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Methods (San Diego, Calif.) Mar 2015Xenophagy is an autophagic phenomenon that specifically involves pathogens and other non-host entities. Although the understanding of the relationship between...
Xenophagy is an autophagic phenomenon that specifically involves pathogens and other non-host entities. Although the understanding of the relationship between autophagosomes and invading organisms has grown significantly in the past decade, the exact steps to confirm xenophagy has been not been thoroughly defined. Here we describe a methodical approach to confirming autophagy, its interaction with bacterial invasion, as well as the specific type of autophagic formation (i.e. autophagosome, autolysosome, phagolysosome). Further, we argue that xenophagy is not limited to pathogen interaction with autophagosome, but also non-microbial entities such as iron.
Topics: Autophagy; Brucella; Host-Pathogen Interactions; Humans; Infections; Lysosomes; Molecular Biology; Phagosomes
PubMed: 25497060
DOI: 10.1016/j.ymeth.2014.12.005 -
MBio Dec 2019Macrophages are well known for their phagocytic activity and their role in innate immune responses. Macrophages eat non-self particles, via a variety of mechanisms, and... (Review)
Review
Macrophages are well known for their phagocytic activity and their role in innate immune responses. Macrophages eat non-self particles, via a variety of mechanisms, and typically break down internalized cargo into small macromolecules. However, some pathogenic agents have the ability to evade this endosomal degradation through a nonlytic exocytosis process termed vomocytosis. This phenomenon has been most often studied for , a yeast that causes roughly 180,000 deaths per year, primarily in immunocompromised (e.g., human immunodeficiency virus [HIV]) patients. Existing dogma purports that vomocytosis involves distinctive cellular pathways and intracellular physicochemical cues in the host cell during phagosomal maturation. Moreover, it has been observed that the immunological state of the individual and macrophage phenotype affect vomocytosis outcomes. Here we compile the current knowledge on the factors (with respect to the phagocytic cell) that promote vomocytosis of from macrophages.
Topics: Animals; Calcium; Cryptococcus neoformans; Humans; Hydrogen-Ion Concentration; Macrophages; Mice; Phagocytosis; Phagosomes; Phenotype
PubMed: 31874916
DOI: 10.1128/mBio.02526-19 -
The European Respiratory Journal Mar 2021Sarcoidosis and tuberculosis are granulomatous pulmonary diseases characterised by heightened immune reactivity to antigens. We hypothesised that an unsupervised...
INTRODUCTION
Sarcoidosis and tuberculosis are granulomatous pulmonary diseases characterised by heightened immune reactivity to antigens. We hypothesised that an unsupervised analysis comparing the molecular characteristics of granulomas formed in response to antigens in patients with sarcoidosis or latent tuberculosis infection (LTBI) would provide novel insights into the pathogenesis of sarcoidosis.
METHODS
A genomic analysis identified differentially expressed genes in granuloma-like cell aggregates formed by sarcoidosis (n=12) or LTBI patients (n=5) in an established human granuloma model wherein peripheral blood mononuclear cells were exposed to antigens (beads coated with purified protein derivative) and cultured for 7 days. Pathway analysis of differentially expressed genes identified canonical pathways, most notably antigen processing and presentation phagolysosomes, as a prominent pathway in sarcoidosis granuloma formation. The phagolysosomal pathway promoted mechanistic target of rapamycin complex 1 (mTORc1)/STAT3 signal transduction. Thus, granuloma formation and related immune mediators were evaluated in the absence or presence of various pre-treatments known to prevent phagolysosome formation (chloroquine) or phagosome acidification (bafilomycin A1) or directly inhibit mTORc1 activation (rapamycin).
RESULTS
In keeping with genomic analyses indicating enhanced phagolysosomal activation and predicted mTORc1 signalling, it was determined that sarcoidosis granuloma formation and related inflammatory mediator release was dependent upon phagolysosome assembly and acidification and mTORc1/S6/STAT3 signal transduction.
CONCLUSIONS
Sarcoidosis granulomas exhibit enhanced and sustained intracellular antigen processing and presentation capacities, and related phagolysosome assembly and acidification are required to support mTORc1 signalling to promote sarcoidosis granuloma formation.
Topics: Granuloma; Humans; Leukocytes, Mononuclear; Phagosomes; Sarcoidosis; Signal Transduction; TOR Serine-Threonine Kinases
PubMed: 32943400
DOI: 10.1183/13993003.02695-2020 -
Biology of the Cell Oct 2017Phagocytosis and autophagy are two distinct pathways that degrade external and internal unwanted particles. Both pathways lead to lysosomal degradation inside the cell,... (Review)
Review
Phagocytosis and autophagy are two distinct pathways that degrade external and internal unwanted particles. Both pathways lead to lysosomal degradation inside the cell, and over the last decade, the line between them has blurred; autophagy proteins were discovered on phagosomes engulfing foreign bacteria, leading to the proposal of LC3-associated phagocytosis (LAP). Many proteins involved in macroautophagy are used for phagosome degradation, although Atg8/LC3 family proteins only decorate the outer membrane of LC3-associated phagosomes, in contrast to both autophagosome membranes. A few proteins distinguish LAP from autophagy, such as components of the autophagy pre-initiation complex. However, most LAP cargo is wrapped in multiple layers of membranes, making them similar in structure to autophagosomes. Recent evidence suggests that LC3 is important for the degradation of internal membranes, explaining why LC3 would be a vital part of both macroautophagy and LAP. In addition to removing invading pathogens, multicellular organisms also use LAP to degrade cell debris, including cell corpses and photoreceptor outer segments. The post-mitotic midbody remnant is another cell fragment, which results from each cell division, that was recently added to the growing list of LAP cargoes. Thus, LAP plays an important role during the normal physiology and homoeostasis of animals.
