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Supplementary data include Figure S1(Structural determinants of ESC inhibitors), Figure S2 (Validation and functional characterization of esMTi), Figure S3 (Generation and characterization of P4H deficient ESCs), Figure S4 (Budesonide activity on A549 lung tumor cells ); Figure S5 (Budesonide activity on SUM159 cells); Table S1 (The primer sequences and application); Table S2 (The Primary Antibodies and application); Table S3 (List of all ESC inhibitors), Table S4 (ESC inhibitors with anti-cancer activity and related references); Table S5 (List of esMT inhibitors), Table S6 (esMT inhibitors with anti-collagen/fibortic effects)

Collagen prolyl hydroxylation (CPH), which is catalyzed by prolyl 4-hydroxylase (P4H), is the most prevalent posttranslational modification in humans and requires vitamin C (VitC). Here, we demonstrate that CPH acts as an epigenetic modulator of cell plasticity. Increased CPH induced global DNA/histone methylation in pluripotent stem and tumor cells and promoted cell state transition (CST). Interfering with CPH by either genetic ablation of P4H subunit alpha-2 (P4HA2) or pharmacologic treatment reverted epigenetic changes and antagonized CST. Mechanistically, we suggest that CPH modifies the epigenetic landscape by reducing VitC for DNA and histone demethylases. Repurposed drugs targeting CPH-mediated metabolic perturbation, such as the antiasthmatic budesonide, blocked metastatic dissemination of breast cancer cells in vivo by preventing mesenchymal transition. Our study provides mechanistic insights into how metabolic cues and epigenetic factors integrate to control CST and paves the way for the development of novel antimetastatic strategies.Significance:A phenotype-based high-throughput screening reveals unforeseen metabolic control of cell plasticity and identifies budesonide as a drug candidate for metastatic cancer.

PDF file 1545 K. Methods and Materials Cell culture, Scratch Assay/Immunfluorescence, siRNA transfection Fig. S1: Archazolid inhibits the acidification of lysosomes. Fig. S2: Archazolid inhibits cancer cell migration. Fig. S3: EGF-R and Her2 expression on the cell surface after archazolid treatment. Fig. S4: EGF-R plays a role in cell polarization. Fig.S5: The downregulation of the V-ATPase subunit c affects the cell migration process also in L3.6pl cells. Fig. S6: Rac1-GFP is less localized in Rab5-induced enlarged endosomes of archazolid treated cells. Fig. S7: Dissemination of 4T1-Luc breast cancer cells is decreased in archazolid A (1mg/kg) pretreated mice. Fig. S8: Scheme proposing the impact of V-ATPase inhibition on cell migration. Fig.S9: Beside the localization in lysosomes the V-ATPase is also localized at the plasma membrane. Fig. S10: Archazolid affects cellular recycling.

AVI file - 4312K, Time-lapse video-recording of a representative JVM3 cell expressing GFP-CCR7 distribution and migrating in a CCL19 gradient (source of CCL19 towards the bottom).

AVI file - 503K, Time-lapse video-recording of a representative JVM3 cells exposed to a CCL19 gradient (source of CCL19 towards the bottom) over a period of 5 min.

AVI file - 1553K, Time-lapse video-recording of a representative JVM3 cell expressing GFP-actin and migrating in a CCL19 gradient (source of CCL19 towards the bottom).

PDF file - 57K, Accession numbers and amplified context sequences of the genes analyzed by quantitative RT-PCR.

PDF file - 54K, Additional information regarding CCR7 internalization.

AVI file - 1602K, Supplemental Movies 6-8 shows Time-lapse video-recording of zoomed sections of the lamellipodium of a representative JVM3 cell expressing GFP-CIP4 and migrating in a CCL19 gradient. The four panels show GFP-CIP4 (green), pseudo-colour scale indicating CIP4 level, transmission and merge.

AVI file - 1134K, Time-lapse video-recording of a representative CIP4 knocked-down JVM3 cells exposed to a CCL19 gradient (source of CCL19 towards the bottom) over a period of 12 min.

PDF file - 93K, CIP4 is dispensable for CCR7 internalization (S1), CIP4 knock-down impairs the polarized morphology of JVM3 cells (S2).

AVI file - 3816K, Time-lapse video-recording of a representative JVM3 cell expressing GFP-CIP4 and migrating over a period of 37 min in a CCL19 gradient (source of CCL19 towards the bottom). The four panels show GFP-CIP4 (green), pseudo-colour scale indicating CIP4 level, transmission and merge.

AVI file - 2015K, Supplemental Movies 6-8 shows Time-lapse video-recording of zoomed sections of the lamellipodium of a representative JVM3 cell expressing GFP-CIP4 and migrating in a CCL19 gradient. The four panels show GFP-CIP4 (green), pseudo-colour scale indicating CIP4 level, transmission and merge.

AVI file - 2141K, Supplemental Movies 6-8 shows Time-lapse video-recording of zoomed sections of the lamellipodium of a representative JVM3 cell expressing GFP-CIP4 and migrating in a CCL19 gradient. The four panels show GFP-CIP4 (green), pseudo-colour scale indicating CIP4 level, transmission and merge.

