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Journal articles on the topic 'Phagosome'
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1
Lu, Nan, Qian Shen, Timothy R. Mahoney, Xianghua Liu, and Zheng Zhou. "Three sorting nexins drive the degradation of apoptotic cells in response to PtdIns(3)P signaling." Molecular Biology of the Cell 22, no. 3 (February 2011): 354–74. http://dx.doi.org/10.1091/mbc.e10-09-0756.
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Apoptotic cells are swiftly engulfed by phagocytes and degraded inside phagosomes. Phagosome maturation requires phosphatidylinositol 3-phosphate [PtdIns(3)P], yet how PtdIns(3)P triggers phagosome maturation remains largely unknown. Through a genome-wide PtdIns(3)P effector screen in the nematode Caenorhabditis elegans, we identified LST-4/SNX9, SNX-1, and SNX-6, three BAR domain-containing sorting nexins, that act in two parallel pathways to drive PtdIns(3)P-mediated degradation of apoptotic cells. We found that these proteins were enriched on phagosomal surfaces through association with PtdIns(3)P and through specific protein–protein interaction, and they promoted the fusion of early endosomes and lysosomes to phagosomes, events essential for phagosome maturation. Specifically, LST-4 interacts with DYN-1 (dynamin), an essential phagosome maturation initiator, to strengthen DYN-1’s association to phagosomal surfaces, and facilitates the maintenance of the RAB-7 GTPase on phagosomal surfaces. Furthermore, both LST-4 and SNX-1 promote the extension of phagosomal tubules to facilitate the docking and fusion of intracellular vesicles. Our findings identify the critical and differential functions of two groups of sorting nexins in phagosome maturation and reveal a signaling cascade initiated by phagocytic receptor CED-1, mediated by PtdIns(3)P, and executed through these sorting nexins to degrade apoptotic cells.
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Clemens, Daniel L., Bai-Yu Lee, and Marcus A. Horwitz. "Francisella tularensis Phagosomal Escape Does Not Require Acidification of the Phagosome." Infection and Immunity 77, no. 5 (February 23, 2009): 1757–73. http://dx.doi.org/10.1128/iai.01485-08.
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ABSTRACT Following uptake, Francisella tularensis enters a phagosome that acquires limited amounts of lysosome-associated membrane glycoproteins and does not acquire cathepsin D or markers of secondary lysosomes. With additional time after uptake, F. tularensis disrupts its phagosomal membrane and escapes into the cytoplasm. To assess the role of phagosome acidification in phagosome escape, we followed acidification using the vital stain LysoTracker red and acquisition of the proton vacuolar ATPase (vATPase) using immunofluorescence within the first 3 h after uptake of live or killed F. tularensis subsp. holarctica live vaccine strain (LVS) by human macrophages. Whereas 90% of the phagosomes containing killed LVS stained intensely for the vATPase and were acidified, only 20 to 30% of phagosomes containing live LVS stained intensely for the vATPase and were acidified. To determine whether transient acidification might be required for phagosome escape, we assessed the impact on phagosome permeabilization of the proton pump inhibitor bafilomycin A. Using electron microscopy and an adenylate cyclase reporter system, we found that bafilomycin A did not prevent phagosomal permeabilization by F. tularensis LVS or virulent type A strains (F. tularensis subsp. tularensis strain Schu S4 and a recent clinical isolate) or by “F. tularensis subsp. novicida,” indicating that F. tularensis disrupts its phagosomal membrane by a mechanism that does not require acidification.
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Sullivan, Jonathan Tabb, Ellen F. Young, Jessica R. McCann, and Miriam Braunstein. "The Mycobacterium tuberculosis SecA2 System Subverts Phagosome Maturation To Promote Growth in Macrophages." Infection and Immunity 80, no. 3 (January 3, 2012): 996–1006. http://dx.doi.org/10.1128/iai.05987-11.
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The ability ofMycobacterium tuberculosisto grow in macrophages is critical to the virulence of this important pathogen. One wayM. tuberculosisis thought to maintain a hospitable niche in macrophages is by arresting the normal process of phagosomes maturing into acidified phagolysosomes. The process of phagosome maturation arrest byM. tuberculosisis not fully understood, and there has remained a need to firmly establish a requirement for phagosome maturation arrest forM. tuberculosisgrowth in macrophages. Other intracellular pathogens that control the phagosomal environment use specialized protein export systems to deliver effectors of phagosome trafficking to the host cell. InM. tuberculosis, the accessory SecA2 system is a specialized protein export system that is required for intracellular growth in macrophages. In studying the importance of the SecA2 system in macrophages, we discovered that SecA2 is required for phagosome maturation arrest. Shortly after infection, phagosomes containing a ΔsecA2mutant ofM. tuberculosiswere more acidified and showed greater association with markers of late endosomes than phagosomes containing wild-typeM. tuberculosis. We further showed that inhibitors of phagosome acidification rescued the intracellular growth defect of the ΔsecA2mutant, which demonstrated that the phagosome maturation arrest defect of the ΔsecA2mutant is responsible for the intracellular growth defect. This study demonstrates the importance of phagosome maturation arrest forM. tuberculosisgrowth in macrophages, and it suggests there are effectors of phagosome maturation that are exported into the host environment by the accessory SecA2 system.
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Rupper, A. C., J. M. Rodriguez-Paris, B. D. Grove, and J. A. Cardelli. "p110-related PI 3-kinases regulate phagosome-phagosome fusion and phagosomal pH through a PKB/Akt dependent pathway in Dictyostelium." Journal of Cell Science 114, no. 7 (April 1, 2001): 1283–95. http://dx.doi.org/10.1242/jcs.114.7.1283.
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The Dictyostelium p110-related PI 3-kinases, PIK1 and PIK2, regulate the endosomal pathway and the actin cytoskeleton, but do not significantly regulate internalization of particles in D. discoideum. Bacteria internalized into (Δ)ddpik1/ddpik2 cells or cells treated with PI 3-kinase inhibitors remained intact as single particles in phagosomes with closely associated membranes after 2 hours of internalization, while in control cells, bacteria appeared degraded in multi-particle spacious phagosomes. Addition of LY294002 to control cells, after 60 minutes of chase, blocked formation of spacious phagosomes, suggesting PI 3-kinases acted late to regulate spacious phagosome formation. Phagosomes purified from control and drug treated cells contained equivalent levels of lysosomal proteins, including the proton pump complex, and were acidic, but in drug treated cells and (Δ)ddpik1/ddpik2 cells phagosomal pH was significantly more acidic during maturation than the pH of control phagosomes. Inhibition of phagosomal maturation by LY294002 was overcome by increasing phagosomal pH with NH(4)Cl, suggesting that an increase in pH might trigger homotypic phagosome fusion. A pkbA null cell line (PKB/Akt) reproduced the phenotype described for cells treated with PI 3-kinase inhibitors and (Δ)ddpik1/ddpik2 cells. We propose that PI 3-kinases, through a PKB/Akt dependent pathway, directly regulate homotypic fusion of single particle containing phagosomes to form multi-particle, spacious phagosomes, possibly through the regulation of phagosomal pH.
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Alvarez-Dominguez, C., R. Roberts, and P. D. Stahl. "Internalized Listeria monocytogenes modulates intracellular trafficking and delays maturation of the phagosome." Journal of Cell Science 110, no. 6 (March 15, 1997): 731–43. http://dx.doi.org/10.1242/jcs.110.6.731.
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Previous studies have shown that early phagosome-endosome fusion events following phagocytosis of Listeria monocytogenes are modulated by the live organism. In the present study, we have characterized more fully the intracellular pathway of dead and live Listeria phagosomes. To examine access of endosomal and lysosomal markers to phagosomes containing live and dead Listeria, quantitative electron microscopy was carried out with intact cells using internalized BSA-gold as a marker to quantify transfer of solute from endosomal and lysosomal compartments to phagosomes. To monitor the protein composition of phagosomal membranes and to quantify transfer of HRP from endosomes and lysosomes to phagosomes, highly enriched phagosomes containing live and dead Listeria were isolated. Enriched phagosomal membranes were used for western blotting experiments with endosomal and lysosomal markers. In this study, we used a listeriolysin-deficient mutant, Listeria(hly-), that is retained within the phagosome following phagocytosis. Western blotting experiments indicate that early endosomal markers (mannose receptor, transferrin receptor) and key fusion factors necessary for early events (NSF, alpha/beta-SNAP) but not late endosomal markers (cation dependent mannose 6-phosphate receptor) or lysosomal proteins (cathepsin D or lamp-1) accumulate on the live-Listeria phagosomal membranes. On the contrary, phagosomes containing dead-Listeria are readily accessible by both endocytic and lysosomal markers. Studies with radiolabeled dead- and live-Listeria(hly-) indicate that, following phagocytosis, degradation of the live microorganism is substantially delayed. These findings indicate that dead-Listeria containing phagosomes rapidly mature to a phagolysosomal stage whereas live-Listeria(hly-) prevents maturation, in part, by avoiding fusion with lysosomes. The data suggest that by delaying phagosome maturation and subsequent degradation, Listeria prolongs survival inside the phagosome/endosome assuring bacterial viability as a prelude to escape into the cytoplasm.
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Lerm, M., Å Holm, Å Seiron, E. Särndahl, K. E. Magnusson, and B. Rasmusson. "Leishmania donovani Requires Functional Cdc42 and Rac1 To Prevent Phagosomal Maturation." Infection and Immunity 74, no. 5 (May 2006): 2613–18. http://dx.doi.org/10.1128/iai.74.5.2613-2618.2006.
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ABSTRACT Leishmania donovani promastigotes survive inside macrophage phagosomes by inhibiting phagosomal maturation. The main surface glycoconjugate on promastigotes, lipophosphoglycan (LPG), is crucial for survival and mediates the formation of a protective shell of F-actin around the phagosome. Previous studies have demonstrated that this effect involves inhibition of protein kinase Cα. The present study shows that functional Cdc42 and Rac1 are required for the formation of F-actin around L. donovani phagosomes. Moreover, we present data showing that phagosomes containing LPG-defective L. donovani, which is unable to induce F-actin accumulation, display both elevated levels of periphagosomal F-actin and impaired phagosomal maturation in macrophages with permanently active forms of Cdc42 and Rac1. We conclude that L. donovani engages Cdc42 and Rac1 to build up a protective coat of F-actin around its phagosome to prevent phagosomal maturation.
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Garin, Jérome, Roberto Diez, Sylvie Kieffer, Jean-François Dermine, Sophie Duclos, Etienne Gagnon, Remy Sadoul, Christiane Rondeau, and Michel Desjardins. "The Phagosome Proteome." Journal of Cell Biology 152, no. 1 (January 8, 2001): 165–80. http://dx.doi.org/10.1083/jcb.152.1.165.
