The late stages of autophagy: how does the end begin?

Autophagy is a catabolic cellular process involving dynamic membrane rearrangement. Here, we review the understanding of autophagy, focusing on the late stages of the process, from the closing of the autophagosome to fusion with the lysosome. We propose the Reverse fusion model, for the closing autophagosome. In this model, autophagosome closure proceeds in a topologically similar but reverse order to membrane fusion during the escape of influenza virus from the endosome. This dynamic process is thought to be directly catalyzed by LC3, an ubiquitin-like molecule. Further, we discuss the dynamics of the Atg16L complex in relation to the LC3 localization in these processes. Finally, the molecular mechanisms involved in the delivery of autophagosomes to the lysosome and fusion are introduced. Several key events exist in each step and seem to be coordinated to faithfully conduct the autophagic process.