Phosphoinositides in the regulation of actin cortex and cell migration.

In order for the cell to function well within a multicellular system, the mechanical properties of the plasma membrane need to meet two different requirements: cell shape maintenance and rearrangement. To achieve these goals, phosphoinositides play key roles in the regulation of the cortical actin cytoskeleton. PI(4,5)P₂is the most abundant phosphoinositide species in the plasma membrane. It maintains cell shape by linking the actin cortex to the membrane via interactions with Ezrin/Radixin/Moesin (ERM) proteins and class I myosins. Although the role of D3-phosphoinositides, such as PI(3,4,5)P₃, in actin-driven cell migration has been a subject of controversy, it becomes evident that the dynamic turnover of the phosphoinositide by the action of metabolizing enzymes, such as 5-phosphatases, is necessary. Recent studies have revealed an important role of PI(3,4)P₂in podosome/invadopodia formation, shedding new light on the actin-based organization of membrane structures regulated by phosphoinositide signaling. This article is part of a Special Issue entitled Phosphoinositides.