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Phagosomes are key organelles for the innate ability of macrophages to participate in tissue remodeling, clear apoptotic cells, and restrict the spread of intracellular pathogens. To understand the functions of phagosomes, we initiated the systematic identification of their proteins. Using a proteomic approach, we identified >140 proteins associated with latex bead–containing phagosomes. Among these were hydrolases, proton pump ATPase subunits, and proteins of the fusion machinery, validating our approach. A series of unexpected proteins not previously described along the endocytic/phagocytic pathways were also identified, including the apoptotic proteins galectin3, Alix, and TRAIL, the anti-apoptotic protein 14-3-3, the lipid raft-enriched flotillin-1, the anti-microbial molecule lactadherin, and the small GTPase rab14. In addition, 24 spots from which the peptide masses could not be matched to entries in any database potentially represent new phagosomal proteins. The elaboration of a two-dimensional gel database of >160 identified spots allowed us to analyze how phagosome composition is modulated during phagolysosome biogenesis. Remarkably, during this process, hydrolases are not delivered in bulk to phagosomes, but are instead acquired sequentially. The systematic characterization of phagosome proteins provided new insights into phagosome functions and the protein or groups of proteins involved in and regulating these functions.
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Lennon-Duménil, Ana-Maria, Arnold H. Bakker, René Maehr, Edda Fiebiger, Herman S. Overkleeft, Mario Rosemblatt, Hidde L. Ploegh, and Cécile Lagaudrière-Gesbert. "Analysis of Protease Activity in Live Antigen-presenting Cells Shows Regulation of the Phagosomal Proteolytic Contents During Dendritic Cell Activation." Journal of Experimental Medicine 196, no. 4 (August 19, 2002): 529–40. http://dx.doi.org/10.1084/jem.20020327.
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Here, we describe a new approach designed to monitor the proteolytic activity of maturing phagosomes in live antigen-presenting cells. We find that an ingested particle sequentially encounters distinct protease activities during phagosomal maturation. Incorporation of active proteases into the phagosome of the macrophage cell line J774 indicates that phagosome maturation involves progressive fusion with early and late endocytic compartments. In contrast, phagosome biogenesis in bone marrow–derived dendritic cells (DCs) and macrophages preferentially involves endocytic compartments enriched in cathepsin S. Kinetics of phagosomal maturation is faster in macrophages than in DCs. Furthermore, the delivery of active proteases to the phagosome is significantly reduced after the activation of DCs with lipopolysaccharide. This observation is in agreement with the notion that DCs prevent the premature destruction of antigenic determinants to optimize T cell activation. Phagosomal maturation is therefore a tightly regulated process that varies according to the type and differentiation stage of the phagocyte.
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VIEIRA, Otilia V., Roberto J. BOTELHO, and Sergio GRINSTEIN. "Phagosome maturation: aging gracefully." Biochemical Journal 366, no. 3 (September 15, 2002): 689–704. http://dx.doi.org/10.1042/bj20020691.
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Foreign particles and apoptotic bodies are eliminated from the body by phagocytic leucocytes. The initial stage of the elimination process is the internalization of the particles into a plasma membrane-derived vacuole known as the phagosome. Such nascent phagosomes, however, lack the ability to kill pathogens or to degrade the ingested targets. These properties are acquired during the course of phagosomal maturation, a complex sequence of reactions that result in drastic remodelling of the phagosomal membrane and contents. The determinants and consequences of the fusion and fission reactions that underlie phagosomal maturation are the topic of this review.
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Lee, Warren L., Moo-Kyung Kim, Alan D. Schreiber, and Sergio Grinstein. "Role of Ubiquitin and Proteasomes in Phagosome Maturation." Molecular Biology of the Cell 16, no. 4 (April 2005): 2077–90. http://dx.doi.org/10.1091/mbc.e04-06-0464.
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Phagosomes undergo multiple rounds of fusion with compartments of the endocytic pathway during the course of maturation. Despite the insertion of vast amounts of additional membrane, the phagosomal surface area remains approximately constant, implying active ongoing fission. To investigate the mechanisms underlying phagosomal fission we monitored the fate of Fcγ receptors (FcγR), which are known to be cleared from the phagosome during maturation. FcγR, which show a continuous distribution throughout the membrane of nascent phagosomes were found at later times to cluster into punctate, vesicular structures, before disappearing. In situ photoactivation of receptors tagged with a light-sensitive fluorescent protein revealed that some of these vesicles detach, whereas others remain associated with the phagosome. By fusing FcγR to pH-sensitive fluorescent proteins, we observed that the cytoplasmic domain of the receptors enters an acidic compartment, indicative of inward budding and formation of multivesicular structures. The topology of the receptor was confirmed by flow cytometry of purified phagosomes. Phagosomal proteins are ubiquitylated, and ubiquitylation was found to be required for formation of acidic multivesicular structures. Remarkably, proteasomal function is also involved in the vesiculation process. Preventing the generation of multivesicular structures did not impair the acquisition of late endosomal and lysosomal markers, indicating that phagosomal fusion and fission are controlled separately.
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Levin, Roni, Gerald R. V. Hammond, Tamas Balla, Pietro De Camilli, Gregory D. Fairn, and Sergio Grinstein. "Multiphasic dynamics of phosphatidylinositol 4-phosphate during phagocytosis." Molecular Biology of the Cell 28, no. 1 (January 2017): 128–40. http://dx.doi.org/10.1091/mbc.e16-06-0451.
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We analyzed the distribution, fate, and functional role of phosphatidylinositol 4-phosphate (PtdIns4P) during phagosome formation and maturation. To this end, we used genetically encoded probes consisting of the PtdIns4P-binding domain of the bacterial effector SidM. PtdIns4P was found to undergo complex, multiphasic changes during phagocytosis. The phosphoinositide, which is present in the plasmalemma before engagement of the target particle, is transiently enriched in the phagosomal cup. Soon after the phagosome seals, PtdIns4P levels drop precipitously due to the hydrolytic activity of Sac2 and phospholipase C, becoming undetectable for ∼10 min. PtdIns4P disappearance coincides with the emergence of phagosomal PtdIns3P. Conversely, the disappearance of PtdIns3P that signals the transition from early to late phagosomes is accompanied by resurgence of PtdIns4P, which is associated with the recruitment of phosphatidylinositol 4-kinase 2A. The reacquisition of PtdIns4P can be prevented by silencing expression of the kinase and can be counteracted by recruitment of a 4-phosphatase with a heterodimerization system. Using these approaches, we found that the secondary accumulation of PtdIns4P is required for proper phagosomal acidification. Defective acidification may be caused by impaired recruitment of Rab7 effectors, including RILP, which were shown earlier to displace phagosomes toward perinuclear lysosomes. Our results show multimodal dynamics of PtdIns4P during phagocytosis and suggest that the phosphoinositide plays important roles during the maturation of the phagosome.
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Klose, Matthias, Johann E. Salloum, Hannes Gonschior, and Stefan Linder. "SNX3 drives maturation of Borrelia phagosomes by forming a hub for PI(3)P, Rab5a, and galectin-9." Journal of Cell Biology 218, no. 9 (July 23, 2019): 3039–59. http://dx.doi.org/10.1083/jcb.201812106.
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The spirochete Borrelia burgdorferi, the causative agent of Lyme disease, is internalized by macrophages and processed in phagolysosomes. Phagosomal compaction, a crucial step in phagolysosome maturation, is driven by contact of Rab5a-positive vesicles with the phagosomal coat. We show that the sorting nexin SNX3 is transported with Rab5a vesicles and that its PX domain enables vesicle–phagosome contact by binding to PI(3)P in the phagosomal coat. Moreover, the C-terminal region of SNX3 recruits galectin-9, a lectin implicated in protein and membrane recycling, which we identify as a further regulator of phagosome compaction. SNX3 thus forms a hub for two distinct vesicle populations, constituting a convergence point for the endosomal recycling machinery, to contribute to phagosome maturation and intracellular processing of borreliae. These data also suggest that the helical shape of B. burgdorferi itself, providing sites of high curvature and thus local PI(3)P enrichment at phagosomes, may be one of the driving elements underlying the efficient elimination of spirochetes by immune cells.
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Steinberg, B. E., K. K. Huynh, and S. Grinstein. "Phagosomal acidification: measurement, manipulation and functional consequences." Biochemical Society Transactions 35, no. 5 (October 25, 2007): 1083–87. http://dx.doi.org/10.1042/bst0351083.
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Phagocytosis holds a central position in the development of a successful innate immune response and in the initiation of the corresponding adaptive response. The destruction of invading pathogens and the presentation of their antigens to lymphoid cells require acidification of the phagosomal lumen. The present review discusses the mechanism of phagosome acidification, with particular reference to the two components of the protonmotive force: the chemical (pH) gradient and the electrical potential across the phagosomal membrane. A method for the in situ measurement of the electrical potential across the phagosomal membrane is described. In addition, we discuss the finding that acidification is not only a consequence, but also a critical determinant of phagosome maturation. Luminal acidification appears to function as a timing device controlling the transition between early and late phagosomes.
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Jeschke, Andreas, Nicole Zehethofer, Buko Lindner, Jessica Krupp, Dominik Schwudke, Ina Haneburger, Marko Jovic, et al. "Phosphatidylinositol 4-phosphate and phosphatidylinositol 3-phosphate regulate phagolysosome biogenesis." Proceedings of the National Academy of Sciences 112, no. 15 (March 30, 2015): 4636–41. http://dx.doi.org/10.1073/pnas.1423456112.
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Professional phagocytic cells ingest microbial intruders by engulfing them into phagosomes, which subsequently mature into microbicidal phagolysosomes. Phagosome maturation requires sequential fusion of the phagosome with early endosomes, late endosomes, and lysosomes. Although various phosphoinositides (PIPs) have been detected on phagosomes, it remained unclear which PIPs actually govern phagosome maturation. Here, we analyzed the involvement of PIPs in fusion of phagosomes with various endocytic compartments and identified phosphatidylinositol 4-phosphate [PI(4)P], phosphatidylinositol 3-phosphate [PI(3)P], and the lipid kinases that generate these PIPs, as mediators of phagosome–lysosome fusion. Phagosome–early endosome fusion required PI(3)P, yet did not depend on PI(4)P. Thus, PI(3)P regulates phagosome maturation at early and late stages, whereas PI(4)P is selectively required late in the pathway.
