Rac2 is critical for neutrophil primary granule exocytosis

Abstract

Neutrophil degranulation is important in many inflammatory disorders, although the intracellular mechanisms underlying this process remain poorly understood. The Rho GTPase, Rac2, has been implicated in control of degranulation in earlier studies. We hypothesized that Rac2 selectively regulates neutrophil primary granule release. Using bone marrow and peritoneal exudate neutrophils from rac2(-/-) mice in comparison with similar cells from wild-type C57Bl/6 mice, we found that primary granule myeloperoxidase and elastase release was absent in Rac2(-/-) neutrophils in response to chemoattractant stimulation, cytochalasin B/f-Met-Leu-Phe (CB/fMLP), and CB/leukotriene B4. Rac2(-/-) neutrophils also failed to exhibit mobilization of the primary granule marker CD63+ during CB/fMLP stimulation as determined by confocal microscopy. Priming of Rac2(-/-) neutrophils with tumor necrosis factor (TNF) or by peritoneal elicitation did not rescue the defect in primary granule release. However, phosphorylation of p38 mitogen-activated protein (MAP) kinase in Rac2(-/-) neutrophils was evident in response to CB/fMLP and/or TNF. Primary granule density and morphology were normal in Rac2(-/-) neutrophils. Secondary specific and tertiary granule release, measured by lactoferrin immunoassay and zymography, was normal in response to CB/fMLP and adhesion to fibronectin. These findings suggest an obligatory role for Rac2 in regulation of primary granule release by neutrophils.

RhoH/TTF Negatively Regulates Leukotriene Production in Neutrophils

“…Rac2, another member of the Rho family, was found to be essential for primary (azurophilic), but not secondary and tertiary granule release of neutrophils (36). In addition, Rac2 was found to be crucial for superoxide production and chemotaxis in neutrophils (34).…”

Selection for a CEACAM Receptor-Specific Binding Phenotype during Neisseria gonorrhoeae Infection of the Human Genital Tract

“…The infections were stopped by centrifugation at 2,400 ϫ g for 3 min at RT. The cell pellets were fixed in 1% PFA and stained with 1.25 g of PE-conjugated rat anti-mouse CEACAM in a total volume of 200 l. Elastase and lactoferrin release assays were performed essentially as described previously (55). Briefly, 10 6 PMNs were exposed to agonists in a total volume of 500 l and then incubated for 1 h at 37°C.…”

P2Y2 Receptor-mediated Lymphotoxin-α Secretion Regulates Intercellular Cell Adhesion Molecule-1 Expression in Vascular Smooth Muscle Cells

“…Small GTPases Rac1, Rac2, and Cdc42 have been implicated in granule exocytosis in mast cells and neutrophils through modulation of the actin cytoskeleton (43,44) and have been associated with cytokine secretion in other cells, such as IL-8 from polarized epithelial cells (45). However, no specific role for Rho GTPases in cytokine secretion from SMC has yet been established.…”