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Medecine Sciences : M/S 2019Phagocytosis and macroautophagy, named here autophagy, are two essential mechanisms of lysosomal degradation of diverse cargos into membrane structures. Both mechanisms... (Review)
Review
Phagocytosis and macroautophagy, named here autophagy, are two essential mechanisms of lysosomal degradation of diverse cargos into membrane structures. Both mechanisms are involved in immune regulation and cell survival. However, phagocytosis triggers degradation of extracellular material whereas autophagy engulfs only cytoplasmic elements. Furthermore, activation and maturation of these two processes are different. LAP (LC3-associated phagocytosis) is a form of phagocytosis that uses components of the autophagy pathway. It can eliminate (i) pathogens, (ii) immune complexes, (iii) threatening neighbouring cells, dead or alive, and (iv) cell debris, such as POS (photoreceptor outer segment) and the midbody released at the end of mitosis. Cells have thus optimized their means of elimination of dangerous components by sharing some fundamental elements coming from the two main lysosomal degradation pathways.
Topics: Animals; Autophagy; Humans; Immune Evasion; Infections; Macrophages; Microtubule-Associated Proteins; Phagocytosis; Phagosomes
PubMed: 31532375
DOI: 10.1051/medsci/2019129 -
Acta Neuropathologica Mar 2024Prader-Willi Syndrome (PWS) is a rare neurodevelopmental disorder of genetic etiology, characterized by paternal deletion of genes located at chromosome 15 in 70% of...
Prader-Willi Syndrome (PWS) is a rare neurodevelopmental disorder of genetic etiology, characterized by paternal deletion of genes located at chromosome 15 in 70% of cases. Two distinct genetic subtypes of PWS deletions are characterized, where type I (PWS T1) carries four extra haploinsufficient genes compared to type II (PWS T2). PWS T1 individuals display more pronounced physiological and cognitive abnormalities than PWS T2, yet the exact neuropathological mechanisms behind these differences remain unclear. Our study employed postmortem hypothalamic tissues from PWS T1 and T2 individuals, conducting transcriptomic analyses and cell-specific protein profiling in white matter, neurons, and glial cells to unravel the cellular and molecular basis of phenotypic severity in PWS sub-genotypes. In PWS T1, key pathways for cell structure, integrity, and neuronal communication are notably diminished, while glymphatic system activity is heightened compared to PWS T2. The microglial defect in PWS T1 appears to stem from gene haploinsufficiency, as global and myeloid-specific Cyfip1 haploinsufficiency in murine models demonstrated. Our findings emphasize microglial phagolysosome dysfunction and altered neural communication as crucial contributors to the severity of PWS T1's phenotype.
Topics: Humans; Mice; Animals; Prader-Willi Syndrome; Microglia; Carrier Proteins; Phenotype; Phagosomes; Adaptor Proteins, Signal Transducing
PubMed: 38556574
DOI: 10.1007/s00401-024-02714-0 -
Proceedings of the National Academy of... Sep 2022Autophagosomes are unique organelles that form de novo as double-membrane vesicles engulfing cytosolic material for destruction. Their biogenesis involves membrane...
Autophagosomes are unique organelles that form de novo as double-membrane vesicles engulfing cytosolic material for destruction. Their biogenesis involves membrane transformations of distinctly shaped intermediates whose ultrastructure is poorly understood. Here, we combine cell biology, correlative cryo-electron tomography (cryo-ET), and extensive data analysis to reveal the step-by-step structural progression of autophagosome biogenesis at high resolution directly within yeast cells. The analysis uncovers an unexpectedly thin intermembrane distance that is dilated at the phagophore rim. Mapping of individual autophagic structures onto a timeline based on geometric features reveals a dynamical change of membrane shape and curvature in growing phagophores. Moreover, our tomograms show the organelle interactome of growing autophagosomes, highlighting a polar organization of contact sites between the phagophore and organelles, such as the vacuole and the endoplasmic reticulum (ER). Collectively, these findings have important implications for the contribution of different membrane sources during autophagy and for the forces shaping and driving phagophores toward closure without a templating cargo.
