Unrestrained Gαi2 Signaling Disrupts Normal Neutrophil Trafficking, Aging, and Clearance

Abstract

Neutrophil trafficking, homeostatic and pathogen elicited, depends upon chemoattractant receptor triggered heterotrimeric G-protein Gi{beta}{gamma} signaling, whose magnitude and kinetics are governed by RGS protein/Gi interactions. Yet how in totality RGS proteins shape neutrophil chemoattractant receptor activated responses remains unclear. Here, we show that C57Bl/6 neutrophils with genomic knock-in of a mutation that disables all RGS protein-Gi2 interactions (G184S) cannot properly balance chemoattractant receptor signaling, nor appropriately respond to inflammatory insults. Mutant neutrophils accumulate in bone marrow, spleen, lung, and liver; despite neutropenia and an intrinsic inability to properly mobilize from bone marrow. In vitro they rapidly adhere to ICAM-1 coated plates, but poorly adhere to blood vessel endotheliums in vivo. Those few neutrophils that cross endotheliums migrate haphazardly. Following Concanavalin-A administration fragmented G184S neutrophils accumulate in liver sinusoids leading to thrombo-inflammation and perivasculitis. Thus, neutrophil Gi2/RGS protein interactions limit and facilitate Gi2 signaling allowing normal neutrophil trafficking, aging, and clearance.