Tissue fluidification and collective motility are pivotal in regulating embryonic morphogenesis, wound healing and tumor metastasis. These processes frequently require that each cell constituent of a tissue coordinates its migration activity and directed motion through the oriented extension of lamellipodia cell protrusions, promoted by RAC1 activity. While the upstream RAC1 regulators in individual migratory cells or leader cells during invasion or wound healing are well characterized, how RAC1 is controlled in follower cells remains unknown. Here, we identify a novel MYO6-DOCK7 axis that is critical for spatially restriction of RAC1 activity in a planar polarized fashion in model tissue monolayers. The MYO6-DOCK7 axis specifically controls the extension of cryptic lamellipodia required to drive tissue fluidification and cooperative mode motion in otherwise solid and static carcinoma cell collectives.HighlightsCollective motion of jammed epithelia requires myosin VI activityThe MYO6-DOCK7 axis is critical to restrict the activity of RAC1 in a planar polarized fashionMYO6-DOCK7-RAC1 activation ensures long-range coordination of movements by promoting orientation and persistence of cryptic lamellipodiaMyosin VI overexpression is exploited by infiltrating breast cancer cells

Endocytosis allows cells to transport particles and molecules across the plasma membrane. In addition, it is involved in the termination of signalling through receptor downmodulation and degradation. This traditional outlook has been substantially modified in recent years by discoveries that endocytosis and subsequent trafficking routes have a profound impact on the positive regulation and propagation of signals, being key for the spatiotemporal regulation of signal transmission in cells. Accordingly, endocytosis and membrane trafficking regulate virtually every aspect of cell physiology and are frequently subverted in pathological conditions. Two key aspects of endocytic control over signalling are coming into focus: context-dependency and long-range effects. First, endocytic-regulated outputs are not stereotyped but heavily dependent on the cell-specific regulation of endocytic networks. Second, endocytic regulation has an impact not only on individual cells but also on the behaviour of cellular collectives. Herein, we will discuss recent advancements in these areas, highlighting how endocytic trafficking impacts complex cell properties, including cell polarity and collective cell migration, and the relevance of these mechanisms to disease, in particular cancer. The canonical function of endocytosis is molecule internalization. Beyond this role, endocytic trafficking has emerged as a process central to the spatiotemporal regulation of cell signalling. Endocytic trafficking thus controls many cellular processes and tissue-wide properties, including cell migration and polarity, and its deregulation has been implicated in pathologies, particularly cancer.

Sheet-like membrane protrusions at the leading edge, termed lamellipodia, drive 2D-cell migration using active actin polymerization. Microspikes comprise actin-filament bundles embedded within lamellipodia, but the molecular mechanisms driving their formation and their potential functional relevance have remained elusive. Microspike formation requires the specific activity of clustered Ena/VASP proteins at their tips to enable processive actin assembly in the presence of capping protein, but the factors and mechanisms mediating Ena/VASP clustering are poorly understood. Systematic analyses of B16-F1 melanoma mutants lacking potential candidate proteins revealed that neither inverse BAR-domain proteins, nor lamellipodin or Abi are essential for clustering, although they differentially contribute to lamellipodial VASP accumulation. In contrast, unconventional myosin-X (MyoX) identified here as proximal to VASP was obligatory for Ena/VASP clustering and microspike formation. Interestingly, and despite the invariable distribution of other relevant marker proteins, the width of lamellipodia in MyoX-KO mutants was significantly reduced as compared to B16-F1 control, suggesting that microspikes contribute to lamellipodium stability. Consistently, MyoX removal caused marked defects in protrusion and random 2D-cell migration. Strikingly, Ena/VASP-deficiency also uncoupled MyoX cluster dynamics from actin assembly in lamellipodia, establishing their tight functional association in microspike formation.Significance StatementUnlike filopodia that protrude well beyond the cell periphery and are implicated in sensing, morphogenesis and cell-to-cell communication, the function of microspikes consisting of actin-filament bundles fully embedded within lamellipodia is less clear. Microspike formation involves specific clustering of Ena/VASP family members at filament-barbed ends to enable processive actin polymerization in the presence of capping protein, but the factors and mechanisms mediating Ena/VASP clustering have remained unknown. Here, we systematically analyzed these processes in genetic knockout mutants derived from B16-F1 cells and show that Ena/VASP clustering at microspike tips involves Lamellipodin, but not inverse BAR-domain proteins, and strictly requires unconventional Myosin-X. Complete loss of microspikes was confirmed with CRISPR/Cas9-mediated MyoX knockout in Rat2 fibroblasts, excluding cell type-specific effects.

Abstract The connection between the properties of a cell tissue and those of the single constituent cells remains to be elucidated. At the purely mechanical level, the degree of rigidity of different cellular components, such as the nucleus and the cytoplasm, modulates the interplay between the cell inner processes and the external environment, while simultaneously mediating the mechanical interactions between neighboring cells. Being able to quantify the correlation between single-cell and tissue properties would improve our mechanobiological understanding of cell tissues. Here we develop a methodology to quantitatively extract a set of structural and motility parameters from the analysis of time-lapse movies of nuclei belonging to jammed and flocking cell monolayers. We then study in detail the correlation between the dynamical state of the tissue and the deformation of the nuclei. We observe that the nuclear deformation rate linearly correlates with the local divergence of the velocity field, which leads to a non-invasive estimate of the elastic modulus of the nucleus relative to the one of the cytoplasm. We also find that nuclei belonging to flocking monolayers, subjected to larger mechanical perturbations, are about two time stiffer than nuclei belonging to dynamically arrested monolayers, in agreement with atomic force microscopy results. Our results demonstrate a non-invasive route to the determination of nuclear relative stiffness for cells in a monolayer. Graphic abstract

The spectrin-based membrane skeleton is a major component of the cell cortex. While expressed by all metazoans, its dynamic interactions with the other cortex components, including the plasma membrane or the acto-myosin cytoskeleton, are poorly understood. Here, we investigate how spectrin re-organizes spatially and dynamically under the membrane during changes in cell mechanics. We find spectrin and acto-myosin to be spatially distinct but cooperating during mechanical challenges, such as cell adhesion and contraction, or compression, stretch and osmolarity fluctuations, creating a cohesive cortex supporting the plasma membrane. Actin territories control protrusions and contractile structures while spectrin territories concentrate in retractile zones and low-actin density/inter-contractile regions, acting as a fence that organize membrane trafficking events. We unveil here the existence of a dynamic interplay between acto-myosin and spectrin necessary to support a mesoscale organization of the lipid bilayer into spatially-confined cortical territories during cell mechanoresponse., The cell cortex that supports the plasma membrane contains spectrin, a protein that interacts with the acto-myosin cytoskeleton. Here, the authors analyze spectrin behavior during cellular mechanoresponse and membrane trafficking, and observe spectrin regulation by myosin-driven contractility.

Circulating tumor cell (CTC) clusters are associated with increased metastatic potential and worse patient prognosis, but are rare, difficult to count, and poorly characterized biophysically. The PillarX device described here is a bimodular microfluidic device (Pillar-device and an X-magnetic device) to profile single CTCs and clusters from whole blood based on their size, deformability, and epithelial marker expression. Larger, less deformable clusters and large single cells are captured in the Pillar-device and sorted according to pillar gap sizes. Smaller, deformable clusters and single cells are subsequently captured in the X-device and separated based on epithelial marker expression using functionalized magnetic nanoparticles. Clusters of established and primary breast cancer cells with variable degrees of cohesion driven by different cell-cell adhesion protein expression are profiled in the device. Cohesive clusters exhibit a lower deformability as they travel through the pillar array, relative to less cohesive clusters, and have greater collective invasive behavior. The ability of the PillarX device to capture clusters is validated in mouse models and patients of metastatic breast cancer. Thus, this device effectively enumerates and profiles CTC clusters based on their unique geometrical, physical, and biochemical properties, and could form the basis of a novel prognostic clinical tool.

The process in which locally confined epithelial malignancies progressively evolve into invasive cancers is often promoted by unjamming, a phase transition from a solid-like to a liquid-like state that occurs in various tissues. Whether this tissue-level mechanical transition impact phenotypes during carcinoma progression remains unclear. We show, here that the large fluctuations in cell density that accompany unjamming result in repeated mechanical deformations of cells and nuclei. Cells react to these protracted mechanical stresses by mounting a mechano-protective response that includes enlarged nuclear size and rigidity, altered heterochromatin distribution, and the remodeling of the perinuclear actin architecture into actin rings. The chronic strains and stresses associated with unjamming together with reduction of Lamin B1 levels eventually result in DNA damage and nuclear envelope ruptures, with the release of cytosolic DNA that activates a cGAS/STING-dependent cytosolic DNA response gene program. This mechanically-driven transcriptional rewiring ultimately results in a change in cell state, with the emergence of malignant traits, including epithelial-to-mesenchymal plasticity phenotypes and chemo-resistance in invasive breast carcinoma. One-Sentence Summary: A solid-to-fluid phase transition promotes a pro-inflammatory transcriptional response in invasive breast carcinoma

The original version of this Article contains an error in Fig. 1e, in which the representative image panel was inadvertently duplicated from Fig. 1d by the publisher. The correct representative image version of Fig. 1e is

As cells migrate and experience forces from their surroundings, they constantly undergo mechanical deformations which reshape their plasma membrane (PM). To maintain homeostasis, cells need to detect and restore such changes, not only in terms of overall PM area and tension as previously described, but also in terms of local, nano-scale topography. Here we describe a novel phenomenon, by which cells sense and restore mechanically induced PM nano-scale deformations. We show that cell stretch and subsequent compression reshape the PM in a way that generates local membrane evaginations in the 100 nm scale. These evaginations are recognized by the I-BAR protein IRSp53, which triggers a burst of actin polymerization mediated by Rac1 and Arp2/3. The actin polymerization burst subsequently re-flattens the evagination, completing the mechanochemical feedback loop. Our results demonstrate a new mechanosensing mechanism for PM shape homeostasis, with potential applicability in different physiological scenarios.TeaserCell stretch cycles generate PM evaginations of ≈100 nm which are sensed by IRSp53, triggering a local event of actin polymerization that flattens and recovers PM shape.

