Rab GTPases mature the LC3-associated midbody phagosome

ARTICLE HISTORY Received 12 December 2016 Revised 16 February 2017 Accepted 16 February 2017 ABSTRACT Post-mitotic midbody remnants have recently been added to the list of structures degraded via LC3associated phagocytosis (LAP). LAP involves proteins of the autophagy pathway to degrade phagosomal contents, mingling 2 pathways that were thought to be distinct. To better characterize how similar LAP is to classical phagocytosis, we asked whether the midbody LAPosome (LC3associated phagosome) matures using Rab GTPases in C. elegans embryos. We found that RAB-5 and RAB-7 appear transiently on midbody LAPosomes and that RAB-7 is required for midbody degradation, suggesting that RAB-5 and RAB-7 direct LAPosome maturation similar to classical phagosomes. Further, we observed that the Rab2 homolog UNC-108 and the major proton pump, the V-type ATPase, are required for acidification of the midbody LAPosome, demonstrating that phagosomes and LAPosomes acidify via a common pathway. Together, these data reveal that Rab GTPases play similar roles during LAPosome maturation and phagosome maturation.