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Current Opinion in Microbiology Oct 2021Leishmania are unusual in being able to survive long-term in the mature phagolysosome compartment of macrophages and other phagocytic cells in their mammalian hosts. Key... (Review)
Review
Leishmania are unusual in being able to survive long-term in the mature phagolysosome compartment of macrophages and other phagocytic cells in their mammalian hosts. Key to their survival in this niche, Leishmania amastigotes switch to a slow growth state and activate a stringent metabolic response. The stringent metabolic response may be triggered by multiple stresses and is associated with decreased metabolic fluxes, restricted use of sugars and fatty acids as carbon sources and increased dependence on metabolic homeostasis pathways. Heterogeneity in expression of the Leishmania stringent response occurs in vivo reflects temporal and spatial heterogeneity in lesion tissues and includes non-dividing dormant stages. This response underpins the capacity of these parasites to maintain long-term chronic infections and survive drug treatments.
Topics: Animals; Fatty Acids; Leishmania; Macrophages; Parasites; Phagosomes
PubMed: 34340099
DOI: 10.1016/j.mib.2021.07.007 -
Microbiology Spectrum Jun 2016Phagocytosis refers to the active process that allows cells to take up large particulate material upon binding to surface receptors. The discovery of phagocytosis in... (Review)
Review
Phagocytosis refers to the active process that allows cells to take up large particulate material upon binding to surface receptors. The discovery of phagocytosis in 1883 by Elie Metchnikoff, leading to the concept that specialized cells are implicated in the defense against microbes, was one of the starting points of the field of immunology. After more than a century of research, phagocytosis is now appreciated to be a widely used process that enables the cellular uptake of a remarkable variety of particles, including bacteria, fungi, parasites, viruses, dead cells, and assorted debris and solid materials. Uptake of foreign particles is performed almost exclusively by specialized myeloid cells, commonly termed "professional phagocytes": neutrophils, monocytes, macrophages, and dendritic cells. Phagocytosis of microbes not only stops or at least restricts the spread of infection but also plays an important role in regulating the innate and adaptive immune responses. Activation of the myeloid cells upon phagocytosis leads to the secretion of cytokines and chemokines that convey signals to a variety of immune cells. Moreover, foreign antigens generated by the degradation of microbes following phagocytosis are loaded onto the major histocompatibility complex for presentation to specific T lymphocytes. However, phagocytosis is not restricted to professional myeloid phagocytes; an expanding diversity of cell types appear capable of engulfing apoptotic bodies and debris, playing a critical role in tissue remodeling and in the clearance of billions of effete cells every day.
Topics: Animals; Humans; Organelle Biogenesis; Phagocytes; Phagocytosis; Phagosomes
PubMed: 27337463
DOI: 10.1128/microbiolspec.MCHD-0013-2015 -
Frontiers in Bioscience (Landmark... Jun 2017Lipids are one of the major subcellular constituents and serve as signal molecules, energy sources, metabolic precursors and structural membrane components in various... (Review)
Review
Lipids are one of the major subcellular constituents and serve as signal molecules, energy sources, metabolic precursors and structural membrane components in various organisms. The function of lipids can be modified by multiple biochemical processes such as (de-)phosphorylation or (de-)glycosylation, and the organization of fatty acids into distinct cellular pools and subcellular compartments plays a pivotal role for the morphology and function of various cell populations. Thus, lipids regulate, for example, phagosome formation and maturation within host cells and thus, are critical for the elimination of microbial pathogens. Vice versa, microbial pathogens can manipulate the lipid composition of phagosomal membranes in host cells, and thus avoid their delivery to phagolysosomes. Lipids of microbial origin belong also to the strongest and most versatile inducers of mammalian immune responses upon engagement of distinct receptors on myeloid and lymphoid cells. Furthermore, microbial lipid toxins can induce membrane injuries and cell death. Thus, we will review here selected examples for mutual host-microbe interactions within the broad and divergent universe of lipids in microbial defense, tissue injury and immune evasion.
