Dissecting autophagosome formation: the missing pieces.

The formation of autophagosomes is the central part of the macroautophagy pathway. Little is known, however, about how the participants in this process affect the membrane dynamics at the phagophore assembly site (PAS). Recently, we demonstrated that Atg8, a lipid-conjugated ubiquitin-like protein, controls the expansion of the phagophore. In addition, we showed that the autophagosome formation process can be traced and dissected by time-lapse fluorescence microscopy observation of GFP-Atg8. These findings constitute one step further in our understanding of autophagosome formation. Key questions remain open, however, on how the actions of other proteins at the PAS are coordinated with that of Atg8 and on the precise role of Atg8.