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Macrophages clear infections by engulfing and digesting pathogens within phagolysosomes. Pathogens escape this fate by engaging in a molecular arms race; they use WxxxE motif-containing "effector" proteins to subvert the host cells they invade and seek refuge within protective vacuoles. Here, we define the host component of the molecular arms race as an evolutionarily conserved polar "hot spot" on the PH domain of ELMO1 (Engulfment and Cell Motility protein 1), which is targeted by diverse WxxxE effectors. Using homology modeling and site-directed mutagenesis, we show that a lysine triad within the "patch" directly binds all WxxxE effectors tested: SifA (Salmonella), IpgB1 and IpgB2 (Shigella), and Map (enteropathogenic Escherichia coli). Using an integrated SifA-host protein-protein interaction network, in silico network perturbation, and functional studies, we show that the major consequences of preventing SifA-ELMO1 interaction are reduced Rac1 activity and microbial invasion. That multiple effectors of diverse structure, function, and sequence bind the same hot spot on ELMO1 suggests that the WxxxE effector(s)-ELMO1 interface is a convergence point of intrusion detection and/or host vulnerability. We conclude that the interface may represent the fault line in coevolved molecular adaptations between pathogens and the host, and its disruption may serve as a therapeutic strategy.

Introduction: Red blood cells (RBCs), also known as erythrocytes, are underestimated in their role in the immune system. In mammals, erythrocytes undergo maturation that involves the loss of nuclei, resulting in limited transcription and protein synthesis capabilities. However, the nucleated nature of non-mammalian RBCs is challenging this conventional understanding of RBCs. Notably, in bony fishes, research indicates that RBCs are not only susceptible to pathogen attacks but express immune receptors and effector molecules. However, given the abundance of RBCs and their interaction with every physiological system, we postulate that they act in surveillance as sentinels, rapid responders, and messengers. Methods: We performed a series of in vitro experiments with Cyprinus carpio RBCs exposed to Aeromonas hydrophila, as well as in vivo laboratory infections using different concentrations of bacteria. Results: qPCR revealed that RBCs express genes of several inflammatory cytokines. Using cyprinid-specific antibodies, we confirmed that RBCs secreted tumor necrosis factor alpha (TNFα) and interferon gamma (IFNγ). In contrast to these indirect immune mechanisms, we observed that RBCs produce reactive oxygen species and, through transmission electron and confocal microscopy, that RBCs can engulf particles. Finally, RBCs expressed and upregulated several putative toll-like receptors, including tlr4 and tlr9, in response to A. hydrophila infection in vivo. Discussion: Overall, the RBC repertoire of pattern recognition receptors, their secretion of effector molecules, and their swift response make them immune sentinels capable of rapidly detecting and signaling the presence of foreign pathogens. By studying the interaction between a bacterium and erythrocytes, we provide novel insights into how the latter may contribute to overall innate and adaptive immune responses of teleost fishes. Keywords: Aeromonas hydrophila (A. hydrophila); Cyprinus carpio; bacteria; cytokines; engulfment; inflammation; red blood cell (RBC); teleost fish. sentinels capable of rapidly detecting and signaling the presence of foreign pathogens. By studying the interaction between a bacterium and erythrocytes, we provide novel insights into how the latter may contribute to overall innate and adaptive immune responses of teleost fishes. [ABSTRACT FROM AUTHOR]

The presence of good clinical and cognitive insight has been linked to depression in people diagnosed with schizophrenia. Clinical and cognitive insight, respectively, refer to the awareness of one's symptoms and need for treatment and to being conscious of modifications in one's reasoning processes. Engulfment, or over-identification to a sick role that becomes the patient's central identity, has been found to mediate the relationship between clinical insight and depression. However, the relationship between engulfment, cognitive insight and depression has not been investigated. Consequently, this study examined the potential mediating role of engulfment in the association between cognitive insight and depression The sample consisted of 140 participants diagnosed with enduring schizophrenia (for at least 3 years). Correlation and mediation analyses were conducted to examine associations between cognitive insight, engulfment and depressive symptomatology Our analyses revealed that cognitive insight was significantly and positively correlated with engulfment. This association was driven by the self-reflectiveness subscale of the Beck Cognitive Insight Scale. Engulfment was significantly correlated with depression. Finally, engulfment mediated the relationship between cognitive insight, and depression. In the context of good cognitive insight, engulfment should be a target for psychological interventions aimed at lowering the risk of depression. [ABSTRACT FROM AUTHOR]

Summary: Rheumatoid arthritis (RA) is a chronic inflammatory disease of the synovial joints that affects ~1% of the human population. Joint swelling and bone erosion, hallmarks of RA, contribute to disability and, sometimes, loss of life. Mechanistically, disease is driven by immune dysregulation characterized by circulating autoantibodies, inflammatory mediators, tissue degradative enzymes, and metabolic dysfunction of resident stromal and recruited immune cells. Cell death by apoptosis has been therapeutically explored in animal models of RA due to the comparisons drawn between synovial hyperplasia and paucity of apoptosis in RA with the malignant transformation of cancer cells. Several efforts to induce cell death have shown benefits in reducing the development and/or severity of the disease. Apoptotic cells are cleared by phagocytes in a process known as efferocytosis, which differs from microbial phagocytosis in its "immuno‐silent," or anti‐inflammatory, nature. Failures in efferocytosis have been linked to autoimmune disease, whereas administration of apoptotic cells in RA models effectively inhibits inflammatory indices, likely though efferocytosis‐mediated resolution‐promoting mechanisms. However, the nature of signaling pathways elicited and the molecular identity of clearance mediators in RA are understudied. Furthermore, canonical efferocytosis machinery elements also play important non‐canonical functions in homeostasis and pathology. Here, we discuss the roles of efferocytosis machinery components in models of RA and discuss their potential involvement in disease pathophysiology. [ABSTRACT FROM AUTHOR]

Comorbidity between schizophrenia and social anxiety disorder (SAD) is found to be considerable. However, contra current conventional psychiatric belief, one might also view social anxiety as appertaining to the schizophrenia spectrum, and not merely as a co-occurring disorder. In this paper, I argue that by comprehensively investigating an unspecific phenomenon, such as social anxiety, we can acquire a grasp of the specific ways-of-being-in-the-world for the person with schizophrenia. In this respect, social anxiety proves revelatory of the Gestalt of schizophrenia, yet, simultaneously, the Gestalt reciprocally illuminates the quality of the social anxiety. I begin by outlining the structure of social anxiety in schizophrenia, which has a qualitatively different structure from social anxiety in itself or in other conditions, since the anxiety primarily is directed toward the social domain as such, i.e., sociality may constitute an ontological threat. Next, I discuss three modalities of social anxiety in schizophrenia: anxiousness about losing uniqueness, fusion anxiety, and engulfment. I end by stressing the importance of the Gestalt-oriented approach in the elucidation of social anxiety in schizophrenia. Additionally, I also introduce some reflections on the relationship between social anxiety and psychosis, and some considerations on psychotherapy for social anxiety in schizophrenia. [ABSTRACT FROM AUTHOR]

Oligodendrocyte precursor cells (OPCs) play diverse roles in the brain, extending beyond their classically recognized contributions to oligodendrogenesis and myelination. In the developing and adult visual system, OPCs have been shown to remodel axons and to eliminate synapses through phagocytic engulfment. The engulfment of synapses by OPCs is influenced by multiple factors, including neural activity and molecular signals from other brain cells. Future work is needed to define the biological consequences and underlying molecular mechanisms of synapse engulfment by OPCs. Oligodendrocyte precursor cells (OPCs) are non-neuronal brain cells that give rise to oligodendrocytes, glia that myelinate the axons of neurons in the brain. Classically known for their contributions to myelination via oligodendrogenesis, OPCs are increasingly appreciated to play diverse roles in the nervous system, ranging from blood vessel formation to antigen presentation. Here, we review emerging literature suggesting that OPCs may be essential for the establishment and remodeling of neural circuits in the developing and adult brain via mechanisms that are distinct from the production of oligodendrocytes. We discuss the specialized features of OPCs that position these cells to integrate activity-dependent and molecular cues to shape brain wiring. Finally, we place OPCs within the context of a growing field focused on understanding the importance of communication between neurons and glia in the contexts of both health and disease. [ABSTRACT FROM AUTHOR]

Biological and biomimetic membranes are based on lipid bilayers, which consist of two monolayers or leaflets. To avoid bilayer edges, which form when the hydrophobic core of such a bilayer is exposed to the surrounding aqueous solution, a single bilayer closes up into a unilamellar vesicle, thereby separating an interior from an exterior aqueous compartment. Synthetic nanovesicles with a size below 100 nanometers, traditionally called small unilamellar vesicles, have emerged as potent platforms for the delivery of drugs and vaccines. Cellular nanovesicles of a similar size are released from almost every type of living cell. The nanovesicle morphology has been studied by electron microscopy methods but these methods are limited to a single snapshot of each vesicle. Here, we review recent results of molecular dynamics simulations, by which one can monitor and elucidate the spatio-temporal remodeling of individual bilayers and nanovesicles. We emphasize the new concept of leaflet tensions, which control the bilayers' stability and instability, the transition rates of lipid flip-flops between the two leaflets, the shape transformations of nanovesicles, the engulfment and endocytosis of condensate droplets and rigid nanoparticles, as well as nanovesicle adhesion and fusion. To actually compute the leaflet tensions, one has to determine the bilayer's midsurface, which represents the average position of the interface between the two leaflets. Two particularly useful methods to determine this midsurface are based on the density profile of the hydrophobic lipid chains and on the molecular volumes. [ABSTRACT FROM AUTHOR]

Endospore formation in Bacillus subtilis provides an ideal model system for studying development in bacteria. Sporulation studies have contributed a wealth of information about the mechanisms of cell-specific gene expression, chromosome dynamics, protein localization, and membrane remodeling, while helping to dispel the early view that bacteria lack internal organization and interesting cell biological phenomena. In this review, we focus on the architectural transformations that lead to a profound reorganization of the cellular landscape during sporulation, from two cells that lie side by side to the endospore, the unique cell within a cell structure that is a hallmark of sporulation in B. subtilis and other spore-forming Firmicutes. We discuss new insights into the mechanisms that drive morphogenesis, with special emphasis on polar septation, chromosome translocation, and the phagocytosis-like process of engulfment, and also the key experimental advances that have proven valuable in revealing the inner workings of bacterial cells.

CD47 acts as a "don't eat me" signal that protects cells from phagocytosis by binding and activating its receptor SIPRA on macrophages. CD47 suppresses multiple different pro-engulfment "eat me" signals, including immunoglobulin G (IgG), complement, and calreticulin, on distinct target cells. This complexity has limited understanding of how the "don't eat me" signal is transduced biochemically. Here, we utilized a reconstituted system with a defined set of signals to interrogate the mechanism of SIRPA activation and its downstream targets. CD47 ligation altered SIRPA localization, positioning SIRPA for activation at the phagocytic synapse. At the phagocytic synapse, SIRPA inhibited integrin activation to limit macrophage spreading across the surface of the engulfment target. Chemical reactivation of integrin bypassed CD47-mediated inhibition and rescued engulfment, similar to the effect of a CD47 function-blocking antibody. Thus, the CD47-SIRPA axis suppresses phagocytosis by inhibiting inside-out activation of integrin signaling in the macrophage, with implications to cancer immunotherapy applications.

The study of bacterial cell biology is limited by difficulties in visualizing cellular structures at high spatial resolution within their native milieu. Here, we visualize Bacillus subtilis sporulation using cryo-electron tomography coupled with cryo-focused ion beam milling, allowing the reconstruction of native-state cellular sections at molecular resolution. During sporulation, an asymmetrically-positioned septum generates a larger mother cell and a smaller forespore. Subsequently, the mother cell engulfs the forespore. We show that the septal peptidoglycan is not completely degraded at the onset of engulfment. Instead, the septum is uniformly and only slightly thinned as it curves towards the mother cell. Then, the mother cell membrane migrates around the forespore in tiny finger-like projections, whose formation requires the mother cell SpoIIDMP protein complex. We propose that a limited number of SpoIIDMP complexes tether to and degrade the peptidoglycan ahead of the engulfing membrane, generating an irregular membrane front.

