Figure 3.

FAK regulation during myoblasts differentiation. The expression of FAK and its phosphorylation are related to specific points in the differentiation of myoblasts into myotubes. FAK is activated by growth factor receptors and regulates the development of myoblasts and the formation of muscle fibers. During the proliferation phase, the activation of growth factor receptors leads to FAK phosphorylation/activation, needed for MYOD expression, while the expression of MYOG is blocked by the binding of MBD2 to its promoter. In the early differentiation phase, phosphorylated-FAK fraction decreases and FAK cytoplasmic interaction with MBD2 promotes the translocation of the FAK/MBD2 complex into the nucleus, where MBD2 interaction with the MYOG promoter is prevented, leading to MYOG expression. During myotubes formation, FAK levels increase, even if not at the same level as in the proliferative phase. In this terminal phase, characterized by MyHC expression, integrins activation induces multiple pathways such as PI3K/AKT/mTOR which crosstalk with FAK to control protein synthesis and the size of the muscle fibers. Figure realized with BioRender.com.