Frontline Science: TNF-? and GM-CSF1 priming augments the role of SOS1/2 in driving activation of Ras, PI3K-?, and neutrophil proinflammatory responses.

ABSTRACT: Circulating neutrophils are, by necessity, quiescent and relatively unresponsive to acute stimuli. In regions of inflammation, mediators can prime neutrophils to react to acute stimuli with stronger proinflammatory, pathogen-killing responses. In neutrophils G protein-coupled receptor (GPCR)-driven proinflammatory responses, such as reactive oxygen species (ROS) formation and accumulation of the key intracellular messenger phosphatidylinositol (3,4,5)-trisphosphate (PIP₃ ), are highly dependent on PI3K-?, a Ras-GTP, and G?? coincidence detector. In unprimed cells, the major GPCR-triggered activator of Ras is the Ras guanine nucleotide exchange factor (GEF), Ras guanine nucleotide releasing protein 4 (RasGRP4). Although priming is known to increase GPCR-PIP₃ signaling, the mechanisms underlying this augmentation remain unclear. We used genetically modified mice to address the role of the 2 RasGEFs, RasGRP4 and son of sevenless (SOS)1/2, in neutrophil priming. We found that following GM-CSF/TNF? priming, RasGRP4 had only a minor role in the enhanced responses. In contrast, SOS1/2 acquired a substantial role in ROS formation, PIP₃ accumulation, and ERK activation in primed cells. These results suggest that SOS1/2 signaling plays a key role in determining the responsiveness of neutrophils in regions of inflammation.

SUBMITTER: Suire S 

PROVIDER: S-EPMC6977543 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature