Rac and Cdc42 play distinct roles in regulating PI(3,4,5)P3 and polarity during neutrophil chemotaxis

Abstract

Neutrophils exposed to chemoattractants polarize and accumulate polymerized actin at the leading edge. In neutrophil-like HL-60 cells, this asymmetry depends on a positive feedback loop in which accumulation of a membrane lipid, phosphatidylinositol (PI) 3,4,5-trisphosphate (PI[3,4,5]P3), leads to activation of Rac and/or Cdc42, and vice versa. We now report that Rac and Cdc42 play distinct roles in regulating this asymmetry. In the absence of chemoattractant, expression of constitutively active Rac stimulates accumulation at the plasma membrane of actin polymers and of GFP-tagged fluorescent probes for PI(3,4,5)P3 (the PH domain of Akt) and activated Rac (the p21-binding domain of p21-activated kinase). Dominant negative Rac inhibits chemoattractant-stimulated accumulation of actin polymers and membrane translocation of both fluorescent probes and attainment of morphologic polarity. Expression of constitutively active Cdc42 or of two different protein inhibitors of Cdc42 fails to mimic effects of the Rac mutants on actin or PI(3,4,5)P3. Instead, Cdc42 inhibitors prevent cells from maintaining a persistent leading edge and frequently induce formation of multiple, short lived leading edges containing actin polymers, PI(3,4,5)P3, and activated Rac. We conclude that Rac plays a dominant role in the PI(3,4,5)P3-dependent positive feedback loop required for forming a leading edge, whereas location and stability of the leading edge are regulated by Cdc42.

Drosophila Hemopoiesis and Cellular Immunity

“…A similar defect has been described in human monocytes (44). In monocytes, the small GTPase Cdc42 is required to recognize and respond to chemotactic signals (45)(46)(47). When Cdc42 signaling was blocked in embryonic plasmatocytes, they were still able to migrate to the wound, but the motility of the plasmatocytes was affected.…”

Extracellular Matrix of Glioblastoma Inhibits Polarization and Transmigration of T Cells: The Role of Tenascin-C in Immune Suppression

“…It is likely that PKA and PI3K are important components of the migration machine but are controlled separately by other integrin signals. Migration-controlling kinases recruited to the leading front of migrating lymphocytes can facilitate actin polymerization (17,18,37). In agreement with these findings, the confocal images showed that phosphorylated ERK partly colocalized with actin on the leading edge of Jurkat cells.…”

“…Migrating lymphocytes are polarized, in which migrationcontrolling kinases, including PI3K and AKT, are recruited to the leading front of migrating cells and may facilitate actin polymerization (17,18). Preventing the adhesion of cells blocks the mitogeninduced activation of the canonical MAPK, which is important for T cell adhesion and migration (19)(20)(21).…”

R-Ras Controls Membrane Protrusion and Cell Migration through the Spatial Regulation of Rac and Rho

“…This suggests that it is through PI3-Kinase that R-Ras can regulate Rho activity to modulate cell migration. So far, PI3-Kinase has been shown to predominantly activate Rac or Cdc42 (Wang et al, 2002;Weiner et al, 2002;Srinivasan et al, 2003). PI3-Kinase can activate several molecules through specialized signaling motifs, including Dbl-homology (DH) domains (reviewed in Zheng, 2001).…”