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Yang, Mabel, Glenn F. W. Walpole, and Johannes Westman. "Maintaining phagosome integrity during fungal infection: do or die?" Microbial Cell 7, no. 12 (December 7, 2020): 323–25. http://dx.doi.org/10.15698/mic2020.12.738.
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Professional phagocytes represent a critical node in innate immunity and tissue homeostasis through their specialized ability to eat, drink, and digest material from the extracellular milieu. The degradative and microbicidal functions of phagocytes rely on the fusion of lysosomes with endosomal compartments such as phagosomes, resulting in the digestion and recycling of internalized prey and debris. Despite these efforts, several particularly dangerous infections result from a class of tenacious pathogens that resist digestion, often surviving and even proliferating within the confines of the phagosomal membrane. One such example, Candida albicans, is a commensal polymorphic fungus that colonizes ~50% of the population and can cause life-threatening infections in immunocompromised patients. Not only can C. albicans survive within phagosomes, but its ingestion by macropahges triggers a yeast-to-hyphal transition promoting rapid intraphagosomal growth (several microns per hour) while imposing a substantial mechanical burden on the phagosomal membrane surrounding the fungus. Preservation of membrane integrity is essential to maintain the hostile internal environment of the phagosome, a functionality of degradative enzymes and oxidative stress. Yet, biological membranes such as phagosomes have a limited capacity to stretch. Using C. albicans as a model intracellular pathogen, our recent work reveals a mechanism by which phagosomes respond to intraphagosomal growth of pathogens by expanding their surface area, and as a result, maintain the integrity of the phagosomal membrane. We hypothesized that this expansion would be facilitated by the delivery and fusion of membrane from extraneous sources with the phagosome. Consistently, macrophages respond to the yeast-to-hyphal transition through a stretch-induced release of phagosomal calcium, leading to recruitment and insertion of lysosomes that accommodate the expansion of the phagolysosome and preserve its integrity. Below, we discuss this calcium-dependent mechanism of lysosome insertion as a means of avoiding phagosomal rupture. Further, we examine the implications of membrane integrity on the delicate balance between the host and pathogen by focusing on fungal stress responses, nutrient acquisition, inflammasome activation, and cell death.
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Chong, Audrey, Tara D. Wehrly, Vinod Nair, Elizabeth R. Fischer, Jeffrey R. Barker, Karl E. Klose, and Jean Celli. "The Early Phagosomal Stage of Francisella tularensis Determines Optimal Phagosomal Escape and Francisella Pathogenicity Island Protein Expression." Infection and Immunity 76, no. 12 (October 13, 2008): 5488–99. http://dx.doi.org/10.1128/iai.00682-08.
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ABSTRACT Francisella tularensis is an intracellular pathogen that can survive and replicate within macrophages. Following phagocytosis and transient interactions with the endocytic pathway, F. tularensis rapidly escapes from its original phagosome into the macrophage cytoplasm, where it eventually replicates. To examine the importance of the nascent phagosome for the Francisella intracellular cycle, we have characterized early trafficking events of the F. tularensis subsp. tularensis strain Schu S4 in a murine bone marrow-derived macrophage model. Here we show that early phagosomes containing Schu S4 transiently interact with early and late endosomes and become acidified before the onset of phagosomal disruption. Inhibition of endosomal acidification with the vacuolar ATPase inhibitor bafilomycin A1 or concanamycin A prior to infection significantly delayed but did not block phagosomal escape and cytosolic replication, indicating that maturation of the early Francisella-containing phagosome (FCP) is important for optimal phagosomal escape and subsequent intracellular growth. Further, Francisella pathogenicity island (FPI) protein expression was induced during early intracellular trafficking events. Although inhibition of endosomal acidification mimicked the early phagosomal escape defects caused by mutation of the FPI-encoded IglCD proteins, it did not inhibit the intracellular induction of FPI proteins, demonstrating that this response is independent of phagosomal pH. Altogether, these results demonstrate that early phagosomal maturation is required for optimal phagosomal escape and that the early FCP provides cues other than intravacuolar pH that determine intracellular induction of FPI proteins.
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Vieira, Otilia V., Cecilia Bucci, Rene E. Harrison, William S. Trimble, Letizia Lanzetti, Jean Gruenberg, Alan D. Schreiber, Philip D. Stahl, and Sergio Grinstein. "Modulation of Rab5 and Rab7 Recruitment to Phagosomes by Phosphatidylinositol 3-Kinase." Molecular and Cellular Biology 23, no. 7 (April 1, 2003): 2501–14. http://dx.doi.org/10.1128/mcb.23.7.2501-2514.2003.
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ABSTRACT Phagosomal biogenesis is central for microbial killing and antigen presentation by leukocytes. However, the molecular mechanisms governing phagosome maturation are poorly understood. We analyzed the role and site of action of phosphatidylinositol 3-kinases (PI3K) and of Rab GTPases in maturation using both professional and engineered phagocytes. Rab5, which is recruited rapidly and transiently to the phagosome, was found to be essential for the recruitment of Rab7 and for progression to phagolysosomes. Similarly, functional PI3K is required for successful maturation. Remarkably, inhibition of PI3K did not preclude Rab5 recruitment to phagosomes but instead enhanced and prolonged it. Moreover, in the presence of PI3K inhibitors Rab5 was found to be active, as deduced from measurements of early endosome antigen 1 binding and by photobleaching recovery determinations. Though their ability to fuse with late endosomes and lysosomes was virtually eliminated by wortmannin, phagosomes nevertheless recruited a sizable amount of Rab7. Moreover, Rab7 recruited to phagosomes in the presence of PI3K antagonists retained the ability to bind its effector, Rab7-interacting lysosomal protein, suggesting that it is functionally active. These findings imply that (i) dissociation of Rab5 from phagosomes requires products of PI3K, (ii) PI3K-dependent effectors of Rab5 are not essential for the recruitment of Rab7 by phagosomes, and (iii) recruitment and activation of Rab7 are insufficient to induce fusion of phagosomes with late endosomes and lysosomes. Accordingly, transfection of constitutively active Rab7 did not bypass the block of phagolysosome formation exerted by wortmannin. We propose that Rab5 activates both PI3K-dependent and PI3K-independent effectors that act in parallel to promote phagosome maturation.
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Al-Haddad, Ahmed, Marion A. Shonn, Bärbel Redlich, Ariel Blocker, Janis K. Burkhardt, Hanry Yu, John A. Hammer, et al. "Myosin Va Bound to Phagosomes Binds to F-Actin and Delays Microtubule-dependent Motility." Molecular Biology of the Cell 12, no. 9 (September 2001): 2742–55. http://dx.doi.org/10.1091/mbc.12.9.2742.
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We established a light microscopy-based assay that reconstitutes the binding of phagosomes purified from mouse macrophages to preassembled F-actin in vitro. Both endogenous myosin Va from mouse macrophages and exogenous myosin Va from chicken brain stimulated the phagosome–F-actin interaction. Myosin Va association with phagosomes correlated with their ability to bind F-actin in an ATP-regulated manner and antibodies to myosin Va specifically blocked the ATP-sensitive phagosome binding to F-actin. The uptake and retrograde transport of phagosomes from the periphery to the center of cells in bone marrow macrophages was observed in both normal mice and mice homozygous for the dilute-lethal spontaneous mutation (myosin Va null). However, in dilute-lethalmacrophages the accumulation of phagosomes in the perinuclear region occurred twofold faster than in normal macrophages. Motion analysis revealed saltatory phagosome movement with temporarily reversed direction in normal macrophages, whereas almost no reversals in direction were observed in dilute-lethal macrophages. These observations demonstrate that myosin Va mediates phagosome binding to F-actin, resulting in a delay in microtubule-dependent retrograde phagosome movement toward the cell center. We propose an “antagonistic/cooperative mechanism” to explain the saltatory phagosome movement toward the cell center in normal macrophages.
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BERÓN, Walter, Luis S. MAYORGA, Maria I. COLOMBO, and Philip D. STAHL. "Recruitment of coat-protein-complex proteins on to phagosomal membranes is regulated by a brefeldin A-sensitive ADP-ribosylation factor." Biochemical Journal 355, no. 2 (April 6, 2001): 409–15. http://dx.doi.org/10.1042/bj3550409.
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Particle internalization in macrophages is followed by a complex maturation process. We have previously observed that proteins bound to phagocytosed particles are sorted from phagosomes into a heterogeneous population of vesicles that fuse with endosomes. However, the mechanism and the protein machinery involved in the formation of these phagosome-derived vesicles are largely unknown. It has been shown that vesicles coated with coat protein complex type I (COPI) have a role in both secretion and endocytosis. To address the possibility that COPI proteins might participate in the formation of phagosome-derived vesicles we studied the recruitment of β-COP to highly purified phagosomes. The binding of β-COP to phagosomal membranes was regulated by nucleotides and inhibited by brefeldin A (BFA). An ADP-ribosylation factor 1 (ARF1) mutant defective in GTP hydrolysis supported the binding of β-COP to phagosomes independently of added nucleotide. AlF4 and Gβγ subunits, agents known to modulate heterotrimeric G-protein activity, were tested in the β-COP binding assay. AlF4 increased β-COP association, whereas binding was inhibited by the addition of Gβγ subunits. Our results suggest that COP proteins are recruited to phagosomal membranes by a mechanism that involves heterotrimeric GTP-binding proteins and a BFA-sensitive ARF. In addition, our findings indicate that COPI proteins are involved in the recycling of components from phagosomes to the cell surface.
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Sivaloganathan, Darshan M., and Mark P. Brynildsen. "Phagosome–Bacteria Interactions from the Bottom Up." Annual Review of Chemical and Biomolecular Engineering 12, no. 1 (June 7, 2021): 309–31. http://dx.doi.org/10.1146/annurev-chembioeng-090920-015024.
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When attempting to propagate infections, bacterial pathogens encounter phagocytes that encase them in vacuoles called phagosomes. Within phagosomes, bacteria are bombarded with a plethora of stresses that often lead to their demise. However, pathogens have evolved numerous strategies to counter those host defenses and facilitate survival. Given the importance of phagosome–bacteria interactions to infection outcomes, they represent a collection of targets that are of interest for next-generation antibacterials. To facilitate such therapies, different approaches can be employed to increase understanding of phagosome–bacteria interactions, and these can be classified broadly as top down (starting from intact systems and breaking down the importance of different parts) or bottom up (developing a knowledge base on simplified systems and progressively increasing complexity). Here we review knowledge of phagosomal compositions and bacterial survival tactics useful for bottom-up approaches, which are particularly relevant for the application of reaction engineering to quantify and predict the time evolution of biochemical species in these death-dealing vacuoles. Further, we highlight how understanding in this area can be built up through the combination of immunology, microbiology, and engineering.
