scholarly journals Transient assembly of F-actin by phagosomes delays phagosome fusion with lysosomes in cargo-overloaded macrophages

2009 ◽  
Vol 122 (16) ◽  
pp. 2935-2945 ◽  
Author(s):  
D. Liebl ◽  
G. Griffiths
Keyword(s):  
Phagosome Fusion

Different Requirements for Early and Late Phases of Azurophilic Granule–Phagosome Fusion

Traffic ◽  
2009 ◽  
Vol 10 (12) ◽  
pp. 1881-1893 ◽  
Author(s):  
Pontus Nordenfelt ◽  
Martin E. Winberg ◽  
Per Lönnbro ◽  
Birgitta Rasmusson ◽  
Hans Tapper
Keyword(s):  
Phagosome Fusion

scholarly journals Virulent Mycobacterium fortuitum Restricts NO Production by a Gamma Interferon-Activated J774 Cell Line and Phagosome-Lysosome Fusion

2002 ◽  
Vol 70 (10) ◽  
pp. 5628-5634 ◽  
Author(s):  
Tânia Regina Marques da Silva ◽  
Juliana Ribeiro de Freitas ◽  
Queilan Chagas Silva ◽  
Cláudio Pereira Figueira ◽  
Eliana Roxo ◽  
...  
Keyword(s):  
Gamma Interferon ◽  
No Production ◽  
Mycobacterium Fortuitum ◽  
Vitro Assay ◽  
J774 Cells ◽  
Nitrogen Radicals ◽  
Ifn Γ ◽  
Phagosome Fusion ◽  
J774 Cell Line

ABSTRACT The virulence of different isolates of Mycobacterium has been associated with two morphologically distinguishable colonial variants: opaque (SmOp) and transparent (SmTr). In this report we used an in vitro assay to compare macrophage (Mφ) responses to SmOp and SmTr Mycobacterium fortuitum variants, taking advantage of the fact that these variants were derived from the same isolate. Cells preactivated or not with gamma interferon (IFN-γ) were infected with SmOp or SmTr M. fortuitum. We showed that SmOp and SmTr induced different levels of nitric oxide (NO) production by IFN-γ-stimulated Mφ. Indeed, the amount of IFN-γ-induced NO production by J774 cells was 4.8 to 9.0 times higher by SmOp (23.1 to 37.7 μM) compared to SmTr infection (3.9 to 4.8 μM) (P = 0.0332), indicating that virulent SmTr bacilli restricted NO production. In addition, IFN-γ-induced NO production by Mφ was higher when correlated with reduction of only avirulent SmOp bacillus viability. SNAP (S-nitroso-N-acetyl-dl-penicillamine)-induced NO production did not modify SmTr viability, indicating its resistance to nitrogen radicals. Electron microscopy studies were performed to evaluate the capacity of phagosomes to fuse with lysosomes labeled with bovine serum albumin-colloidal gold particles. By 24 h postinfection, 69% more phagosome-containing SmOp variant had fused with lysosomes compared to the SmTr-induced phagosomes. In conclusion, these data indicate that virulent SmTr bacilli may escape host defense by restricting IFN-γ-induced NO production, resisting nitrogen toxic radicals, and limiting phagosome fusion with lysosomes.

scholarly journals Virulent Strains of Helicobacter pylori Demonstrate Delayed Phagocytosis and Stimulate Homotypic Phagosome Fusion in Macrophages

2000 ◽  
Vol 191 (1) ◽  
pp. 115-128 ◽  
Author(s):  
Lee-Ann H. Allen ◽  
Larry S. Schlesinger ◽  
Byoung Kang
Keyword(s):  
Helicobacter Pylori ◽  
Mononuclear Phagocytes ◽  
Gastric Epithelium ◽  
Type I ◽  
Causative Role ◽  
Type Ii ◽  
Duodenal Ulcers ◽  
H Pylori ◽  
Phagosome Fusion ◽  
Bacterial Protein Synthesis

Helicobacter pylori colonizes the gastric epithelium of ∼50% of the world's population and plays a causative role in the development of gastric and duodenal ulcers. H. pylori is phagocytosed by mononuclear phagocytes, but the internalized bacteria are not killed and the reasons for this host defense defect are unclear. We now show using immunofluorescence and electron microscopy that H. pylori employs an unusual mechanism to avoid phagocytic killing: delayed entry followed by homotypic phagosome fusion. Unopsonized type I H. pylori bound readily to macrophages and were internalized into actin-rich phagosomes after a lag of ∼4 min. Although early (10 min) phagosomes contained single bacilli, H. pylori phagosomes coalesced over the next ∼2 h. The resulting “megasomes” contained multiple viable organisms and were stable for 24 h. Phagosome–phagosome fusion required bacterial protein synthesis and intact host microtubules, and both chloramphenicol and nocodazole increased killing of intracellular H. pylori. Type II strains of H. pylori are less virulent and lack the cag pathogenicity island. In contrast to type I strains, type II H. pylori were rapidly ingested and killed by macrophages and did not stimulate megasome formation. Collectively, our data suggest that megasome formation is an important feature of H. pylori pathogenesis.

scholarly journals Size-dependent mechanism of cargo sorting during lysosome-phagosome fusion is controlled by Rab34

2012 ◽  
Vol 109 (50) ◽  
pp. 20485-20490 ◽  
Author(s):  
B. Kasmapour ◽  
A. Gronow ◽  
C. K. E. Bleck ◽  
W. Hong ◽  
M. G. Gutierrez
Keyword(s):  
Size Dependent ◽  
Phagosome Fusion ◽  
Dependent Mechanism ◽  
Cargo Sorting

scholarly journals FORMATION OF LIPOFUSCIN-LIKE AUTOFLUORESCENT GRANULES IN THE RETINAL PIGMENT EPITHELIUM REQUIRES LYSOSOME DYSFUNCTION

2021 ◽  
Author(s):  
Cristina Escrevente ◽  
Ana S. Falcão ◽  
Michael J. Hall ◽  
Mafalda Lopes-da-Silva ◽  
Pedro Antas ◽  
...  
Keyword(s):  
Retinal Pigment Epithelium ◽  
Cathepsin D ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Single Pulse ◽  
Photoreceptor Outer Segments ◽  
Lysosomal Ph ◽  
Electron Microscopical ◽  
Phagosome Fusion

AbstractPurposeWe aim to characterize the pathways required for autofluorescent granule (AFG) formation by retinal pigment epithelium (RPE) cells using cultured monolayers.MethodsWe fed RPE monolayers in culture with a single pulse of photoreceptor outer segments (POS). After 24h the cells started accumulating AFGs similar to lipofuscin in vivo. Using this model, we used a variety of light and electron microscopical techniques, flow cytometry and western blot to analyze the formation of AFGs. We also generated a mutant RPE line lacking Cathepsin D by gene editing.ResultsAFGs appear to derive from incompletely digested POS-containing phagosomes and are surrounded after 72h by a single membrane containing lysosome markers. We show by various methods that lysosome-phagosome fusion is required for AFG formation but that impairment of lysosomal pH or catalytic activity, particularly Cathepsin D activity, enhances AF accumulation.ConclusionsWe conclude that lysosomal dysfunction results in incomplete POS degradation and AFG accumulation.

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