Metazoan tissue specification is associated with integration of macrophage lineage cells in sub-tissular niches to promote tissue development and homeostasis. Oncogenic transformation, most prevalently of epithelial cell lineages, results in maladaptation of resident tissue macrophage differentiation pathways to generate parenchymal and interstitial tumor-associated macrophages that largely foster cancer progression. In addition to growth factors, nutrients that can be consumed, stored, recycled, or converted to signaling molecules have emerged as crucial regulators of macrophage responses in tumor. Here, we review how nutrient acquisition through plasma membrane transporters and engulfment pathways control tumor-associated macrophage differentiation and function. We also discuss how nutrient metabolism regulates tumor-associated macrophages and how these processes may be targeted for cancer therapy. Oncogenic transformation drives maladaptation of resident tissue macrophage differentiation pathways to generate tumor-associated macrophages (TAMs) that largely promote cancer progression. Zhang et al. review how metabolism controls TAM development and function. They discuss how nutrients acquired through plasma membrane transporters and engulfment pathways are metabolized to control TAMs and how these processes may be targeted for cancer therapy. [ABSTRACT FROM AUTHOR]

Macrophages are specialized phagocytic cells involved in clearing invading pathogens. Previously we reported that engulfment and cell motility protein 1 (ELMO1) in macrophages mediates bacterial internalization and intestinal inflammation. Here we studied the role of ELMO1 in the fate of internalized targets. ELMO1 is present in the intracellular vesicles and enhances accumulation of the protein LC3B following engulfment of Salmonella or treatment with autophagy-inducing rapamycin. The protein ATG5 and the kinase ULK1 are involved in classical autophagy, while LC3-associated phagocytosis is ULK1 independent. ATG5 but not ULK1 cooperated with ELMO1 in LC3 accumulation after infection, suggesting the ELMO1 preferentially regulated LC3-associated phagocytosis. Because LC3-associated phagocytosis delivers cargo for degradation, the contribution of ELMO1 to the lysosome degradation pathways was evaluated by studying pH and cathepsin B activity. ELMO1-depleted macrophages showed a time-dependent increase in pH and a decrease in cathepsin B activity associated with bacterial survival. Together, ELMO1 regulates LC3B accumulation and antimicrobial responses involved in the clearance of enteric pathogens. This paper investigated how innate immune pathways involving ELMO1 work in a coordinated fashion to eliminate bacterial threats. ELMO1 is present in the phagosome and enhances bacterial clearance by differential regulation of lysosomal acidification and enzymatic activity.

Grain entrapments remain a major concern in the grain storage and handling industry. Even with the adoption of safer technology, enhanced enforcement of OSHA regulations, and considerable investment in training and outreach efforts, grain entrapments continue to occur in significant numbers. The most significant contributing factor to grain entrapment is the presence of out-of-condition grain. A better understanding of existing strategies employed to remove out-of-condition grain from storage is important to provide evidence-based solutions to reduce the perceived need to enter grain storage structures and the grain entrapment associated with this activity. A review of existing strategies for handling out-of-condition grain used previously by farmers and workers with experience in grain storage facilities was conducted. Training programs, extension resources, and published research were reviewed to document existing strategies to remove out-of-condition grain. These strategies were split into three broad categories: outfitting the bin, outside of the bin, and inside the bin. A total of 21 strategies were documented. Each of the strategies was defined and, where possible, the risks and benefits were discussed. The study highlights the importance of researching the safety and effectiveness of each of these strategies in various out-of-condition grain situations and the lack of available knowledge of the effectiveness of each strategy. [ABSTRACT FROM AUTHOR]

Objectives: Although Clostridium perfringens sporulation is a key event in the pathogenesis of food-borne illness, the molecules and underlying mechanisms responsible for regulating sporulation are incompletely understood. The present study sought to identify amino acids that affect sporulation in C. perfringens strain SM101., Methods: A C. perfringens strain was cultured in the chemically defined medium deficient in an amino acid. The bacterial growth was determined by spectrophotometrically measuring culture turbidity and by calculating colony-forming unit. Morphological characteristics were assessed by phase-contrast microscopy with fluorescent staining and by electron microscopy., Results: The amino acids Arg, Cys, Gly, His, Ile, Leu, Met, Phe, Thr, Trp, Tyr, and Val were important for sporulation, and furthermore, Ser reduced sporulation. The mechanism underlying Ser-induced prevention of sporulation was assessed morphologically. The numbers of bacterial cells in sporulation stage II were significantly higher in the presence than in the absence of Ser. In the presence of Ser, almost all cells were in stage II-III, characterized by polar septation-early engulfment, and did not proceed to late engulfment., Conclusions: These results suggest that Ser accelerated the early stage of sporulation of C. perfringens strain SM101, but disturbed the engulfment process, resulting in reduction of sporulation. To the best of our knowledge, this is the first study reporting that an amino acid affects engulfment during the C. perfringens sporulation process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

ABSTRACT During bacterial endospore formation, the developing spore is internalized into the mother cell through a phagocytic-like process called engulfment, which involves synthesis and hydrolysis of peptidoglycan. Engulfment peptidoglycan hydrolysis requires the widely conserved and well-characterized DMP complex, composed of SpoIID, SpoIIM, and SpoIIP. In contrast, although peptidoglycan synthesis has been implicated in engulfment, the protein players involved are less well defined. The widely conserved SpoIIIAH-SpoIIQ interaction is also required for engulfment efficiency, functioning like a ratchet to promote membrane migration around the forespore. Here, we screened for additional factors required for engulfment using transposon sequencing in Bacillus subtilis mutants with mild engulfment defects. We discovered that YrvJ, a peptidoglycan hydrolase, and the MurA paralog MurAB, involved in peptidoglycan precursor synthesis, are required for efficient engulfment. Cytological analyses suggest that both factors are important for engulfment when the DMP complex is compromised and that MurAB is additionally required when the SpoIIIAH-SpoIIQ ratchet is abolished. Interestingly, despite the importance of MurAB for sporulation in B. subtilis, phylogenetic analyses of MurA paralogs indicate that there is no correlation between sporulation and the number of MurA paralogs and further reveal the existence of a third MurA paralog, MurAC, within the Firmicutes. Collectively, our studies identify two new factors that are required for efficient envelop remodeling during sporulation and highlight the importance of peptidoglycan precursor synthesis for efficient engulfment in B. subtilis and likely other endospore-forming bacteria. IMPORTANCE In bacteria, cell envelope remodeling is critical for cell growth and division. This is also the case during the development of bacteria into highly resistant endospores (spores), known as sporulation. During sporulation, the developing spore becomes internalized inside the mother cell through a phagocytic-like process called engulfment, which is essential to form the cell envelope of the spore. Engulfment involves both the synthesis and hydrolysis of peptidoglycan and the stabilization of migrating membranes around the developing spore. Importantly, although peptidoglycan synthesis has been implicated during engulfment, the specific genes that contribute to this molecular element of engulfment have remained unclear. Our study identifies two new factors that are required for efficient envelope remodeling during engulfment and emphasizes the importance of peptidoglycan precursor synthesis for efficient engulfment in the model organism Bacillus subtilis and likely other endospore-forming bacteria. Finally, our work highlights the power of synthetic screens to reveal additional genes that contribute to essential processes during sporulation.

