Probing phosphoinositide functions in signaling and membrane trafficking

The inositol phospholipids (Pls) comprise a family of eight species with different combinations of phosphate groups arranged around the inositol ring. Pls are among the most versatile signaling molecules known, with key roles in receptor-mediated signal transduction, actin remodeling and membrane trafficking. Recent studies have identified effector proteins and specific lipid-binding domains through which Pls signal. These lipid-binding domains can be used as probes to further our understanding of the spatial and temporal control of individual Pl species. New layers of complexity revealed by the use of such probes include the occurrence of Pls at intracellular locations, the identification of phosphatidlylinositol signaling hotspots and the presence of non-membrane pools of Pls in cell nuclei.