Unrestrained G Alpha(I2) Signaling Disrupts Neutrophil Trafficking, Aging, And Clearance

Neutrophil trafficking, homeostatic and pathogen elicited, depends upon chemoattractant receptors triggering heterotrimeric G-protein G alpha(i)beta gamma signaling, whose magnitude and kinetics are governed by RGS protein/G alpha(i) interactions. RGS proteins typically limit G alpha(i) signaling by reducing the duration that G alpha(i) subunits remain GTP bound and able to activate downstream effectors. Yet how in totality RGS proteins shape neutrophil chemoattractant receptor activated responses remains unclear. Here, we show that C57Bl/6 mouse neutrophils containing a genomic knock-in of a mutation that disables all RGS protein-G alpha(i2) interactions (G184S) cannot properly balance chemoattractant receptor signaling, nor appropriately respond to inflammatory insults. Mutant neutrophils accumulate in mouse bone marrow, spleen, lung, and liver; despite neutropenia and an intrinsic inability to properly mobilize from the bone marrow. In vitro they rapidly adhere to ICAM-1 coated plates, but in vivo they poorly adhere to blood vessel endothelium. Those few neutrophils that cross blood vessels and enter tissues migrate haphazardly. Following Concanavalin-A administration fragmented G184S neutrophils accumulate in liver sinusoids leading to thrombo-inflammation and perivasculitis. Thus, neutrophil G alpha(i2)/RGS protein interactions both limit and facilitate G alpha(i2) signaling thereby promoting normal neutrophil trafficking, aging, and clearance.