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Tohyama, Yumi, Hiroyuki Tabata, and Kaoru Tohyama. "Syk Plays an Essential Role in Phagosome-Lysosome Fusion By Facilitating Actin-Remodeling in Complement-Mediated Phagocytosis." Blood 134, Supplement_1 (November 13, 2019): 2315. http://dx.doi.org/10.1182/blood-2019-125061.
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Complement-mediated phagocytosis plays an essential role in host defense against invading pathogens. Phagocytosis requires a dynamic and coordinated reconstruction of the membrane and the underlying cytoskeleton. Pathogens are entrapped into a phagosome and internalized into the cell. Subsequently, the phagosome fuses with lysosomes to form a phagolysosome with gradual acidification. Previous studies showed the pivotal roles of phosphoinositide-mediated signaling and the synchronous actin-remodeling in phagosome formation, but the mechanisms of phagolysosome generation, namely phagosome-lysosome fusion remain largely unexplored. Here we show that phagosome-lysosome fusion requires the collapse of F-actin structure surrounding phagosomes and a tyrosine kinase, Syk plays a key role in this process. To reveal the mechanisms of phagosome-lysosome fusion particularly focusing on Syk, we performed complement-mediated phagocytosis assay using human leukemic HL60 and Syk-knockout (Syk-KO) HL60 cells established by the CRISPR/Cas9 system. Parental HL60 and Syk-KO HL60 were differentiated into macrophage-like cells and incubated with complement-opsonized Candida albicans(C. albicans) or fluorescence-labeled zymosan particles. Syk-KO cells permitted the survival of C. albicansand their escape from the phagosome.In general, after fusion with lysosomes, the phagosome acquires acidic milieu inside the organelle and enhanced bactericidal activity. To confirm the effects of Syk-KO on phagosome acidification, we used two types of fluorescence-labeled zymosan particles: one was labeled with fluorescein isothiocyanate (FITC) whose fluorescent intensity is reduced under decreased pH condition and the other was labeled with Texas Red whose intensity is conserved independent of pH change. Flow cytometric analysis indicated that Syk-KO cells showed insufficient phagosome acidification. These results suggest that Syk facilitates acidification of phagosomes and results in an enhanced bactericidal activity against pathogens following complement-mediated phagocytosis. Since ourprevious study indicated the participation of Syk in dynamics of actin cytoskeleton, we examined the effect of Syk-KO on the distribution of F-actin around phagosomes. Two hours after phagocytosis, pathogen-containing phagosomes of both parental and Syk-KO HL60 cells were already intracellularly distributed. At that time, F-actin structure around phagosomes of parental HL60 cells was hardly invisible but the phagosomes of Syk-KO cells were circumscribed by dense F-actin structure. An F-actin-stabilizing agent, jasplakinolide induced a similar fusion defect in peripheral blood-derived monocytes as observed in Syk-KO cells. Presence of dense F-actin structure surrounding phagosomes seemed to be responsible for inhibiting phagosome-lysosome fusion. In other words, collapse of F-actin structure surrounding phagosomes may be a critical step of phagolysosome generation. Our results demonstrate that actin-remodeling is essential not only for phagosome formation but also for phagosome-lysosome fusion in complement-mediated phagocytosis and that Syk promotes this process. The present study provides new insights into the mechanism controlling phagocytic progression that leads to host defense against pathogens. Disclosures No relevant conflicts of interest to declare.
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Ramachandra, Lakshmi, Jamie L. Smialek, Sam S. Shank, Marilyn Convery, W. Henry Boom, and Clifford V. Harding. "Phagosomal Processing of Mycobacterium tuberculosis Antigen 85B Is Modulated Independently of Mycobacterial Viability and Phagosome Maturation." Infection and Immunity 73, no. 2 (February 2005): 1097–105. http://dx.doi.org/10.1128/iai.73.2.1097-1105.2005.
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ABSTRACT Control of Mycobacterium tuberculosis infection requires CD4 T-cell responses and major histocompatibility complex class II (MHC-II) processing of M. tuberculosis antigens (Ags). We have previously demonstrated that macrophages process heat-killed (HK) M. tuberculosis more efficiently than live M. tuberculosis. These observations suggested that live M. tuberculosis may inhibit Ag processing by inhibiting phagosome maturation or that HK M. tuberculosis may be less resistant to Ag processing. In the present study we examined the correlation between M. tuberculosis viability and phagosome maturation and efficiency of Ag processing. Since heat treatment could render M. tuberculosis Ags more accessible to proteolysis, M. tuberculosis was additionally killed by antibiotic treatment and radiation. Processing of HK, live, radiation-killed (RadK), or rifampin-killed (RifK) M. tuberculosis in activated murine bone marrow macrophages was examined by using an I-Ab-restricted T-cell hybridoma cell line (BB7) that recognizes an epitope derived from Ag 85B. Macrophages processed HK M. tuberculosis more rapidly and efficiently than they processed live, RadK, or RifK M. tuberculosis. Live, RadK, and RifK M. tuberculosis cells were processed with similar efficiencies for presentation to BB7 T hybridoma cells. Furthermore, phagosomes containing live or RadK M. tuberculosis expressed fewer M. tuberculosis peptide-MHC-II complexes than phagosomes containing HK M. tuberculosis expressed. Since only live M. tuberculosis was able to prevent acidification of the phagosome, our results suggest that regulation of phagosome maturation does not explain the differences in processing of different forms of M. tuberculosis. These findings suggest that the mechanisms used by M. tuberculosis to inhibit phagosomal maturation differ from the mechanisms involved in modulating phagosome Ag processing.
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Tilney, Lewis G., Omar S. Harb, Patricia S. Connelly, Camenzind G. Robinson, and Craig R. Roy. "How the parasitic bacterium Legionella pneumophila modifies its phagosome and transforms it into rough ER: implications for conversion of plasma membrane to the ER membrane." Journal of Cell Science 114, no. 24 (December 15, 2001): 4637–50. http://dx.doi.org/10.1242/jcs.114.24.4637.
Full textAbstract:
Within five minutes of macrophage infection by Legionella pneumophila, the bacterium responsible for Legionnaires’ disease, elements of the rough endoplasmic reticulum (RER) and mitochondria attach to the surface of the bacteria-enclosed phagosome. Connecting these abutting membranes are tiny hairs, which are frequently periodic like the rungs of a ladder. These connections are stable and of high affinity - phagosomes from infected macrophages remain connected to the ER and mitochondria (as they were in situ) even after infected macrophages are homogenized. Thin sections through the plasma and phagosomal membranes show that the phagosomal membrane is thicker (72±2 Å) than the ER and mitochondrial membranes (60±2 Å), presumably owing to the lack of cholesterol, sphingolipids and glycolipids in the ER. Interestingly, within 15 minutes of infection, the phagosomal membrane changes thickness to resemble that of the attached ER vesicles. Only later (e.g. after six hours) does the ER-phagosome association become less frequent. Instead ribosomes stud the former phagosomal membrane and L. pneumophila reside directly in the rough ER. Examination of phagosomes of various L. pneumophila mutants suggests that this membrane conversion is a four-stage process used by L. pneumophila to establish itself in the RER and to survive intracellularly. But what is particularly interesting is that L. pneumophila is exploiting a poorly characterized naturally occuring cellular process.
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Yin, Jianhua, Yaling Huang, Pengfei Guo, Siqi Hu, Sawako Yoshina, Nan Xuan, Qiwen Gan, Shohei Mitani, Chonglin Yang, and Xiaochen Wang. "GOP-1 promotes apoptotic cell degradation by activating the small GTPase Rab2 in C. elegans." Journal of Cell Biology 216, no. 6 (April 19, 2017): 1775–94. http://dx.doi.org/10.1083/jcb.201610001.
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Apoptotic cells generated by programmed cell death are engulfed by phagocytes and enclosed within plasma membrane–derived phagosomes. Maturation of phagosomes involves a series of membrane-remodeling events that are governed by the sequential actions of Rab GTPases and lead to formation of phagolysosomes, where cell corpses are degraded. Here we identified gop-1 as a novel regulator of apoptotic cell clearance in Caenorhabditis elegans. Loss of gop-1 affects phagosome maturation through the RAB-5–positive stage, causing defects in phagosome acidification and phagolysosome formation, phenotypes identical to and unaffected by loss of unc-108, the C. elegans Rab2. GOP-1 transiently associates with cell corpse–containing phagosomes, and loss of its function abrogates phagosomal association of UNC-108. GOP-1 interacts with GDP-bound and nucleotide-free UNC-108/Rab2, disrupts GDI-UNC-108 complexes, and promotes activation and membrane recruitment of UNC-108/Rab2 in vitro. Loss of gop-1 also abolishes association of UNC-108 with endosomes, causing defects in endosome and dense core vesicle maturation. Thus, GOP-1 is an activator of UNC-108/Rab2 in multiple processes.
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Flannagan, Ronald S., Tayler J. Farrell, Steven M. Trothen, Jimmy D. Dikeakos, and David E. Heinrichs. "Rapid removal of phagosomal ferroportin in macrophages contributes to nutritional immunity." Blood Advances 5, no. 2 (January 21, 2021): 459–74. http://dx.doi.org/10.1182/bloodadvances.2020002833.
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Abstract Nutrient sequestration is an essential facet of host innate immunity. Macrophages play a critical role in controlling iron availability through expression of the iron transport protein ferroportin (FPN), which extrudes iron from the cytoplasm to the extracellular milieu. During phagocytosis, the limiting phagosomal membrane, which derives from the plasmalemma, can be decorated with FPN and, if functional, will move iron from the cytosol into the phagosome lumen. This serves to feed iron to phagocytosed microbes and would be counterproductive to the many other known host mechanisms working to starve microbes of this essential metal. To understand how FPN is regulated during phagocytosis, we expressed FPN as a green fluorescent protein–fusion protein in macrophages and monitored its localization during uptake of various phagocytic targets, including Staphylococcus aureus, Salmonella enterica serovar Typhimurium, human erythrocytes, and immunoglobulin G opsonized latex beads. We find that FPN is rapidly removed, independently of Vps34 and PI(3)P, from early phagosomes and does not follow recycling pathways that regulate transferrin receptor recycling. Live-cell video microscopy showed that FPN movement on the phagosome is dynamic, with punctate and tubular structures forming before FPN is trafficked back to the plasmalemma. N-ethylmaleimide–sensitive factor, which disrupts soluble NSF attachment protein receptor (SNARE)–mediated membrane fusion and trafficking, prevented FPN removal from the phagosome. Our data support the hypothesis that removal of FPN from the limiting phagosomal membrane will, at the cellular level, ensure that iron cannot be pumped into phagosomes. We propose this as yet another mechanism of host nutritional immunity to subvert microbial growth.