This paper addresses the issue of finding the right distance to the patient in psychoanalytic work with children on the autistic spectrum. It is suggested that, like borderline patients, these children are caught between the fear of being pushed off the caregiver into space, on the one hand, and of being engulfed, on the other. This »claustrophobic-agoraphobic dilemma« (Rey) is considered with regard to factors in the caregiver; to the child’s phantasies concerning the caregiver’s internal figures; and to consequences of autistic children’s heightened sensitivity to the state of mind of other people. The paternal function as the mediator of distance between mother and child is discussed in relation to the »bisexuality of the container« (Houzel) and the clinician’s mental positioning as a parental couple, along with implications for the phrasing of comments. A vignette illustrates the importance of the clinician’s individual identity and private associations in allowing the child to feel seen without being engulfed, and to show capacities that may otherwise be kept hidden. [ABSTRACT FROM AUTHOR]

The interaction between Janus colloids and giant lipid vesicles was experimentally investigated to elucidate the dynamics and mechanisms related to microparticle engulfment by lipid vesicles. Janus (Pt–SiO2 and Pt–MF, where MF is melamine formaldehyde) colloids do not spontaneously adhere to POPC or DOPC bilayers, but by applying external forces via centrifugation we were able to force the contact between the particles and the membranes, which may result in a partial engulfment state of the particle. Surface properties of the Janus colloids play a crucial role in the driven particle engulfment by vesicles. Engulfment of the silica and platinum regions of the Janus particles can be observed, whereas the polymer (MF) region does not show any affinity towards the lipid bilayer. By using fluorescence microscopy, we were able to monitor the particle orientation and measure the rotational dynamics of a single Janus particle engulfed by a vesicle. By adding hydrogen peroxide to the solution, particle self-propulsion was used to perform an active transport of a giant vesicle by a single active particle. Finally, we observe that partially engulfed particles experience a membrane curvature-induced force, which pushes the colloids towards the bottom where the membrane curvature is the lowest. [ABSTRACT FROM AUTHOR]

Here we highlight the increasingly divergent functions of the Caenorhabditis elegans cell elimination genes in the nervous system, beyond their well-documented roles in cell dismantling and removal. We describe relevant background on the C. elegans nervous system together with the apoptotic cell death and engulfment pathways, highlighting pioneering work in C. elegans. We discuss in detail the unexpected, atypical roles of cell elimination genes in various aspects of neuronal development, response and function. This includes the regulation of cell division, pruning, axon regeneration, and behavioral outputs. We share our outlook on expanding our thinking as to what cell elimination genes can do and noting their versatility. We speculate on the existence of novel genes downstream and upstream of the canonical cell death pathways relevant to neuronal biology. We also propose future directions emphasizing the exploration of the roles of cell death genes in pruning and guidance during embryonic development.

The evolution of next-generation neural interfaces toward high-density, high-fidelity, and long-term recordings coupled with the advent of complex fabrication techniques drives the development of 3D nanostructures to bridge the neuron-artificial device interface. This is largely due to several observations of high signal-to-noise ratios recorded from high-aspect-ratio 3D nanoelectrodes enabled by an inimitable mechanical coupling with the neural membrane and, in some cases, direct access to the neural intracellular space. This review details progress in developing 3D electrodes for electrogenic cell interfaces. First, the impacts of nanotopography on the electrical and mechanical coupling of the cell and recording electrodes are discussed, and different conceptual approaches in understanding the biomechanics of cell/3D electrode coupling through experimental work and computational models are described. This work also highlights the latest advances in 3D nanostructures for recording the intracellular activity of cultured neurons and cardiomyocytes with a focus on emerging 3D structures and strategies aimed at improving efficiency and long-term integration with cultured electrogenic cells.

During spore development in bacteria, a polar septum separates two transcriptionally distinct cellular compartments, the mother cell and the forespore. The conserved serine phosphatase SpoIIE is known for its critical role in the formation of this septum and activation of compartment-specific transcription in the forespore. Signaling between the mother cell and forespore then leads to activation of mother cell transcription and a phagocytic-like process called engulfment, which involves dramatic remodeling of the septum and requires a balance between peptidoglycan synthesis and hydrolysis to ensure septal stability and compartmentalization. Using Bacillus subtilis , we identify an additional role for SpoIIE in maintaining septal stability and compartmentalization at the onset of engulfment. This role for SpoIIE is mediated by SpoIIQ, which anchors SpoIIE in the engulfing membrane. A SpoIIQ mutant (SpoIIQ Y28A) that fails to anchor SpoIIE, results in septal instability and miscompartmentalization during septal peptidoglycan hydrolysis, when other septal stabilization factors are absent. Our data support a model whereby SpoIIE and its interactions with the peptidoglycan synthetic machinery contribute to the stabilization of the asymmetric septum early in engulfment, thereby ensuring compartmentalization during spore development.IMPORTANCEBacterial sporulation is a complex process involving a vast array of proteins. Some of these proteins are absolutely critical and regulate key points in the developmental process. Once such protein is SpoIIE, known for its role in the formation of the polar septum, a hallmark of the early stages of sporulation, and activation of the first sporulation-specific sigma factor, σF, in the developing spore. Interestingly, SpoIIE has been shown to interact with SpoIIQ, an important σF-regulated protein that functions during the engulfment stage. However, the significance of this interaction has remained unclear. Here, we unveil the importance of the SpoIIQ-SpoIIE interaction and identify a role for SpoIIE in the stabilization of the polar septum and maintenance of compartmentalization at the onset of engulfment. In this way, we demonstrate that key sporulation proteins, like SpoIIQ and SpoIIE, function in multiple processes during spore development., Competing Interests: The authors declare no conflict of interest.