Topics: Autophagosomes; Cell Membrane; Endoplasmic Reticulum; Macroautophagy; Saccharomyces cerevisiae; Vacuoles
PubMed: 36122245
DOI: 10.1073/pnas.2209823119 -
Communications Biology Oct 2023Phagosome maturation is critical for immune defense, defining whether ingested material is destroyed or converted into antigens. Sec22b regulates phagosome maturation,...
Phagosome maturation is critical for immune defense, defining whether ingested material is destroyed or converted into antigens. Sec22b regulates phagosome maturation, yet how has remained unclear. Here we show Sec22b tethers endoplasmic reticulum-phagosome membrane contact sites (MCS) independently of the known tether STIM1. Sec22b knockdown increases calcium signaling, phagolysosome fusion and antigen degradation and alters phagosomal phospholipids PI(3)P, PS and PI(4)P. Levels of PI(4)P, a lysosome docking lipid, are rescued by Sec22b re-expression and by expression of the artificial tether MAPPER but not the MCS-disrupting mutant Sec22b-P33. Moreover, Sec22b co-precipitates with the PS/PI(4)P exchange protein ORP8. Wild-type, but not mutant ORP8 rescues phagosomal PI(4)P and reduces antigen degradation. Sec22b, MAPPER and ORP8 but not P33 or mutant-ORP8 restores phagolysosome fusion in knockdown cells. These findings clarify an alternative mechanism through which Sec22b controls phagosome maturation and beg a reassessment of the relative contribution of Sec22b-mediated fusion versus tethering to phagosome biology.
Topics: Phagosomes; Phagocytosis; Endoplasmic Reticulum; Phosphatidylinositol Phosphates
PubMed: 37794132
DOI: 10.1038/s42003-023-05382-0 -
Autophagy Sep 2021As part of innate immune defenses, macroautophagy/autophagy targets viruses and viral components for lysosomal degradation and exposes pathogen-associated molecular...
As part of innate immune defenses, macroautophagy/autophagy targets viruses and viral components for lysosomal degradation and exposes pathogen-associated molecular patterns to facilitate recognition. However, viruses evolved sophisticated strategies to antagonize autophagy and even exploit it to promote their replication. In our recent study, we systematically analyzed the impact of individual SARS-CoV-2 proteins on autophagy. We showed that E, M, ORF3a, and ORF7a cause an accumulation of autophagosomes, whereas Nsp15 prevents the efficient formation of autophagosomes. Consequently, autophagic degradation of SQSTM1/p62 is decreased in the presence of E, ORF3a, ORF7a, and Nsp15. Notably, M does not alter SQSTM1 protein levels and colocalizes with accumulations of LC3B-positive membranes not resembling vesicles. Infection with SARS-CoV-2 prevents SQSTM1 degradation and increases lipidation of LC3B, indicating overall that the infection causes a reduction of autophagic flux. Our mechanistic analyses showed that the accessory proteins ORF3a and ORF7a both block autophagic degradation but use different strategies. While ORF3a prevents the fusion between autophagosomes and lysosomes, ORF7a reduces the acidity of lysosomes. In summary, we found that Nsp15, E, M, ORF3a, and ORF7a of SARS-CoV-2 manipulate cellular autophagy, and we determined the molecular mechanisms of ORF3a and ORF7a.
Topics: Autophagosomes; Autophagy; COVID-19; Humans; Lysosomes; SARS-CoV-2
PubMed: 34281462
DOI: 10.1080/15548627.2021.1953847 -
Nature Communications Feb 2023Hereditary sensory and autonomic neuropathy 9 (HSAN9) is a rare fatal neurological disease caused by mis- and nonsense mutations in the gene encoding for Tectonin...
