The coordination of membrane fission and fusion at the end of autophagosome maturation

- Autophagosome closure requires Atg8s to proceed at biologically relevant speeds.
- Autophagosomes recruit diverse SNAREs depending upon their ultimate fate.
- Syntaxin 17 recruitment and autophagosome fission are temporally coordinated.
- Syntaxin 17 supports some, but not all, autophagosome fusion events.

The two major objectives of macroautophagy are to sequester cargo away from the cytoplasm and deliver this material for breakdown in the lysosome. Sequestration is complete when the autophagosome membrane undergoes fission to produce separate inner and outer membranes, while delivery into the lysosome requires fusion of the outer autophagosome membrane with the lysosome membrane. Thus, the merging of membranes through fission and fusion underlies each of the pivotal events in macroautophagic clearance. How these merging events are controlled in the cell is poorly understood. Several recent studies however suggest that the two events may be temporally coordinated and rely upon members of the classic membrane fusion SNARE family as well as the autophagy-specific family of Atg8 proteins.

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