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Fratti, Rutilio A., Jonathan M. Backer, Jean Gruenberg, Silvia Corvera, and Vojo Deretic. "Role of phosphatidylinositol 3-kinase and Rab5 effectors in phagosomal biogenesis and mycobacterial phagosome maturation arrest." Journal of Cell Biology 154, no. 3 (August 6, 2001): 631–44. http://dx.doi.org/10.1083/jcb.200106049.
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Phagosomal biogenesis is a fundamental biological process of particular significance for the function of phagocytic and antigen-presenting cells. The precise mechanisms governing maturation of phagosomes into phagolysosomes are not completely understood. Here, we applied the property of pathogenic mycobacteria to cause phagosome maturation arrest in infected macrophages as a tool to dissect critical steps in phagosomal biogenesis. We report the requirement for 3-phosphoinositides and acquisition of Rab5 effector early endosome autoantigen (EEA1) as essential molecular events necessary for phagosomal maturation. Unlike the model phagosomes containing latex beads, which transiently recruited EEA1, mycobacterial phagosomes excluded this regulator of vesicular trafficking that controls membrane tethering and fusion processes within the endosomal pathway and is recruited to endosomal membranes via binding to phosphatidylinositol 3-phosphate (PtdIns[3]P). Inhibitors of phosphatidylinositol 3′(OH)-kinase (PI-3K) activity diminished EEA1 recruitment to newly formed latex bead phagosomes and blocked phagosomal acquisition of late endocytic properties, indicating that generation of PtdIns(3)P plays a role in phagosomal maturation. Microinjection into macrophages of antibodies against EEA1 and the PI-3K hVPS34 reduced acquisition of late endocytic markers by latex bead phagosomes, demonstrating an essential role of these Rab5 effectors in phagosomal biogenesis. The mechanism of EEA1 exclusion from mycobacterial phagosomes was investigated using mycobacterial products. Coating of latex beads with the major mycobacterial cell envelope glycosylated phosphatidylinositol lipoarabinomannan isolated from the virulent Mycobacterium tuberculosis H37Rv, inhibited recruitment of EEA1 to latex bead phagosomes, and diminished their maturation. These findings define the generation of phosphatidylinositol 3-phosphate and EEA1 recruitment as: (a) important regulatory events in phagosomal maturation and (b) critical molecular targets affected by M. tuberculosis. This study also identifies mycobacterial phosphoinositides as products with specialized toxic properties, interfering with discrete trafficking stages in phagosomal maturation.
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Vieira, Otilia V., Roberto J. Botelho, Lucia Rameh, Saskia M. Brachmann, Tsuyoshi Matsuo, Howard W. Davidson, Alan Schreiber, Jonathan M. Backer, Lewis C. Cantley, and Sergio Grinstein. "Distinct roles of class I and class III phosphatidylinositol 3-kinases in phagosome formation and maturation." Journal of Cell Biology 155, no. 1 (October 1, 2001): 19–26. http://dx.doi.org/10.1083/jcb.200107069.
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Phagosomes acquire their microbicidal properties by fusion with lysosomes. Products of phosphatidylinositol 3-kinase (PI 3-kinase) are required for phagosome formation, but their role in maturation is unknown. Using chimeric fluorescent proteins encoding tandem FYVE domains, we found that phosphatidylinositol 3-phosphate (PI[3]P) accumulates greatly but transiently on the phagosomal membrane. Unlike the 3′-phosphoinositides generated by class I PI 3-kinases which are evident in the nascent phagosomal cup, PI(3)P is only detectable after the phagosome has sealed. The class III PI 3-kinase VPS34 was found to be responsible for PI(3)P synthesis and essential for phagolysosome formation. In contrast, selective ablation of class I PI 3-kinase revealed that optimal phagocytosis, but not maturation, requires this type of enzyme. These results highlight the differential functional role of the two families of kinases, and raise the possibility that PI(3)P production by VPS34 may be targeted during the maturation arrest induced by some intracellular parasites.
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Zimmerli, S., M. Majeed, M. Gustavsson, O. Stendahl, D. A. Sanan, and J. D. Ernst. "Phagosome-lysosome fusion is a calcium-independent event in macrophages." Journal of Cell Biology 132, no. 1 (January 1, 1996): 49–61. http://dx.doi.org/10.1083/jcb.132.1.49.
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Phagosome-lysosome membrane fusion is a highly regulated event that is essential for intracellular killing of microorganisms. Functionally, it represents a form of polarized regulated secretion, which is classically dependent on increases in intracellular ionized calcium ([Ca2+]i). Indeed, increases in [Ca2+]i are essential for phagosome-granule (lysosome) fusion in neutrophils and for lysosomal fusion events that mediate host cell invasion by Trypanosoma cruzi trypomastigotes. Since several intracellular pathogens survive in macrophage phagosomes that do not fuse with lysosomes, we examined the regulation of phagosome-lysosome fusion in macrophages. Macrophages (M phi) were treated with 12.5 microM bis-(2-amino-S-methylphenoxy) ethane-N,N,N',N',-tetraacetic acid tetraacetoxymethyl ester (MAPT/AM), a cell-permeant calcium chelator which reduced resting cytoplasmic [Ca2+]; from 80 nM to < or = 20 nM and completely blocked increases in [Ca2+]i in response to multiple stimuli, even in the presence of extracellular calcium. Subsequently, M phi phagocytosed serum-opsonized zymosan, staphylococci, or Mycobacterium bovis. Microbes were enumerated by 4',6-diamidino-2-phenylindole, dihydrochloride (DAPI) staining, and phagosome-lysosome fusion was scored using both lysosome-associated membrane protein (LAMP-1) as a membrane marker and rhodamine dextran as a content marker for lysosomes. Confirmation of phagosome-lysosome fusion by electron microscopy validated the fluorescence microscopy findings. We found that phagosome-lysosome fusion in M phi occurs noramlly at very low [Ca2+]i (< or = 20 nM). Kinetic analysis showed that in M phi none of the steps leading from particle binding to eventual phagosome-lysosome fusion are regulated by [Ca2+]i in a rate-limiting way. Furthermore, confocal microscopy revealed no difference in the intensity of LAMP-1 immunofluorescence in phagolysosome membranes in calcium-buffered vs. control macrophages. We conclude that neither membrane recognition nor fusion events in the phagosomal pathway in macrophages are dependent on or regulated by calcium.
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Sakurai, Chiye, Hitoshi Hashimoto, Hideki Nakanishi, Seisuke Arai, Yoh Wada, Ge-Hong Sun-Wada, Ikuo Wada, and Kiyotaka Hatsuzawa. "SNAP-23 regulates phagosome formation and maturation in macrophages." Molecular Biology of the Cell 23, no. 24 (December 15, 2012): 4849–63. http://dx.doi.org/10.1091/mbc.e12-01-0069.
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Synaptosomal associated protein of 23 kDa (SNAP-23), a plasma membrane–localized soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE), has been implicated in phagocytosis by macrophages. For elucidation of its precise role in this process, a macrophage line overexpressing monomeric Venus–tagged SNAP-23 was established. These cells showed enhanced Fc receptor–mediated phagocytosis. Detailed analyses of each process of phagocytosis revealed a marked increase in the production of reactive oxygen species within phagosomes. Also, enhanced accumulation of a lysotropic dye, as well as augmented quenching of a pH-sensitive fluorophore were observed. Analyses of isolated phagosomes indicated the critical role of SNAP-23 in the functional recruitment of the NADPH oxidase complex and vacuolar-type H+-ATPase to phagosomes. The data from the overexpression experiments were confirmed by SNAP-23 knockdown, which demonstrated a significant delay in phagosome maturation and a reduction in uptake activity. Finally, for analyzing whether phagosomal SNAP-23 entails a structural change in the protein, an intramolecular Förster resonance energy transfer (FRET) probe was constructed, in which the distance within a TagGFP2-TagRFP was altered upon close approximation of the N-termini of its two SNARE motifs. FRET efficiency on phagosomes was markedly enhanced only when VAMP7, a lysosomal SNARE, was coexpressed. Taken together, our results strongly suggest the involvement of SNAP-23 in both phagosome formation and maturation in macrophages, presumably by mediating SNARE-based membrane traffic.
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Sasaki, Ayaka, Isei Nakae, Maya Nagasawa, Keisuke Hashimoto, Fumiko Abe, Kota Saito, Masamitsu Fukuyama, et al. "Arl8/ARL-8 functions in apoptotic cell removal by mediating phagolysosome formation inCaenorhabditis elegans." Molecular Biology of the Cell 24, no. 10 (May 15, 2013): 1584–92. http://dx.doi.org/10.1091/mbc.e12-08-0628.
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Efficient clearance of apoptotic cells by phagocytes is important for development, tissue homeostasis, and the prevention of autoimmune responses. Phagosomes containing apoptotic cells undergo acidification and mature from Rab5-positive early to Rab7-positive late stages. Phagosomes finally fuse with lysosomes to form phagolysosomes, which degrade apoptotic cells; however, the molecular mechanism underlying phagosome–lysosome fusion is not fully understood. Here we show that the Caenorhabditis elegans Arf-like small GTPase Arl8 (ARL-8) is involved in phagolysosome formation and is required for the efficient removal of apoptotic cells. Loss of function of arl-8 results in the accumulation of apoptotic germ cells. Both the engulfment of the apoptotic cells by surrounding somatic sheath cells and the phagosomal maturation from RAB-5- to RAB-7-positive stages occur in arl-8 mutants. However, the phagosomes fail to fuse with lysosomes in the arl-8 mutants, leading to the accumulation of RAB-7-positive phagosomes and the delayed degradation of apoptotic cells. ARL-8 localizes primarily to lysosomes and physically interacts with the homotypic fusion and protein sorting complex component VPS-41. Collectively our findings reveal that ARL-8 facilitates apoptotic cell removal in vivo by mediating phagosome–lysosome fusion during phagocytosis.
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Clemens, Daniel L., Bai-Yu Lee, and Marcus A. Horwitz. "Virulent and Avirulent Strains of Francisella tularensis Prevent Acidification and Maturation of Their Phagosomes and Escape into the Cytoplasm in Human Macrophages." Infection and Immunity 72, no. 6 (June 2004): 3204–17. http://dx.doi.org/10.1128/iai.72.6.3204-3217.2004.
