Divergent Signals and Cytoskeletal Assemblies Regulate Self-Organizing Polarity in Neutrophils

Abstract

Like neutrophilic leukocytes, differentiated HL-60 cells respond to chemoattractant by adopting a polarized morphology, with F-actin in a protruding pseudopod at the leading edge and contractile actin-myosin complexes at the back and sides. Experiments with pharmacological inhibitors, toxins, and mutant proteins show that this polarity depends on divergent, opposing "frontness" and "backness" signals generated by different receptor-activated trimeric G proteins. Frontness depends upon Gi-mediated production of 3'-phosphoinositol lipids (PI3Ps), the activated form of Rac, a small GTPase, and F-actin. G12 and G13 trigger backness signals, including activation of a second GTPase (Rho), a Rho-dependent kinase, and myosin II. Functional incompatibility causes the two resulting actin assemblies to aggregate into separate domains, making the leading edge more sensitive to attractant than the back. The latter effect explains both the neutrophil's ability to polarize in uniform concentrations of chemoattractant and its response to reversal of an attractant gradient by performing a U-turn.

Wiskott‐Aldrich syndrome protein (WASp) and N‐WASp are involved in the regulation of NK‐cell migration upon NKG2D activation

“…Rac1 is activated by NKG2D ligation, while RhoA activity decreased. This antagonistic activity has been previously described in fibroblast cells [33], and in cell types of the immune system, such as T cells [19] and neutrophils [34]. A balance between Rac and Rho activities is necessary for migratory polarity, with Rac regulating actin polymerization and leading edge formation while RhoA activity is responsible for rear-end organization.…”

Neuropeptide-stimulated cell migration in prostate cancer cells is mediated by RhoA kinase signaling and inhibited by neutral endopeptidase

“…RhoA is a monomeric GTPase that is required for migration in several cell types including neutrophils (Xu et al, 2003), monocytes (Worthylake et al, 2001) and fibroblasts (Sander et al, 1999). We have demonstrated that bombesin and ET-1 activate RhoA and that the RhoA effector, ROCK, is required for bombesinstimulated migration of PC cells.…”

“…Therefore, we considered that the Ga 13 subunit may couple bombesin and ET-1 receptors to RhoA in PC cells. Using a dominant-negative mutant form of Ga 13 to disrupt the interaction between GPCRs and endogenous Ga 13 (Sugimoto et al, 2003), we measured RhoA activation in PC-3 cells transiently transfected with either an empty vector (pCAGGS) or an expression vector encoding a peptide fragment corresponding to the C-terminal 57 amino acid (aa) of Ga 13 (Ga 13 aa 321-377) that exerts a dominant-negative effect on endogenous Ga 13 signaling (Yuan et al, 2001;Arai et al, 2003;Sugimoto et al, 2003;Xu et al, 2003). Transfected cells were incubated with vehicle (PBS), ET-1 (10 nM) or bombesin (10 nM) for 10 min.…”

Polarization and Movement of Keratocytes: A Multiscale Modelling Approach

“…Following the kinetics of Cdc42 activation during individual protrusions, Nalbant et al (2004) found a close correlation between extension and retraction of a lamellipod and the rise and fall of Cdc42 activation. In contrast, active Rho is predominantly found at trailing edge of moving cells (Xu et al, 2003), its levels being inversely correlated to the levels of active Rac in many types of cells (Caron, 2003). For this reason, it is believed that, in migrating cells, active Rho forms a gradient inverse to that of Rac and Cdc42 (Raftopoulou and Hall, 2004).…”