Jäger und Gejagte — wie sich Pilze gegen räuberische Amöben wehren

What seems obvious for most free-living bacteria, also appeals for yeast and filamentous fungi: their natural reservoirs include a variety of micropredators, such as members of the Amoebozoa kingdom. Not only do they share a predatory lifestyle, but their amoeboid motility and way of ingesting living microbial food reveals several similarities to innate immune cells. Understanding how fungi have learned to cope with such environmental phagocytes will shed new light on the evolutionary driving forces of fungal diversity and virulence.

Claisened Hexafluoro Inhibits Metastatic Spreading of Amoeboid Melanoma Cells

Metastatic melanoma is characterized by poor prognosis and a low free-survival rate. Thanks to their high plasticity, melanoma cells are able to migrate exploiting different cell motility strategies, such as the rounded/amoeboid-type motility and the elongated/mesenchymal-type motility. In particular, the amoeboid motility strongly contributes to the dissemination of highly invasive melanoma cells and no treatment targeting this process is currently available for clinical application. Here, we tested Claisened Hexafluoro as a novel inhibitor of the amoeboid motility. Reported data demonstrate that Claisened Hexafluoro specifically inhibits melanoma cells moving through amoeboid motility by deregulating mitochondrial activity and activating the AMPK signaling. Moreover, Claisened Hexafluoro is able to interfere with the adhesion abilities and the stemness features of melanoma cells, thus decreasing the in vivo metastatic process. This evidence may contribute to pave the way for future possible therapeutic applications of Claisened Hexafluoro to counteract metastatic melanoma dissemination.

Integrin-dependent migratory switches regulate the translocation of Toxoplasma-infected dendritic cells across brain endothelial monolayers

Multiple cellular processes, such as immune responses and cancer cell metastasis, crucially depend on interconvertible migration modes. However, knowledge is scarce on how infectious agents impact the processes of cell adhesion and migration at restrictive biological barriers. In extracellular matrix, dendritic cells (DCs) infected by the obligate intracellular protozoan Toxoplasma gondii undergo mesenchymal-to-amoeboid transition (MAT) for rapid integrin-independent migration. Here, in a cellular model of the blood–brain barrier, we report that parasitised DCs adhere to polarised endothelium and shift to integrin-dependent motility, accompanied by elevated transendothelial migration (TEM). Upon contact with endothelium, parasitised DCs dramatically reduced velocities and adhered under both static and shear stress conditions, thereby obliterating the infection-induced amoeboid motility displayed in collagen matrix. The motility of adherent parasitised DCs on endothelial monolayers was restored by blockade of β1 and β2 integrins or ICAM-1, which conversely reduced motility on collagen-coated surfaces. Moreover, parasitised DCs exhibited enhanced translocation across highly polarised primary murine brain endothelial cell monolayers. Blockade of β1, β2 integrins, ICAM-1 and PECAM-1 reduced TEM frequencies. Finally, gene silencing of the pan-integrin-cytoskeleton linker talin (Tln1) or of β1 integrin (Itgb1) in primary DCs resulted in increased motility on endothelium and decreased TEM. Adding to the paradigms of leukocyte diapedesis, the findings provide novel insights in how an intracellular pathogen impacts the migratory plasticity of leukocytes in response to the cellular environment, to promote infection-related dissemination.

Integrin-dependent migratory switches regulate the translocation of Toxoplasma-infected dendritic cells across brain endothelial monolayers

