cannibalism that is prevalent in human cancer, typically triggered by loss of matrix adhesion. Here, we report an alternative mechanism for entosis in human epithelial cells, driven by mitosis. Mitotic entosis is regulated by Cdc42, which controls mitotic morphology. Cdc42 depletion enhances mitotic deadhesion and rounding, and these biophysical changes, which depend on RhoA activation and are phenocopied by Rap1 inhibition, permit subsequent entosis. Mitotic entosis occurs constitutively in some human cancer cell lines and mitotic index correlates with cell cannibalism in primary human breast tumours. Adherent, wild-type cells can act efficiently as entotic hosts, suggesting that normal epithelia may engulf and kill aberrantly dividing neighbours. Finally, we report that Paclitaxel/taxol promotes mitotic rounding and subsequent entosis, revealing an unconventional activity of this drug. Together, our data uncover an intriguing link between cell division and cannibalism, of significance to both cancer and chemotherapy

Entosis Controls a Developmental Cell Clearance in C. elegans.

Metazoan cell death mechanisms are diverse and include numerous non-apoptotic programs. One program called entosis involves the invasion of live cells into their neighbors and is known to occur in cancers. Here, we identify a developmental function for entosis: to clear the male-specific linker cell in C. elegans. The linker cell leads migration to shape the gonad and is removed to facilitate fusion of the gonad to the cloaca. We find that the linker cell is cleared in a manner involving cell-cell adhesions and cell-autonomous control of uptake through linker cell actin. Linker cell entosis generates a lobe structure that is deposited at the site of gonad-to-cloaca fusion and is removed during mating. Inhibition of lobe scission inhibits linker cell death, demonstrating that the linker cell invades its host while alive. Our findings demonstrate a developmental function for entosis: to eliminate a migrating cell and facilitate gonad-to-cloaca fusion, which is required for fertility

Colonization and community development of fish assemblages associated with estuarine artificial reefs

Despite the long history of the development of artificial structures in NSW estuaries there are no studies that provide any comprehensive scientific evaluation of post-deployment goals. We assessed the effectiveness of estuarine artificial reefs as a fisheries enhancement initiative; described the diversity and abundance of species associated with them, and detailed the patterns of colonization and community development associated with an artificial reef deployment in Lake Macquarie, a large coastal barrier lagoon on the southeast coast of Australia. Six artificial reefs (one artificial reef group), constructed from artificial reef units (Reef Balls®), were deployed in December 2005 and sampled six times per season over two years using baited remote underwater video (BRUV). Colonization of the artificial reef group was relatively rapid with the majority of species identified over the two-year study period observed within the first year post-deployment. Overall, 27 species from 17 families were identified. Key colonising species included Pelates sexlineatus (Terapontidae), Acanthopagrus australis (Sparidae), Pagrus auratus (Sparidae) and Rhabdosargus sarba (Sparidae). Species richness showed evidence of potential seasonal fluctuations, being higher in warm water months (Summer/Autumn), and lower in the colder water months (Winter/Spring), while species diversity increased significantly with reef age. Fish assemblage composition remained relatively stable after the first year of sampling, with few discernible patterns in assemblage structure evident after the first year. Distinct separation in reef age groupings was evident during the second year of sampling; a pattern primarily driven by a decrease in abundance of P. sexlineatus, a result of the isolated nature of the artificial reefs and the interrelated effects of density dependence and predation.A despeito da longa história do desenvolvimento de estruturas artificiais nos estuários de NSW, não existem estudos que apresentem uma avaliação global sobre os efeitos obtidos com o estabelecimento dessas estruturas. No presente trabalho abordamos a efetividade dos recifes artificiais estuarinos como iniciativa para aumento da pesca; descrevemos a diversidade e abundância das espécies a eles associadas; descrevemos os padrões de colonização e o desenvolvimento das comunidades associadas a um recife artificial colocado no Lago Macquaire, extensa lagoa de barreira situada na costa sudeste da Australia. Seis recifes artificiais (formando um único grupo), construídos a partir de unidades artificiais (Reef Balls®), foram lançados em Dezembro de 2005 e amostrados seis vezes a cada estação do ano, durante dois anos, utilizando video subaquático remoto (BRUV). A colonizaç��o dentro do grupo de recifes ocorreu de maneira relativamente rápida, sendo que a maioria das espécies identificadas nos dois anos de estudo foi observada durante o primeiro ano de amostragem. Um total de 27 espécies pertencentes a 17 famílias foram identificadas. As espécies chave do processo de colonização foram Pelates sexlineatus (Teraponidae), Acanthopagrus australis (Sparidae), Pagrus auratus (Sparidae) and Rhabdosargus sarba (Sparidea). A riqueza de espécies mostrou evidência de sazonalidade, enquanto a diversidade aumentou significativamente com o aumento da idade do recife. A composição da assembléia de peixes permaneceu relativamente estável após o primeiro ano de amostragem, com poucos padrões identificáveis relativos à estrutura. Durante o segundo ano tornou-se evidente a formação de grupos por idade, padrão primariamente ocasionado pelo decréscimo na abundância de P. sexlineatus; por sua vez este decréscimo mostrou ser resultado da natureza isolada do recife artificial e dos efeitos interdependentes de abundância e predação