Therapeutic options for patients with advanced-stage hepatocellular carcinoma (HCC) are very limited. The only approved first-line treatment is the multi-tyrosine kinase inhibitor sorafenib, which shows low response rates and severe side effects. In particular, the compensatory activation of growth factor receptors leads to chemoresistance and limits the clinical impact of sorafenib. However, combination approaches to improve sorafenib have failed. Here we investigate the inhibition of cyclin-dependent kinase 5 (Cdk5) as a promising combination strategy to improve sorafenib response in HCC. Combination of sorafenib with Cdk5 inhibition (genetic knockdown by short hairpin RNA or CRISPR/Cas9 and pharmacologic inhibition) synergistically impaired HCC progression in vitro and in vivo by inhibiting both tumor cell proliferation and migration. Importantly, these effects were mediated by a mechanism for Cdk5: A liquid chromatography-tandem mass spectrometry-based proteomic approach revealed that Cdk5 inhibition interferes with intracellular trafficking, a process crucial for cellular homeostasis and growth factor receptor signaling. Cdk5 inhibition resulted in an accumulation of enlarged vesicles and respective cargos in the perinuclear region, considerably impairing the extent and quality of growth factor receptor signaling. Thereby, Cdk5 inhibition offers a comprehensive approach to globally disturb growth factor receptor signaling that is superior to specific inhibition of individual growth factor receptors. Conclusion: Cdk5 inhibition represents an effective approach to improve sorafenib response and to prevent sorafenib treatment escape in HCC. Notably, Cdk5 is an addressable target frequently overexpressed in HCC, and with Dinaciclib, a clinically tested Cdk5 inhibitor is readily available. Thus, our study provides evidence for clinically evaluating the combination of sorafenib and Dinaciclib to improve the therapeutic situation for patients with advanced-stage HCC.

Although mutations leading to a compromised nuclear envelope cause diseases such as muscular dystrophies or accelerated aging, the consequences of mechanically induced nuclear envelope ruptures are less known. Here, we show that nuclear envelope ruptures induce DNA damage that promotes senescence in non-transformed cells and induces an invasive phenotype in human breast cancer cells. We find that the endoplasmic reticulum (ER)-associated exonuclease TREX1 translocates into the nucleus after nuclear envelope rupture and is required to induce DNA damage. Inside the mammary duct, cellular crowding leads to nuclear envelope ruptures that generate TREX1-dependent DNA damage, thereby driving the progression of in situ carcinoma to the invasive stage. DNA damage and nuclear envelope rupture markers were also enriched at the invasive edge of human tumors. We propose that DNA damage in mechanically challenged nuclei could affect the pathophysiology of crowded tissues by modulating proliferation and extracellular matrix degradation of normal and transformed cells.

The accurate quantification of cellular motility and of the structural changes occurring in multicellular aggregates is critical in describing and understanding key biological processes, such as wound repair, embryogenesis and cancer invasion. Current methods based on cell tracking or velocimetry either suffer from limited spatial resolution or are challenging and time-consuming, especially for three-dimensional (3D) cell assemblies. Here we propose a conceptually simple, robust and tracking-free approach for the quantification of the dynamical activity of cells via a two-step procedure. We first characterise the global features of the collective cell migration by registering the temporal stack of the acquired images. As a second step, a map of the local cell motility is obtained by performing a mean squared amplitude analysis of the intensity fluctuations occurring when two registered image frames acquired at different times are subtracted. We successfully apply our approach to cell monolayers undergoing a jamming transition, as well as to monolayers and 3D aggregates that exhibit a cooperative unjamming-via-flocking transition. Our approach is capable of disentangling very efficiently and of assessing accurately the global and local contributions to cell motility.

Spatially controlled, cargo-specific endocytosis is essential for development, tissue homeostasis, and cancer invasion and is often hijacked by viral infections 1. Unlike clathrin-mediated endocytosis, which exploits cargo-specific adaptors for selective protein internalization, the clathrin and dynamin-independent endocytic pathway (CLIC-GEEC, CG-pathway) has until now been considered a bulk internalization route for the fluid phase, glycosylated membrane proteins and lipids 2,3. Although the core molecular players of CG endocytosis have been recently defined, no cargo-specific adaptors are known and evidence of selective protein uptake into the pathway is lacking 3. Here, we identify the first cargo-specific adaptor for CG-endocytosis and demonstrate its clinical relevance in breast cancer progression. By combining unbiased molecular characterization and super-resolution imaging, we identified the actin-binding protein swiprosin-1 (EFHD2) as a cargo-specific adaptor regulating integrin internalization via the CG-pathway. Swiprosin-1 couples active Rab21-associated integrins with key components of the CG-endocytic machinery, IRSp53 and actin. Swiprosin-1 is critical for integrin endocytosis, but not for other CG-cargo and supports integrin-dependent cancer cell migration and invasion, with clinically relevant implications for breast cancer. Our results demonstrate a previously unknown cargo selectivity for the CG-pathway and opens the possibility to discover more adaptors regulating it.