Both physiological and evolutionary criteria of biological individuality are underpinned by the idea that an individual is a functionally integrated whole. However, a precise account of functional integration has not been provided so far, and current notions are not developed in the details, especially in the case of composite systems. To address this issue, this paper focuses on the organisational dimension of two representative associations of prokaryotes: biofilms and the endosymbiosis between prokaryotes. Some critical voices have been raised against the thesis that biofilms are biological individuals. Nevertheless, it has not been investigated which structural and functional obstacles may prevent them from being fully integrated physiological or evolutionary units. By contrast, the endosymbiotic association of different species of prokaryotes has the potential for achieving a different type of physiological integration based on a common boundary and interlocked functions. This type of association had made it possible, under specific conditions, to evolve endosymbionts into fully integrated organelles. This paper therefore has three aims: first, to analyse the organisational conditions and the physiological mechanisms that enable integration in prokaryotic associations; second, to discuss the organisational differences between biofilms and prokaryotic endosymbiosis and the types of integration they achieve; finally, to provide a more precise account of functional integration based on these case studies. [ABSTRACT FROM AUTHOR]

• Discussing how unwanted cells and unwanted comparts in living cells are removed. • Discussing how PtdSer is maintained to the inner side of the membrane. • Discussing how PtdSer is exposed on the cell surface. • Discussing how PtdSer is recognized by phagocytes for engulfment. • Discussing how the PtdSer exposure /recognition systems work in brain. Phospholipids are asymmetrically distributed at the plasma membrane. Phosphatidylserine (PtdSer) is exclusively located in the inner leaflet of the cell membrane while phosphatidylcholine (PtdCho) and glycolipids are mainly located in the outer leaflet of the membrane. However, this asymmetry is disrupted in various physiological situations, and PtdSer is exposed on the cell surface. In platelets, exposed PtdSer functions as a scaffold for the coagulation reaction, while in dead cells, exposed PtdSer serves as an "Eat-me" signal for efferocytosis. In the developing brain, synaptic connections are over-formed during the fetal period, but about half of the neurons are removed by apoptosis, and synaptic and dendritic compartments of living neurons are also removed by phagocytes. During these processes, glial cells such as microglia and astrocyte engulf unwanted dead cells and compartments in living cells using several phagocytic receptors, recognizing PtdSer by direct binding or an indirect way using secreted molecules. Based on recent findings, we will discuss how the compartments in living neurons are eliminated for the neuronal circuit plasticity. [ABSTRACT FROM AUTHOR]

Bacterial sporulation is a conserved process utilized by members of Bacillus genus and Clostridium in response to stress such as nutrient or temperature. Sporulation initiation is triggered by stress signals perceived by bacterial cell that leads to shutdown of metabolic pathways of bacterial cells. The mechanism of sporulation involves a complex network that is regulated at various checkpoints to form the viable bacterial spore. Engulfment is one such check point that drives the required cellular rearrangement necessary for the spore assembly and is mediated by bacterial proteolytic machinery that involves association of various Clp ATPases and ClpP protease. The present study highlights the importance of degradation of an anti-sigma factor F, SpoIIAB by ClpCP proteolytic machinery playing a crucial role in culmination of engulfment process during the sporulation in Bacillus anthracis. [ABSTRACT FROM AUTHOR]

When host cells are exposed to foreign particles, dead cells, or cell hazards, a sophisticated process called phagocytosis begins. During this process, macrophages, dendritic cells, and neutrophils engulf the target by expanding their membranes. Phagocytosis of apoptotic cells is called efferocytosis. This process is of significant importance as billions of cells are eliminated daily without provoking inflammation. Both phagocytosis and efferocytosis depend on Ca2+ signaling. A big family of Ca2+ permeable channels is transient receptor potentials (TRPs) divided into nine subfamilies. We aimed to review their roles in phagocytosis. The present review article shows that various TRP channels such as TRPV1, 2, 3, 4, TRPM2, 4, 7, 8, TRPML1, TRPA1, TRPC1, 3, 5, 6 have roles at various stages of phagocytosis. They are involved in the phagocytosis of amyloid β, α-synuclein, myelin debris, bacteria, and apoptotic cells. In particular, TRPC3 and TRPM7 contribute to efferocytosis. These effects are mediated by changing Ca2+ signaling or targeting intracellular enzymes such as Akt. In addition, they contribute to the chemotaxis of phagocytic cells towards targets. Although a limited number of studies have assessed the role of TRP channels in phagocytosis and efferocytosis, their findings indicate that they have critical roles in these processes. In some cases, their ablation completely abolished the phagocytic function of the cells. As a result, TRP channels are potential targets for developing new therapeutics that modulate phagocytosis. [ABSTRACT FROM AUTHOR]

Transmembrane protein engulfment receptors expressed on the surface of phagocytes engage ligands on apoptotic cells and debris to initiate a sequence of events culminating in material internalization and immunologically beneficial outcomes. Engulfment receptors are modular, comprised of functionally independent extracellular ligation domains and cytosolic signaling motifs. Cognate kinases, adaptors, and phosphatases regulate engulfment by controlling the degree of receptor activation in phagocyte plasma membranes, thus acting as receptor-proximal signaling modules. Here, we review recent efforts to reprogram phagocytes using modular synthetic receptors composed of antibody-based extracellular domains fused to engulfment receptor signaling domains. To aid the development of new phagocyte reprogramming methods, we then define the kinases, adaptors, and phosphatases that regulate a conserved family of engulfment receptors. Finally, we discuss current challenges and opportunities for the field.

Transmembrane protein engulfment receptors expressed on the surface of phagocytes engage ligands on apoptotic cells and debris to initiate a sequence of events culminating in material internalization and immunologically beneficial outcomes. Engulfment receptors are modular, comprised of functionally independent extracellular ligation domains and cytosolic signaling motifs. Cognate kinases, adaptors, and phosphatases regulate engulfment by controlling the degree of receptor activation in phagocyte plasma membranes, thus acting as receptor-proximal signaling modules. Here, we review recent efforts to reprogram phagocytes using modular synthetic receptors composed of antibody-based extracellular domains fused to engulfment receptor signaling domains. To aid the development of new phagocyte reprogramming methods, we then define the kinases, adaptors, and phosphatases that regulate a conserved family of engulfment receptors. Finally, we discuss current challenges and opportunities for the field. [ABSTRACT FROM AUTHOR]

Effective and efficient efferocytosis of dead cells and associated cellular debris are critical to tissue homeostasis and healing of injured tissues. This important task was previously thought to be restricted to professional phagocytes (PPs). However, accumulating evidence has revealed another type of phagocyte, the amateur phagocyte (AP), which can also participate in efferocytosis. APs are non-myeloid progenitor/nonimmune cells that include differentiated cells (e.g., epithelial cells, fibroblasts, and endothelial cells [ECs]) and stem cells (e.g., neuronal progenitor cells and mesenchymal cells) and can be found throughout the human body. Studies have shown that APs have two prominent roles: identifying and removing dead cells presumably before PPs reach the site of injury and assisting PPs in the removal of cell corpses and the resolution of inflamed tissue. With respect to the engulfment and degradation of dead cells, APs are slower and less efficient than PPs. However, APs are fundamental to preventing the spread of inflammation over a large area. In this review, we present the diversity and characteristics of healthy and non-neoplastic APs in mammals. We also propose a hypothetical mechanism of the efferocytosis of immunoglobulin G (IgG)-opsonized myelin debris by ECs (APs). Furthermore, the ingestion and clearance of dead cells can induce proinflammatory or anti-inflammatory cytokine production, endothelial activation, and cellular fate transition, which contribute to the progression of disease. An understanding of the role of APs is necessary to develop effective intervention strategies, including potential molecular targets for clinical diagnosis and drug development, for inflammation-related diseases. [ABSTRACT FROM AUTHOR]

The interaction between Janus colloids and giant lipid vesicles was experimentally investigated to elucidate the dynamics and mechanisms related to microparticle engulfment by lipid vesicles. Janus (Pt–SiO2 and Pt–MF, where MF is melamine formaldehyde) colloids do not spontaneously adhere to POPC or DOPC bilayers, but by applying external forces via centrifugation we were able to force the contact between the particles and the membranes, which may result in a partial engulfment state of the particle. Surface properties of the Janus colloids play a crucial role in the driven particle engulfment by vesicles. Engulfment of the silica and platinum regions of the Janus particles can be observed, whereas the polymer (MF) region does not show any affinity towards the lipid bilayer. By using fluorescence microscopy, we were able to monitor the particle orientation and measure the rotational dynamics of a single Janus particle engulfed by a vesicle. By adding hydrogen peroxide to the solution, particle self-propulsion was used to perform an active transport of a giant vesicle by a single active particle. Finally, we observe that partially engulfed particles experience a membrane curvature-induced force, which pushes the colloids towards the bottom where the membrane curvature is the lowest.

Involution is the process of post-lactational mammary gland regression to quiescence and it involves secretory epithelial cell death, stroma remodeling and gland repopulation by adipocytes. Though reportedly accompanying apoptosis, the role of autophagy in involution has not yet been determined. We now report that autophagy-related (ATG) proteins mediate dead cell clearance and suppress inflammation during mammary involution. In vivo, Becn1(+/-) and Atg7-deficient mammary epithelial cells (MECs) produced 'competent' apoptotic bodies, but were defective phagocytes in association with reduced expression of the MERTK and ITGB5 receptors, thus pointing to defective apoptotic body engulfment. Atg-deficient tissues exhibited higher levels of involution-associated inflammation, which could be indicative of a tumor-modulating microenvironment, and developed ductal ectasia, a manifestation of deregulated post-involution gland remodeling. In vitro, ATG (BECN1 or ATG7) knockdown compromised MEC-mediated apoptotic body clearance in association with decreased RAC1 activation, thus confirming that, in addition to the defective phagocytic processing reported by other studies, ATG protein defects also impair dead cell engulfment. Using two different mouse models with mammary gland-associated Atg deficiencies, our studies shed light on the essential role of ATG proteins in MEC-mediated efferocytosis during mammary involution and provide novel insights into this important developmental process. This work also raises the possibility that a regulatory feedback loop exists, by which the efficacy of phagocytic cargo processing in turn regulates the rate of engulfment and ultimately determines the kinetics of phagocytosis and dead cell clearance.

Autophagy is a catabolic process through which damaged organelles and protein aggregates are delivered to lysosomes for degradation. Autophagy genes are reported to promote exposure of "eat me" signals on the surface of apoptotic cells, but whether they function in engulfing cells is not clear. Recently, we found that the autophagy mutants atg-18 and epg-5 are defective in removing apoptotic cells derived from the C. elegans Q neuroblast, a phenotype that can be fully rescued by expression of ATG-18 and EPG-5 in the engulfing cell. Loss of ATG-18 or EPG-5 does not affect cell corpse engulfment but causes defects in phagosomal recruitment of RAB-5 and RAB-7 and formation of phagolysosomes. EPG-5, ATG-18 and LGG-1 are sequentially recruited to phagosomes, suggesting that they function at different steps of phagosomal maturation. Our studies indicate that autophagy genes function sequentially to promote apoptotic cell corpse degradation in the engulfing cell.

Summary: Macrophages must not only be responsive to an array of different stimuli, such as infection and cellular damage, but also perform phagocytosis within the diverse and complex tissue environments found in vivo. This requires a high degree of morphological and therefore cytoskeletal plasticity. Here, we use the exceptional genetics and in vivo imaging of Drosophila embryos to study macrophage phagocytic versatility during apoptotic corpse clearance. We find that macrophage phagocytosis is highly robust, arising from their possession of two distinct modes of engulfment that utilize exclusive suites of actin-regulatory proteins. “Lamellipodial phagocytosis” is Arp2/3-complex-dependent and allows cells to migrate toward and envelop apoptotic corpses. Alternatively, Diaphanous and Ena drive filopodial phagocytosis to reach out and draw in debris. Macrophages switch to “filopodial phagocytosis” to overcome spatial constraint, providing the robust plasticity necessary to ensure that whatever obstacle they encounter in vivo, they fulfil their critical clearance function.

The breast tumors that are most difficult to eradicate with chemotherapy have wild-type TP53 and preferentially enter senescence after treatment. One factor contributing to the persistence of senescent cells in residual disease: acquisition of a novel phenotype that allows cannibalism of entire cells and engulfment of other substrates.

