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Complement- and IgG-mediated phagocytosis in human macrophages in calcium dependent and involves synoptotagmin IV
Linköping University, Department of Molecular and Clinical Medicine, Medical Microbiology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Molecular and Clinical Medicine, Medical Microbiology. Linköping University, Faculty of Health Sciences.
Molecular NeuroPathoBiology Laboratory, The Imperial Cancer Research Fund, London, UK.
Linköping University, Department of Molecular and Clinical Medicine, Medical Microbiology. Linköping University, Faculty of Health Sciences.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Calcium regulates membrane fusion events during phagolysosome formation in neutrophil granulocytes and vesicle fusion at the neural synapse. Calcium is also required for uptake of IgG-opsonised particles by human neutrophils. The role of calcium during macrophage phagocytosis is less clear. Here we show that phagocytosis of IgG- or serum-opsonised prey is strictly calcium dependent in human monocyte-derived macrophages. We also show the presence and involvement of synaptotagmin II and IV in human macrophages and in the murine macrophage cell line J774. Synaptotagmin IV displayed a granular distribution in resting human macrophages with some translocation to the plasma membrane. Synaptotagrnin IV did not eo localise with the nucleus, the endoplasmic reticulum or the Golgi apparatus. During phagocytosis of IgG- or serum-opsonised prey we observed a distinct, transient translocation of synaptotagmin IV to the phagosome. The kinnetics of synaptotagmin IV translocation was similar to Rab5. LAMP-1, a marker of late endosomes and mature phagolysosomes fused with the phagosome at a later time point. Our results show that complement- and IgG-mediated phagocytosis are dependent on calcium in human macrophages and indicate a role for synaptotagmin IV in the calcium dependent fusion of the phagosome with components of the early endocytic pathway.

National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-84708OAI: oai:DiVA.org:liu-84708DiVA: diva2:561235
Available from: 2012-10-17 Created: 2012-10-17 Last updated: 2012-10-17Bibliographically approved
In thesis
1. Regulation of phagocytosis and phagolysosome fusion in human leukocytes
Open this publication in new window or tab >>Regulation of phagocytosis and phagolysosome fusion in human leukocytes
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Professional phagocytes such as neutrophil granulocytes and macrophages are an esential part of the innate immune system. The neutrophils form the first line of defence against invading microorganisms and are important for rapid killing of the intruders. Macrophages arrive later at the site of infection, kill micoorganisms, degrade dead cells, present antigens and secrete substances that orchestrate the inflammatory response. Neutrophils and macrophages ingest and kill microorganisms in a process called phagocytosis, where calcium signalling has shown to be involved. Inside the cell the microorganism is enclosed in a phagosome, that sequentially fuses with various intracellular vesicles to form a phagolysosome in which the intruder is killed. Killing is achieved through the actions of lytic enzymes, nitrogen oxide (NO) and reactive oxygen metabolites (ROM). Studies on the regulation of phagocytosis are essential since many pathogens are able to survive by interfering with this process. In the first study we investigated intracellular signalling in human neutrophils following engagement of a phagocytic receptor, complement receptor 3 (CR3). For this, we used antibody-coated PANSORBINS® which bound to the ß-chain of CR3 without inducing phagocytosis. We found that these particles elicited an intracellular production of ROM which was dependent on the cytoskeleton and on phospholipase D. In the second study, we showed that the putative calcium-sensor synaptotagmin II is present in neutrophils and is involved in phagocytosis. Synaptotagmin II was found on the specific granules and translocated to the phagosome in a calcium-dependent manner during eR-mediated phagocytosis and to the plasma membrane after stimulation with the formylated peptide, N-formyl-methionyl-leucyl-phenylalanine. In the third study, we demonstrate the presence of synaptotagmin IV in human macrophages. Synaptotagmin IV translocated transiendy to macrophage phagosomes during eR- and FcγR-mediated phagocytosis. We also found that eR- and FcyR-mediated uptake was calcium dependent in these cells. In the fourth study, we show that lipophosphoglycan (LPG) from Leishmania donovani induced elevated levels of periphagosomal F-actin, inhibition of phagolysosome maturation and diminished production of ROM in neutrophils during eR-mediated phagocytosis. Together, our data show that generation of ROM occurs early during eR-mediated phagocytosis and could be involved in intracellular signalling, that synaptotagmins are present in professional phagocytes and could act as calcium sensors in phagosomal maturation and secretion, and that LPG can be used as a tool to investigate how actin can regulate phagosomal maturation in neutrophils.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2003. 64 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 818
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26661 (URN)11227 (Local ID)91-7373-509-4 (ISBN)11227 (Archive number)11227 (OAI)
Public defence
2003-11-06, Aulan, Hälsans Hus, Universitetet, Linköping, 09:00 (Swedish)
Opponent
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-10-17Bibliographically approved

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Johansson, CarinRasmusson, BirgittaStendahl, Olle

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