Spatially controlled, cargo-specific endocytosis is essential for development, tissue homeostasis and cancer invasion. Unlike cargo-specific clathrin-mediated endocytosis, the clathrin- and dynamin-independent endocytic pathway (CLIC-GEEC, CG pathway) is considered a bulk internalization route for the fluid phase, glycosylated membrane proteins and lipids. While the core molecular players of CG-endocytosis have been recently defined, evidence of cargo-specific adaptors or selective uptake of proteins for the pathway are lacking. Here we identify the actin-binding protein Swiprosin-1 (Swip1, EFHD2) as a cargo-specific adaptor for CG-endocytosis. Swip1 couples active Rab21-associated integrins with key components of the CG-endocytic machinery-Arf1, IRSp53 and actin-and is critical for integrin endocytosis. Through this function, Swip1 supports integrin-dependent cancer-cell migration and invasion, and is a negative prognostic marker in breast cancer. Our results demonstrate a previously unknown cargo selectivity for the CG pathway and a role for specific adaptors in recruitment into this endocytic route.

While mutations leading to a fragile envelope of the cell nucleus are well known to cause diseases such as muscular dystrophies or accelerated aging, the pathophysiological consequences of the recently discovered mechanically induced nuclear envelope ruptures in cells harboring no mutation are less known. Here we show that repeated loss of nuclear envelope integrity in nuclei experiencing mechanical constraints promotes senescence in nontransformed cells, and induces an invasive phenotype including increased collagen degradation in human breast cancer cells, both in vitro and in a mouse xenograft model of breast cancer progression. We show that these phenotypic changes are due to the presence of chronic DNA damage and activation of the ATM kinase. In addition, we found that depletion of the cytoplasmic exonuclease TREX1 is sufficient to abolish the DNA damage in mechanically challenged nuclei and to suppress the phenotypes associated with the loss of nuclear envelope integrity. Our results also show that TREX1-dependent DNA damage induced by physical confinement of tumor cells inside the mammary duct drives the progression of in situ breast carcinoma to the invasive stage. We propose that DNA damage in mechanically challenged nuclei could affect the pathophysiology of crowded tissues by modulating proliferation and extracellular matrix degradation of normal and transformed cells.

Cellular protrusions mediated by the membrane-deforming I-BAR domain protein IRSp53 are involved in cell migration, including metastasis. However, the role of IRSp53 in cell proliferation remains unclear. Here, we examined the role of IRSp53 in cell proliferation and found that it acts through secretion. Coculture of gingiva squamous carcinoma Ca9-22 cells and their IRSp53-knockout cells restored proliferation to parental Ca9-22 cell levels, suggesting possible secretion dependent on IRSp53. Notably, the amounts of microvesicle fraction proteins that were secreted into the culture medium were reduced in the IRSp53-knockout cells. The IRSp53-knockout cells exhibited decreased phosphorylation of mitogen-activated protein kinase, suggesting the decrease in the proliferation signals. The phosphorylation was restored by the addition of the microvesicles. In mice xenograft Ca9-22 cells, IRSp53-containing particles were secreted around the xenograft, indicating that IRSp53-dependent secretion occurs in vivo. In a tumor mice model, IRSp53 deficiency elongated lifespan. In some human cancers, the higher levels of IRSp53 mRNA expression was found to be correlated with shorter survival years. Therefore, IRSp53 is involved in tumor progression and secretion for cellular proliferation.

The spectrin cytoskeleton is a major component of the cell cortex. While ubiquitously expressed, its dynamic interaction with the other cortex components, including the plasma membrane or the acto-myosin cytoskeleton, is poorly understood. Here, we investigated how the spectrin cytoskeleton re-organizes spatially and dynamically under the membrane during changes in cell mechanics. We found spectrin and acto-myosin cytoskeletons to be spatially distinct but cooperating during mechanical challenges, such as cell adhesion and contraction, or compression, stretch and osmolarity fluctuations, creating a cohesive cortex supporting the plasma membrane. Actin territories control protrusions and contractile structures while spectrin territories concentrate in retractile zones and low-actin density/inter-contractile regions, acting as a fence to organize membrane trafficking events. We unveil here the existence of a dynamic interplay between acto-myosin and spectrin cytoskeletons necessary to support a mesoscale organization of the lipid bilayer into spatially-confined cortical territories during cell mechanoresponse.

Establishment of apical–basal cell polarity is necessary for generation of luminal and tubular structures during epithelial morphogenesis. Molecules acting at the membrane/ actin interface are expected to be crucial in governing these processes. Here, we show that the I-BAR-containing IRSp53 protein is restricted to the luminal side of epithelial cells of various glandular organs, and is specifically enriched in renal tubules in human, mice, and zebrafish. Using three-dimensional cultures of renal MDCK and intestinal Caco-2 cysts, we show that IRSp53 is recruited early after the first cell division along the forming apical lumen, and is essential for formation of a single lumen and for positioning of the polarity determinants aPKC and podocalyxin. Molecularly, IRSp53 directly binds to and controls localization of the inactive form of the small GTPase RAB35, a tethering factor for apical determinants. The interaction of IRSp53 with the actin capping protein EPS8 is critical for restricting IRSp53 localization. Correlative light and electron microscopy shows that IRSp53 loss perturbs the shape and continuity of the opposing apical membrane during the initial phase of lumenogenesis, which leads to preservation of multiple cytoplasmic bridges that interrupt the continuity of the nascent lumen. At the organism level, genetic removal of IRSp53 results in abnormal renal tubulogenesis, with defects in tubular polarity and architectural organization in both IRSp53 zebrafish mutant lines and IRSp53-KO murine models. Thus, IRSp53 acts as a platform for spatiotemporal regulation of assembly of the multi-protein complexes that shape the luminal membrane during the early steps of epithelial lumen morphogenesis.