Multiple cellular processes, such as immune responses and cancer cell metastasis, crucially depend on interconvertible migration modes. However, knowledge is scarce on how infectious agents impact the processes of cell adhesion and migration at restrictive biological barriers. In extracellular matrix, dendritic cells (DCs) infected by the obligate intracellular protozoan Toxoplasma gondii undergo mesenchymal-to- amoeboid transition (MAT) for rapid integrin-independent migration. Here, in a cellular model of the blood-brain barrier, we report that parasitised DCs adhere to polarised endothelium and shift to integrin-dependent motility, accompanied by elevated transendothelial migration (TEM). Upon contact with endothelium,parasitised DCs dramatically reduced velocities and adhered under both static and shear stress conditions, thereby obliterating the infection-induced amoeboid motility displayed in collagen matrix. The motility of adherent parasitised DCs on endothelial monolayers was restored by blockade of β1 and β2 integrins or ICAM-1, which conversely reduced motility on collagen-coated surfaces. Moreover, parasitised DCs exhibited enhanced translocation across highly polarised primary murine brain endothelial cell monolayers. Blockade of β1, β2 integrins, ICAM-1 and PECAM-1 reduced TEM frequencies. Finally, gene silencing of the pan-integrin-cytoskeleton linker talin ( Tln1 ) or of β1 integrin ( Itgb1 ) in primary DCs resulted in increased motility on endothelium and decreased TEM. Adding to the paradigms of leukocyte diapedesis, the findings provide novel insights in how an intracellular pathogen impacts the migratory plasticity of leukocytes in response to the cellular environment, to promote infection-related dissemination.

Integrin-dependent Migratory Switches Regulate the Translocation of Toxoplasma-infected Dendritic Cells Across Brain Endothelial Monolayers

Multiple cellular processes, such as immune responses and cancer cell metastasis, crucially depend on the interconversion between distinct migratory states. However, knowledge is scarce on how infectious agents impact the processes of cell migration at restrictive biological barriers. In extracellular matrix, dendritic cells (DCs) infected by the obligate intracellular protozoan Toxoplasma gondii undergo mesenchymal-to-amoeboid transition (MAT) for rapid integrin-independent migration. Here, in a cellular model of the blood-brain barrier, we report that parasitised DCs shift to integrin-dependent motility and adhesion on polarised endothelium, accompanied by elevated transendothelial migration (TEM). Upon contact with endothelium, parasitised DCs dramatically reduced velocities and adhered under both static and shear stress conditions, thereby obliterating the infection-induced amoeboid motility displayed in collagen matrix. The motility of adherentparasitised DCs on endothelial monolayers was restored by blockade of β1 and β2 integrins or ICAM-1, which conversely reduced motility on collagen-coated surfaces. Moreover, parasitised DCs exhibited enhanced translocation across highly polarised primary murine brain endothelial cell monolayers. Blockade of β1, β2 integrins, ICAM-1 and PECAM-1 reduced TEM frequencies. Finally, gene silencing of the pan-integrin-cytoskeleton linker talin ( Tln1 ) or of β1 integrin ( Itgb1 ) in primary DCs resulted in increased motility on endothelium and decreased TEM. Adding to the paradigms of leukocyte diapedesis, the findings provide novel insights in how an intracellular pathogen modulates the migratory properties of leukocytes in response to the cellular environment, to promote infection-related dissemination.

A flagellate-to-amoeboid switch in the closest living relatives of animals

Amoeboid cell types are fundamental to animal biology and broadly distributed across animal diversity, but their evolutionary origin is unclear. The closest living relatives of animals, the choanoflagellates, display a polarized cell architecture (with an apical flagellum encircled by microvilli) that resembles that of epithelial cells and suggests homology, but this architecture differs strikingly from the deformable phenotype of animal amoeboid cells, which instead evoke more distantly related eukaryotes, such as diverse amoebae. Here, we show that choanoflagellates subjected to confinement become amoeboid by retracting their flagella and activating myosin-based motility. This switch allows escape from confinement and is conserved across choanoflagellate diversity. The conservation of the amoeboid cell phenotype across animals and choanoflagellates, together with the conserved role of myosin, is consistent with homology of amoeboid motility in both lineages. We hypothesize that the differentiation between animal epithelial and crawling cells might have evolved from a stress-induced switch between flagellate and amoeboid forms in their single-celled ancestors.

