Rac-specific nucleotide exchange factor Asef mediates lung endothelial barrier protection by hepatocyte growth factor

This study tested the role of Asef in the HGF-induced activation of endothelial cell (EC) cytoskeletal dynamics and vascular endothelial barrier protective response in vitro and in two-hit animal model of ALI. HGF induced membrane translocation of Asef and stimulated its Rac-specific nucleotide exchange activity. Expression of constitutively activated Asef mutant mimicked effects of HGF on enhancement of peripheral actin cytoskeleton. By contrast, siRNA-induced Asef knockdown or expression of dominant negative Asef attenuated HGF-induced Rac activation which was evaluated using Rac-GTP pulldown assay and FRET analysis with Rac biosensor. Asef knockdown attenuated HGF-induced peripheral accumulation of actin polymerization activator cortactin. Asef knockdown compromised HGF protection against thrombin-induced RhoA GTPase activation, Rho-dependent cytoskeleton remodeling and EC permeability. Intravenous HGF injection attenuated lung inflammation and vascular leak in the two-hit model of ALI caused by excessive mechanical ventilation and injection of thrombin signaling peptide TRAP6. This effect was lost in Asef-/- mice. This study shows for the first time the critical role of Asef in HGF-mediated protection against endothelial hyperpermeability and lung injury.Funding: HL089257, HL107920.
Source: European Respiratory Journal - Category: Respiratory Medicine Authors: Tags: 3.3 Mechanisms of Lung Injury and Repair Source Type: research