Tissue self-organization into defined and well-controlled three-dimensional structures is essential during development for the generation of organs. A similar, but highly deranged process might also occur during the aberrant growth of cancers, which frequently display a loss of the orderly structures of the tissue of origin, but retain a multicellular organization in the form of spheroids, strands, and buds. The latter structures are often seen when tumors masses switch to an invasive behavior into surrounding tissues. However, the general physical principles governing the self-organized architectures of tumor cell populations remain by and large unclear. In this work, we perform in-vitro experiments to characterize the growth properties of glioblastoma budding emerging from monolayers. We further propose a theoretical model and its finite element implementation to characterize such a topological transition, that is modelled as a self-organised, non-equilibrium phenomenon driven by the trade–off of mechanical forces and physical interactions exerted at cell-cell and cell–substrate adhesions. Notably, the unstable disorder states of uncontrolled cellular proliferation macroscopically emerge as complex spatio–temporal patterns that evolve statistically correlated by a universal law.

Using real-time TIRF microscopy imaging, we identify sites of clathrin and dynamin-independent CLIC/GEEC (CG) endocytic vesicle formation. This allows spatio-temporal localisation of known molecules affecting CG endocytosis; GBF1 (a GEF for ARF1), ARF1 and CDC42 which appear sequentially over 60 s, preceding scission. In an RNAi screen for BAR domain proteins affecting CG endocytosis, IRSp53 and PICK1, known interactors of CDC42 and ARF1, respectively, were selected. Removal of IRSp53, a negative curvature sensing protein, abolishes CG endocytosis. Furthermore, the identification of ARP2/3 complex at CG endocytic sites, maintained in an inactive state reveals a function for PICK1, an ARP2/3 inhibitor. The spatio-temporal sequence of the arrival and disappearance of the molecules suggest a mechanism for a clathrin and dynamin-independent endocytic process. Coincident with the loss of PICK1 by GBF1-activated ARF1, CDC42 recruitment leads to the activation of IRSp53 and the ARP2/3 complex, resulting in a burst of F-actin polymerisation potentially powering scission., Several endocytic pathways operate simultaneously at the cell surface, including the clathrin and dynamin-independent CLIC/GEEC (CG) pathway. Here the authors show that small GTPases and BAR domain proteins regulate branched actin to make clathrin and dynamin-independent endocytic vesicles.

Cell monolayers provide an interesting example of active matter, exhibiting a phase transition from flowing to jammed states as they age. Here we report experiments and numerical simulations illustrating how a jammed cellular layer rapidly reverts to a flowing state after a wound. Quantitative comparison between experiments and simulations shows that cells change their self-propulsion and alignment strength so that the system crosses a phase transition line, which we characterize by finite-size scaling in an active particle model. This wound-induced unjamming transition is found to occur generically in epithelial, endothelial and cancer cells.

KRAS is the key mutated gene in pancreatic ductal adenocarcinoma (PDAC). Emerging evidence indicates that KRas modulates endocytic uptake. The present study aimed to explore the fate of early endosomal trafficking under the control of KRas expression in PDAC. Surprisingly, PANC-1 cells lacking KRas exhibited significantly enlarged early and late endosomes containing internalized dextran and epidermal growth factor. Endosome enlargement was accompanied by reduced endosomal degradation. Both KRas silencing and lysosomal blockade caused an upregulation of the master regulator of early endosome biogenesis, RAB5A, which is likely responsible for the expansion of the early endosomal compartment, because simultaneous KRAS/RAB5A knockdown abolished endosome enlargement. In contrast, early endosome shrinkage was seen in MIA PaCa-2 cells despite RAB5A upregulation, indicating that distinct KRas-modulated responses operate in different metabolic subtypes of PDAC. In conclusion, mutant KRAS promotes endosomal degradation in PDAC cell lines, which is impaired by KRAS silencing. Moreover, KRAS silencing activates RAB5A upregulation and drives PDAC subtype-dependent modulation of endosome trafficking.

