**4. Understanding autophagosomes: a non-traditional membrane vesicle**

Current efforts to better understand autophagy are focused on the molecular details leading to the formation of autophagosomes, a double-membraned vesicle unlike any other in size and structure, that serves as the hallmark of autophagy. These approaches have mainly focused on understanding the intracellular trafficking of autophagy-related transmembrane proteins that are thought to help deliver lipids to the growing autophagosome via vesicle transport. Insights have also been obtained from assessing the influence of lipid-dependent enzymes as well as lipidsynthesis and transport pathways on autophagy. For example, mutation of PI3K enzymes severely impairs autophagy [32, 33], pointing at the importance PI and some of its phosphorylated forms in autophagic processes. In these ways, we have identified that PE and PI lipids play an important role in autophagy (**Table 2**) [14, 34–41]. We discuss these findings below.
