Figure 2.

Intracellular signaling pathways activated by guidance cues. Members of the Rho subfamily of small GTPases, which includes Rac, Rho, and Cdc42, have been well established to mediate the chemotropic responses of growth cones through controlling cytoskeletal dynamics (Hall and Lalli, 2010). Rac and Rho activate LIM kinase (LIMK) through PAK and ROCK, and LIMK regulates the cofilin-mediated actin depolymerization. The mTOR pathway is also activated by several cue-induced responses through the PI3K and/or MAPKs pathways. mTOR regulates mRNA translation through phosphorylation of downstream targets (Brown et al., 1995; Brunn et al., 1997; Burnett et al., 1998). Cue-induced local mRNA translation modulates other guidance pathways through the spatiotemporal up-regulation of signaling components such as Rho A and cofilin (Wu et al., 2005; Piper et al., 2006). Arrows do not necessarily indicate direct interactions. Cue, guidance cue; Receptor, guidance cue receptor.