Unrestrained Gαi2 Signaling Disrupts Neutrophil Trafficking, Aging, and Clearance

Abstract

Neutrophil trafficking, homeostatic and pathogen elicited, depends upon chemoattractant receptors triggering heterotrimeric G-protein Gα_iβγ signaling, whose magnitude and kinetics are governed by RGS protein/Gα_i interactions. RGS proteins typically limit Gα_i signaling by reducing the duration that Gα_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-Gα_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 Gα_i2/RGS protein interactions both limit and facilitate Gα_i2 signaling thereby promoting normal neutrophil trafficking, aging, and clearance.

Keywords: G-protein; RGS protein; chemoattractants; chemotaxis; intravital; neutrophil; trafficking.