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Different Requirements for Early and Late Phases of Azurophilic Granule–Phagosome Fusion
Author(s) -
Nordenfelt Pontus,
Winberg Martin E.,
Lönnbro Per,
Rasmusson Birgitta,
Tapper Hans
Publication year - 2009
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2009.00986.x
Subject(s) - phagosome , azurophilic granule , biology , microbiology and biotechnology , granule (geology) , secretion , phagocytosis , exocytosis , biochemistry , immunology , inflammation , myeloperoxidase , paleontology
Phagocytosis and killing of microorganisms are complex processes that involve tightly regulated membrane traffic events. Because many signaling molecules associate with membrane rafts and because these structures can be found on azurophilic granules, we decided to investigate raft recruitment and the signaling requirements for azurophilic granule secretion during phagosome maturation. At the site of phagocytosis of immunoglobulin G‐opsonized prey in human neutrophils, we found that early secretion of azurophilic granules was both raft‐ and calcium‐dependent. Subsequently, rafts at the phagocytic site were internalized with the prey. At the fully formed phagosome, the fusion of azurophilic granules was no longer dependent on rafts or calcium. These findings were found to be true also when using Streptococcus pyogenes bacteria as prey, and depletion of calcium affected the kinetics of bacterial intracellular survival. These findings suggest that the mechanisms for delivery of azurophilic content to nascent and sealed phagosomes, respectively, differ in their dependence on calcium and membrane rafts.