In animals, the midbody coordinates the end of cytokinesis when daughter cells separate through abscission. The midbody was thought to be sequestered via macroautophagy, but recent evidence suggests that midbodies are primarily released and phagocytosed. It was unknown, however, whether autophagy proteins play a role in midbody phagosome degradation. Here, we show that midbodies are released in C. elegans embryos using the ZF1 degradation tag. Released midbodies are known to be internalized via actin-driven phagocytosis, which we show requires RAB-5 GTPase to localize the Class III Phosphoinositide 3-Kinase (PI3K) complex at the cortex. Autophagy-associated BEC-1/Beclin 1 and the Atg8/LC3/GABARAP homologs LGG-1 and LGG-2 localize around the midbody phagosome and are required for midbody degradation. In contrast, proteins required specifically for macroautophagy, such as UNC-51/ULK1/Atg1 and EPG-8/Atg14, are not required for midbody degradation. These data suggest that the C. elegans midbody is degraded via LC3-associated phagocytosis (LAP), not macroautophagy. Our findings reconcile the two prevailing models on the role of phagocytic and autophagy proteins and establish a new non-canonical role for autophagy proteins in midbody degradation.
- Received April 1, 2016.
- Accepted August 18, 2016.
- © 2016. Published by The Company of Biologists Ltd
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