The clearance of dead cells is a fundamental process in the maintenance of tissue homeostasis. Genetic studies in Drosophila melanogaster, Caenorhabditis elegans, and mammals have identified two evolutionarily conserved signaling pathways that act redundantly to regulate this engulfment process: the ced-1/-6/-7 and ced-2/-5/-12 pathways. Of these engulfment genes, only the ced-7/ABCA1 ortholog remains to be identified in D. melanogaster. Homology searches have revealed a family of putative ced-7/ABCA1 homologs encoding ATP-binding cassette (ABC) transporters in D. melanogaster. To determine which of these genes functions similarly to ced-7/ABCA1, we analyzed mutants for engulfment phenotypes in oogenesis, during which nurse cells (NCs) in each egg chamber undergo programmed cell death (PCD) and are removed by neighboring phagocytic follicle cells (FCs). Our genetic analyses indicate that one of the ABC transporter genes, which we have named Eato (Engulfment ABC Transporter in the ovary), is required for NC clearance in the ovary and acts in the same pathways as drpr, the ced-1 ortholog, and in parallel to Ced-12 in the FCs. Additionally, we show that Eato acts in the FCs to promote accumulation of the transmembrane receptor Drpr, and promote membrane extensions around the NCs for their clearance. Since ABCA class transporters, such as CED-7 and ABCA1, are known to be involved in lipid trafficking, we propose that Eato acts to transport membrane material to the growing phagocytic cup for cell corpse clearance. Our work presented here identifies Eato as the ced-7/ABCA1 ortholog in D. melanogaster, and demonstrates a role for Eato in Drpr accumulation and phagocytic membrane extensions during NC clearance in the ovary.

Cancer is a multistep process. In the early phases of this disease, mutations in oncogenes and tumor suppressors are thought to promote clonal expansion. These mutations can increase cell competitiveness, allowing tumor cells to grow within the tissue by eliminating wild type host cells. Recent studies have shown that cell competition can also function in later phases of cancer. Here, we examine the existing evidence linking cell competition and tumorigenesis. We focus on the mechanisms underlying cell competition and their contribution to disease pathogenesis. [ABSTRACT FROM AUTHOR]

Programmed cell death occurs as a normal part of oocyte development in Drosophila. For each egg that is formed, 15 germline-derived nurse cells transfer their cytoplasmic contents into the oocyte and die. Disruption of apoptosis or autophagy only partially inhibits the death of the nurse cells, indicating that other mechanisms significantly contribute to nurse cell death. Recently, we demonstrated that the surrounding stretch follicle cells non-autonomously promote nurse cell death during late oogenesis and that phagocytosis genes including draper, ced-12, and the JNK pathway are crucial for this process. When phagocytosis genes are inhibited in the follicle cells, events specifically associated with death of the nurse cells are impaired. Death of the nurse cells is not completely blocked in draper mutants, suggesting that other engulfment receptors are involved. Indeed, we found that the integrin subunit, αPS3, is enriched on stretch follicle cells during late oogenesis and is required for elimination of the nurse cells. Moreover, double mutant analysis revealed that integrins act in parallel to draper. Death of nurse cells in the Drosophila ovary is a unique example of programmed cell death that is both non-apoptotic and non-cell autonomously controlled.

The study of bacterial cell biology is limited by difficulties in visualizing cellular structures at high spatial resolution within their native milieu. Here, we visualize Bacillus subtilis sporulation using cryo-electron tomography coupled with cryo-focused ion beam milling, allowing the reconstruction of native-state cellular sections at molecular resolution. During sporulation, an asymmetrically-positioned septum generates a larger mother cell and a smaller forespore. Subsequently, the mother cell engulfs the forespore. We show that the septal peptidoglycan is not completely degraded at the onset of engulfment. Instead, the septum is uniformly and only slightly thinned as it curves towards the mother cell. Then, the mother cell membrane migrates around the forespore in tiny finger-like projections, whose formation requires the mother cell SpoIIDMP protein complex. We propose that a limited number of SpoIIDMP complexes tether to and degrade the peptidoglycan ahead of the engulfing membrane, generating an irregular membrane front.

In vitro cocultures of macrophages and apoptotic cells (ACs) provide a practical and useful tool to study efferocytosis. Here, we describe a method for automated quantification and imaging of recognition and engulfment of apoptotic cells by primary macrophages using imaging flow cytometry (IFC). IFC-based analysis allows us to successfully quantify efferocytosis, clearly distinguishing phagocytic from nonphagocytic macrophages and, more importantly, from those in recognition stage, which is not achievable by standard flow cytometrical analysis. To this end, we established a universally employable analysis pipeline to address efferocytosis that can be easily adapted to any macrophage population from samples of different origins., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Particles in molten steel, including argon-gas bubbles, slag droplets, and non-metallic inclusions, are removed into the surface-slag layer or captured by the solidifying steel-shell during continuous steel casting. Captured particles often become serious defects in the final steel product, so understanding particle-capture mechanisms is important for steel quality. Slab casters often have a straight mold and upper-strand prior to a curved lower-strand. The present work investigates particle capture in such a caster using computational modeling with a standard k-ε model for molten-steel flow, a discrete phase model for inclusion transport, and an advanced capture criterion for inclusion entrapment and engulfment into the steel shell. A new postprocessing methodology is presented and applied to predict inclusion-capture rates in commercial cast product. The locations and size distributions of particles captured into the shell, and actual capture rates are quantified. The model predictions are validated with ultrasonic-test plant measurements of the locations of large particles captured in a steel slab. The results reveal how large-inclusion capture accumulates in the beginning of the curved strand, leading to a capture band in the slab inside radius. Finally, the capture fractions and locations due to all capture mechanisms are compared for different inclusion sizes, and the implications are discussed.

Highlights • Confined space incidents can result in multiple fatalities. • Risk assessment and control measures are required before any confined space entry. • Confined space rescue procedures should be established before any entry. • The hierarchy of rescue is self-rescue, non-entry rescue, and entry rescue. • The proposed procedure will protect rescuers, bystanders, and reduce fatalities. Abstract Each year, workers are killed in incidents involving confined spaces. To minimise and control the risks so far as reasonably practicale, confined space work should be thoroughly considered and carefully planned before any entry. Unfortunately, when would-be rescuers attempt the rescue of fellow workers, multiple fatalities can result. Confined space rescue should always be a deliberate undertaking, planned prior to the confined space entry taking place, and conducted by trained personnel. This paper proposes a five step procedure to safely undertake confined space entry rescue, mindful of the hierarchy for protection (rescuers, bystanders, and casualties); and of the hierarchy of the level of confined space rescue (self-rescue, non-entry rescue, and entry rescue). The proposed confined space rescue procedure is a simplified and broad-based process for the preparation and conduct of a confined space rescue by on-site or in-house rescue teams, and is an adaptation of the procedures used by professional emergency services. The five step procedure is described by the acronym REALE. Step 1 is Reconnaissance of the rescue task. Step 2 is Elimination or reduction of hazards. Step 3 is Accessing the casualty, in which a minimal number of rescuers enter the confined space and make contact with the casualty. Step 4 is the provision of Life-saving first aid to the casualty. Step 5 is the Extrication of the casualty as required. The proposed procedure is suitable for adoption by rescue teams regardless of country or jurisdiction as it meets the requirements for all regulations and standards. [ABSTRACT FROM AUTHOR]

