Fig. 4. Some targets for Rho linked to actin reorganization. Rho via ROCK can stimulate myosin light chain (MLC) phosphorylation through inactivation of MLC phosphatase and also probably through direct phosphorylation of MLC. ROCK together with Dia induces stress fibre formation. Dia is dependent on Src for its contribution to stress fibres and has also been reported to interact with IRSp53, which can mediate Arp2/3-complex-induced actin polymerization (see Fig. 3). ROCK can also phosphorylate a number of other target proteins that may contribute to actin reorganization, including LIMK, which inhibits cofilin-mediated actin depolymerization. Rho can also regulate the activity of PI (4)P 5-kinases (PI 5-K) to induce an increase in PtdIns(4,5)P₂ levels and thereby affect capping proteins, as indicated for Rac in Fig. 3.