Topics: Animals; Autophagy; Autophagy-Related Protein 8 Family; Humans; Lysosomes; Microtubule-Associated Proteins; Phagocytosis; Phagosomes
PubMed: 28755428
DOI: 10.1111/boc.201700028 -
Current Opinion in Cell Biology Feb 2018Phagocytosis is a complex and elegant mechanism requiring finely coordinated deformation and restructuring of the membrane and the underlying cytoskeleton. Here we... (Review)
Review
Phagocytosis is a complex and elegant mechanism requiring finely coordinated deformation and restructuring of the membrane and the underlying cytoskeleton. Here we discuss the early events of receptor clustering and engagement required for signal transduction and actin remodeling. In addition, we summarize recent studies of the mechanisms whereby the nascent phagosome seals and evolves into a degradative phagolysosome by a process that seemingly involves the autophagic machinery. These studies provided new insights of the molecular basis of this long-appreciated, essential homeostatic process.
Topics: Actins; Animals; Autophagy; Cytoskeleton; Dictyostelium; Membrane Proteins; Phagocytosis; Phagosomes; Signal Transduction
PubMed: 29471269
DOI: 10.1016/j.ceb.2018.01.009 -
Frontiers in Immunology 2021The rapid and efficient phagocytic clearance of apoptotic cells, termed efferocytosis, is a critical mechanism in the maintenance of tissue homeostasis. Removal of... (Review)
Review
The rapid and efficient phagocytic clearance of apoptotic cells, termed efferocytosis, is a critical mechanism in the maintenance of tissue homeostasis. Removal of apoptotic cells through efferocytosis prevents secondary necrosis and the resultant inflammation caused by the release of intracellular contents. The importance of efferocytosis in homeostasis is underscored by the large number of inflammatory and autoimmune disorders, including atherosclerosis and systemic lupus erythematosus, that are characterized by defective apoptotic cell clearance. Although mechanistically similar to the phagocytic clearance of pathogens, efferocytosis differs from phagocytosis in that it is immunologically silent and induces a tissue repair response. Efferocytes face unique challenges resulting from the internalization of apoptotic cells, including degradation of the apoptotic cell, dealing with the extra metabolic load imposed by the processing of apoptotic cell contents, and the coordination of an anti-inflammatory, pro-tissue repair response. This review will discuss recent advances in our understanding of the cellular response to apoptotic cell uptake, including trafficking of apoptotic cell cargo and antigen presentation, signaling and transcriptional events initiated by efferocytosis, the coordination of an anti-inflammatory response and tissue repair, unique cellular metabolic responses and the role of efferocytosis in host defense. A better understanding of how efferocytic cells respond to apoptotic cell uptake will be critical in unraveling the complex connections between apoptotic cell removal and inflammation resolution and maintenance of tissue homeostasis.
Topics: Antigen Presentation; Apoptosis; Gene Expression Regulation; Homeostasis; Humans; Inflammation; Phagocytes; Phagocytosis; Phagosomes; Signal Transduction
PubMed: 33959122
DOI: 10.3389/fimmu.2021.631714 -
International Journal of Molecular... Feb 2023Phagocytosis is one of the most polarised of all cellular activities. Both the stimulus (the target for phagocytosis) and the response (its internalisation) are focussed... (Review)
Review
Phagocytosis is one of the most polarised of all cellular activities. Both the stimulus (the target for phagocytosis) and the response (its internalisation) are focussed at just one part of the cell. At the locus, and this locus alone, pseudopodia form a phagocytic cup around the particle, the cytoskeleton is rearranged, the plasma membrane is reorganised, and a new internal organelle, the phagosome, is formed. The effect of signals from the stimulus must, thus, both be complex and yet be restricted in space and time to enable an effective focussed response. While many aspects of phagocytosis are being uncovered, the mechanism for the restriction of signalling or the effects of signalling remains obscure. In this review, the details of the problem of restricting chemical intracellular signalling are presented, with a focus on diffusion into the cytosol and of signalling lipids along the plasma membrane. The possible ways in which simple diffusion is overcome so that the restriction of signalling and effective phagocytosis can be achieved are discussed in the light of recent advances in imaging, biophysics, and cell biochemistry which together are providing new insights into this area.