JAK-dependent activation of the rho module of integrin affinity triggering mediates chemokine-induced leukocyte adhesion. However, the signaling events linking JAKs to rho small GTPase activation by chemokines is still incompletely described. In this study, we show that son of sevenless 1 (SOS1), rho guanine nucleotide exchange factor (GEF)1 (ARHGEF1), and dedicator of cytokinesis (DOCK)2 GEFs mediate CXCL12-induced LFA-1 activation in human primary T lymphocytes. Downregulated expression of SOS1, ARHGEF1, and DOCK2 impairs LFA-1–mediated rapid T lymphocyte adhesion as well as underflow arrest on ICAM-1 induced by CXCL12. Moreover, LFA-1 affinity triggering by CXCL12 is impaired by SOS1, ARHGEF1, and DOCK2 downregulation. Notably, the three GEFs are all critically involved in chemokine-induced RhoA and Rac1 activation, thus suggesting the occurrence of a SOS1 specificity shift in the context of chemokine signaling. Accordingly, SOS1, ARHGEF1, and DOCK2 are tyrosine phosphorylated upon chemokine signaling with timing coherent with rapid LFA-1 affinity activation. Importantly, chemokine-induced tyrosine phosphorylation of these GEFs is fully mediated by JAK protein tyrosine kinases. Unexpectedly, and differently from VAV1, tyrosine phosphorylation of SOS1, ARHGEF1, and DOCK2 is completely inhibited by pertussis toxin pretreatment, thus suggesting different routes of rho-GEF triggering upon CXCR4 engagement. Taken together, these findings reveal a deeper level of complexity in the rho-signaling module, with at least four different rho-GEFs cooperating in the regulation of chemokine-induced integrin activation, possibly suggesting the emergence of stochastic concurrency in signaling mechanisms controlling leukocyte trafficking.

The subversion of endocytic routes leads to malignant transformation and has been implicated in human cancers. However, there is scarce evidence for genetic alterations of endocytic proteins as causative in high incidence human cancers. Here, we report that Epsin 3 (EPN3) is an oncogene with prognostic and therapeutic relevance in breast cancer. Mechanistically, EPN3 drives breast tumorigenesis by increasing E-cadherin endocytosis, followed by the activation of a β-catenin/TCF4-dependent partial epithelial-to-mesenchymal transition (EMT), followed by the establishment of a TGFβ-dependent autocrine loop that sustains EMT. EPN3-induced partial EMT is instrumental for the transition from in situ to invasive breast carcinoma, and, accordingly, high EPN3 levels are detected at the invasive front of human breast cancers and independently predict metastatic rather than loco-regional recurrence. Thus, we uncover an endocytic-based mechanism able to generate TGFβ-dependent regulatory loops conferring cellular plasticity and invasive behavior., It is unclear if genetic alterations in endocytic proteins play a causal role in high incidence human cancers. Here, the authors report the oncogenic role of Epsin3 (EPN3) in breast cancer, and show EPN3 to drive tumorigenesis through induction of a partial epithelial mesenchymal transition state and a TGFβ-dependent regulatory loop that promotes cellular plasticity and invasive behaviour.

International audience; Cells going through mitosis undergo precisely timed changes in cell shape and organisation, which serve to ensure the fair partitioning of cellular components into the two daughter cells. These structural changes are driven by changes in actin filament and microtubule dynamics and organisation. While most evidence suggests that the two cytoskeletal systems are remodelled in parallel during mitosis, recent work in interphase cells has implicated the centrosome in both microtubule and actin nucleation, suggesting the potential for regulatory crosstalk between the two systems. Here, by using both in vitro and in vivo assays to study centrosomal actin nucleation as cells pass through mitosis, we show that mitotic exit is accompanied by a burst in cytoplasmic actin filament formation that depends on WASH and the Arp2/3 complex. This leads to the accumulation of actin around centrosomes as cells enter anaphase and to a corresponding reduction in the density of centrosomal microtubules. Taken together, these data suggest that the mitotic regulation of centrosomal WASH and the Arp2/3 complex controls local actin nucleation, which may function to tune the levels of centrosomal microtubules during passage through mitosis.

Antimicrobial peptides (AMPs) are the body’s natural innate immune defense against a spectrum of pathogenic insults and provide an attractive strategy towards combating the growing problem of antibiotic resistant microorganisms. The prophylactic use of AMPs is contingent upon understanding the regulatory mechanisms governing the release of AMPs from intracellular stores, which occurs via the non-conventional secretory pathway. Analysis of S100A7 (Psoriasin), an abundant AMP in the skin, from its endogenous stores within differentiated keratinocytes has revealed an unexpected biphasic secretory response to bacterial exposure. The core components regulating S100A7 secretion are NFκB/p38MAPK, caspase-1 and IL-1α. The early activation of this core machinery is mediated by toll-like receptor signaling, whereas the chronic response is regulated by the wound-healing machinery mediated by Caspase-8 downregulation. Interestingly, in inflammatory skin diseases in which S100A7 is excessively released, there is a concomitant downregulation of caspase-8, indicating that these pathological scenarios are commandeering the normal wound healing response. These results highlight the potential benefits of targeting intracellular wound healing pathways as a means of exerting control over the release of AMPs from the skin in both homeostatic and disease conditions.