Topics: Animals; Autophagy; Bacteria; Fungi; Host-Pathogen Interactions; Humans; Lipid Metabolism; Lipids; Phagosomes; Signal Transduction
PubMed: 28410133
DOI: 10.2741/4559 -
Cellular and Molecular Life Sciences :... Mar 2018Autophagy is a highly regulated process in eukaryotes to maintain homeostasis and manage stress responses. Understanding the regulatory mechanisms and key players... (Review)
Review
Autophagy is a highly regulated process in eukaryotes to maintain homeostasis and manage stress responses. Understanding the regulatory mechanisms and key players involved in autophagy will provide critical insights into disease-related pathogenesis and potential clinical treatments. In this review, we describe the hallmark events involved in autophagy, from its initiation, to the final destruction of engulfed targets. Furthermore, based on structural and biochemical data, we evaluate the roles of key players in these processes and provide rationale as to how they control autophagic events in a highly ordered manner.
Topics: Animals; Autophagy; Humans; Lysosomes; Membrane Fusion; Models, Biological; Phagosomes; Protein Binding
PubMed: 28939950
DOI: 10.1007/s00018-017-2657-z -
Cellular Microbiology Aug 2014Human neutrophils represent the predominant leucocyte in circulation and the first responder to infection. Concurrent with ingestion of microorganisms, neutrophils... (Review)
Review
Human neutrophils represent the predominant leucocyte in circulation and the first responder to infection. Concurrent with ingestion of microorganisms, neutrophils activate and assemble the NADPH oxidase at the phagosome, thereby generating superoxide anion and hydrogen peroxide. Concomitantly, granules release their contents into the phagosome, where the antimicrobial proteins and enzymes synergize with oxidants to create an environment toxic to the captured microbe. The most rapid and complete antimicrobial action by human neutrophils against many organisms relies on the combined efforts of the azurophilic granule protein myeloperoxidase and hydrogen peroxide from the NADPH oxidase to oxidize chloride, thereby generating hypochlorous acid and a host of downstream reaction products. Although individual components of the neutrophil antimicrobial response exhibit specific activities in isolation, the situation in the environment of the phagosome is far more complicated, a consequence of multiple and complex interactions among oxidants, proteins and their by-products. In most cases, the cooperative interactions among the phagosomal contents, both from the host and the microbe, culminate in loss of viability of the ingested organism.
Topics: Cytoplasmic Granules; Humans; Hydrogen Peroxide; Hypochlorous Acid; Neutrophils; Oxidation-Reduction; Peroxidase; Phagocytosis; Phagosomes
PubMed: 24844117
DOI: 10.1111/cmi.12312 -
Methods in Molecular Biology (Clifton,... 2023Phagocytosis is carried out by cells such as macrophages of the immune system, whereby particulates like bacteria and apoptotic bodies are engulfed and sequestered...
Phagocytosis is carried out by cells such as macrophages of the immune system, whereby particulates like bacteria and apoptotic bodies are engulfed and sequestered within phagosomes for subsequent degradation. Hence, phagocytosis is important for infection resolution and tissue homeostasis. Aided by the innate and adaptive immune system, the activation of various phagocytic receptors triggers a cascade of downstream signaling mediators that drive actin and plasma membrane remodeling to entrap the bound particulate within the phagosome. Modulation of these molecular players can lead to distinct changes in the capacity and rates of phagocytosis. Here, we present a fluorescence microscopy-based technique to quantify phagocytosis using a macrophage-like cell line. We exemplify the technique through the phagocytosis of antibody-opsonized polystyrene beads and Escherichia coli. This method can be extended to other phagocytes and phagocytic particles.
Topics: Phagocytosis; Macrophages; Phagosomes; Microscopy, Fluorescence; Fluorescent Antibody Technique
PubMed: 37365459
DOI: 10.1007/978-1-0716-3338-0_3 -
Insect Biochemistry and Molecular... Jun 2019Phagocytosis is an evolutionarily conserved mechanism that plays a key role in both host defence and tissue homeostasis in multicellular organisms. A range of surface... (Review)
Review
Phagocytosis is an evolutionarily conserved mechanism that plays a key role in both host defence and tissue homeostasis in multicellular organisms. A range of surface receptors expressed on different cell types allow discriminating between self and non-self (or altered) material, thus enabling phagocytosis of pathogens and apoptotic cells. The phagocytosis process can be divided into four main steps: 1) binding of the phagocyte to the target particle, 2) particle internalization and phagosome formation, through remodelling of the plasma membrane, 3) phagosome maturation, and 4) particle destruction in the phagolysosome. In this review, we describe our present knowledge on phagocytosis in the fruit fly Drosophila melanogaster, assessing each of the key steps involved in engulfment of both apoptotic cells and bacteria. We also assess the physiological role of phagocytosis in host defence, development and tissue homeostasis.