Topics: Phagocytosis; Phagosomes; Pseudopodia; Cytoskeleton; Cytosol
PubMed: 36769146
DOI: 10.3390/ijms24032825 -
EMBO Reports Aug 2014Autophagy is the main cellular catabolic process responsible for degrading organelles and large protein aggregates. It is initiated by the formation of a unique membrane... (Review)
Review
Autophagy is the main cellular catabolic process responsible for degrading organelles and large protein aggregates. It is initiated by the formation of a unique membrane structure, the phagophore, which engulfs part of the cytoplasm and forms a double-membrane vesicle termed the autophagosome. Fusion of the outer autophagosomal membrane with the lysosome and degradation of the inner membrane contents complete the process. The extent of autophagy must be tightly regulated to avoid destruction of proteins and organelles essential for cell survival. Autophagic activity is thus regulated by external and internal cues, which initiate the formation of well-defined autophagy-related protein complexes that mediate autophagosome formation and selective cargo recruitment into these organelles. Autophagosome formation and the signaling pathways that regulate it have recently attracted substantial attention. In this review, we analyze the different signaling pathways that regulate autophagy and discuss recent progress in our understanding of autophagosome biogenesis.
Topics: Animals; Autophagy; Energy Metabolism; Humans; Microtubule-Associated Proteins; Oxidation-Reduction; Phagosomes; Signal Transduction; Vesicular Transport Proteins
PubMed: 25027988
DOI: 10.15252/embr.201439076 -
Future Microbiology Jul 2016Invasion of macrophages and replication within an acidic and degradative phagolysosome-like vacuole are essential for disease pathogenesis by Coxiella burnetii, the... (Review)
Review
Invasion of macrophages and replication within an acidic and degradative phagolysosome-like vacuole are essential for disease pathogenesis by Coxiella burnetii, the bacterial agent of human Q fever. Previous experimental constraints imposed by the obligate intracellular nature of Coxiella limited knowledge of pathogen strategies that promote infection. Fortunately, new genetic tools facilitated by axenic culture now allow allelic exchange and transposon mutagenesis approaches for virulence gene discovery. Phenotypic screens have illuminated the critical importance of Coxiella's type 4B secretion system in host cell subversion and discovered genes encoding translocated effector proteins that manipulate critical infection events. Here, we highlight the cellular microbiology and genetics of Coxiella and how recent technical advances now make Coxiella a model organism to study macrophage parasitism.
Topics: Apoptosis; Autophagy; Bacterial Secretion Systems; Coxiella burnetii; HeLa Cells; Host-Pathogen Interactions; Humans; Macrophages; Mutagenesis; Phagosomes; Protein Transport; Type IV Secretion Systems; Virulence
PubMed: 27418426
DOI: 10.2217/fmb-2016-0044 -
American Journal of Physiology. Lung... Sep 2021Patients with cystic fibrosis (CF) have defective macrophage phagocytosis and efferocytosis. Several reports demonstrate that neutrophil elastase (NE), a major...
Patients with cystic fibrosis (CF) have defective macrophage phagocytosis and efferocytosis. Several reports demonstrate that neutrophil elastase (NE), a major inflammatory protease in the CF airway, impairs macrophage phagocytic function. To date, NE-impaired macrophage phagocytic function has been attributed to cleavage of cell surface receptors or opsonins. We applied an unbiased proteomic approach to identify other potential macrophage targets of NE protease activity that may regulate phagocytic function. Using the murine macrophage cell line, RAW 264.7, human blood monocyte-derived macrophages, and primary alveolar macrophages from Cftr-null and wild-type littermate mice, we demonstrated that NE exposure blocked phagocytosis of bio-particles. We performed liquid chromatography-tandem mass spectroscopy (LC-MS/MS) proteomic analysis of the conditioned media from RAW264.7 treated either with active NE or inactive (boiled) NE as a control. Out of 840 proteins identified in the conditioned media, active NE upregulated 142 proteins and downregulated 211 proteins. NE released not only cell surface proteins into the media but also cytoskeletal, mitochondrial, cytosolic, and nuclear proteins that were detected in the conditioned media. At least 32 proteins were associated with the process of phagocytosis including 11 phagocytic receptors [including lipoprotein receptor-related protein 1 (LRP1)], 7 proteins associated with phagocytic cup formation, and 14 proteins involved in phagocytic maturation (including calpain-2) and phagolysosome formation. NE had a broad effect on the proteome required for regulation of all stages of phagocytosis and phagolysosome formation. Furthermore, the NE sheddome/secretome included proteins from other macrophage cellular domains, suggesting that NE may globally regulate macrophage structure and function.
Topics: Adolescent; Adult; Animals; Child; Child, Preschool; Cystic Fibrosis Transmembrane Conductance Regulator; Female; Humans; Leukocyte Elastase; Lysosomes; Macrophages; Male; Mice; Mice, Mutant Strains; Phagocytosis; Phagosomes; RAW 264.7 Cells
PubMed: 34261337
DOI: 10.1152/ajplung.00499.2019