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ABSTRACT Francisella tularensis, the agent of tularemia, is an intracellular pathogen, but little is known about the compartment in which it resides in human macrophages. We have examined the interaction of a recent virulent clinical isolate of F. tularensis subsp. tularensis and the live vaccine strain with human macrophages by immunoelectron and confocal immunofluorescence microscopy. We assessed the maturation of the F. tularensis phagosome by examining its acquisition of the lysosome-associated membrane glycoproteins (LAMPs) CD63 and LAMP1 and the acid hydrolase cathepsin D. Two to four hours after infection, vacuoles containing live F. tularensis cells acquired abundant staining for LAMPs but little or no staining for cathepsin D. However, after 4 h, the colocalization of LAMPs with live F. tularensis organisms declined dramatically. In contrast, vacuoles containing formalin-killed bacteria exhibited intense staining for all of these late endosomal/lysosomal markers at all time points examined (1 to 16 h). We examined the pH of the vacuoles 3 to 4 h after infection by quantitative immunogold staining and by fluorescence staining for lysosomotropic agents. Whereas phagosomes containing killed bacteria stained intensely for these agents, indicating a marked acidification of the phagosomes (pH 5.5), phagosomes containing live F. tularensis did not concentrate these markers and thus were not appreciably acidified (pH 6.7). An ultrastructural analysis of the F. tularensis compartment revealed that during the first 4 h after uptake, the majority of F. tularensis bacteria reside within phagosomes with identifiable membranes. The cytoplasmic side of the membranes of ∼50% of these phagosomes was coated with densely staining fibrils of ∼30 nm in length. In many cases, these coated phagosomal membranes appeared to bud, vesiculate, and fragment. By 8 h after infection, the majority of live F. tularensis bacteria lacked any ultrastructurally discernible membrane separating them from the host cell cytoplasm. These results indicate that F. tularensis initially enters a nonacidified phagosome with LAMPs but without cathepsin D and that the phagosomal membrane subsequently becomes morphologically disrupted, allowing the bacteria to gain direct access to the macrophagic cytoplasm. The capacity of F. tularensis to alter the maturation of its phagosome and to enter the cytoplasm is likely an important element of its capacity to parasitize macrophages and has major implications for vaccine development.
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Via, L. E., R. A. Fratti, M. McFalone, E. Pagan-Ramos, D. Deretic, and V. Deretic. "Effects of cytokines on mycobacterial phagosome maturation." Journal of Cell Science 111, no. 7 (April 1, 1998): 897–905. http://dx.doi.org/10.1242/jcs.111.7.897.
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One of the major mechanisms permitting intracellular pathogens to parasitize macrophages is their ability to alter maturation of the phagosome or affect its physical integrity. These processes are opposed by the host innate and adaptive immune defenses, and in many instances mononuclear phagocytes can be stimulated with appropriate cytokines to restrict the growth of the microorganisms within the phagosomal compartment. Very little is known about the effects that cytokines have on phagosome maturation. Here we have used green fluorescent protein (GFP)-labeled mycobacteria and a fixable acidotropic probe, LysoTracker Red DND-99, to monitor maturation of the mycobacterial phagosome. The macrophage compartments that stained with the LysoTracker probe were examined first. This dye was found to colocalize preferentially with the late endosomal and lysosomal markers rab7 and Lamp1, and with a fluid phase marker chased into the late endosomal compartments. In contrast, LysoTracker showed only a minor overlap with the early endosomal marker rab5. Pathogenic mycobacteria are believed to reside in nonacidified vacuoles sequestered away from late endosomal compartments as a part of their intracellular survival strategy. We examined the status of mycobacterial phagosomes in macrophages from IL-10 knockout mice, in quiescent cells, and in mononuclear phagocytes stimulated with the macrophage-activating cytokine IFN-(gamma). When macrophages were derived from the bone marrow of transgenic IL-10 mice lacking this major deactivating cytokine, colocalization of GFP-fluorescing mycobacteria with the LysoTracker staining appeared enhanced, suggestive of increased acidification of the mycobacterial phagosome relative to macrophages from normal mice. When bone marrow-derived macrophages from normal mice or a J774 murine macrophage cell line were stimulated with IFN-(gamma) and LPS, this resulted in increased colocalization of mycobacteria and LysoTracker, but no statistically significant enhancement was observed in IL-10 transgenic animals. These studies are consistent with the interpretation that proinflammatory and anti-inflammatory cytokines affect maturation of mycobacterial phagosomes. Although multiple mechanisms are likely to be at work, we propose the existence of a direct link between cytokine effects on the host cell and phagosome maturation in the macrophage.
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Cheng, Shiya, Kun Wang, Wei Zou, Rui Miao, Yaling Huang, Haibin Wang, and Xiaochen Wang. "PtdIns(4,5)P2 and PtdIns3P coordinate to regulate phagosomal sealing for apoptotic cell clearance." Journal of Cell Biology 210, no. 3 (August 3, 2015): 485–502. http://dx.doi.org/10.1083/jcb.201501038.
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Phagocytosis requires phosphoinositides (PIs) as both signaling molecules and localization cues. How PIs coordinate to control phagosomal sealing and the accompanying switch of organelle identity is unclear. In this study, we followed dynamic changes in PIs during apoptotic cell clearance in Caenorhabditis elegans. We found that phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) and phosphatidylinositol-3-phosphate (PtdIns3P), which accumulate transiently on unsealed and fully sealed phagosomes, respectively, are both involved in phagosome closure. We identified PtdIns3P phosphatase MTM-1 as an effector of PtdIns(4,5)P2 to promote phagosomal sealing. MTM-1 coordinates with the class II PI3 kinase PIKI-1 to control PtdIns3P levels on unsealed phagosomes. The SNX9 family protein LST-4 is required for sealing, and its association with unsealed phagosomes is regulated by PtdIns(4,5)P2, PIKI-1, and MTM-1. Loss of LST-4 or its retention on phagosomes disrupts sealing and suppresses PtdIns3P accumulation, indicating close coupling of the two events. Our findings support a coincidence detection mechanism by which phagosomal sealing is regulated and coupled with conversion from PtdIns(4,5)P2 enrichment on unsealed phagosomes to PtdIns3P enrichment on fully sealed phagosomes.
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Shi, Li, Priscila C. Albuquerque, Eszter Lazar-Molnar, Xintao Wang, Laura Santambrogio, Attila Gácser, and Joshua D. Nosanchuk. "A Monoclonal Antibody to Histoplasma capsulatum Alters the Intracellular Fate of the Fungus in Murine Macrophages." Eukaryotic Cell 7, no. 7 (May 16, 2008): 1109–17. http://dx.doi.org/10.1128/ec.00036-08.
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ABSTRACT Monoclonal antibodies (MAbs) to a cell surface histone on Histoplasma capsulatum modify murine infection and decrease the growth of H. capsulatum within macrophages. Without the MAbs, H. capsulatum survives within macrophages by modifying the intraphagosomal environment. In the present study, we aimed to analyze the affects of a MAb on macrophage phagosomes. Using transmission electron and fluorescence microscopy, we showed that phagosome activation and maturation are significantly greater when H. capsulatum yeast are opsonized with MAb. The MAb reduced the ability of the organism to regulate the phagosomal pH. Additionally, increased antigen processing and reduced negative costimulation occur in macrophages that phagocytose yeast cells opsonized with MAb, resulting in more-efficient T-cell activation. The MAb alters the intracellular fate of H. capsulatum by affecting the ability of the fungus to regulate the milieu of the phagosome.
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Tian, Wei, Xing Jun Li, Natalie D. Stull, Wenyu Ming, Chang-Il Suh, Sarah A. Bissonnette, Michael B. Yaffe, Sergio Grinstein, Simon J. Atkinson, and Mary C. Dinauer. "FcγR-stimulated activation of the NADPH oxidase: phosphoinositide-binding protein p40phox regulates NADPH oxidase activity after enzyme assembly on the phagosome." Blood 112, no. 9 (November 1, 2008): 3867–77. http://dx.doi.org/10.1182/blood-2007-11-126029.
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AbstractThe phagocyte NADPH oxidase generates superoxide for microbial killing, and includes a membrane-bound flavocytochrome b558 and cytosolic p67phox, p47phox, and p40phox subunits that undergo membrane translocation upon cellular activation. The function of p40phox, which binds p67phox in resting cells, is incompletely understood. Recent studies showed that phagocytosis-induced superoxide production is stimulated by p40phox and its binding to phosphatidylinositol-3-phosphate (PI3P), a phosphoinositide enriched in membranes of internalized phagosomes. To better define the role of p40phox in FcγR-induced oxidase activation, we used immunofluorescence and real-time imaging of FcγR-induced phagocytosis. YFP-tagged p67phox and p40phox translocated to granulocyte phagosomes before phagosome internalization and accumulation of a probe for PI3P. p67phox and p47phox accumulation on nascent and internalized phagosomes did not require p40phox or PI3 kinase activity, although superoxide production before and after phagosome sealing was decreased by mutation of the p40phox PI3P-binding domain or wortmannin. Translocation of p40phox to nascent phagosomes required binding to p67phox but not PI3P, although the loss of PI3P binding reduced p40phox retention after phagosome internalization. We conclude that p40phox functions primarily to regulate FcγR-induced NADPH oxidase activity rather than assembly, and stimulates superoxide production via a PI3P signal that increases after phagosome internalization.
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Clemens, D. L., and M. A. Horwitz. "The Mycobacterium tuberculosis phagosome interacts with early endosomes and is accessible to exogenously administered transferrin." Journal of Experimental Medicine 184, no. 4 (October 1, 1996): 1349–55. http://dx.doi.org/10.1084/jem.184.4.1349.
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Previous studies have demonstrated that the Mycobacterium tuberculosis phagosome in human monocyte-derived macrophages acquires markers of early and late endosomes, but direct evidence of interaction of the M. tuberculosis phagosome with the endosomal compartment has been lacking. Using the cryosection immunogold technique, we have found that the M. tuberculosis phagosome acquires exogenously added transferrin in a time-dependent fashion. Near-maximal acquisition of transferrin occurs within 15 min, kinetics of acquisition consistent with interaction of the M. tuberculosis phagosome with early endosomes. Transferrin is chased out of the M. tuberculosis phagosome by incubation of the infected macrophages in culture medium lacking human transferrin. Phagosomes containing latex beads or heat-killed M. tuberculosis, on the other hand, do not acquire staining for transferrin. These and other findings demonstrate that M. tuberculosis arrests the maturation of its phagosome at a stage at which the phagosome interacts with early and late endosomes, but not with lysosomes. The transferrin endocytic pathway potentially provides a novel route for targeting antimicrobials to the M. tuberculosis phagosome.