Hereditary sensory and autonomic neuropathy 9 (HSAN9) is a rare fatal neurological disease caused by mis- and nonsense mutations in the gene encoding for Tectonin β-propeller repeat containing protein 2 (TECPR2). While TECPR2 is required for lysosomal consumption of autophagosomes and ER-to-Golgi transport, it remains elusive how exactly TECPR2 is involved in autophagy and secretion and what downstream sequels arise from defective TECPR2 due to its involvement in these processes. To address these questions, we determine molecular consequences of TECPR2 deficiency along the secretory pathway. By employing spatial proteomics, we describe pronounced changes with numerous proteins important for neuronal function being affected in their intracellular transport. Moreover, we provide evidence that TECPR2's interaction with the early secretory pathway is not restricted to COPII carriers. Collectively, our systematic profiling of a HSAN9 cell model points to specific trafficking and sorting defects which might precede autophagy dysfunction upon TECPR2 deficiency.
Topics: Autophagosomes; Autophagy; Golgi Apparatus; Protein Transport; Proteomics; Secretory Pathway; Carrier Proteins; Nerve Tissue Proteins
PubMed: 36797266
DOI: 10.1038/s41467-023-36553-6 -
FEBS Letters Sep 2022Plant selective (macro)autophagy is a highly regulated process where eukaryotic cells spatiotemporally degrade some of their constituents that have become superfluous or... (Review)
Review
Plant selective (macro)autophagy is a highly regulated process where eukaryotic cells spatiotemporally degrade some of their constituents that have become superfluous or harmful. The identification and characterization of the factors determining this selectivity make it possible to integrate selective (macro)autophagy into plant cell physiology and homeostasis. The specific cargo receptors and/or scaffold proteins involved in this pathway are generally not structurally conserved, as are the biochemical mechanisms underlying recognition and integration of a given cargo into the autophagosome in different cell types. This review discusses the few specific cargo receptors described in plant cells to highlight key features of selective autophagy in the plant kingdom and its integration with plant physiology, aiming to identify evolutionary convergence and knowledge gaps to be filled by future research.
Topics: Autophagosomes; Autophagy; Homeostasis; Plant Cells
PubMed: 35638898
DOI: 10.1002/1873-3468.14412 -
Frontiers in Immunology 2021Phagocytosis is the cellular defense mechanism used to eliminate antigens derived from dysregulated or damaged cells, and microbial pathogens. Phagocytosis is therefore...
Phagocytosis is the cellular defense mechanism used to eliminate antigens derived from dysregulated or damaged cells, and microbial pathogens. Phagocytosis is therefore a pillar of innate immunity, whereby foreign particles are engulfed and degraded in lysolitic vesicles. In hexacorallians, phagocytic mechanisms are poorly understood, though putative anthozoan phagocytic cells (amoebocytes) have been identified histologically. We identify and characterize phagocytes from the coral and the sea anemone . Using fluorescence-activated cell sorting and microscopy, we show that distinct populations of phagocytic cells engulf bacteria, fungal antigens, and beads. In addition to pathogenic antigens, we show that phagocytic cells engulf self, damaged cells. We show that target antigens localize to low pH phagolysosomes, and that degradation is occurring within them. Inhibiting actin filament rearrangement interferes with efficient particle phagocytosis but does not affect small molecule pinocytosis. We also demonstrate that cellular markers for lysolitic vesicles and reactive oxygen species (ROS) correlate with hexacorallian phagocytes. These results establish a foundation for improving our understanding of hexacorallian immune cell biology.
Topics: Animals; Anthozoa; Biomarkers; Cytokines; Cytoplasmic Vesicles; Flow Cytometry; Hydrogen-Ion Concentration; Immunity, Innate; Phagocytes; Phagocytosis; Phagosomes; Sea Anemones
PubMed: 34381444
DOI: 10.3389/fimmu.2021.662803 -
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