DOCK2 and DOCK5 Act Additively in Neutrophils To Regulate Chemotaxis, Superoxide Production, and Extracellular Trap Formation

Abstract

Neutrophils are highly motile leukocytes that play important roles in the innate immune response to invading pathogens. Neutrophils rapidly migrate to the site of infections and kill pathogens by producing reactive oxygen species (ROS). Neutrophil chemotaxis and ROS production require activation of Rac small GTPase. DOCK2, an atypical guanine nucleotide exchange factor (GEF), is one of the major regulators of Rac in neutrophils. However, because DOCK2 deficiency does not completely abolish fMLF-induced Rac activation, other Rac GEFs may also participate in this process. In this study, we show that DOCK5 acts with DOCK2 in neutrophils to regulate multiple cellular functions. We found that fMLF- and PMA-induced Rac activation were almost completely lost in mouse neutrophils lacking both DOCK2 and DOCK5. Although β2 integrin–mediated adhesion occurred normally even in the absence of DOCK2 and DOCK5, mouse neutrophils lacking DOCK2 and DOCK5 exhibited a severe defect in chemotaxis and ROS production. Similar results were obtained when human neutrophils were treated with CPYPP, a small-molecule inhibitor of these DOCK GEFs. Additionally, we found that DOCK2 and DOCK5 regulate formation of neutrophil extracellular traps (NETs). Because NETs are involved in vascular inflammation and autoimmune responses, DOCK2 and DOCK5 would be a therapeutic target for controlling NET-mediated inflammatory disorders.

Rac GTPase Activating Protein ARHGAP25 Regulates Leukocyte Transendothelial Migration in Mice

“…6). Deficiency in various RacGEFs was reported to result in decreased amount of GTP-bound Rac and a decrease in phagocyte migration (16,37,38) (i.e., changes opposite to our findings in animals lacking ARHGAP25). We thus ascribe the alteration of leukocyte trafficking in ARHGAP25-deficient animals to cytoskeletal reorganization due to elevation of RacGTP concentration.…”

The focal adhesion-associated proteins DOCK5 and GIT2 comprise a rheostat in control of epithelial invasion

“…13 In addition, DOCK5 promotes myoblast fusion, mast cell degranulation, and neutrophil chemotaxis. 14, 15 Here we identify a role for DOCK5 in epithelial cell motility and invasion. Mechanistically, we show that the FA-associated protein GIT2 suppresses interaction of Crk with DOCK5, thus preventing activation of a Crk-p130Cas-DOCK5 signaling cascade required for plasma membrane protrusion and FA turnover.…”

Rac‐GTPases and Rac‐GEFs in neutrophil adhesion, migration and recruitment

“…Murine deficiency in the DOCK‐type Rac‐GEF DOCK2 causes profound defects in neutrophil chemoattractant signalling, thus impairing actin polarization, leading edge formation and migration speed, although these cells retain β2‐integrin‐mediated adhesion and directional sensing . Although deficiency in the DOCK2‐homologue DOCK5 has little effect on its own, combined deficiency exacerbates the migration defect caused by the absence of DOCK2 . The importance of these DOCK GEFs for neutrophil recruitment in vivo remains to be tested.…”

“…The importance of these DOCK GEFs for neutrophil recruitment in vivo remains to be tested. Interestingly, treatment of isolated neutrophils with the small‐molecule DOCK inhibitor CPYPP has similar effects on migration as the mouse knockout . The efficacy of this inhibitor is currently rather limited (a general problem with Rac‐GEF inhibitors), but it certainly merits further development.…”