Fig. 3. Signaling pathways for cell migration mediated by Erk. Growth factors, such as PDGF, EGF and FGF, activate Erk through the Ras-Raf-MEK1/2-Erk signaling module. Activated Erk regulates membrane protrusions and focal adhesion turnover via phosphorylating MLCK and promotes focal adhesion disassembly via phosphorylating and activating calpain. Phosphorylation of FAK and paxillin by Erk may regulate focal adhesion dynamics, probably by influencing the paxillin-FAK interaction. Orange lines represent speculative pathways.