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Jacobs, Mary Ellen, Leroi V. DeSouza, Haresha Samaranayake, Ronald E. Pearlman, K. W. Michael Siu, and Lawrence A. Klobutcher. "The Tetrahymena thermophila Phagosome Proteome." Eukaryotic Cell 5, no. 12 (September 29, 2006): 1990–2000. http://dx.doi.org/10.1128/ec.00195-06.
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ABSTRACT In vertebrates, phagocytosis occurs mainly in specialized cells of the immune system and serves as a primary defense against invading pathogens, but it also plays a role in clearing apoptotic cells and in tissue remodeling during development. In contrast, unicellular eukaryotes, such as the ciliate Tetrahymena thermophila, employ phagocytosis to ingest and degrade other microorganisms to meet their nutritional needs. To learn more about the protein components of the multistep process of phagocytosis, we carried out an analysis of the Tetrahymena phagosome proteome. Tetrahymena cells were fed polystyrene beads, which allowed for the efficient purification of phagosomes. The protein composition of purified phagosomes was then analyzed by multidimensional separation coupled with tandem mass spectrometry. A total of 453 peptides were identified that resulted in the identification of 73 putative phagosome proteins. Twenty-eight of the proteins have been implicated in phagocytosis in other organisms, indicating that key aspects of phagocytosis were conserved during evolution. Other identified proteins have not previously been associated with phagocytosis, including some of unknown function. Live-cell confocal fluorescence imaging of Tetrahymena strains expressing green fluorescent protein-tagged versions of four of the identified phagosome proteins provided evidence that at least three of the proteins (including two with unknown functions) are associated with phagosomes, indicating that the bulk of the proteins identified in the analyses are indeed phagosome associated.
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Steele-Mortimer, Olivia, Maryse St-Louis, Martin Olivier, and B. Brett Finlay. "Vacuole Acidification Is Not Required for Survival ofSalmonella enterica Serovar Typhimurium within Cultured Macrophages and Epithelial Cells." Infection and Immunity 68, no. 9 (September 1, 2000): 5401–4. http://dx.doi.org/10.1128/iai.68.9.5401-5404.2000.
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ABSTRACT Phagosome acidification is an important component of the microbicidal response by infected eukaryotic cells. Thus, intracellular pathogens that reside within phagosomes must either block phagosome acidification or be able to survive at low pH. In this work, we studied the effect of phagosomal acidification on the survival of intracellular Salmonella enterica serovar Typhimurium in different cell types. Bafilomycin A1, a specific inhibitor of the vacuolar proton-ATPases, was used to block acidification of salmonella-containing vacuoles. We found that in several epithelial cell lines, treatment with bafilomycin A1 had no effect on intracellular survival or replication. Furthermore, although acidification was essential for Salmonella intracellular survival in J774 cultured macrophages, as reported previously (13), it is not essential in other macrophage cell lines. These data suggest that vacuolar acidification may play a role in intracellular survival of salmonellae only under certain conditions and in specific cell types.
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Goyette, Guillaume, Jonathan Boulais, Nicholas J. Carruthers, Christian R. Landry, Isabelle Jutras, Sophie Duclos, Jean-François Dermine, et al. "Proteomic Characterization of Phagosomal Membrane Microdomains During Phagolysosome Biogenesis and Evolution." Molecular & Cellular Proteomics 11, no. 11 (August 20, 2012): 1365–77. http://dx.doi.org/10.1074/mcp.m112.021048.
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After their formation at the cell surface, phagosomes become fully functional through a complex maturation process involving sequential interactions with various intracellular organelles. In the last decade, series of data indicated that some of the phagosome functional properties occur in specialized membrane microdomains. The molecules associated with membrane microdomains, as well as the organization of these structures during phagolysosome biogenesis are largely unknown. In this study, we combined proteomics and bioinformatics analyses to characterize the dynamic association of proteins to maturing phagosomes. Our data indicate that groups of proteins shuffle from detergent-soluble to detergent-resistant membrane microdomains during maturation, supporting a model in which the modulation of the phagosome functional properties involves an important reorganization of the phagosome proteome by the coordinated spatial segregation of proteins.
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Tranchemontagne, Zachary R., Ryan B. Camire, Vanessa J. O'Donnell, Jessfor Baugh, and Kristin M. Burkholder. "Staphylococcus aureus Strain USA300 Perturbs Acquisition of Lysosomal Enzymes and Requires Phagosomal Acidification for Survival inside Macrophages." Infection and Immunity 84, no. 1 (October 26, 2015): 241–53. http://dx.doi.org/10.1128/iai.00704-15.
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Methicillin-resistantStaphylococcus aureus(MRSA) causes invasive, drug-resistant skin and soft tissue infections. Reports thatS. aureusbacteria survive inside macrophages suggest that the intramacrophage environment may be a niche for persistent infection; however, mechanisms by which the bacteria might evade macrophage phagosomal defenses are unclear. We examined the fate of theS. aureus-containing phagosome in THP-1 macrophages by evaluating bacterial intracellular survival and phagosomal acidification and maturation and by testing the impact of phagosomal conditions on bacterial viability. Multiple strains ofS. aureussurvived inside macrophages, and in studies using the MRSA USA300 clone, the USA300-containing phagosome acidified rapidly and acquired the late endosome and lysosome protein LAMP1. However, fewer phagosomes containing live USA300 bacteria than those containing dead bacteria associated with the lysosomal hydrolases cathepsin D and β-glucuronidase. Inhibiting lysosomal hydrolase activity had no impact on intracellular survival of USA300 or otherS. aureusstrains, suggesting thatS. aureusperturbs acquisition of lysosomal enzymes. We examined the impact of acidification onS. aureusintramacrophage viability and found that inhibitors of phagosomal acidification significantly impaired USA300 intracellular survival. Inhibition of macrophage phagosomal acidification resulted in a 30-fold reduction in USA300 expression of the staphylococcal virulence regulatoragrbut had little effect on expression ofsarA,saeR, orsigB. Bacterial exposure to acidic pHin vitroincreasedagrexpression. Together, these results suggest thatS. aureussurvives inside macrophages by perturbing normal phagolysosome formation and that USA300 may sense phagosomal conditions and upregulate expression of a key virulence regulator that enables its intracellular survival.
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Okai, Blessing, Natalie Lyall, Neil A. R. Gow, Judith M. Bain, and Lars-Peter Erwig. "Rab14 Regulates Maturation of Macrophage Phagosomes Containing the Fungal Pathogen Candida albicans and Outcome of the Host-Pathogen Interaction." Infection and Immunity 83, no. 4 (February 2, 2015): 1523–35. http://dx.doi.org/10.1128/iai.02917-14.
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Avoidance of innate immune defense is an important mechanism contributing to the pathogenicity of microorganisms. The fungal pathogenCandida albicansundergoes morphogenetic switching from the yeast to the filamentous hyphal form following phagocytosis by macrophages, facilitating its escape from the phagosome, which can result in host cell lysis. We show that the intracellular host trafficking GTPase Rab14 plays an important role in protecting macrophages from lysis mediated byC. albicanshyphae. Live-cell imaging of macrophages expressing green fluorescent protein (GFP)-tagged Rab14 or dominant negative Rab14, or with small interfering RNA (siRNA)-mediated knockdown of Rab14, revealed the temporal dynamics of this protein and its influence on the maturation of macrophage phagosomes following the engulfment ofC. albicanscells. Phagosomes containing liveC. albicanscells became transiently Rab14 positive within 2 min following engulfment. The duration of Rab14 retention on phagosomes was prolonged for hyphal cargo and was directly proportional to hyphal length. Interference with endogenous Rab14 did not affect the migration of macrophages towardC. albicanscells, the rate of engulfment, the overall uptake of fungal cells, or early phagosome processing. However, Rab14 depletion delayed the acquisition of the late phagosome maturation markers LAMP1 and lysosomal cathepsin, indicating delayed formation of a fully bioactive lysosome. This was associated with a significant increase in the level of macrophage killing byC. albicans. Therefore, Rab14 activity promotes phagosome maturation duringC. albicansinfection but is dysregulated on the phagosome in the presence of the invasive hyphal form, which favors fungal survival and escape.
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Roberts, Esteban A., Jennifer Chua, George B. Kyei, and Vojo Deretic. "Higher order Rab programming in phagolysosome biogenesis." Journal of Cell Biology 174, no. 7 (September 18, 2006): 923–29. http://dx.doi.org/10.1083/jcb.200603026.
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Phagosomes offer kinetically and morphologically tractable organelles to dissect the control of phagolysosome biogenesis by Rab GTPases. Model phagosomes harboring latex beads undergo a coordinated Rab5–Rab7 exchange, which is akin to the process of endosomal Rab conversion, the control mechanisms of which are unknown. In the process of blocking phagosomal maturation, the intracellular pathogen Mycobacterium tuberculosis prevents Rab7 acquisition, thus, providing a naturally occurring tool to study Rab conversion. We show that M. tuberculosis inhibition of Rab7 acquisition and arrest of phagosomal maturation depends on Rab22a. Four-dimensional microscopy revealed that phagosomes harboring live mycobacteria recruited and retained increasing amounts of Rab22a. Rab22a knockdown in macrophages via siRNA enhanced the maturation of phagosomes with live mycobacteria. Conversely, overexpression of the GTP-locked mutant Rab22aQ64L prevented maturation of phagosomes containing heat-killed mycobacteria, which normally progress into phagolysosomes. Moreover, Rab22a knockdown led to Rab7 acquisition by phagosomes harboring live mycobacteria. Our findings show that Rab22a defines the critical checkpoint for Rab7 conversion on phagosomes, allowing or disallowing organellar transition into a late endosomal compartment. M. tuberculosis parasitizes this process by actively recruiting and maintaining Rab22a on its phagosome, thus, preventing Rab7 acquisition and blocking phagolysosomal biogenesis.
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Jiang, Mei, Julian Esteve-Rudd, Vanda S. Lopes, Tanja Diemer, Concepción Lillo, Agrani Rump, and David S. Williams. "Microtubule motors transport phagosomes in the RPE, and lack of KLC1 leads to AMD-like pathogenesis." Journal of Cell Biology 210, no. 4 (August 10, 2015): 595–611. http://dx.doi.org/10.1083/jcb.201410112.