Uveal melanoma cells use ameboid and mesenchymal mechanisms of cell motility crossing the endothelium

Uveal melanomas (UM) are malignant cancers arising from the pigmented layers of the eye. UM cells spread through the bloodstream, and circulating UM cells are detectable in patients before metastases appear. Extravasation of UM cells is necessary for formation of metastases, and transendothelial migration (TEM) is a key step in extravasation. UM cells execute TEM via a stepwise process involving the actin-based processes of ameboid blebbing and mesenchymal lamellipodial protrusion. UM cancers are driven by oncogenic mutations that activate Gαq/11, and this activates TRIO, a guanine nucleotide exchange factor (GEF) for RhoA and Rac1. We found that pharmacologic inhibition of Gαq/11 in UM cells reduced TEM. Inhibition of the RhoA pathway blocked amoeboid motility but led to enhanced TEM; in contrast, inhibition of the Rac1 pathway decreased mesenchymal motility and reduced TEM. Inhibition of Arp2/3 complex allowed cells to transmigrate without intercalation, a direct mechanism similar to the one often displayed by immune cells. BAP1-deficient (+/-) UM subclones displayed motility behaviors and increased levels of TEM, similar to the effects of RhoA inhibitors. We conclude that RhoA and Rac1 signaling pathways, downstream of oncogenic Gαq/11, combine with pathways regulated by BAP1 to control the motility and transmigration of UM cells. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text]

A flagellate-to-amoeboid switch in the closest living relatives of animals

The evolution of different cell types was a key process of early animal evolution1–3. Two fundamental cell types, epithelial cells and amoeboid cells, are broadly distributed across the animal tree of life4,5 but their origin and early evolution are unclear. Epithelial cells are polarized, have a fixed shape and often bear an apical cilium and microvilli. These features are shared with choanoflagellates – the closest living relatives of animals – and are thought to have been inherited from their last common ancestor with animals1,6,7. The deformable amoeboid cells of animals, on the other hand, seem strikingly different from choanoflagellates and instead evoke more distantly related eukaryotes, such as diverse amoebae – but it has been unclear whether that similarity reflects common ancestry or convergence8. Here, we show that choanoflagellates subjected to spatial confinement differentiate into an amoeboid phenotype by retracting their flagella and microvilli, generating blebs, and activating myosin-based motility. Choanoflagellate cell crawling is polarized by geometrical features of the substrate and allows escape from confined microenvironments. The confinement-induced amoeboid switch is conserved across diverse choanoflagellate species and greatly expands the known phenotypic repertoire of choanoflagellates. The broad phylogenetic distribution of the amoeboid cell phenotype across animals9–14 and choanoflagellates, as well as the conserved role of myosin, suggests that myosin-mediated amoeboid motility was present in the life history of their last common ancestor. Thus, the duality between animal epithelial and crawling cells might have evolved from a temporal phenotypic switch between flagellate and amoeboid forms in their single-celled ancestors3,15,16.

Uveal melanoma cells use ameboid and mesenchymal mechanisms of cell motility crossing the endothelium

SUMMARYUveal melanomas (UM) are malignant cancers arising from the pigmented layers of the eye. UM cells spread through the bloodstream, and circulating UM cells are detectable in patients before metastases appear. Extravasation of UM cells, notably transendothelial migration (TEM), is a key step in formation of metastases. UM cells execute TEM via a stepwise process of intercalation into the endothelial monolayer involving the actin-based processes of ameboid blebbing and mesenchymal lamellipodial protrusion. UM cancers are driven by oncogenic mutations in Gαq/11, which activate TRIO, a guanine nucleotide exchange factor (GEF) for RhoA and Rac1. Pharmacologic inhibition of Gαq/11 in UM cells reduced TEM. Inhibition of the RhoA pathway blocked amoeboid motility but led to enhanced TEM; in contrast, inhibition of the Rac1 pathway decreased mesenchymal motility and reduced TEM. Inhibition of Arp2/3 also inhibited mesenchymal motility, but invasion was less affected; in this case, the amoeboid blebbing behavior of the cells led to transmigration without intercalation, a direct mechanism similar to that of immune cells. BAP1-deficient (+/−) UM subclones displayed motility behavior and increased levels of TEM, similar to effects of RhoA inhibitors. We conclude that RhoA and Rac1 signaling pathways, downstream of oncogenic Gαq/11, combine with pathways regulated by BAP1 to control the motility and transmigration of UM cells.