Phosphoinositides in autophagy: current roles and future insights

Today, the importance of autophagy in physiological processes and pathological conditions is undeniable. Initially, autophagy merely was described as an evolutionarily conserved mechanism to maintain metabolic homeostasis in times of starvation; however, in recent years it is now apparent that autophagy is a powerful regulator of many facets of cellular metabolism, that its deregulation contributes to various human pathologies, including cancer and neurodegeneration, and that its modulation has considerable potential as a therapeutic approach. Different lipid species, including sphingolipids, sterols, and phospholipids, play important roles in the various steps of autophagy. In particular, there is accumulating evidence indicating the minor group of phospholipids called the phosphoinositides as key modulators of autophagy, including the signaling processes underlying autophagy initiation, autophagosome biogenesis and maturation. In this review, we discuss the known functions to date of the phosphoinositides in autophagy and attempt to summarize the kinases and phosphatases that regulate them as well as the proteins that bind to them throughout the autophagy program. We will also provide examples of how the control of phosphoinositides and their metabolizing enzymes is relevant to understanding many human diseases.