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Rab27a and Rab27b Regulate Neutrophil Azurophilic Granule Exocytosis and NADPH oxidase Activity by Independent Mechanisms
Author(s) -
Johnson Jennifer L.,
Brzezinska Agnieszka A.,
Tolmachova Tanya,
Munafo Daniela B.,
Ellis Beverly A.,
Seabra Miguel C.,
Hong Hong,
Catz Sergio D.
Publication year - 2010
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.1600-0854.2009.01029.x
Subject(s) - exocytosis , azurophilic granule , biology , nadph oxidase , degranulation , microbiology and biotechnology , granule (geology) , reactive oxygen species , secretion , immunology , biochemistry , inflammation , myeloperoxidase , receptor , paleontology
Neutrophils rely on exocytosis to mobilize receptors and adhesion molecules and to release microbicidal factors. This process should be strictly regulated because uncontrolled release of toxic proteins would be injurious to the host. In vivo studies showed that the small GTPase Rab27a regulates azurophilic granule exocytosis. Using mouse neutrophils deficient in Rab27a ( Rab27a ash/ash ), Rab27b [ Rab27b knockout (KO)] or both [ Rab27a/b double KO (DoKo)], we investigated the role of the Rab27 isoforms in neutrophils. We found that both Rab27a and Rab27b deficiencies impaired azurophilic granule exocytosis. Rab27a ash/ash neutrophils showed upregulation of Rab27b expression which did not compensate for the secretory defects observed in Rab27a‐deficient cells, suggesting that Rab27 isoforms play independent roles in neutrophil exocytosis. Total internal reflection fluorescence microscopy analysis showed that Rab27a ash/ash and Rab27b KO neutrophils have a decreased number of azurophilic granules near the plasma membrane. The effect was exacerbated in Rab27a/b DoKo neutrophils. Rab27 ‐deficient neutrophils showed impaired activation of the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase at the plasma membrane although intraphagosomal reactive oxygen species (ROS) production was not affected. Exocytosis of secretory vesicles in Rab27‐deficient neutrophils was functional, suggesting that Rab27 GTPases selectively control the exocytosis of neutrophil granules.