Summary: Antimicrobial peptides (AMPs) are the body’s natural innate immune defense against a spectrum of pathogens and can also modulate cell proliferation, chemotaxis, angiogenesis, wound healing, and immune cell activity. Harnessing these diverse functions for prophylactic use is contingent upon understanding the regulatory mechanisms governing their unconventional secretion from cells. Analysis of the secretion of S100A7 (Psoriasin), an abundant AMP stored in differentiated keratinocytes of the skin, has revealed an unexpected biphasic secretory response to bacterial exposure. The core components regulating S100A7 secretion are NFκB/p38MAPK, caspase-1, and interleukin (IL)-1α. The initial activation of this core machinery is mediated by Toll-like receptor signaling, whereas the chronic response is mediated by Caspase-8 downregulation. Interestingly, there is a concomitant downregulation of Caspase-8 in inflammatory skin diseases wherein S100A7 is constitutively released. These results highlight the potential of targeting these components to control the release of AMPs from the skin in both homeostatic and disease conditions. : The global explosion of antibiotic-resistant microorganisms has spurred interest in alternative strategies to combat these “superbugs.” Antimicrobial peptides (AMPs) have emerged as a promising solution. Bhatt et al. show downregulation of epidermal caspase-8 can mediate sustained release of AMPs from the skin and provide an effective defense against infection. keywords: caspase, antimicrobial peptides, skin, TLR, IL-1, NFkB, psoriasis, antibiotic resistance

The mechanisms of tumor cell dissemination and the contribution of membrane trafficking in this process are poorly understood. Through a functional siRNA screening of human RAB GTPases, we found that RAB2A, a protein essential for ER‐to‐Golgi transport, is critical in promoting proteolytic activity and 3D invasiveness of breast cancer (BC) cell lines. Remarkably, RAB2A is amplified and elevated in human BC and is a powerful and independent predictor of disease recurrence in BC patients. Mechanistically, RAB2A acts at two independent trafficking steps. Firstly, by interacting with VPS39, a key component of the late endosomal HOPS complex, it controls post‐endocytic trafficking of membrane‐bound MT1‐MMP, an essential metalloprotease for matrix remodeling and invasion. Secondly, it further regulates Golgi transport of E‐cadherin, ultimately controlling junctional stability, cell compaction, and tumor invasiveness. Thus, RAB2A is a novel trafficking determinant essential for regulation of a mesenchymal invasive program of BC dissemination.

Background: Breast cancer (BC) is the most frequent tumor in women worldwide. BC lethality is caused by aggressive, therapy-resistant metastases (mBC). Preliminary data have shown that mBC lesions are invariably embedded into a densely packed network of fibrous extracellular matrix, making the metastatic microenvironment a potent inducer of mechanical inputs, ultimately leading to the activation of the transcription factors YAP/TAZ. Aberrant mechano-signaling could thus represent a vulnerability of metastasis, which can be exploited to develop new therapeutic strategies. To investigate how metastatic outgrowth is regulated by the physical properties of the microenvironment, and how the altered mechano-transduction of human BC metastasis can be exploited to define new unconventional therapies, we designed and activated METAMECH, a Master Observational Trial (MOT). MOTs are trial constructs hybridizing a canonical observational trial with a multiplex sample-collection platform, aimed to empower the bi-directional collaboration between pre-clinical and clinical research, an essential prerequisite to feed and implement precision oncology. Methods: METAMECH (IFOM-CPO007/2019/PO006) is a MOT that will follow a stage-mixed cohort of at least 500 BC patients throughout their course of treatments, until death or a minimum of 5 years. METAMECH has been designed to streamline the study of the co-evolutionary landscape between tumor and host cells across all BC subtypes. METAMECH is a resource for integrative clinical and imaging data and fresh and archival sample collection which will allow to auction mechanotransduction mechanisms supporting the outgrowth of human metastases, mine for new potentially actionable targets and permit the selection of appropriate patients for mechano-biology experimentally-driven trials. METAMECH is a multi-tiers research scaffold that will allow to integrate the clinical and basic aspects of the project, to optimize patients enrollment and the logistic of longitudinal collection of theirs data/samples. A customized data lake is being designed for data storage, analysis and retrieval. To facilitate patients access, METAMECH has been designed as a flexible infrastructure organized in TIERS, which allow to pursue different objectives: TIER0/1, Retrieving/Recording: to retrospectively and prospectively access to selected cohorts of clinically annotated BC samples to validate/discover mechanotransduction-linked biomarkers and create a mechano-classifier; TIER2, Modelling: to develop pertinent experimental models to study the aberrant mechanisms underlying the metastatic outgrowth and define mechanotransduction-targeting therapeutic strategies; TIER3, Linking: to access data and samples of patients enrolled in Proof-of-Concept trials to prove the efficacy and study/understand resistance mechanisms of mechanotransduction-targeting therapies. Citation Format: Paolo Luraghi, Luca Lazzari, Maria Vittoria Dieci, Serena Bellani, Chiara Soffientini, Rosario Rizzuto, Antonio Rosato, Vincenzo Costanzo, Giorgio Scita, Giannino Del Sal, Massimiliano Pagani, Marco Foiani, Claudio Tripodo, Silvio Bicciato, Giovanni Blandino, Alberto Zambelli, Valter Torri, Matteo Fassan, PierFranco Conte, Silvia Marsoni, Stefano Piccolo. METAMECH -A Master Observational Trial empowering mechanobiology translational research and mechanobased proof of concept trials in breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT261.