Rho GTPase CDC42 regulates directionality and random movement via distinct MAPK pathways in neutrophils

Abstract

Neutrophil transmigration into tissue is a multiple-step process that results from a coordinated rearrangement of the cytoskeleton and adhesion complexes. Assembly and disassembly of actin and adhesion structures dictate motility behavior, while polarity and gradient sensing provide directionality to the cell movement. Here, using mice deficient in the CDC42 regulator CDC42 GTPase-activating protein (CDC42GAP), we demonstrate that CDC42 activity separately regulates neutrophil motility and directionality. CDC42GAP ؊/؊ neutrophils showed increased motility, while directed migration was defective. Podosome-like structures present at the leading edge in wild-type neutrophils were significantly reduced in CDC42GAP ؊/؊ cells. CDC42GAP ؊/؊ neutrophils also showed increased lateral and tail filopodia-like formation, and excess membrane protrusions. We further suggest that CDC42GAP-mediated extracellular signal-regulated kinase (ERK) activity regulates motility associated with podosome-like structures at the cell leading edge, while CDC42GAP-induced p38 MAPK phosphorylation regulates directed migration by antagonizing filopodia assembly. Overall, this study reveals that CDC42 activity regulates both motility and directionality in neutrophils, but via distinct mitogen-activated protein kinase ( IntroductionNeutrophils are critical in the inflammatory process. The recruitment of neutrophils to sites of inflammation requires a series of highly regulated adhesive and chemotactic events. These cellular activities result from the activation of signals from various receptors, including adhesion molecules such as selectins and integrins, and chemokine receptors. Failure to regulate any of these events may lead to abnormal innate immune responses, including immunodeficiency or aberrant inflammatory reactions. Although the process of neutrophil extravasation has been well studied, the intracellular molecular events that ultimately regulate these processes still remain to be understood in detail, particularly in physiologic settings.Cell migration is a multiple-step process that results from a coordinated rearrangement of the cytoskeleton and adhesion complexes. 1 Upon chemoattractant stimulation, cells polarize and form lamellipodia containing F-actin at the leading edge oriented toward the source of stimulation and a contractile uropod. The lamellipodia are stabilized to the substratum by the assembly of adhesion complexes, which mature into focal adhesions. These complexes serve as traction forces necessary for the translocation of the cell body. Completion of cell migration requires actin disruption to allow both adhesion complex turnover at the leading edge and retraction of the tail. Thus, the cytoskeleton, through assembly and disassembly of F-actin and adhesion structures, is believed to dictate motility behavior, while polarity and gradient sensing give direction to the cell movement.The key integrators of signals emanating from chemokine receptors and integrin molecules that coordinate these processes are members of the...

Coordination of IL-7 receptor and T-cell receptor signaling by cell-division cycle 42 in T-cell homeostasis

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The role of CR3 (CD11b/CD18) and CR4 (CD11c/CD18) in complement-mediated phagocytosis and podosome formation by human phagocytes

“…Whether human neutrophils have podosomes is still debated. Neutrophils isolated from mice and pretreated with fMLP formed podosome-like structures, containing and actin core and a vinculin ring, on fibrinogen coated slips (Szczur, 2006). In this study we detected the formation of actin rich dots evenly spread on the contact surface of human neutrophils adhered to fibrinogen.…”

Coordinated RhoA signaling at the leading edge and uropod is required for T cell transendothelial migration

“…For example, inhibitors of the closely related Rho isoforms RhoA, RhoB, and RhoC and/or their downstream targets, ROCKs, have been reported to reduce leukocyte adhesion by inhibiting activation of the integrin LFA-1 (Giagulli et al, 2004) and to reduce migration and chemotaxis by inhibiting contraction of the uropod at the rear (Alblas et al, 2001;Vicente-Manzanares et al, 2002;Smith et al, 2003;Worthylake and Burridge, 2003). In knockout mice, Cdc42, Rac1, and Rac2 contribute to the recruitment of leukocytes to inflamed sites (Roberts et al, 1999;Yamauchi et al, 2004;Szczur et al, 2006;Filippi et al, 2007), although their exact role in the individual steps of TEM is not yet defined. Studies using leukocytes from knockout mice have identified roles for Cdc42 and the Rac guanine nucleotide exchange factor (GEF) Tiam1 (Szczur et al, 2006;Gérard et al, 2009) in TEM.…”