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The degradation of phagosomes, derived from the ingestion of photoreceptor outer segment (POS) disk membranes, is a major role of the retinal pigment epithelium (RPE). Here, POS phagosomes were observed to associate with myosin-7a, and then kinesin-1, as they moved from the apical region of the RPE. Live-cell imaging showed that the phagosomes moved bidirectionally along microtubules in RPE cells, with kinesin-1 light chain 1 (KLC1) remaining associated in both directions and during pauses. Lack of KLC1 did not inhibit phagosome speed, but run length was decreased, and phagosome localization and degradation were impaired. In old mice, lack of KLC1 resulted in RPE pathogenesis that was strikingly comparable to aspects of age-related macular degeneration (AMD), with an excessive accumulation of RPE and sub-RPE deposits, as well as oxidative and inflammatory stress responses. These results elucidate mechanisms of POS phagosome transport in relation to degradation, and demonstrate that defective microtubule motor transport in the RPE leads to phenotypes associated with AMD.
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Okada, Mami, Christopher D. Huston, Barbara J. Mann, William A. Petri, Kiyoshi Kita, and Tomoyoshi Nozaki. "Proteomic Analysis of Phagocytosis in the Enteric Protozoan Parasite Entamoeba histolytica." Eukaryotic Cell 4, no. 4 (April 2005): 827–31. http://dx.doi.org/10.1128/ec.4.4.827-831.2005.
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ABSTRACT Proteomic analysis of phagosomes isolated from Entamoeba histolytica by liquid chromatography and mass spectrometry identified 85 proteins involved in surface recognition, actin cytoskeleton rearrangement, vesicular trafficking, and degradation. Phagosome localization of representative proteins was verified by immunofluorescence assay. This study should provide a basis for molecular identification and characterization of phagosome biogenesis.
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Clemens, D. L., and M. A. Horwitz. "Characterization of the Mycobacterium tuberculosis phagosome and evidence that phagosomal maturation is inhibited." Journal of Experimental Medicine 181, no. 1 (January 1, 1995): 257–70. http://dx.doi.org/10.1084/jem.181.1.257.
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We have used the cryosection immunogold technique to study the composition of the Mycobacterium tuberculosis phagosome. We have used quantitative immunogold staining to determine the distribution of several known markers of the endosomal-lysosomal pathway in human monocytes after ingestion of either M. tuberculosis, Legionella pneumophila, or polystyrene beads. Compared with the other phagocytic particles studied, the M. tuberculosis phagosome exhibits delayed clearance of major histocompatibility complex (MHC) class I molecules, relatively intense staining for MHC class II molecules and the endosomal marker transferrin receptor, and relatively weak staining for the lysosomal membrane glycoproteins, CD63, LAMP-1, and LAMP-2 and the lysosomal acid protease, cathepsin D. In contrast to M. tuberculosis, the L. pneumophila phagosome rapidly clears MHC class I molecules and excludes all endosomal-lysosomal markers studied. In contrast to both live M. tuberculosis and L. pneumophila phagosomes, phagosomes containing either polystyrene beads or heat-killed M. tuberculosis stain intensely for lysosomal membrane glycoproteins and cathepsin D. These findings suggest that (a) M. tuberculosis retards the maturation of its phagosome along the endosomal-lysosomal pathway and resides in a compartment with endosomal, as opposed to lysosomal, characteristics; and (b) the intraphagosomal pathway, i.e., the pathway followed by several intracellular parasites that inhibit phagosome-lysosome fusion, is heterogeneous.
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Fairn, Gregory D., Koji Ogata, Roberto J. Botelho, Philip D. Stahl, Richard A. Anderson, Pietro De Camilli, Tobias Meyer, Shoshana Wodak, and Sergio Grinstein. "An electrostatic switch displaces phosphatidylinositol phosphate kinases from the membrane during phagocytosis." Journal of Cell Biology 187, no. 5 (November 30, 2009): 701–14. http://dx.doi.org/10.1083/jcb.200909025.
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Plasmalemmal phosphatidylinositol (PI) 4,5-bisphosphate (PI4,5P2) synthesized by PI 4-phosphate (PI4P) 5-kinase (PIP5K) is key to the polymerization of actin that drives chemotaxis and phagocytosis. We investigated the means whereby PIP5K is targeted to the membrane and its fate during phagosome formation. Homology modeling revealed that all PIP5K isoforms feature a positively charged face. Together with the substrate-binding loop, this polycationic surface is proposed to constitute a coincidence detector that targets PIP5Ks to the plasmalemma. Accordingly, manipulation of the surface charge displaced PIP5Ks from the plasma membrane. During particle engulfment, PIP5Ks detached from forming phagosomes as the surface charge at these sites decreased. Precluding the change in surface charge caused the PIP5Ks to remain associated with the phagosomal cup. Chemically induced retention of PIP5K-γ prevented the disappearance of PI4,5P2 and aborted phagosome formation. We conclude that a bistable electrostatic switch mechanism regulates the association/dissociation of PIP5Ks from the membrane during phagocytosis and likely other processes.
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Wang, Y. L., and M. B. Goren. "Differential and sequential delivery of fluorescent lysosomal probes into phagosomes in mouse peritoneal macrophages." Journal of Cell Biology 104, no. 6 (June 1, 1987): 1749–54. http://dx.doi.org/10.1083/jcb.104.6.1749.
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It has previously been inferred that the fusion of a macrophage secondary lysosome with a phagosome delivers the entire lysosomal contents uniformly to the phagosome. We found, however, that different fluorescent lysosomal probes can enter phagosomes at remarkably different rates, even though they are initially sequestered together in the same organelles. Thus, sulforhodamine is almost exclusively delivered to yeast-containing phagosomes within 2 h of phagocytosis. But fluoresceinated, high molecular weight dextran accumulates in the same phagosomes only over a period of approximately 24 h. We postulate that the delivery of lysosomal contents may involve an intermittent and incremental process in which individual components can be selectively and sequentially transferred.
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Henry, Rebecca M., Adam D. Hoppe, Nikhil Joshi, and Joel A. Swanson. "The uniformity of phagosome maturation in macrophages." Journal of Cell Biology 164, no. 2 (January 12, 2004): 185–94. http://dx.doi.org/10.1083/jcb.200307080.
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Many studies of endocytosis and phagocytosis presume that organelles containing a single kind of internalized particle exhibit invariant patterns of protein and phospholipid association as they mature inside cells. To test this presumption, fluorescent protein chimeras were expressed in RAW 264.7 macrophages, and time-lapse ratiometric fluorescence microscopy was used to measure the maturation dynamics of individual phagosomes containing IgG-opsonized erythrocytes. Quantitative analysis revealed consistent patterns of association for YFP chimeras of β-actin, Rab5a, Rab7, and LAMP-1, and no association of YFP chimeras marking endoplasmic reticulum or Golgi. YFP-2xFYVE, recognizing phosphatidylinositol 3-phosphate (PI(3)P), showed two patterns of phagosome labeling. Some phagosomes increased labeling quickly after phagosome closure and then lost the label within 20 min, whereas others labeled more slowly and retained the label for several hours. The two patterns of PI(3)P on otherwise identical phagosomes indicated that organelle maturation does not necessarily follow a single path and that some features of phagosome maturation are integrated over the entire organelle.
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Artavanis-Tsakonas, Katerina, Pia V. Kasperkovitz, Eliseo Papa, Michael L. Cardenas, Nida S. Khan, Annemarthe G. Van der Veen, Hidde L. Ploegh, and Jatin M. Vyas. "The Tetraspanin CD82 Is Specifically Recruited to Fungal and Bacterial Phagosomes prior to Acidification." Infection and Immunity 79, no. 3 (December 13, 2010): 1098–106. http://dx.doi.org/10.1128/iai.01135-10.
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ABSTRACTCD82 is a member of the tetraspanin superfamily, whose physiological role is best described in the context of cancer metastasis. However, CD82 also associates with components of the class II major histocompatibility complex (MHC) antigen presentation pathway, including class II MHC molecules and the peptide-loading machinery, as well as CD63, another tetraspanin, suggesting a role for CD82 in antigen presentation. Here, we observe the dynamic rearrangement of CD82 after pathogen uptake by imaging CD82-mRFP1 expressed in primary living dendritic cells. CD82 showed rapid and specific recruitment toCryptococcus neoformans-containing phagosomes compared to polystyrene-containing phagosomes, similar to CD63. CD82 was also actively recruited to phagosomes containing other pathogenic fungi, includingCandida albicansandAspergillus fumigatus. Recruitment of CD82 to fungal phagosomes occurred independently of Toll-like receptor (TLR) signaling. Recruitment was not limited to fungi, as bacterial organisms, includingEscherichia coliandStaphylococcus aureus, also induced CD82 recruitment to the phagosome. CD82 intersected the endocytic pathway used by lipopolysaccharide (LPS), implicating CD82 in trafficking of small, pathogen-associated molecules. Despite its partial overlap with lysosomal compartments, CD82 recruitment toC. neoformans-containing phagosomes occurred independently of phagosome acidification. Kinetic analysis of fluorescence imaging revealed that CD82 and class II MHC simultaneously appear in the phagosome, indicating that the two proteins may be associated. Together, these data show that the CD82 tetraspanin is specifically recruited to pathogen-containing phagosomes prior to fusion with lysosomes.
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Kelley, Victoria A., and Jeffrey S. Schorey. "Mycobacterium's Arrest of Phagosome Maturation in Macrophages Requires Rab5 Activity and Accessibility to Iron." Molecular Biology of the Cell 14, no. 8 (August 2003): 3366–77. http://dx.doi.org/10.1091/mbc.e02-12-0780.
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Many mycobacteria are intramacrophage pathogens that reside within nonacidified phagosomes that fuse with early endosomes but do not mature to phagolysosomes. The mechanism by which mycobacteria block this maturation process remains elusive. To gain insight into whether fusion with early endosomes is required for mycobacteria-mediated inhibition of phagosome maturation, we investigated how perturbing the GTPase cycles of Rab5 and Rab7, GTPases that regulate early and late endosome fusion, respectively, would affect phagosome maturation. Retroviral transduction of the constitutively activated forms of both GTPases into primary murine macrophages had no effect on Mycobacterium avium retention in an early endosomal compartment. Interestingly, expression of dominant negative Rab5, Rab5(S34N), but not dominant negative Rab7, resulted in a significant increase in colocalization of M. avium with markers of late endosomes/lysosomes and increased mycobacterial killing. This colocalization was specific to mycobacteria since Rab5(S34N) expressing cells showed diminished trafficking of endocytic tracers to lysosomes. We further demonstrated that maturation of M. avium phagosomes was halted in Rab5(S34N) expressing macrophages supplemented with exogenous iron. These findings suggest that fusion with early endosomes is required for mycobacterial retention in early phagosomal compartments and that an inadequate supply of iron is one factor in mycobacteria's inability to prevent the normal maturation process in Rab5(S34N)-expressing macrophages.