Abstract SY09-03: Entosis: Adhesion, autophagy, and murder

Abstract Cancers arise when cells evade homeostatic mechanisms that restrain their growth. A variety of homeostatic mechanisms, such as apoptosis, proliferation arrest, and senescence, maintain appropriate cell numbers in multicellular organisms and limit the formation of tumors. Acting in concert with these programs is autophagy. Autophagy is a regulated cellular degradative pathway, which may be tumor suppressive in some contexts by promoting cell death or inhibiting genomic instability, but may also promote tumor growth by enhancing cell survival. Recently we described a new cellular mechanism called entosis that, like autophagy, may influence human cancers in complex, context-dependent ways. Entosis underlies the formation of cell-in-cell structures, where live cells are engulfed inside of their neighbors. These cell structures are reported in a variety of human cancers, but their significance is unknown. The majority of engulfed cells undergo cell death, suggesting that entosis could be a novel mechanism of tumor suppression. Paradoxically, cell-in-cell structures also promote the development of aneuploidy by disrupting cell division. Aneuploidy is thought to drive tumor progression and is a hallmark of aggressive cancers. Thus, like autophagy, entosis has two potential influences on human tumors – tumor suppression or tumor promotion. Detachment of cells from extracellular matrix is one major mechanism that induces entosis. Within secretory glands such as the mammary gland, epithelial cells are normally organized into a single polarized layer that is adherent to a basement membrane and surrounds a hollow lumen. In early-stage tumors, such as ductal carinoma in-situ (DCIS), cells detach from the basement membrane, and populate the luminal space inside the mammary duct. As epithelial cells require attachment to matrix for survival, a common gain-of-function for breast tumor cells is the ability to survive in the absence of anchorage to the basement membrane. Indeed, one hallmark of many cancer types is the ability of cells to grow in an anchorage-independent fashion. In breast tumors, cell-in-cell structures are found in DCIS tumors, and also late-stage invasive tumors, in matrix-deprived regions. In cultured cells, cell-in-cell structures are prevalent under anchorage-independent conditions, such as growth in soft agar, where entosis may act as a barrier to transformed growth. Interestingly, although cell-in-cell structures are found in human tumors, most tumor cell lines do not exhibit a high rate of entosis compared to non-tumor cells, suggesting that this program is generally suppressed in most cancers. Cell-in-cell formation occurs by an unusual mechanism involving the formation of adherens junctions between host cells and their targets, followed by engulfment that is driven by Rho-dependent contractile force in internalizing cells, which invade into their hosts. Tumor cells likely do not exhibit entosis owing to compromised cell adhesion, as many breast tumor cell lines, for example, do not express epithelial (E- and P-) cadherins, or α-catenin. We have shown previously that epithelial cadherins, as well as contractile force mediated by Rho, are required for entosis in epithelial cell lines. Here we demonstrate that restoration of epithelial adhesion in tumor cells, by re-expression of E- or P-cadherin, is sufficient to activate entosis, and entotic cell death. As restoration of epithelial adhesion is known to block tumor formation, entosis may be a new mechanism whereby cell adhesion can inhibit transformed growth. Because entotic cells are engulfed alive, they actually exhibit multiple fates. Whereas the majority undergo a nonapoptotic form of cell death, a smaller percentage are able to survive for extended periods inside of their hosts, and some manage to escape from host cells altogether, emerging unharmed. Cell death involves conversion of the entotic vacuole into a lysosomal compartment, but the cellular pathways that control cell fate are not known. Here we demonstrate that the fate of entotic cells is controlled by the autophagy pathway. Autophagy proteins are normally involved in the formation of double-membrane autophagosomes that mediate bulk cytoplasmic and organelle degradation in cells under conditions of starvation. In epithelial cell lines and tumor cells with restored cell adhesion, we find that autophagy proteins modify entotic vacuole membranes, by a sequence of events including PtdIns(3)P formation and recruitment of Light Chain 3 (LC3). LC3 is lipidated at the entotic vacuole membrane in a manner dependent on core autophagy machinery including ATG5 and ATG7, but not on the mTor-regulated ULK-ATG13-FIP200 complex that is required for autophagy. LC3 lipidation facilitates lysosome fusion to the entotic vacuole, leading to necrotic-like death and degradation of internalized cells, which are murdered by their hosts. Importantly, disruption of autophagy machinery within host cells rescues internalized cells from death, demonstrating a non-cell-autonomous killing activity. Conversely, depletion of autophagic proteins within internalized cells induces apoptosis, due to a cell-autonomous requirement for autophagy in the nutrient deprived environment of the host cell vacuole. The complete rescue of cells from entotic cell death therefore requires the simultaneous inhibition of autophagy and apoptosis, a situation commonly found in human tumors. Accordingly, suppression of entotic cell death promotes the anchorage independent growth of cells in soft agar, a model of tumorgenicity. Together, these data define a non-cell-autonomous mechanism of cell death, resembling a cell murder, involving autophagy machinery. As entosis is controlled by epithelial adhesion and autophagy, it represents a novel mechanism of cell death that may suppress tumor growth by using known tumor suppressive machinery. Alternatively, while entosis may suppress tumor growth by eliminating detached cells, it is also a strong inducer of aneuploidy, and this feature could be positively selected in some cancers. Our data define a novel cellular mechanism, entosis, that like autophagy, may have multiple, even opposing, influences on tumor growth. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr SY09-03. doi:10.1158/1538-7445.AM2011-SY09-03</jats:p