DOCK2 is a Rac activator that regulates motility and polarity during neutrophil chemotaxis

Abstract

Neutrophils are highly motile leukocytes, and they play important roles in the innate immune response to invading pathogens. Neutrophil chemotaxis requires Rac activation, yet the Rac activators functioning downstream of chemoattractant receptors remain to be determined. We show that DOCK2, which is a mammalian homologue of Caenorhabditis elegans CED-5 and Drosophila melanogaster Myoblast City, regulates motility and polarity during neutrophil chemotaxis. Although DOCK2-deficient neutrophils moved toward the chemoattractant source, they exhibited abnormal migratory behavior with a marked reduction in translocation speed. In DOCK2-deficient neutrophils, chemoattractant-induced activation of both Rac1 and Rac2 were severely impaired, resulting in the loss of polarized accumulation of F-actin and phosphatidylinositol 3,4,5-triphosphate (PIP3) at the leading edge. On the other hand, we found that DOCK2 associates with PIP3 and translocates to the leading edge of chemotaxing neutrophils in a phosphatidylinositol 3-kinase (PI3K)–dependent manner. These results indicate that during neutrophil chemotaxis DOCK2 regulates leading edge formation through PIP3-dependent membrane translocation and Rac activation.

Parallel Phosphatidylinositol 3-Kinase (PI3K)-dependent and Src-dependent Pathways Lead to CXCL8-mediated Rac2 Activation and Chemotaxis

“…Studies in lymphocyte migration also indicated that Dock2 was fully functional to mediate T and B cell chemotaxis in vitro and in vivo in cells lacking PI3K (46). However, Kunisaki et al (22) reported that prolonged inhibition of PI3K with very high concentrations of LY294002 (400 M) did inhibit Dock2 recruitment in mouse neutrophils in response to a fMLP gradient. Moreover, neutrophils isolated from Dock2 knockout mice exhibited inhibition of Rac activation and chemotaxis in response to fMLP stimulation (22).…”

“…However, Kunisaki et al (22) reported that prolonged inhibition of PI3K with very high concentrations of LY294002 (400 M) did inhibit Dock2 recruitment in mouse neutrophils in response to a fMLP gradient. Moreover, neutrophils isolated from Dock2 knockout mice exhibited inhibition of Rac activation and chemotaxis in response to fMLP stimulation (22). In contrast, our Dock2 knockdown HL60 cells showed compromised Rac2 activation, but little inhibition of chemotaxis in response to a CXCL8 gradient in the microfluidic gradient chamber assay.…”

“…Dock2 is a leukocyte-specific Dock180 family member that plays a critical role in leukocyte polarization and migration by stimulating Rac activity (22). The binding of ELMO1 to Dock2, and often with another adaptor protein, CrkL, forms a multicomponent complex that binds and activates the inactive form of Rac (23,24).…”

Opening up on ELMO regulation

“…1,3 Recent studies in mice have uncovered important in vivo roles for DOCK180, DOCK5 and DOCK2 in myoblast fusion, cardiovascular development, osteoclast-mediated bone resorption and immune homeostasis. [7][8][9][10][11] Recent human data has also closely linked deficiencies in DOCK8 to hyper IgE syndromes that can be corrected by transplantation of healthy hematopoietic stem cells in afflicted patients. 12,13 Similarly, studies in cancer cells have highlighted that DOCK3, via its Rac GEF activity, promotes a mesenchymal type of movement 14 while DOCK10, via its Cdc42 GEF activity, supports amoeboid migration.…”

WD40-repeat proteins control the flow of Gβγ signaling for directional cell migration

“…5 This in turn recruits RhoGEFs such as DOCK2 and αPix, which activate Rac and Cdc42 to promote F-actin polymerization and cell polarization. 10,11 In recent years, much work has gone into identifying the mechanisms underlying spatially localized activation of PI3Ks. In Dictyostelium and neutrophils, amplification of the PIP3 signal is mediated by the reciprocal translocation of PI3K to the leading edge and phosphatases, such as phosphatase and tension homology (PTEN), to the lateral and trailing edge of cells.…”