Topics: Animals; Drosophila melanogaster; Immunity, Innate; Phagocytosis; Phagosomes
PubMed: 30953686
DOI: 10.1016/j.ibmb.2019.04.002 -
Advances in Experimental Medicine and... 2020Calcium (Ca) is a ubiquitous second messenger involved in the regulation of numerous cellular functions including vesicular trafficking, cytoskeletal rearrangements and... (Review)
Review
Calcium (Ca) is a ubiquitous second messenger involved in the regulation of numerous cellular functions including vesicular trafficking, cytoskeletal rearrangements and gene transcription. Both global as well as localized Ca signals occur during phagocytosis, although their functional impact on the phagocytic process has been debated. After nearly 40 years of research, a consensus may now be reached that although not strictly required, Ca signals render phagocytic ingestion and phagosome maturation more efficient, and their manipulation make an attractive avenue for therapeutic interventions. In the last decade many efforts have been made to identify the channels and regulators involved in generating and shaping phagocytic Ca signals. While molecules involved in store-operated calcium entry (SOCE) of the STIM and ORAI family have taken center stage, members of the canonical, melastatin, mucolipin and vanilloid transient receptor potential (TRP), as well as purinergic P2X receptor families are now recognized to play significant roles. In this chapter, we review the recent literature on research that has linked specific Ca-permeable channels and regulators to phagocytic function. We highlight the fact that lipid mediators are emerging as important regulators of channel gating and that phagosomal ionic homeostasis and Ca release also play essential parts. We predict that improved methodologies for measuring these factors will be critical for future advances in dissecting the intricate biology of this fascinating immune process.
Topics: Animals; Calcium; Calcium Signaling; Humans; Phagocytosis; Phagosomes
PubMed: 32399828
DOI: 10.1007/978-3-030-40406-2_7 -
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 -
Methods in Molecular Biology (Clifton,... 2015Autophagy (self-eating) is a highly conserved, vesicular pathway that cells use to eat pieces of themselves, including damaged organelles, protein aggregates or invading...
Autophagy (self-eating) is a highly conserved, vesicular pathway that cells use to eat pieces of themselves, including damaged organelles, protein aggregates or invading pathogens, for self-preservation and survival (Choi et al., N Engl J Med 368:651-662, 2013; Lamb et al., Nat Rev Mol Cell Biol 14:759-774, 2013). Autophagy can be delineated into three major vesicular compartments (the phagophore, autophagosome, autolysosome, see Fig. 1). The initial stages of the pathway involve the formation of phagophores (also called isolation membranes), which are open, cup-shaped membranes that expand and sequester the cytosolic components, including organelles and aggregated proteins or intracellular pathogens. Closure of the phagophore creates an autophagosome, which is a double-membrane vesicle. Fusion of the autophagosome with the lysosome, to form an autolysosome, delivers the content of the autophagosome into the lysosomal lumen and allows degradation to occur.Autophagy is a dynamic process that is initiated within 15 min of amino acid starvation in cell culture systems (Köchl et al., Traffic 7:129-145, 2006) and is likely to occur as rapidly in vivo (Mizushima et al., J Cell Biol 152:657-668, 2001). To initiate studies on the formation of the autophagosomes, and trafficking to and from the autophagic pathway, an ideal starting approach is to do a morphological analysis in fixed cells. Additional validation of the morphological data can be obtained using simple Western blot analysis. Here we describe the most commonly used morphological technique to study autophagy, in particular, using the most reliable marker, microtubule-associated protein 1A/1B-light chain 3 (LC3). In addition, we describe a second immunofluorescence assay to determine if autophagy is being induced, using an antibody to WD repeat domain, phosphoinositide interacting 2 (WIPI2), an effector of the phosphatidylinositol (3)-phosphate (PI3P) produced during autophagosome formation.
Topics: Animals; Autophagy; Blotting, Western; Humans; Lysosomes; Microscopy, Fluorescence; Microtubule-Associated Proteins; Phagosomes
PubMed: 25702116
DOI: 10.1007/978-1-4939-2309-0_12