The aim of the current systematic review is to examine relationships among illness identity and illness-specific variables, adherence, and health-related outcomes. Studies were included if they (a) presented quantitative data on illness identity’s relationship with adherence or health-related outcomes, (b) included chronic medical illness samples, (c) were peer-reviewed, and (d) were available in English. PubMed and EBSCOhost were searched. Quality was evaluated using the EPHPP Tool. Twelve papers were included. Moderate evidence supports the relationship between engulfment, enrichment, and illness complexity. Moderate evidence supports relationships between multiple identities and adherence as well as with various health-related outcomes. There is somewhat consistent evidence for associations between engulfment and negative health-related outcomes. It may be important to inform healthcare providers of possible identity challenges that patients face and their associations with adherence and health-related outcomes. Routine illness identity screening may allow for identification of individuals who would benefit from increased support. [ABSTRACT FROM AUTHOR]

Apoptotic cells expressing phosphatidylserine (PS) on their cell surface are directly or indirectly recognized by phagocytes through PS-binding proteins. The PS-binding protein Tim-4 secures apoptotic cells to phagocytes to facilitate the engulfment of apoptotic cells. However, the molecular mechanism by which Tim-4 transduces signals to phagocytes during Tim-4-mediated efferocytosis is incompletely understood. Here, we report that Tim-4 collaborates with Mertk during efferocytosis through a biochemical interaction with Mertk. Proximal localization between the two proteins in phagocytes was observed by immunofluorescence and proximal ligation assays. Physical association between Tim-4 and Mertk, which was mediated by an interaction between the IgV domain of Tim-4 and the fibronectin type-III domain of Mertk, was also detected with immunoprecipitation. Furthermore, the effect of Mertk on Tim-4-mediated efferocytosis was abolished by GST-MertkFnIII, a soluble form of the fibronectin type-III domain of Mertk that disrupts the interaction between Tim-4 and Mertk. Taken together, the results from our study suggest that a physical interaction between Tim-4 and Mertk is necessary for Mertk to enhance efferocytosis mediated by Tim-4.

BackgroundTo optimize healthcare use of adults with congenital heart disease, all important predictors of healthcare utilization should be identified. Clinical and psychological characteristics (eg, age and depression) have been found to be associated with healthcare use. However, the concept of illness identity, which assesses the degree to which congenital heart disease is integrated into one's identity, has not yet been investigated in association with healthcare use. Hence, the purpose of the study is to examine the predictive value of illness identity for healthcare use. Methods and ResultsIn this ambispective analytical observational cohort study, 216 adults with congenital heart disease were included. The self‐reported Illness Identity Questionnaire was used to assess illness identity states: engulfment, rejection, acceptance, and enrichment. After 1 year, self‐reported healthcare use for congenital heart disease or other reasons over the past 6 months was assessed including hospitalizations; visits to general practitioner; visits to medical specialists; and emergency room visits. Binary logistic and negative binomial regression analyses were conducted, adjusting for age, sex, disease complexity, and depressive and anxious symptoms. The more profoundly the heart defect dominated one's identity (ie, engulfment), the more likely this person was to be hospitalized (odds ratio=3.76; 95% confidence interval=1.43–9.86), to visit a medical specialist (odds ratio=2.32; 95% confidence interval=1.35–4.00) or a general practitioner (odds ratio=1.78; 95% confidence interval=1.01–3.17), because of their heart defect. ConclusionsIllness identity, more specifically engulfment, has a unique predictive value for the occurrence of healthcare encounters. This association deserves further investigation, in which the directionality of effects and the contribution of illness identity in terms of preventing inappropriate healthcare use should be determined.

For half of a century, it has been known that non-professional phagocytes, such as fibroblasts, endothelial, and epithelial cells, are capable of efferocytosis (engulfment of apoptotic cells). Non-professional phagocytes differ from professional phagocytes in the range and efficiency of engulfment. Much of the recognition and underlying signaling machinery between non-professional and professional phagocytes is the same, but it is not known how the engulfment capacity of non-professional phagocytes is controlled. Moreover, the signaling networks involved in cell corpse recognition, engulfment, and phagosome maturation are only partially understood. The Drosophila ovary provides an excellent system to investigate the regulation of phagocytic activity by epithelial cells, a major class of non-professional phagocytes. During Drosophila oogenesis, mid-stage egg chambers undergo apoptosis of the germline in response to nutrient deprivation. Epithelial follicle cells then undergo major cell shape changes and concomitantly engulf the germline material. Our previous work has established that Draper and the integrin α-PS3/β-PS heterodimer are required in follicle cells for germline cell clearance. In addition, we have characterized phagosome maturation pathways, and found that the JNK pathway amplifies the engulfment response. In this review, we discuss recent advances on the interplay between engulfment pathways in the follicular epithelium for cell clearance in the Drosophila ovary. We also provide a comparison to apoptotic cell clearance mechanisms in C. elegans and mammals, illustrating strong conservation of efferocytosis mechanisms by non-professional phagocytes.

The breast tumors that are most difficult to eradicate with chemotherapy have wild-type TP53 and preferentially enter senescence after treatment. One factor contributing to the persistence of senescent cells in residual disease: acquisition of a novel phenotype that allows cannibalism of entire cells and engulfment of other substrates. [ABSTRACT FROM AUTHOR]

The uptake of nanoparticles into cells often involves their engulfment by the plasma membrane and a fission of the latter. Understanding the physical mechanisms underlying these uptake processes may be achieved by the investigation of simple model systems that can be compared to theoretical models. Here, we present experiments on a massive uptake of silica nanoparticles by giant unilamellar lipid vesicles (GUVs). We find that this uptake process depends on the size of the particles as well as on the thermodynamic state of the lipid membrane. Our findings are discussed in the light of several theoretical models and indicate that these models have to be extended in order to capture the interaction between nanomaterials and biological membranes correctly.