Rac GTPase Activating Protein ARHGAP25 Regulates Leukocyte Transendothelial Migration in Mice

Abstract

ARHGAP25 is a Rac-specific GTPase-activating protein that is expressed primarily in hematopoietic cells. The involvement of ARHGAP25 in regulating the recruitment of leukocytes to inflammatory sites was investigated in genetically modified mice. Using intravital microscopy, we show that Arhgap25 deficiency affects all steps of leukocyte recruitment with a predominant enhancement of transendothelial migration of neutrophilic granulocytes. Increased transmigration of Arhgap25-deficient leukocytes is demonstrated in inflamed cremaster muscle venules, in a peritonitis model, and in an in vitro chemotaxis assay. Using bone marrow chimeric mice lacking ARHGAP25 in the hematopoietic compartment, we show that enhanced migration in the absence of ARHGAP25 is due to defective leukocyte function. In search for potential mechanisms of ARHGAP25-regulated migration of neutrophils, we detected an increase in the amount of active, GTP-bound Rac and Rac-dependent cytoskeletal changes in the absence of ARHGAP25, suggesting a critical role of ARHGAP25 in counterbalancing the Rac-activating effect of nucleotide exchange factors. Taken together, using Arhgap25-deficient mice, we identified ARHGAP25 as a relevant negative regulator of leukocyte transendothelial migration.

Role of negative regulation of immune signaling pathways in neutrophil function

“…Increased trafficking of RhoA/B deficient PMN was also observed in vivo following sterile inflammation induced by thioglycolate [38]. ARHGAP25 is a Rac-specific GAP expressed by PMN, and similar to what was found for RhoA, it has been reported that loss of ARHGAP25 expression leads to a pro-inflammatory phenotype with increased PMN Rac activation and elevated transmigration into inflamed tissues [39]. Bcr and Abr are GAPs that contain binding sites for a number of signal transduction proteins including tyrosine kinases, serine/threonine kinases and scaffolding proteins.…”

“…GTPase-activating proteins (GAPS), have been shown to suppress PMN functions such as phagocytosis, ROS production, and degranulation by inhibiting the activation of Rac and F-actin polymerization [39, 40, 56, 57, 61]. Vav-1 and TIPE-2 also inhibits Rac activation and therefore, suppress ROS production [59, 60].…”

“…38 ARHGAP25 is a Racspecific GAP expressed by PMN, and similar to what was found for RhoA, it has been reported that loss of ARHGAP25 expression leads to a pro-inflammatory phenotype with increased PMN Rac activation and elevated transmigration into inflamed tissues. 39 Bcr and Abr are GAPs that contain binding sites for a number of signal transduction proteins including tyrosine kinases, serine/threonine kinases and scaffolding proteins. Interestingly, increased PMN accumulation in the lungs of double mutant Abr −/− Bcr −/− mice following LPS injection has been reported, 40 suggesting that Bcr and Abr are PMN cell signaling mediators that down regulate PMN trafficking responses.…”

“…2). 39,40,56,57,61 Vav-1 and TIPE-2 also inhibits Rac activation and therefore, suppress ROS production. 59,60 Phosphatases such as PTP1B and PTEN negatively regulates phagocytosis.…”

Regulation of Cell Morphology and Migration by a Rho GTPase Activating Protein FilGAP

“…Depletion of FilGAP in normal epithelial MDCK (Madin Darby canine kidney) cells also increased the migration speed and cell scattering induced by Hepatocyte growth factor (Nakahara et al, 2015). ARHGAP25 is expressed primarily in hematopoietic cells and regulates leukocyte migration (Csépányi-Kömi et al, 2016). ARHGAP22 suppresses EGF-induced lamellae formation and cell spreading on fibronectin (Mori et al, 2014) and regulates cell migration downstream of Akt signaling in fibroblasts (Rowland et al, 2011).…”